Beetles and Pollination

Andrew Kness on

Cerruti R2 Hooks$ and Anahí Espíndola*
$Associate Professor and Extension Specialist, CMNS, Department of Entomology
*Assistant Professor, CMNS, Department of Entomology. Twitter: @Analyssi

Note: This is the third article of our series on pollinators. The initial articles can be found at the vegetable and fruit headlines news June special editions and Maryland Agronomy News Blog.

Introduction

Much has been written about bee (Hymenoptera) and butterfly (Lepidoptera) pollinators. Flies (Diptera) have also gotten their fair share of press regarding their pollination services. However, beetles (Coleoptera), which represent the largest insect order and are among the first flower-visiting insects in history, don’t receive similar admiration from pollinator enthusiasts and paparazzi. Nevertheless, even now, beetles are considered essential pollinators; and are especially important pollinators of some of the first flowering plants to evolve, such as magnolias and spicebush (Fig. 1). Beetles are attracted mostly to flowers that emit musky, yeasty, spicy, rotten or fermented odors. It just so happens that spicebush and magnolia flowers contain spicy pollen and produce aromatic oils, respectively, each of which serves as a lure for their beetle pollinators.

beetle on flower
Fig. 1. Asian multicolored lady beetle on spicebush. Photo: J. Gallagher (CC)

There are 380,000 named living species of beetles, constituting nearly one-fourth of all known animal species on our planet. Beetles are so abundant that there are more species of beetles than of any other known group of animals. Among insects, beetles make up about 40% of all known species, and this may be due to their amazing ecological diversity, which allowed them to evolve impressive diverse morphological features. In the context of pollination, due to their sheer numbers, beetles contribute to a considerable amount of plant pollination. Even though the most consistent pollinators today belong to other insect orders, beetles do contribute significantly to the pollination of specific plants. Further, because beetles were one of the first insects to establish pollen-based relationships with plants, they have been described as key contributors to the reproduction of the first groups of flowering plant species.

Beetle history as pollinators

Beetles have been a predominant group of floral visitors and pollinators since very early times in the evolution of plants. Beetles have been evolving for roughly 250 million years, and are recognized among the first insects acting as pollinators of flowering plants. Indeed, until recently, many beetles and other insects were identified as pollinators of non-flowering plants (e.g. conifers, ginkgos, cycads). However, many ancient fossils indicate that plants today that are mostly wind-pollinated, relied strongly on insects for pollination in the past. Interestingly, a very recent study of fossil beetles found in amber (like the fossil insects from Jurassic Park!) provided the oldest account of flowering plant pollination. In this study, four different species of extinct beetles having lived 99 million years ago were found to carry pollen of flowering and non-flowering plants. While the non-flowering plant pollen corresponded to different species of cycads, pollen from flowering plants belonged to a newly described species of water lilies (Fig. 2). This not only pushed back the time of the first known fossil record of pollination, it also represents a clear link of how pollination of flowering plants may have evolved from pollinators that were visiting non-flowering plants. In comparison to other insect species currently known to visit flowers, beetles are now the oldest known pollinators of flowering plants, predating the oldest pollen-rich bee fossil by roughly 30 million years.

Fig. 2. Left: Water lily; Right: Cycads. Photos: A. Scottow and K. Norstog, respectively (CC).

Modern-day beetle pollinators visit many different types of plants, feeding on pollen, floral parts, and sometimes on nectar. While most beetles that act as pollinators are not specialized in their floral choices, beetles that visit flowers have some morphological traits that make them relatively efficient in transferring pollen. In fact, many of these beetles are hairy, allowing for pollen grains to stick on them and be transferred among plants. Further, some beetle groups have modified mandibles, with a brush-like structure or elongated proboscis, which allows them to more readily collect pollen and feed on nectar, respectively. While the vast majority of generalist beetle species visit well known plants such as carrot, buttercup, sunflower or cabbage, some beetle species are specialist pollinators of descendants of plants they visited millions of years ago: water lilies, custard apples, magnolias, all spice plants. For these latter plants, it is suspected that the evolution of beetles that they are associated with was driven by the diversification of their host plants. Relative to this point, part of the amazing morphological diversity that we see in extant beetle species is due to their long-dated interaction with these plants. Further, because these latter plant groups are usually associated with tropical or Mediterranean environments, it has been assumed for a long time that beetle pollination is most important in warm climates.

Beetles and magnolia’s special bond

Pollination by beetles seems to have strongly influenced the evolution of angiosperm flowers. Many million years ago, plants and pollinators began specializing and adapting traits that benefited each other’s requirements; and beetles were among the earliest pollinators to take part in nature’s matching adventures. Thus, flowers of lineages such as magnolias are paired with beetles as their primary pollinators (Fig. 3). Today, this flower’s characteristics are recognized as those that make up a “typical” beetle flower. These flowers are bowl-shaped and provide a cave-like structure for beetles to use as shelter. Beetles pollinating these flowers feed on pollen and sweet floral secretions. Though Magnolias from some areas are pollinated by several beetle families, some Magnolias from tropical areas have very specialized interactions, and are only effectively pollinated by few beetle species.

longhorned beetle on white flower
Figs. 3. Long horned beetle on Magnolia grandiflora. Photo: D. Hill (CC)

But how do beetles pollinate Magnolias? The story goes that beetles enter the flower carrying pollen from a previous floral visit, and passively deposit the pollen onto female structures while roaming about in the flower and feeding on stigmatic secretions. While these visits are happening, pollen of the flower is released, and while beetles feed on it, they also get it all over themselves. At the end of the flowering cycle, the flower wilts, and the messy beetles move on to another wide-open flower, where pollen is transferred and collection from the new flower initiates. This relationship between Magnolias and their beetle pollinators has evolved over millions of years of interactions. For example, magnolia plants have evolved strategies to “direct” beetle feeding away from reproductive parts of the flower. Basically, the plant sacrifices pollen and leaf tissue for the service of pollination. More specifically, beetles feed on other areas of the flower and are thus distracted from feeding on female parts of the flower which needs to stay in tacked so that it can produce seeds. Related to this, it has been suggested that this beetle-pollination relationship has led to an increase in the number of stamens produced by the plant, which insures that some are still present and ready to participate in plant reproduction after beetles finish their feast. Moreover, magnolia has developed securities that ban access by other insects during critical pollination phases and produces a fruity-smell that attracts beetles to the flowers.

Why do beetles visit flowers?

To understand beetle pollination, it is important to realize that most beetles visit flowers to feed on pollen, and sometimes on floral structures (e.g. petals, anthers) or secretions (e.g. stigmatic secretions). In fact, beetles rarely visit flowers for the typical nectar that other famous pollinators seek, and this reward is actually often absent or moderately produced in flowers beetles frequent. The most important reward beetles are after when visiting flowers is protein-rich pollen. Pollen beetles (Nitidulidae), longhorn beetles (Cerambycidae), leaf beetles (Chrysomelidae), rove beetles (Staphylinidae), scarabs (Scarabeidae), tumbling flower beetles (Mordellidae) and weevils (Curculionidae) are common pollen feeders of many flowers. Tumbling flower beetles are commonly found feeding on flowers of the carrot family, which purportedly contain a good pollen source. Though most beetles visit flowers solely for pollen, there are some species that desire more. Many beetle families such as checkered beetles (Cleridae; Fig. 4), and blister beetles (Meloidae) are known to use other floral resources. Indeed, some prefer to simply eat the flowers and will gnaw flower tissue, eat pollen and lick floral exudates. However, in the case of some beetles, flowers represent much more than just a place to get free food. For example, monkey beetles (Scarabaeidae), a primary pollinator of the peacock moraeas plant in South Africa, frequent flowers of this plant for pollen, nectar and mating, while beetles from South America are attracted by heat-producing Aroid plants and a series of water lilies, in which they feed and reproduce. More locally, many beetles, including soldier beetles, often use the same flower that they frequent in search of food for mating (Fig. 5). Besides using flowers as sources of food and mating, beetles sometimes use them as their residence and a place to prey on other insects. For example, predatory beetles often hide within flowers, waiting for soft-bodied insects to visit. Ladybeetles, which are well known predators, visit flowers to feast on aphids and may sip some nectar when available. Beetles may also use flower blooms as a place to hide from predators. Some beetles may also enter flowers because the temperature within their blossom is more preferable to external environmental conditions. Thus, beetle-pollinated flowers include either sufficient nutritional rewards, place to warm up, mate and hunt or serve as a refuge from natural enemies.

black and yellow beetle on white flower
Fig. 4. Ornate checkered beetle Trichodes ornatus visiting a flower. Photo: J. Gallagher (CC)
red beetles on yellow flower
Fig. 5 Soldier beetle feeding and mating on same flower. Photo: S. Nygaard (CC)

Beetle importance as pollinators

Beetles make up the largest group of pollinating animals because of their large numbers and are the most diverse group of pollinators in the US. More than 77,000 beetle species are estimated to visit flowers. Of the world’s almost 350,000 flowering plant species, beetles are believed by some to be responsible for visiting nearly 90%. Cantharophily (cross-pollination of flowers by beetles) is more common in tropical areas especially in tropical-Mediterranean regions and is often not considered important to pollination in temperate regions. Relative to this, the native paw-paws and atemoya are some of the only crops in the U.S. known to be pollinated by beetles. However, an estimated 52 native plant species are pollinated by beetles in North America north of Mexico, and there are several common temperate ornamental plants that are beetle pollinated. Beetles may also be particularly important in semi-desertic areas, such as South Africa and southern California. Beetles are important for the production of crops that are exclusively beetle-pollinated, such as atemoyas or paw-paws. To this point, a relatively recent study found that atemoya orchards in Australia directly benefit from the presence of wild beetle species in surrounding forests, and that increasing the presence of natural habitats around cropping areas improves fruit set and production. From this respect, the presence of wild beetles is an extremely valuable ecosystem service, which if present, can help some industries which rely on hand-pollination cut labor cost.

