Category: Insects

Optimizing Early Season Pest Management for Maryland Field Corn

Maria Cramer, PhD Candidate and Kelly Hamby, Entomology Extension Specialist
Department of Entomology, University of Maryland

Background

Research Questions

  1. Are the NST Poncho 250® and the in-furrow pyrethroid Capture LFR® effective at controlling pests and increasing yield in high-input (Bt) or low-input (non-Bt) field corn in Maryland?
  2. Do Poncho and Capture hurt slug predators and flare up slug damage?

Study Design

In order to capture the range of pest pressures and growing conditions in Maryland, we replicated our study across 3 UMD research farms (Keedysville, Beltsville, and Queenstown) and over 3 years (2020-2022). At each location we planted one field of a Bt hybrid and one field of a similarly-yielding non-Bt hybrid as early as possible in the growing season (Table 1). In 2020 our Bt hybrid was LC1196 VT2P (Local Seed, Memphis, TN) which expresses Cry1A.105/Cry2Ab2 proteins. In 2021 and 2022 we planted P1197YHR (Pioneer Hi-bred International. Johnston, IA) which contains Cry1Ab and Cry1F proteins. We planted P1197LR (Pioneer Hi-bred International, Inc. Johnston, IA) for our non-Bt hybrid all three years. All hybrids had excellent yield potential and were grown with standard no-till practices. In each field we established 3 replicates of 3 treatments at planting: 1) an untreated control, with bare seed and no in-furrow product, 2) an in-furrow pyrethroid treatment using Capture LFR® (active ingredient: bifenthrin, rate: 13.6 fl oz/acre), and 3) an NST treatment using Poncho® (active ingredient: clothianidin, rate: 0.25 mg/seed). Each replicate consisted of 24 rows of corn at 30 inch row spacing, and was 200 feet long.

Year Location Planting date Sampling dates
2020 Keedysville May 18 June 8
Beltsville May 21 June 10
Queenstown May 13 June 3 and 4
2021 Keedysville May 14 June 1 and 3
Beltsville May 17 June 2
Queenstown May 4 May 25 and 26
2022 Keedysville May 26 June 10
Beltsville June 2 June 21
Queenstown May 12 May 31

Question 1: Are the NST Poncho 250® and the in-furrow pyrethroid Capture LFR® effective at controlling pests and increasing yield in high-input (Bt) or low-input (non-Bt) field corn in Maryland?

Data Collection

In order to evaluate how the treatments affected pest pressure, we visually sampled V2-V3 corn for types of pest damage (Figure 1), recording the number of plants and area damaged. We counted the number of healthy and stunted plants to determine if the treatments impacted stand. Because neonicotinoids can sometimes stimulate plant growth unrelated to pest damage7,8, we measured plant height to determine if plant growth was impacted by either treatment. At the end of the growing season, we measured stand again and harvested the corn to collect yield data.

Figure 1. Diagnostic seedling pest damage: a) soil pest, b) cutworm, c) armyworm, d) slug, e) stinkbug, f) miscellaneous feeding damage from a spotted cucumber beetle.

Results and Takeaways for Question 1

Poncho reduced insect damage more consistently than Capture LFR (in both Bt and non-Bt corn) and increased Bt corn stand. Capture LFR sometimes reduced insect damage (in non-Bt corn), but never improved stand.

We compared the number of seedlings with any type of pest damage between treatments and found that Poncho decreased damage about 62% in Bt corn and about 66% in non-Bt corn (Figure 2a and 2b). Compared to the control, Capture did not reduce damage in the Bt corn, but did reduce damage by about half in the non-Bt. Poncho increased stand about 8% compared to control in the Bt corn (25,731 ± 456 plants per acre and 23,623 ± 714 plants per acre, respectively), but did not improve it for non-Bt. Capture did not impact stand for either Bt or non-Bt corn.

Figure 2. Mean % ± SE of seedling A) Bt and B) non-Bt corn plants damaged by pests. Data were collected across three UMD research farms from 2020-2022. Within each graph, treatment bars with different letter above them are significantly different from each other.

There were no yield benefits from using either insecticide in either corn. This was likely due to a lack of economic pest pressure.

Non-Bt and Bt yields were the same across treatments (Figure 3A and 3B). This was probably because pest pressure was so low. Even though Poncho and Capture decreased pest damage, pests were below treatment thresholds—for example, armyworm damage in the control ranged from 0% to 5.4% of Bt plants, and 0% to 22.9% of non-Bt plants, in both cases below the treatment threshold of 35%9. Cutworm damage was similarly low ranging from 1% to 6.3% in Bt control and 0.5% to 3.8% in non-Bt control, also below the treatment threshold of 10% feeding damage9.

