Category: Crops

Growing Giant Miscanthus on Marginal Land

Sarah Hirsh, Agriculture Agent | shirsh@umd.edu; Haley Sater, Agriculture Agent; and Jon Moyle, Extension Poultry Specialist
University of Maryland Extension

Giant miscanthus (Miscanthus × giganteus) is a perennial warm season grass known for its high biomass yield and adaptability to various growing conditions. This species of miscanthus is a sterile hybrid typically propagated by rhizomes. It can grow up to 12 feet tall with roots 8 feet deep. Giant miscanthus reaches its full biomass yield potential in the third growing season, where it can yield 10 to 15 tons per acre (Heaton et al., 2010). Giant miscanthus is used in Maryland as a bedding material in poultry houses. It can also be used as a biomass crop for fiber-based products, a bioenergy crop, and has environmental uses including erosion control, carbon sequestration, and as a buffer against nutrient runoff.

Figure 1. Giant miscanthus growing on land affected by severe deer damage, saltwater intrusion, and waterlogging.

The University of Maryland Extension performed a three-year research trial growing giant miscanthus on marginal land facing severe deer pressure, saltwater intrusion and waterlogging (Figure 1).

Figure 2. Giant miscanthus plot yields (+/- standard error) after first and second years of growth.

We found that giant miscanthus successfully grew with only a slight yield reduction. In the 10-acre field where the experiment was conducted, 20 one-meter square plots were harvested to calculate biomass yield. Yield on average in year one was 2.8 tons dry biomass per acre and yield on average in year two was 4.8 tons per acre (Figure 2). Average first- and second-year yields on prime land for growing miscanthus would be 3 tons per acre and 5-6 tons per acre, respectively. Giant miscanthus does not reach its full biomass yield potential until the third growing season, where it can ideally yield between 7-12 tons per acre (Kalmbach, et al., 2020).

In the 20 one-meter square plots where yield was taken, levels of sodium (Na) in the field ranged from 57-510 ppm Na, with an average of 174 ppm Na. This level of Na would cause stress that would result in yield loss to corn or soybean. A normal range of Na in Delmarva row-crop land is 5-40 ppm (Delmarva Saltwater Intrusion, University of Delaware, 2024). Higher concentrations of Na correlated somewhat with miscanthus biomass yield, more so in the second year than in the first year (Figure 3).

Figure 3. Correlation between giant miscanthus plot yields and soil sodium levels.
Figure 4. Giant miscanthus growing in year-round waterlogged part of field; Soil moisture data collection from plot two.

The entire study field stayed waterlogged during the winter months. The duration of waterlogging was observed to affect giant miscanthus growth and yield potential. Areas of the field where the soil stayed saturated throughout the winter and summer months had dramatically reduced giant miscanthus growth compared to areas of the field where the soil stayed saturated in the winter months but only intermittently during the summer months. In the year-round waterlogged parts of the field, giant miscanthus had shorter stand height, weaker stems and experienced lodging (Figure 4). The miscanthus grew equally well in the parts of the field that were intermittently flooded in the summer compared to the driest parts of the field (based on soil moisture sensor data; Figure 4).

The field had heavy deer pressure based on edge-of-field wildlife camera photos and observed deer tracks and paths in the field (Figure 5). However, no deer browsing of giant miscanthus was observed in the field.

Figure 5. Deer image from Bushnell wildlife camera (left) and deer tracks within field (right). Photos by H. Sater.

Research conducted on Maryland farms has demonstrated that giant miscanthus is a versatile and resilient crop that can be grown on marginal land where other traditional agronomic crops can no longer be profitably grown. Its ability to withstand deer damage, saltwater intrusion and waterlogging make it a valuable option for farmers in Maryland looking to diversify their crops and improve the sustainability of their operations. However, access to equipment and markets may be barriers to farmers growing giant miscanthus, and we do not recommend this crop prior to addressing these factors.

Sources cited:

Agriculture and Salt Issues. (2024). Delmarva Saltwater Intrusion, University of Delaware, October, 10, 2024, sites.udel.edu/delmarvasalt/home-page/agriculture-and-salt-issues/.

Heaton, E., Moore, K., Salas-Fernandez, M., Hartzler, B. Liebman, M. and Barnhart, S. (2010). Giant Miscanthus for Biomass Production. Iowa State Fact Sheet. AG201. https://store.extension.iastate.edu/product/12611

Kalmbach, B., Toor, G., & Ruppert, D. (2020). Soil Fertility Recommendations-Nitrogen, Phosphorus, and Potassium Requirements of Miscanthus (EB-443).