Despite contributing to the pollination of many plants, beetles’ roles in ecosystem services are generally assumed to revolve around their scavenging and organic matter decomposition. Part of this misconception may be attributable to the fact that flower-visiting beetles are less active on flowers than are many flies, butterflies and bees, and for that reason they are usually considered inefficient pollinators. Further, some scientists claim that beetle pollination is among the most destructive: most beetles eat their way through petals and other flower parts, they defecate within the flower, and then spread the mixture of feces and pollen. Still, beetles are recognized as the primary pollen transporters for numerous plant families, especially phylogenetically basal plants such as magnolias and water lilies. For this reason, it is unfair to not recognize beetles as vital pollinators who play a unique role in wild plant reproduction and food production.

Beetle floral preference

Flower description. Flowers dependent on beetle pollinators contain a foreseeable list of features that differ considerably from flowers primarily pollinated by other insect orders. Flowers visited by beetles may be large solitary (e.g. magnolias, water lilies) or clusters of small flowers (goldenrods, Fig. 6; Spirea, Fig. 7). Beetles are generally clumsy and rough fliers, compared to more delicate and/or agile flying insect pollinators (e.g. butterflies, bees, flies). To accommodate these clumsy fliers, beetle-pollinated flowers tend to be large and their rewards easily accessible. Further, the volume of individual flowers is typically large enough to accommodate several beetles within the same floral cup. Beetle-pollinated flowers usually have open corollas, solitary and heavily-constructed, though some may contain many tiny clustered flowers. Beetles also frequent flat to dish-shaped or bowl-shaped flowers, as these features provide them an easy platform for landing and often a good place for shelter.

beetle on yellow flower
Fig. 6. Goldenrod soldier beetle on goldenrod. Photo: D. Hill (CC)

Relatively large beetles can often damage flowers, or their pollinating parts, especially when feeding on pollen with their large mouth-parts. However, many flowers resist this damage either by producing many more flowers than what would be sufficient for reproduction, or by physically protecting the most important parts of their reproductive organs (e.g. the ovaries) from beetles. Some beetle-pollinated flowers such as some Aroids present structures that function as traps, preventing beetles from leaving the flower before the end of the plant reproductive cycle. Others floral traits that prove beneficial to beetle attraction include nocturnal (but also diurnal) blooms, plant heat production, and the presence of floral structures that provide protection to beetles.

white flowers
Fig. 7. Spirea flower. Photo: S. Braun (CC)

Flower color. Although many beetles can see color and UV light, they use color mostly as a short-distance cue for floral choice. Indeed, it seems that most beetles base their long-distance floral location on floral odors. In terms of floral coloration, most beetles are attracted to dull-colored, greenish or white, and reddish brown or dark flowers. Flower size is not a good indicator of floral choice, since flowers preferred by beetles can be large or small and clustered.

Floral odors. Many flowers pollinated exclusively by beetles display strong fragrances. Odors that serve as primary beetle attractants are numerous and not always pleasant, including smells of decaying plant or animal material, fermented fruits or spices. Indeed, when locating flowers, beetles are attracted to a variety of scents and although there are not many plants pollinated primarily by beetles, flowers that do depend on them are typically characterized by the presence of discernible fragrances that acts as a primary long-distance attractant.

Pollen load and heat. Many beetle species eat pollen, so it is understandable that plants they frequent produce plenty of easily-accessible pollen. This also ensures that there is enough pollen that remains for pollinating the flower after the beetles complete their meal. In addition to pollen, beetle flowers often use heat as a reward for pollination. Some incredible plants are capable of producing heat, which attracts and likely increases the activity level of beetles while visiting their flowers. These heat-producing beetle-attracting flowers belong to families Nymphaeaceae, Illiciaceae and Magnoliaceae.

How to Protect beetles?

Planting swaths of wild flowers, native shrubs and trees, as well as urban green spaces will provide good habitats for adult beetles and other pollinators. Similarly, since some beetles deposit their eggs in soil or loose-leaf litter, it is critical to eliminate the use of synthetic fertilizers and toxic pesticides that threaten their life above and below the soil. This is especially important for soldier beetle larvae which are carnivorous, consequently foraging for aphid eggs, worms, slugs, and other prey among assorted plant debris. As they feed, soldier beetle larvae reduce the number of soft-bodied insects, such as aphids. Adopting organic land management practices such as planting pollinator habitat, conservation strips and cover crops, using mulch for weed control, and adding compost and diverse plantings to arable lands, helps to build and protect beetle biodiversity.

Summary

Though currently recognized as being among the oldest known pollinators of flowering plants, beetles usually don’t get their due as major pollinators. This is partially attributable to their suspected inability to move pollen through long distances and their destructive behavior while feeding on pollen and floral structures. Notwithstanding, beetles are central in the pollination of many plant species in temperate areas and are popularly known for their pollination services in tropical and Mediterranean ecosystems. In temperate regions, beetles contribute to the pollination of Magnolias and all spice bushes. In terms of crops, beetles are important in the production of some tropical fruits such as atemoyas and local paw-paws, allowing these crops to be produced without hand-pollination. Pollinating-beetle conservation involves protecting established ecosystems and increasing the presence of wild habitats by establishing natural resources such as wild flowers, native shrubs and trees. Financial support for the publication of this article is via USDA NIFA EIPM grant award numbers 2017-70006-27171.

Web-Based Resistance Management Tools

Andrew Kness on

Kurt Vollmer, Weed Management Specialist 
University of Maryland

If you attended the agronomy meetings this past winter, you heard me talk about the importance of using multiple strategies to mitigate herbicide resistance. Rotating and using multiple sites-of-action (SOA), is one strategy that helps prevent weeds and other pests from adapting to a single pesticide group. This can be challenging with so many products on the market. Take Action (https://iwilltakeaction.com) is a farmer-focused education platform designed to help farmers manage herbicide, fungicide and insect resistance. Several tools can be downloaded from this website to aid in your pest control decisions. Among these is an app (https://iwilltakeaction.com/app) that allows the user to

  • Quickly identify herbicide, fungicide or insecticide brands or active ingredient SOA numbers,
  • see a list of other SOA numbers to help diversify his or her weed control program,
  • and search the herbicide, fungicide or insecticide last used to prevent the use of similar SOAs

In addition, the GROW IWM website (https://growiwm.org) provides excellent information on how to use integrated weed management practices for herbicide resistant weeds.

Using partridge pea (Chamaecrista fasciculata) to increase natural enemies in neighboring soybeans

Andrew Kness on

Laura C. Moore^,*, Alan W. Leslie#, Cerruti RR Hooks$,* and Galen P. Dively+,*
Former graduate student^, Associate Professor and Extension Specialist$, Professor Emeritus+, CMNS, Department of Entomology*, Agriculture Extension Agent, Charles County#

Introduction

Increasing floral diversity within agricultural fields has been proposed as a method to bolster natural enemies and subsequently reduce pest populations. A key factor that enhances predator and parasitoid populations is the availability of nectar and/or pollen food subsidies from flowering plants. Many natural enemies, particularly hymenopteran (wasps) parasitoids, require carbohydrates for successful reproduction and overall fitness. However, monoculture cropping systems are relatively weed-free and generally lack floral resources required by many natural enemies. A literature review showed that the successful establishment of certain parasitoids in cropping systems depended on the presence of nectar-bearing weeds. In addition to providing natural enemies nectar and pollen to eat, flowering plants can supply alternative hosts or prey, shelter, overwintering sites and a more suitable microclimate.

Many conservation projects have been implemented by farmers to increase beneficial services on arable lands. In Maryland, the opportunity to practice conservation biological control exists within the Conservation Reserve Enhancement Program (CREP). Conservation biological control is a pest management approach that manipulates agricultural systems so as to promote pest suppression by naturally occurring predators, parasitoids and pathogens. The CREP seeks to establish riparian buffers in Maryland to improve water quality, filter sediments and nutrients from runoff and provide wildlife habitat. However, these buffers can be engineered to support communities of natural enemies and serve as corridors for their movement into neighboring crops.

The aim of this study was to determine whether buffer strips could be used as insectary plants to enhance beneficial arthropods (insects and spiders) within neighboring soybeans. Insectary plants are plants grown with cash crops to attract, feed and shelter insect parasitoids and predators so as to enhance their natural control of insect pests. We monitored pest and beneficial arthropods in the buffer insectary plants and neighboring soybean plantings and tried to link arthropods found in buffer plants with pest management in neighboring soybeans.

Abbreviated Experimental Procedures

Insectary buffer test plants. Partridge pea and purple tansy are commonly used to enhance floral resources along field margins for pollinator plantings and to enhance communities of natural enemies in adjacent crops. Partridge pea is a native annual legume and is widely used in seed mixes of CREP riparian buffers because it readily reseeds itself, is competitive when grown with grass mixes, and provides nutritional seed for game birds. As an insectary plant, partridge pea has a long bloom period and each leaf petiole has an extrafloral nectary at its base, which produces nectar throughout the growing season. A diverse assemblage of pollinators and natural enemies are attracted to partridge pea. Purple tansy has a long flowering period, high-quality nectar and pollen production, and is reported as being a valuable insectary plant. Proso millet is a warm season annual grass that lacks floral resources. As such, it served as a grass control to determine how added vegetation diversity in the absence of floral resources would impact natural enemies.