Figure 3. Mean yield ± standard error in bushels per acre corrected to 15.5% moisture of A) Bt corn and B) non-Bt corn. Yield data from 2020-2022 across three UMD research farms. Treatments did not significantly impact yield.

Takeaway: Pest pressure and yield were similar between the Bt and non-Bt varieties, and non-Bt yielded well without any insecticides. In general, without pre-existing pest problems in a given field, at-planting insecticides are unlikely to pay off in Maryland.

Question 2: Do Poncho and Capture hurt slug predators and flare up slug damage?

Data Collection

To assess the effect of treatments on slug biocontrol agents, we measured slug predatory ground beetles and predation. We measured predatory beetles with pitfall traps for three consecutive weeks. Because the predators that eat slugs also attack caterpillars, we used sentinel caterpillars to see how much predation was occurring (Figure 4). We placed sentinel caterpillars in the plots overnight, collected them the following morning, and assessed signs of damage from predators. To determine if slugs were flared up by the treatments, we measured slug abundance once a week for 6 weeks beginning between 14 to 21 days after planting and measured slug-damaged seedlings during V2-V3.

Figure 4. Sentinel caterpillars placed in field overnight and collected in the morning to determine predator activity.

Results and Takeaways for Question 2

Predation on sentinel caterpillars was not decreased by insecticides.

We measured the percent of sentinel prey that were damaged by predators overnight (Figure 5) and saw no relationship between treatment and predation rates (Figure 6). This suggests that the insecticides did not decrease predator activity in treated plots. We did generally see some level of predation all weeks at our locations, indicating that predators are usually present in seedling corn.

Figure 5. Top: predators feeding on sentinel prey. Bottom: examples of damaged prey proportions. Images: M. Cramer, University of Maryland.
Figure 6. Mean ± SE % sentinel prey caterpillars consumed across three UMD research farms from 2020-2022. Control, Capture, and Poncho did not significantly differ.

Predator abundance was not altered by insecticides.

When we measured the weekly counts of ground beetles, we found similar results between treatments. This was true when we looked at all ground beetles (predators, omnivores, and seed-eaters), as well as when we looked only at predatory beetles (Figure 7A and 7B).

Figure 7. Mean ± SE count of A) all ground beetles, and B) specifically predatory ground beetles, caught per week in pitfall traps across three UMD research farms from 2020-2022. No significant differences.

Slug natural enemies did occur throughout the study, suggesting that biocontrol could be more intentionally leveraged.

The two most abundant ground beetle species in our study were both predators. One of these species, Chlaenius tricolor (Figure 8) is a slug predator that consumes slugs in agricultural ecosystems5,10. Although its abundance was not affected by treatments, it was present at all locations in all years, suggesting that it is a particularly important slug natural enemy in Maryland crops.

Figure 8. Chlaenius tricolor, a slug predator that was found throughout the study. Photo credit: ©Molanic 2023: https://www.inaturalist.org/photos/314013175.

Neither insecticide increased slug abundance or slug damage.

If treatments had negatively affected predators, we would expect to see more slugs and damage in the insecticide plots. However, when we compared slug counts between treatments, we found that the insecticide treatments were not different from the control (Figure 9). Slug damage to the seedling corn was also similar across the control and insecticide treatments (Figure 10).

Figure 9. Mean number of slugs per replicate plot ± SE the week closest to seedling sampling across three UMD research farms from 2020-2022. No significant differences.
Figure 10. Mean ± SE % of corn seedlings damaged by slugs across three UMD research farms from 2020-2022. Control. No significant differences.

While slugs can be damaging in many crops, the worst slug damage in our study did not affect corn stand or yield, suggesting that corn is generally tolerant of slug damage at the levels we observed in this study.

Slug damage was scarce across years and locations except in 2021 at Keedysville. Even in that case where a high proportion of seedlings (42% ± 4% on average) were damaged by slugs, we did not see an associated decrease in stand or yield. Corn seedlings were able to outgrow the slug damage as the weather warmed, even when they appeared severely defoliated. The seedling resilience we observed is supported by work on hail damage in corn which shows that as long as the growing point is intact, corn can regrow from complete defoliation11.

Even though we did not see non-target effects in this study, both pyrethroids and neonicotinoids can decrease natural enemies in crop fields6,12–14.

Acknowledgments

We would like to thank the farm managers and staff of WYEREC, WMREC, and CMREC Beltsville for their expertise and assistance. We would also like to thank the Hamby lab’s many undergraduate researchers for helping complete this project with all their hard work.