UMD-TAPS: A New Kind of Farmer Participatory Research and Field Day

Shannon Dill, Principal Agriculture Agent | sdill@umd.edu
Nicole Fiorellino, Assistant Professor & Extension Agronomist
and Kelly Hamby, Associate Professor and Extension Entomologist
University of Maryland

What is TAPS?

The Testing Ag Performance Solutions (TAPS) program was developed by the University of Nebraska-Lincoln (https://taps.unl.edu/) as a zero-risk opportunity for farmers to gain experience with novel agronomic practices that are executed at a University research center, structured similarly to a yield competition. Over the last 8 years, the program has expanded across multiple states and cropping systems. Teams of farmers compete to see who can manage their “farm” to achieve the best overall profitability, input use efficiency, and yield for a given crop. Options include agronomic (variety selection, fertility, irrigation), pest management, and economic (crop insurance, forward contracting) decisions. 

Why develop a UMD-TAPS program? 

On-farm trials provide valuable opportunities for farmers and Extension personnel to work together to try alternatives and determine whether they work for an operation. However, the practices that can be examined may be limited by the available land and equipment. If practices do not work as expected there may also be lost yield or other financial costs to the operation. TAPS enables participants to try practices that they might not otherwise have access to, for example irrigation, or to try practices that might otherwise be too risky. In-season management decisions kept confidential, with all choices and awards presented at an end-of-season banquet to facilitate peer learning. The program is flexible from year to year, and in Maryland, we want participants to steer the management practices that are included in the competition.

2024 UMD-TAPS pilot 

In 2024, we piloted this program with Extension faculty serving as participants and began with irrigated soybeans. The trial was executed at the Wye Research and Education Center, and each participant selected management options that were executed on replicated, randomized small plots. Participants receive a “menu” of both pre-plant and in-season management options to select. For the first year, we provided seven soybean varieties with maturity groups ranging from 3.2 to 4.8. Participants selected seeding rates of 80,000, 100,000, or 120,000 seeds per acre and chose irrigated or dryland. We also monitored slugs and provided slug bait options. A variety of crop insurance plans were offered and participants could forward contract at any point in the season by listing the CBOT closing price for the date. Unsold bushels received market price on the day of harvest at Mountaire and participants could determine the day that they wanted to harvest. We are currently in the process of calculating overall profitability, input use efficiency, and yield to determine winners. 

2025 UMD-TAPS and beyond 

In 2025, we hope to run the competition with farmer participants and will be advertising over the winter. We have built a strong partnership with the National TAPS collaborators and will use their portal in 2025 to facilitate easier communication with participants. Moving forward, we also hope to expand to additional research and education centers and possibly include a separate corn competition. We look forward to hosting field days where participants and others can come visit their replicated plots. We look forward to incorporating other ideas from our participants. If you are interested in participating in TAPS in 2025 or learning more about it, please add your contact information to this form.

TAPS Presentation at Mid-Atlantic Crop School

We are excited to have the creators of the TAPS program from UNL presenting about the TAPS program at Mid-Atlantic Crop Management School in Ocean City next week. If you are already registered for the event, we hope you will consider attending this talk.

Acknowledgements

We would like to thank John Draper, Tom Eason, and Reagan Milby at the Wye Research and Education Center for their assistance managing the plots and irrigation, Arthur Young, Shea Ill, Maria Cramer, and Em Kohanski from the Hamby lab for monitoring slugs, and Gene Hahn, Louis Thorne, and Audrey Sultenfuss from the Fiorellino lab for assistance managing and harvesting plots. We appreciate the funding provided by the Maryland Soybean Board. 

Population Dynamics of Stink Bugs Within Cover Crops on the Eastern Shore of Maryland

Emily Zobel, Senior Agriculture Agent Associate | ezobel@umd.edu
Dwayne Joseph, Agriculture Agent; and Haley Sater, Agriculture Agent
University of Maryland Extension

Figure 1. Photo of a stink bug on a sweep net. Photo by N. Krambeck. 