Experimental design. Field experiments were conducted over two years at the Central Maryland Research and Education Center in Beltsville, MD. In year 1, 16 plots of soybean were seeded on May 11. Each plot consisted of 20 soybean rows spaced 35 cm (15 in) apart and bordered on each side by an insectary buffer strip (Fig. 1). The test buffer strips consisted of 1) purple tansy, 2) partridge pea, 3) 50:50 seed mixture of purple tansy + partridge pea, or 4) proso millet. Each soybean plot-buffer combination was replicated four times. Seeds of partridge pea, purple tansy, and proso millet were planted with a no-till drill in rows 23 cm (9 in) apart at a rate of roughly 12,000 seeds per ha (4856 per ac) on the day soybeans were planted.

Fig. 1. Illustration of a soybean-buffer treatment plot in year 1. Soybean plots were bordered on each side with buffer insectary plants. Buffers included purple tansy, partridge pea, 50:50 seed mixture of partridge pea/purple tansy or proso millet.

The year 1 study showed that purple tansy was unsuitable for the hot summer conditions in Maryland Thus, it was not used in the year 2 experiment, which focused solely on partridge pea as the insectary buffer plant. The year 2 experiment included 14 strip plantings of full season soybean at five different locations (Fig. 2). Soybeans were planted no-till in 75 cm (30 in) wide rows during May. Each strip was bordered at one end with a partridge pea buffer and at the other end with a mixed grass border of fescue (Festuca spp.) and orchardgrass (Dactylis spp.).

Fig. 2. Aerial view of experimental layout in year 2. Study consisted of 14 contour strips of full-season soybeans and adjoining partridge pea buffers (indicated by black polygons) at one end of each strip. Grassy areas were on opposite ends of soybean strips without a buffer.

Arthropod population assessments. Abundances of arthropods active in the plant canopy were measured with yellow sticky cards secured to bamboo poles. Further, sweep-net samples were taken in July and August to estimate green cloverworm (Hypena scabra) numbers. The green cloverworm served as a bioindicator of changes in pest populations potentially caused by enhanced natural enemy activity. The larger field size in year 2 allowed sticky cards to be placed throughout the soybean strip. One card was placed in the center of each partridge pea buffer, and additional cards were placed at distances of 3, 6, 12, 18 and 24 m (10 ft to 79 ft) from the border on both sides of each soybean strip (total of 10 sticky cards per strip). Sampling was conducted weekly or biweekly. In year 2, pitfall traps were also installed in the ground adjacent to each sticky card to estimate the abundance of surface-dwelling arthropods over 7-day intervals.

Summary of Results

Year 1 Study – comparison of four insectary buffers parasitoid abundance. Three families of parasitoids Mymaridae, Scelionidae and Trichogrammatidae comprised 83.9% of the total of parasitic wasps captured on sticky cards. Families Ceraphronidae, Braconidae and Eulophidae comprised an additional 12.5% of the wasp parasitoid group. Of these parasitoids, mymarids were the most abundant and there were 73-78% higher sticky card captures of this wasp in partridge pea compared to purple tansy and millet buffers. However, significantly fewer mymarids were captured in soybeans adjacent to partridge pea than adjacent to purple tansy or millet. Scelionid parasitoids were more abundant in millet and purple tansy buffers but their numbers were similar in soybeans regardless of the neighboring buffer type. Trichogrammatid abundance was greatest in millet early in the season and in buffers with partridge pea by season end. Two families of fly parasitoids (Tachinidae and Sarcophagidae) averaged 9.4 and 4.4 flies per sticky card in insectary buffers and soybean plots, respectively. The abundance of sarcophagid flies was significantly higher in buffers with partridge pea than millet or purple tansy alone. Similarly, soybeans adjacent to partridge pea were inhabited by more tachinids and sarcophagids than soybeans adjacent to millet or purple tansy.

Predator abundance. Overall predator abundance was significantly higher in purple tansy and millet compared to partridge pea or mixed (partridge pea + purple tansy) buffers. Mean captures per card were 5.0 in partridge pea, 6.8 in mixed, 8.5 in purple tansy, and 10.3 in millet. However. similar predator numbers were captured in soybean plots adjacent to all four buffer types.

Insect herbivores (plant feeders). Sweep net counts of green cloverworm were statistically similar in soybean plots adjacent to the four different buffer types. Overall numbers per 10 sweeps averaged 24.6, 27.0, 18.0, and 23.0 in soybeans adjacent to millet, purple tansy, mixed and partridge pea buffers, respectively. The bulk of other insect herbivores captured on sticky cards were mainly aphids, leafhoppers, planthoppers and plant bugs. Mean numbers captured per card were 86.1 (millet), 113.2 (purple tansy), 57.6 (mixed) and 53.7 (partridge pea).

3.2. Year 2 Study partridge pea vs. natural grass vegetation

Parasitoid abundance. The most abundant parasitoids belonged to families Mymaridae, Trichogrammatidae and Scelionidae in order of abundance, and together comprised 84.3% of the total hymenopteran parasitoids captured. Each family responded differently to the partridge pea treatment. Mymarid abundance was higher overall in partridge pea buffers but did not enhance their abundance in neighboring soybeans (Fig. 3). Significantly fewer trichogrammatids were captured in partridge pea compared to numbers captured in soybean with and without the partridge pea buffer. Mean captures of dipteran parasitoids per sticky card abundance were significantly higher in soybean neighboring partridge pea, with the exception of the first and last sampling dates.

Fig. 3. A) Mean number (±SE) of mymarid parasitoids captured per sticky card in partridge pea buffer, soybean neighboring buffer, and soybean without buffer in year 2. Data for soybean were averaged over all sampling distances (3, 6, 12, 18 and 24 m) from the field edges. B) Mean number in soybean at different distances from field edges with and without a partridge pea buffer.

Predator abundance. Long-legged flies, minute pirate bugs, and big-eyed bugs comprised 81.4% of the total predatory arthropods captured. Soldier beetles, fireflies and lady beetles represented an additional 11.6%. Mean abundance of predators per sticky card was 11.5 ± 1.1 in buffer, 4.1 ± 0.16 in soybean neighboring buffer and 4.9 ± 0.18 in soybean without buffer. Abundance of predators was significantly lower in soybean neighboring the partridge pea buffer (Fig. 4). However, this was largely due to the activity of long-legged flies, which were more attracted to the partridge pea buffer. Still, their numbers were significantly lower in soybean strips neighboring partridge pea compared to soybeans without partridge pea buffers.

Fig. 4. A) Mean number (±SE) of arthropod predators captured per sticky card in partridge pea buffer, soybean neighboring buffer and soybean without buffer in year 2. Data for soybean were averaged over all sampling site distances (3, 6, 12, 18 and 24 m) from the field edges. B) Mean number in soybean at different distances from field edges with and without a partridge pea buffer. Arthropod predator guild consisted of long-legged flies, minute pirate bugs, big-eyed bug, soldier beetles, fireflies and lady beetles.

Insect herbivores/pests. Thrips, leafhoppers, treehoppers, froghoppers and planthoppers comprised over 95% of herbivores captured on sticky cards. The total number of herbivores per sticky card averaged 108.2 in the partridge pea buffer, 96.3 in soybean neighboring buffer, and 96.4 in soybean without buffer. Thus, herbivore numbers did not differ significantly in the buffer and soybeans.

Pitfall trap predators. A total of 56,296 arthropods were identified from pitfall trap samples. Of predators captured in pitfall traps, ants, spiders, soldier beetle larvae, rove beetle adults and larvae, and ground beetle adults and larvae were the most abundant. Ant numbers were significantly lower in soybeans neighboring partridge pea on all sampling dates.

Discussion

Year 1 study was conducted to determine if pure and mixed buffer strips of partridge pea and purple tansy could attract greater numbers of beneficial arthropods than non-floral strips of millet, and whether these buffers enhance beneficial arthropod abundance in neighboring soybeans. Purple tansy was not a suitable insectary plant as it was not well adapted to the seasonal period of the study in Maryland. Furthermore, purple tansy would probably be less desirable to establish and maintain as a buffer strip due to its relatively high seed price, slow growth characteristic and greater susceptibility to weed competition. Moreover, purple tansy was quickly out-competed by partridge pea in the mixed planting to the extent that the pure and mixed buffers containing partridge pea attracted similar arthropod communities.

Overall, results consistently showed that partridge pea attracted and supported high populations of natural enemies and potential hosts and prey, with abundances significantly greater than levels found in adjacent soybeans. Sticky card captures of wasp and fly parasitoids in year 1 were more than 70% higher overall in buffers containing partridge pea compared to other buffer types. Similarly, populations of all beneficial arthropods captured by sticky card and pitfall sampling in year 2 were approximately 80 to 72% higher, respectively, in partridge pea buffers compared to the soybean crop.

Parasitoids. Mymarid wasps were notably the most common parasitoids captured on sticky cards and consistently more abundant in partridge pea compared to soybean. These tiny wasps parasitize insect eggs in concealed sites within plant tissues or the soil and are important natural control agents of economically important leafhopper pests. In year 1, mymarids reached levels in partridge pea buffers that were four-fold higher than those in soybean plots, yet significantly lower levels of mymarids were captured in soybean adjoining these buffers. This suggests that the partridge pea lured mymarids from neighboring soybeans. High numbers of mymarids were also captured in partridge pea in year 2 but their abundance in soybeans was not enhanced. This suggests that partridge pea may provide some parasitoids and their associated hosts with all resources required for survival and reproduction. This would in effect provide no incentive for these parasitoids to forage within neighboring crops.