Sources:

  1. Kullik, S. A., Sears, M. K. & Schaafsma, A. W. Sublethal Effects of Cry 1F Bt Corn and Clothianidin on Black Cutworm (Lepidoptera: Noctuidae) Larval Development. J. Econ. Entomol. 104, 484–493 (2011).
  2. North, J. H. et al. Value of neonicotinoid insecticide seed treatments in mid-south corn (Zea mays) production systems. J. Econ. Entomol. 111, 187–192 (2018).
  3. Reisig, D. & Goldsworthy, E. Efficacy of Insecticidal Seed Treatments and Bifenthrin In-Furrow for Annual White Grub, 2016. Arthropod Manag. Tests 43, 1–2 (2017).
  4. Sappington, T. W., Hesler, L. S., Clint Allen, K., Luttrell, R. G. & Papiernik, S. K. Prevalence of sporadic insect pests of seedling corn and factors affecting risk of infestation. J. Integr. Pest Manag. 9, (2018).
  5. Douglas, M. R., Rohr, J. R. & Tooker, J. F. Neonicotinoid insecticide travels through a soil food chain, disrupting biological control of non-target pests and decreasing soya bean yield. J. Appl. Ecol. 52, 250–260 (2015).
  6. Dubey, A., Lewis, M. T., Dively, G. P. & Hamby, K. A. Ecological impacts of pesticide seed treatments on arthropod communities in a grain crop rotation. J. Appl. Ecol. 57, 936–951 (2020).
  7. Ding, J. et al. Thiamethoxam, clothianidin, and imidacloprid seed treatments effectively control thrips on corn under field conditions. J. Insect Sci. 18, (2018).
  8. Preetha, G. & Stanley, J. Influence of neonicotinoid insecticides on the plant growth attributes of cotton and okra. J. Plant Nutr. 35, 1234–1245 (2012).
  9. Flessner, M. & Taylor, S. V. 2021 Field Crops Pest Management Guide. Virginia Cooperative Extension (2021) doi:10.1016/B978-0-12-394807-6.00031-9.
  10. Eskelson, M. J., Chapman, E. G., Archbold, D. D., Obrycki, J. J. & Harwood, J. D. Molecular identification of predation by carabid beetles on exotic and native slugs in a strawberry agroecosystem. Biol. Control 56, 245–253 (2011).
  11. Thomason, W. & Battaglia, M. Early defoliation effects on corn plant stands and grain yield. Agron. J. 5024–5032 (2020) doi:10.1002/agj2.20402.
  12. Disque, H. H., Hamby, K. A., Dubey, A., Taylor, C. & Dively, G. P. Effects of clothianidin-treated seed on the arthropod community in a mid-Atlantic no-till corn agroecosystem. Pest Manag. Sci. 75, 969–978 (2019).
  13. Bhatti, M. A. et al. Field Evaluation of the Impact of Corn Rootworm (Coleoptera: Chrysomelidae)–Protected <I>Bt</I> Corn on Foliage-Dwelling Arthropods. Environ. Entomol. 34, 1336–1345 (2006).
  14. Taravati, S., Mannion, C., McKenzie, C. & Osborne, L. Lethal and Sublethal Effects of Selected Systemic and Contact Insecticides on Nephaspis oculata (Coleoptera: Coccinellidae), in a Tri-Trophic System. J. Econ. Entomol. 112, 543–548 (2018).

Scout for Aphids in Small Grains

Kelly Hamby, Associate Professor and Extension Specialist, University of Maryland and
David Owens, Extension Entomologist, University of Delaware

Figure 1. Barley Yellow Dwarf patch in a field of malting barley, March 2023. Photo: David Owens, Univ. of Delaware.

Last season, aphids transmitted an unusual amount of barley yellow dwarf virus (BYDV) to wheat and barley across the Delmarva Peninsula. BYDV is particularly important when it infects plants in the fall. Fall BYDV infections can stunt plants (noticed as early as green-up, Figure 1) and cause more serious yield loss than spring infections. Our most common small grain aphid species are bird cherry oat aphid (Figure 2) and English grain aphid, although bird cherry oat aphid are associated with greater and more severe incidence of BYDV.

Figure 2. Bird cherry-oat aphids.

Historically, planting after the Hessian fly-free date (Table 1) reduced the likelihood of fall BYDV infection. However, fly-free dates were calculated more than 100 years ago, and it is now not uncommon for our first killing frosts to occur in late October or even November. Long falls with milder weather allow more time for aphids to colonize fields and potentially transmit the virus. Small grains varieties vary in their susceptibility to BYDV, and planting varieties with at least some tolerance can help. Unfortunately, resistant varieties are not available in barley. Finally, monitoring and managing the aphid vectors may be necessary.