Most fly parasitoids found on sticky cards were tachinids or sarcophagids. The vast majority of hosts of tachinid flies are plant-feeding insects. Their level of parasitism can vary greatly, from less than 1% to approaching 100%, depending on such factors as the size of a host and parasitoid population, and environmental conditions. During both study years, their overall abundance in partridge pea was 62.3% higher than levels in soybean. In year 2, this effect was heightened at the field edge next to buffers, suggesting that higher numbers of parasitic flies encroached into the neighboring soybeans but enter only a short distance within the crop.

Predators. In year 1, predators captured on sticky cards were 65% more abundant in the millet and purple tansy buffers. This response was mainly attributed to the abundance of long-legged flies. These predatory flies hover while searching for small, soft-bodied arthropods, particularly other flies, aphids, spider mites, larvae of small insects and thrips. However, abundances of long-legged flies in soybean plots were not affected by buffer type in year 1. Long-legged flies were also the predominant predators active in the plant canopy in year 2, with overall numbers 2-3 times higher in partridge pea buffers compared to levels found in soybeans. However, their abundance was significantly lower in soybean neighboring partridge pea, particularly at sampling sites closest to the field edge. This is further evidence that the partridge pea acted as a natural enemy sink.

Of the ground-dwelling predators captured by pitfall traps, ants were the predominant group and their abundance was significantly higher in partridge pea than adjoining soybeans. Their numbers were significantly lower in soybean plantings adjacent to partridge pea than grassy check treatment on all sampling dates, implying again that partridge pea acted as a natural enemy sink by luring ants away from soybean. Populations of other ground-dwelling predators, which consisted mainly of spiders, rove beetles, soldier beetles and ground beetles, showed a definite preference for partridge pea compared to soybeans. However, their abundances in the crop were not affected by partridge pea presence.

Herbivores. Sticky card captures each study year indicated that partridge pea harbored significantly more insect herbivores compared to soybean. The majority of herbivores were aphids, leafhoppers, planthoppers and plant bugs. In year 1, number of green cloverworm, as well as other herbivores in soybean were similar regardless of the buffer treatment.

Conclusion

This study demonstrated that partridge pea provides floral resources and alternative food for a diverse community of natural enemies and herbivores. However, its presence as a monoculture buffer did not result in increased number of major natural enemies in neighboring soybeans. Taken together, partridge pea planted as a monoculture acted more as a natural enemy sink by attracting beneficial arthropods away from soybean, potentially decreasing natural control efforts. For this reason, a monoculture of partridge pea may not be an ideal insectary planting if the ultimate goal is to maximize natural enemy efficacy in neighboring soybean fields.

In conservation reserve practices, monocultures of partridge pea are more commonly planted as a wildlife habitat to provide food for bobwhite quail and other wildlife and as flowering habitat for different pollinator taxa. Because the foliage is potentially poisonous to cattle and re-seeding plants can aggressively fill in voids when used as part of a seed mix, conservationists recommend for herbaceous riparian buffers that the total seed mix consist of no less than 1% and no more than 4% partridge pea. However, decisions about the deployment of insectary plants as a monoculture or part of a riparian buffer mix planting should take into consideration the attractiveness and resources provided to natural enemies and their hosts/prey by the insectary habitat in comparison to those provided by the neighboring cash crop. Simple addition of a highly attractive flowering buffer adjacent to a crop could be counterintuitive to natural biological control efforts.

Acknowledgements

Financial support for field studies and publishing results was provided by the Northeast Sustainable Agriculture Research and Education Grants Program, Maryland Soybean Board and USDA NIFA EIPM grant number 2017-70006-27171.

Department Announces Mail-In Applications for Cover Crop Program

Andrew Kness on

CONTACT: Jason Schellhardt 410-841-5888
Megan Guilfoyle, 410-841-5889

ANNAPOLIS, MD (June 18, 2020) — The Maryland Department of Agriculture today announced that this year’s cover crop sign-up will be conducted entirely by mail from July 1 through July 17. The popular conservation program provides farmers with cost-share assistance to offset seed, labor, and equipment costs associated with planting cover crops on their fields in fall to build healthy soils and protect the Chesapeake Bay.

“To help ensure the health and safety of our farmers and local soil conservation district staff, we have switched to a mail-in registration process for this year’s cover crop sign-up,” said Secretary Joe Bartenfelder. “As we continue to safely reopen the state, it is important for Maryland farmers to know they can continue to count on the department for assistance in protecting valuable water and soil resources.”

Farmers who participated in last year’s cover crop program will receive registration packets in the mail later this month. The packet includes an application, program flyer, step-by-step instructions, and return envelope that has been pre-addressed to a local soil conservation district. Beginning July 1, applications will also be available on the program’s website. To be considered for cost-share, applications must be postmarked by July 17. Farmers who have questions or need assistance with their applications should contact their local soil conservation district.

Eligible farmers can receive up to $60/acre in cost-share grants to incorporate traditional cover crops into their fields this fall. The maximum payment for aerial seeding with incentives is $65/acre. Here are some additional highlights:

  • The base payment is $40/acre for incorporated seed and $45/acre for aerial seed or aerial ground seeding.
  • A $10/acre early planting incentive is offered for incorporated seed.
  • Farmers who aerial seed or aerial ground seed cover crops into standing corn on or before September 10 qualify for a $10/acre incentive payment.
  • Incentives to terminate cover crops after May 1, 2021 may be available.
  • Farmers may plant cover crops after corn, soybeans, sorghum, tobacco, vegetables, and — new this year — hemp and millet.

Cover crops are important to the health of the Chesapeake Bay and the productivity of Maryland’s farmland. In the fall, cold-hardy cereal grains are planted as cover crops in newly harvested fields. As they grow, cover crops provide a living, protective cover against erosion and nutrient runoff while building the soil’s organic matter for the next year’s crop.

To help create diversity, eligible cover crop species may be mixed with radishes and legumes, including clover, Austrian winter peas, and hairy vetch using a variety of two and three-species mixes.

Farmers are required to include a completed current Nutrient Management Plan Certification with their cover crop applications. This form may be downloaded from the website, and must be signed by both the farm operator and the person who prepared the farm’s Nutrient Management Plan.

Maryland’s Cover Crop Program is administered by the Maryland Department of Agriculture and the state’s 24 soil conservation districts through the Maryland Agricultural Water Quality Cost-Share (MACS) Program. Applicants must be in good standing with MACS and in compliance with Maryland’s nutrient management regulations. Other restrictions and conditions apply. Funding for the 2020-2021 Cover Crop program is provided by the Chesapeake Bay Restoration Fund and the Chesapeake and Atlantic Coastal Bays Trust Fund.

Here is the website for more information. https://mda.maryland.gov/resource_conservation/Pages/cover_crop.aspx

June 2020 WASDE Report

Andrew Kness on

Dale Johnson, Farm Management Specialist
University of Maryland

Information from USDA WASDE report

Attached is the summary for the June 11 WASDE. June is the second month for estimates of the new crop year (2020/21).

Corn

There was a slight adjustment of an additional 5 million bushel to the 2019/20120 crop estimate which carried forward to the beginning stocks of the 2020/2021 crop year. There were no other changes to the corn estimates.The historically high ending stocks estimate of 3.3 billion bushel and stocks-to-use ratio of 22.5% continue to suppress prices. There was a slight uptick in December futures the past few days and corn settled at $3.43 per bushel on June 11.

Soybeans

Just like corn, there was a slight adjustment of an additional 5 million bushel to the 2019/20120 crop estimate which carried forward to the beginning stocks of the 2020/2021 crop year. The crushing estimate was adjusted up 15 million bushel with no other changes to the soybean estimates. The ending stocks estimate of 395 million bushel and stocks-to-use ratio of 9.1% is not bearish. New crop prices have ticked up the past few days and November soybeans settled at $8.77 per bushel on report day.

Wheat

Just like corn and soybeans, there was an adjustment of an additional 5 million bushel to the 2019/20120 crop estimate which carried forward to the beginning stocks of the 2020/2021 crop year. There were no other changes to the wheat estimates. The ending stocks of 925 million bushel and stocks-to-use ration of 44.6 is below the five year average. 2020/21 wheat prices have trended down the past few days and July 2021 soft red winter wheat settled at $5.30 on June 11.

Download the report as a pdf here: 2020 June WASDE summary

 

Flies and Pollination: More than Just Aphid Slayers and Nuisances

Andrew Kness on

Cerruti R2 Hooks$ and Anahí Espíndola*
$Associate Professor and Extension Specialist
Assistant Professor*, CMNS, Department of Entomology
University of Maryland

Introduction

Insects, especially bees (Hymenoptera), are often considered the most important group of pollinators worldwide. Howbeit, there are other insect orders which are now confirmed to be of similar importance, but receive limited attention for their contribution to pollination. The most important of these groups is flies (Diptera; Fig. 1), which in addition to the familiar house and fruit flies, consist of less-known flies such as syrphids and bee-flies (Fig. 2). Flies have been estimated to contribute to the pollination of at least 70% of food crops, and are the dominant group of pollinators in some environmental settings such as areas in high altitude and latitude, where bees are absent or scarce. Pollination by flies is known as myophily and is economically important. For instance, the annual economic value of fly pollination has been estimated to be US $300 billion. Flies are listed as key pollinators of hundreds of species of cultivated plants (e.g., cacao, mango, cashew, avocado, oilseed rape). Further, the emerging importance of fly pollination is such that flies are currently used commercially to pollinate onion, chive, carrot, strawberry and blackberry crops, and they are being seriously explored as a new managed pollination system for crops.

fly on flower
Fig. 1. Diptera (fly) with pollen on its back. Photo: ninfaj (CC)

Among all fly families, a few stand out for their strong and widespread contributions to plant pollination: Syrphidae (including syrphids) and Bombyliidae (bee-flies). Together, these groups have been described as contributors to the pollination of a large percentage of plant species, and have been equaled to bees in terms of their ability to pollinate plants. The reason why these two fly groups are important pollinators partially lies in their biology and morphology. As adults they feed exclusively on nectar and/or pollen, meaning that they are consistent flower visitors. Further, their fuzzy appearance, with hairs covering their bodies assists them in transferring pollen between plants.

Bombyliids or bee-flies

The main focus of this article is on syrphids. However, a short overview of bee-flies is provided here as they are also important dipteran pollinators (Fig. 2, right). Bee-flies are flies that externally resemble bumblebees because their bodies are rounded and extremely hairy. They are easily recognizable because of their elongated and forward-pointing feeding apparatus which they can’t retract. Bee-flies can be found regularly in fields hovering around flowers. Unlike Syrphids, these flies are specialized for feeding almost exclusively on nectar, and for that reason they are meticulous flower visitors, collecting nectar from each individual flower present on a plant. Because they have elongated mouth parts, these flies visit open and tubular flowers. Though bee-flies are extremely important pollinators of many wild plants especially in temperate regions, only very recently has it been shown that they contribute significantly to the pollination of some crops and that they are exceptionally abundant in farmlands.

hover fly and bee fly
Fig. 2. Left: Hoverfly; right: bee-fly. Photos: J. Gallagher and J. Christopherson (CC).

Syrphids (aka hoverflies or flower-flies)

The family Syrphidae, which syrphids belong to is arguably the most recognized group of fly pollinators. While the name flower-flies implies that these dipterans are seen often on flowers, their alternative name “hoverflies” refers to their ability to hover in midflight. Syrphids are ubiquitous and consist of more than 6,000 species worldwide. They can be found in all regions of the world except Antarctica. Syrphids are particularly abundant in habitats of high altitude and latitude, and are important pollinators in forest ecosystems. As adults, syrphids visit generalist flowers, actively foraging on nectar and pollen. Syrphids display a variety of morphologies, such as the marmalade hoverfly, Episyrphus balteatus, and the “drone fly” Eristalis tenax, an excellent bumblebee mimic (Fig. 3).

Fig. 3. Left: Marmalade hoverfly (Episyrphus balteatus); Right: Drone fly (Eristalis sp) – left and tricolored bumble bee (Bombus ternarius) – right. Photos: gailhampshire (CC); K.P. McFarland (CC)

Appearance and life stages

Syrphid adults range in size from ¼ to ~ ¾ inch (3 to 13 mm), and can be metallic, black and yellow, or black and red. These markings and colorations allow them to look like wasps or bees, which is thought to have evolved as a means of protection against predation. However, unlike bees and wasps, syrphids have only two wings (versus four in bees and wasps) that are not held over the back of the body when at rest. Syrphids can fly extremely well, and are able to hover and quickly change directions while in-flight. A characteristic of all syrphids is that they are covered in hairs at least partially, and because this allows for pollen to stick to their bodies they can be efficient pollinators. Though all syrphids are at least partially hairy, some bumblebee or bee mimics are extreme, allowing for an abundant amount of pollen to be transferred between flowers.

Generally, females lay single white eggs on leaves near aphid infestations or other suitable food source for the species (decaying matter, aquatic habitats, etc.). Syrphid eggs are ~ 1/8 inch (3 mm) long and resembles small rice grains. Larvae or maggots hatch from eggs in about 3 days and range in color from creamy white, to green or brown. Larvae develop through several stages (instars) before pupating on the host plant or in the soil. Syrphid larvae are blind and in most species are legless spindle-shaped maggots that vary in color from creamy-white to green or brown, and most display a yellow longitudinal stripe on their back. Larvae differ in size and are roughly the same length as adults, which varies by species and development stage. Larvae look somewhat slug-like and taper to a point at the head end. The skin of the last stage larva forms the oblong, teardrop shaped green puparium, which eventually turns into a tan-brown colored pupa from which the adult emerges (Fig. 4).

syrphid pupa on leaf
Fig. 4. Syrphid pupa. Photo: K. Schulz (CC)

Food/nutrient source

Nutrition in syrphids varies across life-stages. The larvae of some species feed on aphids and other soft-bodied pests of multiple cropping systems. These insectivorous larvae have sucking piercing mouthparts and often lift their prey from the plant surface using their jaws while sucking them dry. Other larvae may feed on pollen, plant material, decaying animal matter, dung and fungus, among other food sources. Nearly all syrphids are pollinators at the adult stage. The adult nutrition is based on the consumption of nectar and/or pollen, and sometimes of insect-produced honeydew. To feed on these resources, adults have sponge-like mouthparts with special conduits that allow for absorbing nectar and pollen grains in solution. A diet based on pollen and nectar is rich in sugars and proteins (pollen is extremely protein-rich), and it has been shown that adult females require feeding on pollen for egg and ovary development. In a study involving sorghum (Sorghum bicolor), larvae and adults of both sexes of the corn-feeding syrphid, Toxomerus politus (Fig. 5) were observed visiting sorghum flowers, where females also laid eggs. It was noted that the highest adult visitation rates occurred when pollen was mature. In that study, because more females than males visited sorghum flowers, this was interpreted as females needing greater pollen amounts to develop their reproductive organs and eggs. Larvae of this insectivorous species were also observed feeding on sorghum pollen. These findings indicate that some syrphids may feed on pollen during their entire life. Toxomerus politus is known to also routinely feed on corn pollen.

syrphid fly on flower
Fig. 5. Corn-feeding syrphid fly (Toxomerus politus). Photo: R. Crook (CC)

Flower selection

The flower preferences of adult syrphids, and their role in pollination is not well known for many species. However, a large amount of work has recently started to accumulate on this topic. Generally, we know that syrphids prefer yellow and white diurnal flowers, especially those that are radially-symmetric, small and open. Their mouthpart length has some influence on flower selection and varies according to whether they eat nectar, pollen or both. Usually, pollen feeders have a short thick tongue and prefer white and yellow flowers with readily accessible pollen. Pollen and nectar feeders tend to have a much longer, narrower tongue, appropriate for extracting nectar from narrower flowers.

Because they tend to visit generalist flowers (e.g., flat, open and usually grouping many flowers together), syrphids are traditionally viewed as generalized flower visitors. Syrphids have good trichromatic vision, and use floral coloration as a cue for floral visits. Some studies reported that selectivity of some flowers is similar between syrphids within the same subfamilies with comparable body size. Others have reported that selection is dependent on certain plant traits; and that some species are very specialized and have a strong preference for a few plants. However, those preferences can change according to local flower availability and plant phenology, and it is known that syrphids have innate floral preferences, but are also capable of associative learning (i.e., associating floral colors with preferred nectar qualities). Further, because of their ability to learn, males can become very territorial, defending specific selected flowering plants that they identify as their territory. As stated above, syrphids prefer generalist flowers, mostly belonging to the carrot, aster, buttercup, mustard, rose and carnation plant families. When collecting nectar from these plants, syrphids are also quite efficient, visiting systematically all flowers. It is also for this reason that they are considered good pollinators.

Ecosystem services

Pollination. Though syrphids interact directly with pollen by either actively or passively collecting it, only recently, syrphids (and other flies) have been recognized as important pollinators. Indeed, in a series of very recent global analyses, it was estimated that the contribution of syrphids to pollination could be equaled to that of bees, at least in some cases. In contrast to bees, syrphids are more mobile and capable of traveling longer distances, likely dispersing pollen greater distances. Further, many syrphid species are migratory, and these migration events contribute to extreme pollen dispersal, which in Britain has been quantified as involving a number of individuals not much different to that of British managed honeybees at peak population size. Even though it has been long thought that syrphids are mostly “incidental” pollinators, recent studies demonstrate that most individuals are consistent in their floral choices, which tends to suggest that they are not only abundant but also efficient pollinators. Supporting this, some experiments indicate that even though syrphids may carry less pollen grains than bumblebees or bees, flowers visited exclusively by syrphids are better pollinated than those visited exclusively by bumblebees. In addition to mostly visiting a larger variety of flowers than honeybees, syrphids are generally more abundant in natural and agricultural habitats than wild bees. Moreover, syrphids may fill niches that are not covered by larger pollinators. For example, large bumble bees tend to visit large flowers; and the flower complex of some plants such as Solidago virgaurea is small and thus can be effectively pollinated by small syrphid flies (Fig. 6).

syrphid fly on yellow flower
Fig. 6. Syrphid fly visiting Solidago virgaurea flowers. Photo: T. Juuyoh (CC)

Because of these new discoveries, syrphids are gaining increased interest as legitimate pollinators of agricultural systems. This has led some to consider the use of managed syrphid populations to pollinate crops. A recent global analysis of crops and wildflowers indicated that 72 and 70%, respectively, are visited by syrphids. In terms of fruit set, syrphids appear to be more effective at pollination than honeybees in a range of systems. For instance, syrphids are considered vital pollinators of crops such as oilseed rape Brassica napa (Fig. 7) and wild radish (Raphanus raphanistrum). Further, field studies have estimated the effectiveness of strawberry pollination by the aphidophagous syrphid species, Episyrphus balteatus and Eupeodes latifasciatus, and a mix of four syrphid taxa. These studies indicated that syrphid visitation increased strawberry yields by over 70% and doubled the proportion of marketable fruit, underlining their importance for strawberry pollination and production.

syrphid fly in yellow flower
Fig. 7. Syrphid fly visiting rape flower. Photo: S. Horrigan (CC)

Syrphids also provide key pollinating services to wildflowers, apple trees, soft fruits and other agricultural crops in the mustard family such as broccoli, cabbage and rapeseed, and have been used to successfully pollinate peppers in greenhouses. Though syrphids are key contributors to pollination services, the increased awareness of their importance has been partly due to the global decline in wild and managed bee populations. With the observed decline, there is a need for a greater understanding of the role of syrphid and other flies in plant pollination. It is very likely that the contribution of syrphids to pollination is such that its management could mitigate losses of native bee pollinators, at least in some regions of the world.