Identifying bird cherry-oat aphid: A magnifying hand lens is required to identify aphids. Bird cherry-oat aphid ranges from orange green to olive green to greenish black. Wingless individuals typically have a reddish orange patch around the base of the cornicles (tail pipes). Winged individuals tend to be very dark. Their legs, cornicles, and antennae are similar in color to their bodies and medium in size.

Monitoring and thresholds: Typically, monitoring aphids in the fall and at green-up provides the best chance of identifying and mitigating BYDV risk. Scout ten locations per field avoiding field margins and look at 1 ft of row in each, making sure to look at the crown (at or below ground level), at the stem, and on the undersides of leaves. English grain aphids tend to feed on the uppermost portions of the plants while bird cherry oat aphids tend to cluster on the lower portions, especially in barley.

University extension threshold recommendations vary by region. In southern states, 6 aphids/row-ft is considered justification for a treatment in the fall. North Carolina uses a threshold of 20 aphids/row-ft where BYDV has been a problem and cold weather is not in the 7 day forecast. For other small grains, consider increasing the threshold to 25-50 aphids per foot of row.

In 2022, one of the malting barley fields sampled averaged 17 aphids per row-ft in early November. Because of unusually warm winter weather in which average temperatures were greater than 38 degrees, aphid populations peaked in one field at 235 aphids per row-ft that had averaged 1.8 per row-ft in November. This highlights the need to regularly monitor aphid populations during periods of mild weather.

Natural enemies: A number of natural enemies feed upon or parasitize aphids and they often do a good job keeping aphid populations down. One natural enemy per 50-100 aphids should be sufficient to control aphid populations. In addition, they are good at finding aphids even when their populations are low. Small wasps that develop within aphids leaving behind “mummy” aphids (Figure 3A), lady beetles, lacewing larvae (Figure 3B), and flower fly larvae (Figure 3C) are especially common aphid natural enemies. Insecticides will also kill these natural enemies.

Figure 3. Aphid natural enemies A) parasitoid wasp and golden or tan colored “mummy” aphids, B) lacewing larva eating aphids, C) flower fly larva eating aphids. Images: David Cappaert, Bugwood.org.

Insecticides: Seed treatments (e.g., Cruiser, Gaucho) provide some protection from fall aphids, but do not continue to provide protection into the spring and are not economic in years where aphids do not occur. Due to the differences in economics and BYDV susceptibility of malting barley varieties, seed treatments may be more useful than in feed barley or wheat. We generally recommend a foliar insecticide when aphid populations reach threshold. Small grain aphids are generally quite susceptible to insecticides. Pyrethroid products (e.g., Warrior) or a pyrethroid-neonicotinoid mix (e.g., Endigo, labeled for barley only) work well for aphid control.

 

Table 1. Hessian fly-free dates for Maryland and Delaware counties

State County Date
Maryland Allegany Sept. 27
Anne Arundel Oct. 7
Baltimore Oct. 2
Calvert Oct. 8
Caroline Oct. 7
Carroll Sept. 28
Cecil Oct. 3
Charles Oct. 8
Dorchester Oct. 9
Frederick Oct. 2
Garrett Sept. 20
Harford Oct. 1
Howard Oct. 2
Kent Oct. 6
Montgomery Oct. 4
Prince George’s Oct. 7
Queen Anne’s Oct. 7
Somerset Oct. 10
St. Mary’s Oct. 9
Talbot Oct. 8
Washington Oct. 1
Wicomico Oct. 10
Worcester Oct. 11
Delaware Kent Oct. 8
New Castle Oct. 3
Sussex Oct. 10

More information:

Kleczewski, N., Cissel, B., Whalen, J. 2016. Barley Yellow Dwarf Management in Small Grains. http://cdn.extension.udel.edu/wp-content/uploads/2015/10/14051904/BYDV-Final-Draft-9-12-16.pdf.

Flanders, K., Herbert, A., Buntin, D., Johnson, D., Bowen, K., Murphy, J. F., Chapin, J., Hagan, A. 2006. Barley Yellow Dwarf in Small Grains in the Southeast. https://entomology.ca.uky.edu/files/efpdf1/ef150.pdf.

Owens, D. and B. Cissel. Insect Control in Small Grains (for Grain only) – 2020. https://www.udel.edu/content/dam/udelImages/canr/pdfs/extension/sustainable-agriculture/pest-management/Insect_Control_in_Small_Grains_2020.pdf.

 

Beneficial Stink Bugs in Crops

James Heffley, Agriculture Extension Summer Intern and Kelly Nichols, Agriculture Agent 
University of Maryland Extension, Montgomery County

Figure 1. Adult spined soldier bug. Image: Bugwood.org.

Podisus maculiventris, better known as the spined soldier bug (Figure 1), is a close relative of the invasive brown marmorated stink bug (BMSB, Figure 2). However, the spined soldier bug is not only deemed nonthreatening to crops, gardens, and ornamentals, but is beneficial to their health. It is important to identify which type of stink bugs you are dealing with before you move forward with pest management.

Figure 2. Adult brown marmorated bug. Image: Bugwood.org.

Brown marmorated stink bugs pose a threat to agronomic crops especially corn and soybeans. Their quick reproduction habits and knack for hiding can be a dangerous combination for this invasive species. They feed directly on leaves and fruits and can kill small seedlings as well. Regular field scouting is the best practice for managing this pest. Control can be achieved by eliminating weed host plants that inhabit BMSB. These insects are drawn to living on mullein, mustard, and dock. They can also be accustomed to milkweed, plantain and select types of thistles.

The spined soldier bug is a beneficial insect that can be extremely helpful in consuming other unwanted pests in the field including select caterpillars and beetles. They can live on almost any field crop or in any garden setting. Females lay over 25 loose egg masses. If you come across spined soldier bugs in your fields, it is best to leave them be and let them proceed with their natural, biological control. In some cases, spined soldier bug nymphs can be purchased and released into the field for pest management.

How do we tell them apart? The brown marmorated stink bugs have a brownish grey body. Adults are approximately 17mm long and have rounded edges around their bodies and backside. Their backs are spotted and their heads are rounded as well. The spined soldier bug has distinct sharp shoulders and backs that protrude into points. Adults are about 13mm in length and have smaller heads than the BMSB. Spined soldier bugs also have a dark line on their forewings.

Maryland Regional Crop Reports: July 2023

Reports are for crop conditions up to July 6, 2023.

Western Maryland

Rain has been hit or miss here but crops are still looking good considering the erratic precipitation patterns of late. Barley harvest is complete and wheat harvest is in full swing. Disease was low but test weights and yields are still being accessed. Hay yields continue to suffer but hopefully El Nino will kick in and we will get more much needed precipitation.—Jeff Semler, Washington Co.

Central Maryland 

Frederick County has received notable rainfall in the last few weeks that has prevented potentially drastic crop condition reductions following the spell of hot and dry weather in May and June. Early corn is approaching the later stages of vegetative development, while most of the crop remains in the V8-9 stages. Soybeans are generally in notable shape, even with the early season drought. Scouted fields remain generally low in typical pests though Japanese Beetles have emerged and are maintaining a watchful eye. Soybean aphids were observed in two fields, however with more recent rains and populations well below IPM threshold values, they may remain an afterthought. Wheat harvest has progressed well with field average yields reported in the 80-110 bu/ac range. Crop moisture however has remained a touch higher than desirable. Additionally, maintain a watchful eye over earlier fields that have dried recently and have received rains–reports of low falling-numbers from local mills indicate the presence of sprouted wheat. Barley yields were outstanding as some growers noted personal bests in the 150-170 bu/ac range.—Mark Townsend, Frederick Co.

Northern Maryland

For the better part of 6 weeks, most of the region received very, very little rainfall; however, that has changed in the past two weeks where we have had multiple storms, bringing anywhere from an half inch to several inches of rain per storm. This rain was much-needed for the corn and soybean crop, as well as hay and pasture. Barley harvest wrapped up prior to the rains with very strong yields. Since wheat has matured it has been difficult to find enough dry weather to cut it. So far, wheat yields are very good with no DON but unfortunately test weights and falling numbers are declining in some areas. Earliest planted corn is in tassel, although most of it is only about 5-6’ tall. The dry April, May, and the bulk of June, coupled with relatively mild temperatures and low light intensity from the Canada wildfires, has resulted in some of the shortest corn in memory. Moisture is present as we go into tassel and silking, so hopefully we get decent pollination. Soybeans are also growing slowly but are rebounding; some early maturities are starting to flower. Regrowth on hay is very slow.—Andy Kness, Harford Co.