Pest suppression. One of the reasons why there is an increased interest in managing syrphids in agricultural landscapes is that they contribute simultaneously to many ecosystem services. In addition to pollination, syrphids are efficient natural enemies of insect pests (Fig. 8). In addition to aphids, syrphid larva feed on thrips, leafhoppers, scales, psyllids, mealybugs, whiteflies and other soft bodied insects, and are commonly found on crops infested by aphids (e.g., fruit trees, grains, corn, alfalfa, grapes, vegetables and ornamentals) as well as wild host plants. They have also been noted as predators of small European corn borer and corn earworm larvae. A single syrphid larva can consume 20 to 30 aphids per day and up to 400 during its development. The syrphid, E. balteatus was estimated to consume a maximum of 396 aphids in wheat during its larval stage. Further, research has shown that when syrphid larvae are numerous, they can reduce aphid populations by 70 to 100%. Because of the ecological nature of their very different life stages, syrphids can serve as well-rounded agricultural allies (i.e., controlling pests at the larval stage and contributing to pollination and fruit/seed production at the adult stage). On this point, syrphids have been shown to benefit strawberry plantings by consuming aphids (aphid control) during their larval stage and pollinating strawberry flowers (enhancing yield) at the adult stage.

syrphid fly larvae feeding in aphid
Fig. 8. Syrphid larvae feeding on aphid. Photo: M. Yokoyama (CC)

Syrphid conservation

There has been considerable research on the responses of insect pollinators to disturbances caused by agricultural intensification, including loss and fragmentation of natural habitats, altered land use, reduced floral diversity and agri-chemical usage. Syrphids appear to be less impacted by land use changes than bees, as many species are capable of using resources in highly altered habitats, including agricultural fields. However, due to recent losses of domesticated pollinators (e.g., honeybees), there is a need for land managers to establish practices that conserve wild pollinator communities. The diversity of life history strategies exhibited by non-bee pollinators such as syrphids necessitates an approach to conservation that may differ from those used to conserve bees.

The efficacy of aphidophagous syrphids in controlling pests and the conservation of syrphids in general can be improved by planting different flowering plants in protected areas of landscapes. Syrphids feed on pollen and nectar. As such, planting a diversity of flowering plants in the landscape contiguous to crops can serve as a source of nutrients for adults, and bring them in close proximity to crops infested with aphids and/or other small soft bodied pests. Syrphids are especially attracted to flowering plants in the mustard and carrot families, to small-flowered herbs and to sweet alyssum. Studies have shown that planting sweet alyssum in collards and apple orchards increased the number of syrphid flies resulting in reduced aphid infestations and likely higher syrphid populations. In addition to providing syrphids a source of nutrient and enhancing their abilty to suppress pest populations, creative use of flower strips and other vegetation may lead to better pollination of cash crops. Further, because the larval stages of some syrphid species develops on decaying matter, providing habitat for these species to develop (e.g., hedgerows, no-till practices) is key to maintaining large syrphid populations in and close to fields. Finally, avoidance of broad spectrum insecticide usage will be of benefit, especially in flowering crops, as their use can be harmful to syrphids.

Summary

For a long time, bees were considered the superior pollinators, and most other pollinator groups were relegated to agricultural and ecological studies. More recently, studies have shown that flies, and in particular syrphids (aka hover- or flower-flies) play an essential role in the pollination of wild and cultivated plants. Syrphids are now recognized to visit roughly 70% of all wildflowers and crops, and in some cases contributing equally or more than bees to pollination services. Further, their pollination service has an annual estimated value of approximately US $300 billion. Moreover, unlike bees, syrphids have been shown to provide multiple ecosystem services, such as pest control and the degradation of decaying matter (during their larval stages), as well as pollination in their adult stage. The few studies that exist on the evolution of syrphid populations indicate that many species are in decline and that some may be stable. Syrphid conservation plans should take into consideration their variable ecology, promoting the use of land management practices that support their larval and adult stages (e.g., hedgerows, diverse flower plantings, no-till practices, reduction of pesticide use). Financial support for the publication of this article came from a USDA NIFA EIPM grant (award number 2017-70006-27171).

EPA Offers Clarity to Farmers in Light of Recent Court Vacatur of Dicamba Registrations

Andrew Kness on

EPA press release

WASHINGTON (June 8, 2020) — Today, the U.S. Environmental Protection Agency (EPA) issued a key order providing farmers with needed clarity following the Ninth Circuit Court of Appeals’ June 3, 2020 vacatur of three dicamba registrations. Today’s cancellation order outlines limited and specific circumstances under which existing stocks of the three affected dicamba products can be used for a limited period of time. EPA’s order will advance protection of public health and the environment by ensuring use of existing stocks follows important application procedures.

“At the height of the growing season, the Court’s decision has threatened the livelihood of our nation’s farmers and the global food supply,” said EPA Administrator Andrew Wheeler. “Today’s cancellation and existing stocks order is consistent with EPA’s standard practice following registration invalidation, and is designed to advance compliance, ensure regulatory certainty, and to prevent the misuse of existing stocks.”

EPA’s order will mitigate some of the devastating economic consequences of the Court’s decision for growers, and particularly rural communities, at a time they are experiencing great stress due to the COVID-19 public health emergency.

Details of the Order

EPA’s order addresses sale, distribution, and use of existing stocks of the three affected dicamba products – XtendiMax with vapor grip technology, Engenia, and FeXapan.

  1. Distribution or sale by any person is generally prohibited except for ensuring proper disposal or return to the registrant.
  2. Growers and commercial applicators may use existing stocks that were in their possession on June 3, 2020, the effective date of the Court decision. Such use must be consistent with the product’s previously-approved label, and may not continue after July 31, 2020.

Background

On June 3, 2020, the Ninth Circuit Court of Appeals issued an order vacating EPA’s pesticide registrations containing the active ingredient dicamba: Xtendimax with Vaporgrip Technology (EPA Reg. No. 524-617); Engenia – (EPA Reg. No. 7969-345); and FeXapan – (EPA Reg. No. 352-913).

Dicamba is a valuable pest control tool that farmers nationwide planned to use during the 2020 growing season. Since the Court issued its opinion, the agency has been overwhelmed with letters and calls from farmers citing the devastation of this decision on the millions of acres of crops, millions of dollars already invested by farmers, and threat to America’s food supply.

Contact Us to ask a question, provide feedback, or report a problem.

Moths, Butterflies, and Pollination

Andrew Kness on

Cerruti R2 Hooks$ and Anahí Espíndola*
$Associate Professor and Extension Specialist and *Assistant Professor, CMNS, Department of Entomology
University of Maryland

Insect pollinators play an essential role in the maintenance of wild plant diversity and agricultural productivity. Indeed, global studies have shown that the vast majority of plants require animal pollination to produce fruit and seed. In temperate regions, major pollinator groups include bees (Hymenoptera), syrphid (Diptera), as well as butterflies and moths (Lepidoptera). In contrast to bees, Lepidoptera are not considered efficient pollinators of most cultivated plants. Nevertheless, they are vital pollinators of many flowering plants, especially in the wild as well as managed lands such as parks and yards.

Fig. 1. Hawkmoth. Photo: J. Patrick (CC)

The pollinating taxa of Lepidoptera are mainly in the moth families Sphingidae (hawk moths; Fig. 1), Noctuidae (owlet moths) and Geometridae (geometer moths), and the butterfly families Hesperiidae (skippers) and Papilionoidea (common butterflies). The adult stage of these lepidopterans obtains their nutrients and water from nectar of various flowers; and while exploiting flowers for food, pollination may occur. Moths and butterflies have different pollinator niches, as butterflies are very active during the day (diurnal) and visit open flowers during the morning hours and under full sunlight. Contrarily, moths are more active during the evening and night hours (nocturnal). As a response to this, some flowers may seek to increase pollination by changing color during a 24-hour period to attract butterflies during the day and moths at night. For example, Quisqualis indica flowers change color from white to pink to red which may be associated with a shift from moth to butterfly pollination (Fig. 2). A study conducted in China verified that different pollinators are attracted to each floral color stage; primarily moths at night and bees and butterflies during the day. Further, fruit set was higher for white than pink or red flowers indicating that moths contributed more to its reproductive success. While adult butterflies and moths are important pollinators, their larvae – often called caterpillars – may be economically important pests in agricultural, forest and urban environments. In some instances, their status as agricultural villains as caterpillars override their positive image as ecosystem service providers as adults.

Fig. 2. Quisqualis indica. Photo: D. Valke (CC)

Nectar and pollen consumption

Adult butterflies diet choice varies between species, populations, generations, sexes, age groups and individuals. Most adult lepidopterans feed on fluid resources such as nectar, decomposing animals, dung and fruit sap (Fig. 3) and others may not feed at all as adults. Butterflies consume nectar by active suction using their elongated mouthparts (called proboscis), and usually avoid highly concentrated nectar because of its high viscosity.

Fig. 3. Butterfly feeding on fruit – Photo: mrkittums (CC)

Nutritionally, nectar serves as a source of water, carbohydrates and amino acids; the latter allowing butterflies to meet their nitrogen requirements. Interestingly, butterfly-pollinated flowers tend to have higher concentrations of amino acids than do flowers pollinated by bees and other animals. This is remarkable since insects like butterflies, whose larval stages feed on plant foliage and adult stages on nectar have long been assumed to obtain most or all of their nitrogen-rich compounds needed for reproduction from larval feeding. Going against this assumption, it has been shown that both nectar consumption and larval food intake can affect the life span and fecundity (number of offsprings produced) of some butterfly species. For example, a recent study found that nitrogen-rich compounds (amino acids) present in nectar significantly increased the fecundity of the nectar-feeding butterfly Araschnia levana. However, their fecundity was enhanced only if the female fed on a poor-quality plant as a larva. This suggests that nectar can act as a necessary dietary complement if a butterfly fed on a nitrogen-poor plant as a larva.