Upper and Mid Shore

Barley harvest finished during drought conditions with record yields. Wheat harvest has been underway for 2 weeks in between storms/ humidity/wildfire smoke. Test weight was above 60 lbs per bushel to start with, but as expected, has lowered after the stretch of rainy weather. Like barley, yields have been record breaking. While wheat harvest has been underway for 2 weeks, it’s only half complete. Even with 2 weeks of rainy weather, there are areas in the region that is still relatively dry. The storms have been spotty. Some areas have had 6 rain events with a grand total of less than an inch while other areas are over 5”.  Corn and full season beans look much better, but will need significant additional rain for decent yields. With beans blooming and corn tasseling, farmers are concerned about poor light quality resulting from the smoke filled atmosphere from wildfires up north. This is a new phenomenon for our region with very little research data available. Let’s hope for west winds with blue sky!—Jim Lewis, Caroline Co.

Lower Shore

Wheat harvest is underway. Corn maturity is varied. Early planted corn is tasseling. Corn that was planted late is still in early vegetative stages. Double-crop soybean is being planted. Full season soybean is 6-12” tall on average, in vegetative stage. There were scattered rain storms over the past couple of weeks, with some areas receiving significantly more rain than others. Non-irrigated crops in areas that had limited rain are showing signs of water stress, particularly in sandier soils. Herbicide-resistant ragweed and marestail are apparent in fields across the region.—Sarah Hirsh, Somerset Co.

Southern Maryland

We have seen dry and we’ve seen wet this month. Most areas of the region received decent rains in the last two weeks. Crops responded well. Corn is now tasseling with moisture just in time for pollination. Our corn crop is much shorter in stature than normal, but the crop overall looks good. Soybeans follow much of the same story. Early planted beans have canopied. The barley crop is now off. The wheat harvest season has been challenging, with limited harvest windows. Good news is the wheat crop has been excellent in terms of both yield and quality. Double crop beans are going in as soon as the wheat comes off. Vegetable crops are just beginning to come off. Heavy rains have hampered quality of some vegetable crops.—Ben Beale, St. Mary’s Co.

*Regions (counties):
Western: Garrett, Allegany, Washington. Central: Frederick, Montgomery, Howard. Northern: Harford, Baltimore, Carroll. Upper & Mid Shore: Cecil, Kent, Caroline, Queen Anne, Talbot. Lower Shore: Dorchester, Somerset, Wicomico. Southern: St. Mary’s, Anne Arundel, Charles, Calvert, Prince George’s

Interested in ‘Planting Green’ but Worried about Stands and Slugs?

Ray Weil, Professor of Soil Science | rweil@umd.edu
University of Maryland, College Park

Planting Green refers to no-till planting a primary crop into an actively growing cover crop before killing it mechanically or with an herbicide. This advanced soil health practice allows cover crops to grow longer, offering improved soil health and long-term agronomic outcomes. But for many farmers, the idea of planting through shoulder-high cover crops seems risky.  All that cover crop biomass might result in poor crop stands and more slugs. Fortunately, a few farmers have been planting green now for many years, and their experience and research data show that great stands and yields can be achieved with proper planning and equipment adjustments. Research also suggests that planting green may increase soil water available to the crop during the heat of summer, and even reduce slug damage instead of exacerbating it.

That’s why we (a group of University of Maryland Researchers and Extension Educators) have partnered with pioneering farmers who have long-term experience and success in planting green on their own operations across a variety of farm enterprises and soil types. The team is planning to conduct field research, on-farm trials, and demonstration days to better support Maryland farmers interested in adopting this enhanced cover-crop management practice.

We are looking to collaborate with farmers who might host replicated on-farm trials comparing several treatments, or simple side-by-side strip demonstrations (farmers would choose specific cover crops and termination strategies) – all supported by the research team and a panel of experienced farmers. Data would be collected and aggregated to evaluate soil health, agronomic, and farm management outcomes. Farmers could choose to enroll in our farmer-to-farmer mentoring program to receive additional technical assistance from researchers and farmer-mentors experienced in planting green.

It’s definitely time to plan your next cover crop moves for the coming fall and spring. If you are interested in participating (especially if you have slug problems!) or just want to learn more about cover crops and planting green, please contact one of us as soon as possible!

Sarah Hirsh, UMD Extension Educator, Somerset County: (410) 651-1350 shirsh@umd.edu

Dwayne Joseph, UMD Extension Educator, Kent County: (443) 480-8369, dwaynej@umd.edu

Mark Townsend, UMD Extension Educator, Frederick County: (301) 600-3578, mtownsen@umd.edu

Ray Weil, Professor of Soil Science, UMD, Dept. of Env. Sci. &Tech: (301) 405-1314, rweil@umd.edu

Maryland Regional Crop Reports: June 2023

Reports are for crop conditions up to June 1, 2023.