Another nitrogen-rich floral reward is pollen. Nectar-consuming butterflies come into contact with pollen while visiting flowers, but the vast majority of butterflies is unable to feed on pollen. However, butterflies of the neotropical genera Heliconius and Laparus (Lepidoptera: Nymphalidae; Fig. 4) evolved a feeding technique in which amino acids are extracted from pollen grains, rather than fortuitously during their pursuit of nectar. These butterflies collect and accumulate large pollen loads, and the production of saliva helps keep it attached to their proboscis while they gently chew the pollen to consume its amino acids. Pollen feeding is thought to increase Heliconius longevity and egg production.

 

Fig. 4. Heliconius numata with pollen load -Photo: http://www.heliconius.org

Butterflies efficiency as pollinators

It has been suggested that for most plant species, butterflies visit flowers less frequently than bees and deposit less pollen per visit. With a few notable exceptions such as yucca moths, adult lepidopterans show little floral specialization, preferring flowers with large landing surfaces, deep, narrow corollas that can accommodate their elongated mouths, and plants displaying many flowers in close proximity. Butterflies prefer visiting large flower heads, and when searching flowers for nectar, pollen grains attach to various body extremities (e.g., mouth parts, head) depending on the plant’s floral architecture. However, because butterflies’ legs and mouth parts are elongated, most of their body does not enter in direct contact with the plant’s pollen. Consequently, butterflies pick up less pollen on their bodies than bees, and most of it is usually deposited on or around their heads and mouth parts. This pollen is then transferred to the surface of the stigma when the butterfly reaches for nectar in a new flower. Because little pollen is usually carried by butterflies, and the fact that – unlike bees – they don’t have specialized structures for carrying pollen, butterflies are less successful than bees at moving pollen between flowers. Although not as efficient as bees, butterflies can be very effective pollinators, and among the insect fauna they qualify as essential pollinators. In many instances, a decline in the butterfly fauna is attributed to a decrease in nectar-rich and economically or culturally important wild plant species. Further, butterflies can be important in agricultural systems. For example, a survey of pollinators associated with macadamia in NE Brazil found that macadamia yields mainly benefited from pollination by butterflies rather than bees. Consequently, butterflies were responsible for > 50% of floral visits to macadamia flower. Moreover, their pollination of some vegetable crops contributes strongly to seed production.

Many flowers, including some orchids, are completely dependent on butterflies for pollination, and a member of the pea family, the peacock flower (Caesalpinia pulcherrima; Fig. 5) is largely dependent on butterflies for pollination, with pollen being mainly carried on their wings. In addition to butterflies, some moths have a special relationship with specific plants. For example, the yucca plant (Hesperoyucca whipplei) is pollinated by the yucca moth (Tegeticula maculata) with which it has a symbiotic relationship. The gravid female moth gathers pollen grains from flowers at night and forms them into a ball. She carries the ball in her mouth to another yucca flower. She then inserts her ovipositor into the ovary wall of the flower and deposits a single egg and then pushes the pollen into the stigma, thus pollinating the flower. The larva hatches in late spring or summer, and feeds on some of the developing seeds. Emergence of the adult moth occurs while yucca plants are again in bloom, allowing the cycle to continue.

Fig. 5. Orange sulphur butterfly feeding on peacock flower Caesalpinia pulcherrima – Photo: Anne Reeves (CC)

Flower structure and mouthparts

The body architecture (e.g., body size, mouth shape) and behavior of pollinators with respect to the flower’s dimension and morphology, are some of the factors that define which floral visitors are effective pollinators. Many studies of plant-pollinator interactions provide evidence that the morphological match between the flower shape and size, and the length of pollinators’ mouthparts influences pollination success. In relation to this, it has been observed that flowers and their pollinators engage in a series of reciprocal adaptive or coevolutionary cycles. In these cycles, plants that have the “best” floral shape for a specific pollinator are capable of producing more seeds, while pollinators that are capable of obtaining more nectar from an individual flower visit will also obtain greater energy required to produce more offsprings. When the pollinator and plant requirements align like this, plants tend to evolve floral shapes that match their “best” pollinator, while pollinators tend to evolve specific floral preferences and morphologies that match the plant. Over many generations, this leads to the establishment of floral preferences in pollinators, and a convergence in floral shapes of flowers visited by a given type of pollinator. It is for this reason that butterflies and hummingbirds are seen more often visiting long-necked or trumpet shaped flowers, than other pollinators; and these flower types are better pollinated by butterflies or hummingbirds than other pollinator groups. The result of these coevolutionary processes can be seen in many cases of pollination, but some of the most impressive examples are those having led to the evolution of extremely long proboscides (up to 14 inches) in some lepidopterans (Fig. 6), which match the length of the floral tube of their preferred flowers.

Fig. 6. Malagasy hawk moth visiting the ghost orchid. Photo: Minden Pictures / SuperStock.

How do moths and butterflies locate flowers

In order to locate floral resources, lepidopterans use a series of cues, such as specific colors, shapes, sizes and odors. As stated previously, moths are major nocturnal pollinators of a diverse range of plant species but have been historically considered to contribute little to overall pollination. However, recent research has rejected this notion, demonstrating that nocturnal moths contribute strongly to pollination, even to the point of compensating for poor pollination by diurnal pollinators. Moths are attracted to pale or white flowers with an open cup or tubular shape, heavy with fragrance and dilute nectar, and typically open in late afternoon to night. In turn, these plants are also specialized in pollination by moths, with these attractive traits having evolved through millions of years of coevolution. An example of these plants includes the creeping buttercup or honeysuckle, which tend to emit a strong fragrance at night.

Unlike moths, butterflies are diurnal and typically visit flowers under heavy sunlight, preferring those displayed in clusters and offering large nectar rewards (Fig. 7). Flowers specialized in pollination by butterflies are often brightly colored (red, yellow, orange), lack an apparent scent and secrete relatively dilute nectar in narrow elongated floral tubes. Examples of butterfly flowers are goldenrods and Asters, which provide a large landing surface as well as abundant and accessible nectar. Some of these preferences in butterflies are due to the butterfly’s good perception of color, which in most cases covers a wider range of the spectrum than human vision. Indeed, various studies have demonstrated that some pollinators rely strongly on color to make their foraging decisions, and this is certainly the case of butterflies. Similar to hummingbirds, butterflies have a good perception of the color red and as such, are attracted to red flowers. Further, many lepidopterans are able to distinguish various shades of yellow. To this point, an experiment consisting of potted daylily and nightlily showed that swallowtail butterflies preferentially visited reddish or orange-colored flowers and hawkmoths favored yellowish flowers. Similar to many insects, butterflies are capable of seeing ultraviolet light, which allows them to follow special nectar markings present on flowers that are only visible under that type of light. Correspondingly to how butterflies and moths are able to sense odors of their preferred flowers, studies have shown that butterflies may also sense the nectar amino acid content of different flowers, preferring those with high versus low amino acid content. For instance, studies found that, when given the choice, the cabbage white butterfly (Pieris rapae) preferred feeding on artificial flowers containing sugar-amino acid mixes, versus sugar-only nectar of Lantana camara (a perennial shrub).

Fig. 7. Fritillary butterfly feeding on goldenrod – Photo: hedera.baltica (CC)

Butterfly flower avoidance

As with all organisms, butterflies have their own natural enemies at the immature and adult stages. Egg, larva and pupa of butterflies and moths are vulnerable to parasitism and predation. Adult stages may suffer mortality from mammalian and arthropod predation. For instance, when visiting flowers, butterflies may be vulnerable to arthropod predators such as mantises and spiders (Fig. 8). Studies have shown that butterflies are capable of avoiding flowers with predator cues. For example, similar to bees, they have been shown to avoid flowers with artificial spiders and models of spider forelimbs. In another study conducted in a butterfly pavilion, visiting butterflies stayed away from flowers containing dead mantises.

Fig. 8. Crab spider feeding on a skipper butterfly – Photo: MattysFlicks (CC)

Howbeit, it is debatable whether butterflies were responding to the mantis’s cues or were simply avoiding flowers containing foreign objects. Still, some studies seem to agree that at least some avoidance is due to visual recognition. Interestingly, the degree of avoidance recorded in these studies indicated that it was weaker in butterflies reared in the pavilion than in wild butterflies. This tends to indicate that a part of this avoidance is learned and a reflection of previous predation experiences.

Butterfly conservation

Drivers of pollinator and butterfly losses. Many insect pollinators that provide vital services are declining and multiple factors have been implicated. In Europe, noticeable drops have been observed for butterflies, wild bees and hoverflies. Similarly, lepidopterists in the US are reporting that butterflies are in decline. Butterflies face a wide range of threats including habitat loss, changes in land management and land use, climate change, disease, pesticides and invasive organisms. Another driver of pollinator decline is agriculture intensification, which results in loss and fragmentation of pollinator-diverse habitats such as semi-natural grasslands, and is also associated with increased chemical use. Other factors associated with human activity have also been identified as contributors to pollinator loss. For instance, pollutants and urbanization can negatively affect the richness and abundance of native plant species used by pollinators, and thus lead to poor pollinator communities. Anthropogenic changes in the landscape can sometimes affect pollinators in surprising and indirect ways. For instance, changes in land use can lead to increased encroachment of plants such as some shrubs that are not congenial to butterflies and an associated decrease in butterfly richness and abundance by negatively impacting herbaceous plant cover and diversity. Further, enhanced shrub covering may indirectly affect pollinators by increasing their predation by perching birds.