Western Maryland

To say we are dry would be an understatement. Corn planting is winding down and the last of the full-season beans will soon be finished up too. Barley and wheat are in full head a bit ahead of normal, whatever that is. The dry weather is a good thing for cereals as the conditions are poor for fungal growth. It will be interesting to see what effect the dry weather will have on test weight and yield. First cutting alfalfa and most of the grass hay is in the barn or silo. Rain will be important very soon for forage regrowth and corn and bean growth. The cool evenings and overnights have been the only blessing but heat is on the way.—Jeff Semler, Washington Co.

Central Maryland 

Frederick County has finished planting corn. There may be the occasional field that remains, but this is the exception. Early corn is at the V4-5 stage while later planted fields are approaching V2. Seedling diseases have been nearly non-existent in scouted fields, though wireworm pressure has been observed in both corn and soybean fields. Soybeans are 90% planted; early beans are around V2 while most are VC-V1.  The majority of the hay crop is made and in the barn. Annual weeds have emerged and are approaching a foot tall in some fields, though weed pressure has remained limited given the dry weather and resulting effective burndown applications. Second cutting alfalfa is underway, some weevil pressure had been observed in the occasional field though generally there has been relatively limited pressure. Most barley is at or near soft-dough stage, while the wheat crop has finished flowering and is moving into grain fill. Both small grain crops appear in good to great condition given the limited disease pressure.—Mark Townsend, Frederick Co.

Northern Maryland

We got through the entire month of May without any measurable precipitation. Such weather has made for great conditions for making hay, and this is one of the few times in recent memory where pretty much all of the first cutting hay crop was put up before June 1; although yields did appear to suffer in some fields due to the dry weather. 99% of the corn crop is planted and emerged, with earliest planted corn around V5-6. Almost all full-season soybeans have been planted and are anywhere from just planted to V3-4. Both corn and soybeans have yet to show wilting, but they are both growing very slowly due to the lack of rain. Fortunately we are running well below with temperatures in the 70s most of the month. Wheat is just starting to turn and appears to have very little disease pressure; we will see how the dry spring affects yield and test weight. We are hoping for a bit of rain in the coming weeks.—Andy Kness, Harford Co.

Upper and Mid Shore

Early planted corn greened up, but definitely has reduced yield potential. Later planted corn looks great- good color and uniform. Early beans are finally outgrowing slug feeding. Like corn, later beans look great. Barley harvest will begin 1st week of June. Wheat is starting to turn. There was great hay made last week. Soil conditions across the region are getting dry.—Jim Lewis, Caroline Co.

Lower Shore

Wheat and barley are drying down. Corn has been planted, and is generally around V1 to V5 stage. Most soybean has been planted and early soybean plantings have emerged. Herbicide-resistant weeds, such as common ragweed, marestail, and palmer amaranth, are starting to emerge. Scout and spray early to stay ahead on control. Some farmers have utilized late-terminated cover crops to help manage weed pressure through providing a mulch on the soil surface. Deer are prevalent in fields and causing damage on corn and soybean seedlings.—Sarah Hirsh, Somerset Co.

Southern Maryland

Temperatures finally touched the 80°F mark this week. Cooler temperatures and lack of rainfall has slowed crop progress in May. Most corn fields are a kaleidoscope of yellow shades and uneven stands. Black cutworms, slugs, wireworms and seed corn maggot are active across the region. We received scattered showers last weekend that helped crop conditions improve in most areas. Soybeans follow much of the same story. Early planted beans look decent. Barley is drying down with harvest expected any day. Wheat will not be far behind. Ryegrass continues to be a challenge for producers in both burndown situations in corn and beans, as well as small grains. My thought is the cooler weather is affecting the performance of glyphosate, especially on larger plants. The pockets of glyphosate resistant ryegrass are expanding in our area as well. The drier weather has been good for making hay- we saw a lot of balers in the field last week.—Ben Beale, St. Mary’s Co.

*Regions (counties):

Western: Garrett, Allegany, Washington. Central: Frederick, Montgomery, Howard. Northern: Harford, Baltimore, Carroll. Upper & Mid Shore: Cecil, Kent, Caroline, Queen Anne, Talbot. Lower Shore: Dorchester, Somerset, Wicomico. Southern: St. Mary’s, Anne Arundel, Charles, Calvert, Prince George’s

Bt and Herbicide Tolerant Traits in Corn and Current Resistance of Target Insect Pests

Galen Dively, Professor Emeritus | galen@umd.edu
University of Maryland, College Park

Listed below are the corn trait packages to make it easier to understand seed guides, sales material and bag tags. It is an abbreviated version of the Bt trait table plus related extension materials free online at: https://www.texasinsects.org/bt-corn-trait-table.html. Information listed Includes the name of each trait package, bag tag code, Bt toxins expressed (Cry1 types and Vip3A for caterpillars, Cry3 types for rootworms), refuge requirement (RIB=% refuge in the bag or REF=% structured refuge) and herbicide tolerance (GLY= glyphosate /Roundup-Ready, LL=glufosinate/Liberty Link, 2,4D or group 1 ‘fops’ type herbicides). Note that older trait packages, with limited or no commercial availability, are listed, so you can look back and interpret previous year’s planting records, seed guides, and research results.

The widely adopted use of Bt corn has resulted in major benefits to growers and the general public. However, resistance evolution in target insect populations has become a major threat to the sustainability of these crops. In some parts of the US Corn Belt, western corn rootworm rapidly adapted to Bt corn, and currently, some populations show resistance to all commercially available Cry3 traits. The high dose expression of Cry1 and Cry2 traits continues to provide excellent control and areawide suppression of the European corn borer in the US; however, the first case of resistance to the Cry1F toxin was reported in Nova Scotia in 2018 and resistance to other Cry toxins was recently confirmed in several eastern Canadian provinces. For corn earworm, we now have widespread field-evolved resistance to all Cry toxins in Bt corn. However, the Vip3A trait still provides excellent protection against this pest but studies show early stages of resistance developing since 2017, mainly in the southern states. Fall armyworm has been targeted by the Cry1F toxin since 2003, without any evidence of field-evolved resistance until 2010 when widespread control failures in Bt corn were reported in Puerto Rico and recent studies show high levels of resistance in several southeastern U.S. states.

Wet Cool Spring May Increase Slug Damage

Maria Cramer, Graduate Student and Kelly Hamby, Entomology Specialist
Department of Entomology, University of Maryland, College Park

Recently planted field crops may be at risk from slug damage due to the heavy rains and cooler temperatures we have experienced in the mid-Atlantic from the end of April into the beginning of May. Therefore, the UMD fact sheet “Managing Slugs in Field Crops Using IPM Principles” may be of interest. This fact sheet summarizes the most up-to-date research on managing slugs in our area. Highlights include:

  1. Identify the pest and monitor. Make sure the issue is slugs. If it is cool and overcast you may find slugs (Figure 1A+B) or slug eggs (Figure 2) in crop residue. Otherwise, as they are nocturnal, you may only find their damage on plants (Figure 3A+B). Corn is generally tolerant to defoliation, while soybeans are at risk if the growing point of the plant is damaged.
  2. Prevent. If you have not planted yet and if possible, use row cleaners and adjust the planter so that the seed slot fully closes to reduce the risk of damage. In the long term, reducing insecticidal seed treatments may favor slug predatory insects and harvestmen.
  3. Treat. If you use a slug bait, maximize efficacy by applying just prior to slug activity (in the afternoon or evening when weather is still and mild), but not before periods of heavy rain which may make the active ingredient less effective. Remember, the label is the law. Make sure the product you use is registered in your state and for your crop(s). Follow all application restrictions.
Figure 1. A) Gray garden slug and B) Marsh slug.
Figure 2. Slug eggs in corn residue.
Figure 3. A) Foliar feeding in corn with dried mucus, and B) feeding on soybean cotyledons showing characteristic pitting.

2023-2024 Agronomy Guide Avalable

The 2023-2024 version of the Penn State Agronomy Guide is available at https://extension.psu.edu/agronomy-guide. This is available as a digital download for $15, printed copy for $35, or a print and digital bundle for $45. They are offering a 25% discount through March 25. Enter the code CROPS-8GS in the “apply a discount code” section at checkout.

2022 Mid-Atlantic Crop Management School

Registration is now open for the Mid-Atlantic Crop Management School, which will be held in-person at the Princess Royale in Ocean City, MD from November 15 – 17, 2022. The school offers a 2 ½ day format with a variety of breakout sessions. Emphasis is placed on new and advanced information with group discussion and interaction encouraged. Individuals needing training in soil and water, nutrient management, crop management, and pest management can create their own schedule by choosing from 5 program options offered each hour.

New this year for CCAs: we are offering  specialty CCA certification credits in sustainability and precision agriculture. Specialty credits count toward recertification for the associated specialty certification or can be applied toward your overall CCA recertification credit requirements (for individuals not holding a specialty certification). We also anticipate offering state nutrient management credits for DE, MD, PA, VA, and WV and state pesticide credits for DE, MD, NJ, PA, VA, and WV.

Online registration will close at 11:59 p.m. EST on Monday, November 7, 2022. Registration Fees are $325 by October 15, and $375 from October 16 through November 7. We look forward to seeing you there.

Registration and program details are online at: https://go.umd.edu/crop22registration.