Should bee and butterfly conservation plans be the same? The ecology of lepidopterans differs from that of bees. For example, bees require nectar and pollen throughout their life, while butterflies only utilize nectar as adults. Further, most caterpillars are leaf-feeders and do not require any parental care, while bees must collect pollen and nectar to support their brood and themselves. Moreover, while most bee species develop in relatively protected habitats (i.e., their nests), caterpillars are exposed while feeding on their host plants, vulnerable to predation, parasitism and climatic factors. These differences may require some alterations in conservation efforts aimed at protecting butterflies and bees. For example, butterfly-friendly environments must contain plants that support the larval and adult stages, and land management practices need to be appropriate for preserving plant species needed in caterpillar diets. Failing to do so would lead to low caterpillar survival or death, and the eventual loss of the butterfly population.

Conserving butterflies. To help save butterflies and other pollinators, it is recommended that a diversity of colorful, wildlife-friendly plants full of nectar be planted in gardens, yards, urban and recreational areas and on/nearby arable lands. Floral diversity is a pre-requisite for enhancing butterfly conservation, especially in urban environments. To better ensure butterflies have access to resources throughout the year, flowers with a range of bloom time (early spring through fall) and morphological features should be planted. Further, a habitat hospitable to butterflies and moths provides food for caterpillars, nectar-bearing flowers for adults, and consists of at least some native species. Indeed, although a few can feed on exotic plants, most caterpillar species are specialized on native plant species. Likewise, although some caterpillars are polyphagous, most are restricted to a few or just one plant species. Protecting land for butterflies does not equate to transforming all land into a fully protected area. Indeed, land in public settings, such as roadway medians, roadsides, landscaped parks, and even railway embankments have the potential to support large populations of pollinators. Confirming this, studies found that bee and butterfly species richness and abundance were higher in railway embankments than in grasslands. Further, they demonstrated that in that context non-vegetated ground negatively affected butterfly populations, since their diversity positively depended on species richness of native plants. For this same reason, open forests also tend to harbor higher pollinator diversity than forests with a very closed canopy. Further, actions can be taken to improve the pollinator friendliness of different public lands. For instance, roadside management plans can be designed to benefit pollinators (Fig. 9). Roadsides with abundant and diverse native wildflowers managed with judicious mowing and herbicide use can become diverse pollinator habitats. Furthermore, research indicates that roadsides with high-quality habitat reduce pollinator mortality as insects remain in the roadside as opposed to leaving in search of flowers.

Fig. 9. Roadside pollinator habitat – Photo: Minnesota Department of Transportation

Land management tactics for increasing plant diversity (intercropping, cover cropping, insectary plants, flower borders, etc.) are often used to enhance populations of natural enemies in cropping systems. When this practice is used to augment natural enemy efficacy, it is often called conservation biological control. However, this same tactic can be used to concomitantly conserve biocontrol agents and pollinators, while enhancing other services to cropping system (i.e., pest suppression). In a similar context, the idea of companion planting can also represent a way to combine production with pollinator protection in agricultural landscapes. Companion planting is a traditional husbandry practice whereby a second plant species is planted alongside a crop with the goal of improving yield. Using a flowering species as a companion plant can make arable lands more congenial to pollinators resulting in improved pollination services and crop yield. A recent study examined the use of borage, Borago officinalis (Fig. 10), as a companion plant in strawberry. Borage plants were found to significantly increase yield and quality of strawberries, suggesting an increase in insect pollination per plant.

Fig. 10. Butterfly visiting a borage plant. Photo: www.seedvilleusa.com

Summary

Immature stages of some moths and butterflies are viewed negatively because of their harm to agriculture. However, adult lepidopterans are mostly cherished for their aesthetic beauty, and less recognized for their contribution to pollination. Howbeit, lepidopterans are vital contributors to the pollination of wild plants and domesticated crops; and though their efficiency at crop pollination does not reach the level of bees in most systems, there are instances in which their services are of greater value (as for pollination of macadamia nuts), or compensating diurnal pollination (as shown for nocturnal moths). Moreover, while bees are more likely to pollinate fruit crops, butterflies are primary pollinators for many vegetables and herbs, especially those in the carrot, sunflower, legume, mint and Brassica family. Although pollination of these vegetable crops is not needed for producing the edible portion of the crop, it is required for seed production, in which future plantings require. This suggests that efforts being directed to protect bee pollinators should similarly integrate moth and butterfly conservation. To this point, because the ecology of bees and lepidopterans differ especially with respect to resource requirements during their immature stage, plans directed at conserving bee and lepidopteran pollinators should take these differences into consideration. Financial support for the publication of this article is via USDA NIFA EIPM grant award numbers 2017-70006-27171.

Maryland Regional Crop Reports: June 2020

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Reports are for crop conditions up to June 4, 2020.

Western Maryland

Corn planting is winding down and much of what has been planted is up. Soybean planting is going fast and furious. Wheat is flowering and barley is turning. First cutting alfalfa is finished. Grass hay has been challenging to get dry with intermittent rains but much of it is in the barn. First cutting has been down this year due mainly to the cooler temperatures.—Jeff Semler, Washington Co.

Central Maryland

A majority of the corn and soybeans were planted over the last week and a half as the weather turned warmer. Rain at the end of last week paused planting, but I would expect the rest to be finished this week. May was certainly a drier month compared to the last couple of years, but so far this year, the county is slightly above normal rainfall for the year. In my walks around my neighborhood, I have noticed marestail that is a couple inches tall. Be sure to scout your fields, as marestail is best controlled when it is 4 inches or less!–Kelly Nichols, Frederick Co.

Lower Shore

Corn is 95% planted and soybean is 40% planted. Winter wheat is drying down. Herbicide-resistant weeds are starting to be apparent in burnt-down fields.–Sarah Hirsh, Somerset Co.

Northern Maryland

With a slow start to the 2020 planting season, conditions have dried and warmed nicely, allowing for nearly all of the corn and full season soybeans to be planted in short-order. Much of what is planted has emerged and is doing well, although there is some slug damage in some fields. Earliest planted corn is approaching V6. Wheat is finished flowering and the cool spring will make for reduced head blight symptoms, but DON levels could still be high; we will see as we get closer to harvest. Dry weather has made for a good first cutting of grass hay. Soil moisture is decent as the region has received some timely showers.—Andy Kness, Harford Co.

Upper and Mid Shore

Most of the corn and full season beans are planted and emerged. Some of both suffered some slug damage during the week of cool rain. They were able to feed 24 hrs/day with very little sunshine and wind. Side-dress nitrogen applications and post emergent herbicide applications on corn are in full swing. Compared to past years’ crop stages, we are about 2 weeks behind average crop growth. Barley is mature and drying down. Good quality and quantity hay has been made in the last week.—Jim Lewis, Caroline Co.

Southern Maryland

Intermittent rains have provided good growing conditions. Temperatures remained below average for the latter part of May but are warming up now with temperatures hitting 90°F this week. Additional rains will be needed to maintain topsoil moisture. Corn growth is behind most years. Early fields are approaching 12 inches tall and will be ready for side dress N applications this week. We are seeing more variability across fields with differences in soil type combined with cool wet conditions exaggerating emergence and growth across the field. Most corn grew out of frost damage without any noticeable effect. We had some slug damage and issues with soil crusting in some fields. Most folks are finishing up full season soybean planting and emergence has been very good. Barley and wheat is also behind. Barley should be ready to harvest in a few days and wheat is drying down now. The wheat and barley crop look good in the field. Annual ryegrass continues to be a problem across the region in small grain fields. There was a lot of nice dry hay made in the last three weeks. Cool season grass stands have responded well given the cooler temperatures and second cutting is shaping up to be a good one. Tobacco planting is also behind with growers playing catch up this week. —Ben Beale, St. Mary’s Co.

EPA Releases Temporary Guidance on Respiratory Protection During COVID-19

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This original announcement was published by the EPA on June 1, 2020. Click here for more.

There is no higher priority for EPA than protecting the health and safety of Americans, especially during the COVID-19 public health emergency. EPA has heard from states and stakeholders about Personal Protective Equipment shortages in the agricultural sector. To respond to these reports and to help ensure the health and safety of America’s farmers, EPA is providing temporary guidance regarding respiratory protection requirements for agricultural pesticide handlers. Our guidance aligns with recent OSHA memos on respirators while addressing EPA’s responsibilities under FIFRA and the Agricultural Worker Protection Standard (WPS).

Additional Information

The temporary guidance outlines approaches to address the unavailability of required respiratory protection and respiratory fit testing that should first be exhausted before considering any alternative options. Options include:

  • Use alternative NIOSH-approved respirators offering equivalent or greater respiratory protection than those required on the pesticide label;
  • Hire commercial applicator services with enough respirators and respiratory protection capabilities;
  • Opt to use agricultural pesticide products that do not require respirators; or
  • Delay pesticide applications until another compliant option is available.

If the above options are exhausted, EPA’s guidance provides additional options with strict terms, conditions, and exhaustion requirements to minimize potential incremental risks to workers:

  • Reuse and extended use of disposable N95 filter facepiece respirator;
  • Use of “expired” respirators;
  • Use of respirators certified in certain other countries or jurisdictions meeting protective conditions outlined; or
  • Delay the annual respirator “fit test.”

This is a temporary policy. EPA will assess the continued need for and scope of this temporary guidance on a regular basis. To read the guidance in full and to learn more about EPA’s Worker Protection Standard, visit this webpage.