There is emerging concern among growers on the Eastern Shore of Maryland that our warmer winters and longer cover crop growing season may allow several stink bug species to overwinter and utilize cover crops for shelter and food. These stink bugs could then move into soybean fields after cover crop termination, potentially causing feeding injury and damping off damage to soybean seedlings. Fall-planted cover crops offer many benefits to soil health and the environment, so a survey was conducted during the 2024 growing season to investigate whether cover crops provide a suitable overwintering habitat for stink bugs.

Species of phytophagous stink bugs that are known economic pests of soybean include the brown stink bug, Euschistus servus (Say), green stink bug, Acrosternum hilare (Say), and the brown marmorated stink bug (Halyomorpha halys). Stink bugs use their piercing-sucking mouthparts to feed on the foliage and pods of soybeans, causing discolored, shriveled beans, reducing both the yield and quality of the crop.

Stink bugs typically overwinter as adults in protected areas such as fence rows, grassy field borders, under stones, or tree bark. Most species have one generation per year. They become active during the first warm spring days, typically in April. Females usually start depositing eggs in June. Nymphs hatch from these eggs and pass through five instars before becoming adults, with approximately five weeks elapsing between hatching and adult emergence. Adult stink bugs generally reach their highest population levels in September, when they can become an economic problem for soybeans.

To determine if stink bugs use late-season cover crops as overwintering habitat, 37 cover crop fields were sampled on the Eastern Shore of Maryland between mid-April and mid-May. The majority of fields surveyed were planted in a wheat-only cover crop. Densities of adults and nymphs were determined by taking ten sweeps with a standard sweep net at five to ten areas across each field. Fourteen fields were sampled twice before the cover crop was terminated. The other fields were sampled once due to weather constraints before terminating the cover crop. Eight fields were sampled again in June when soybean plants were 6-12 inches high. 

Ninety-nine stink bugs were counted across the 51 scouting times, averaging 1.94 stink bugs per field per scouting date.  94% of the species counted were adult native brown stink bugs. The majority of stink bugs (79%) were counted during the last week of April and the first week of May. Along with stink bugs, 225 ladybird beetle adults and larvae were counted. Fifteen stink bugs were found during the scouting of soybean seedlings in June. The low number of stink bugs found in 2024 in spring cover crops suggests they are not overwintered in cover crops, and adding an insecticide to cover crop burndown spray is unnecessary to control them.  

We want to thank all the farmers who allowed us to sample their fields. If you are interested in participating in this study in 2025, please contact Emily Zobel at ezobel@umd.edu or (410) 228-8800. The Maryland Soybean Board provided financial support for this project (project # 80333).

Assessing Herbicide Tank Mixes for Postemergence Weed Control in Soybean

Kurt Vollmer, Extension Weed Management Specialist | kvollmer@umd.edu
University of Maryland Extension

Research was conducted at the Wye Research and Education Center to evaluate herbicide tank mixes for postemergence weed control in herbicide-tolerant soybean. As herbicide-resistant weeds continue to drive weed management decisions, options are needed to not only provide effective weed control, but also preserve the value of available herbicides.

Figure 1. Example probabilities of developing resistance when using Herbicide A, Herbicide B, and Herbicides A and B. Using two different herbicide groups decreases the probability that a weed will become resistant to both herbicide groups.

Tank mixing multiple, effective herbicide groups is one tactic that can be used to impede herbicide resistance. By including multiple, effective herbicide groups when making an application, there is a lower probability that a weed species will develop resistance to all herbicides used (Fig. 1). Furthermore, tank-mixing different herbicide groups can have a synergistic effect, where the combined effect of two or more groups is greater than the effects of each herbicide alone. For example, previous research has shown Enlist One + Liberty to be more effective in controlling as common ragweed and Palmer amaranth, compared to each individual herbicide.

Furthermore, including a residual herbicide in the tank when making a postemergence application may be necessary for full-season control of certain weeds, such as Palmer amaranth. Including herbicides with both foliar and residual activity, such as fomesafen (Reflex), in tank with other effective herbicides can help to preserve the utility of these herbicides.

This research examined the effectiveness of tank mixing of herbicides with foliar (2,4-D, fomesafen) and residual (fomesafen, ­S-metolachlor) for early and late postemergence weed control in soybean. Plots (10 ft. x 25 ft.) were arranged in a randomized complete block design with 4 replicates. Herbicide treatments consisted of applying Reflex (fomesafen), Reflex + Dual Magnum (S-metolachlor), Reflex + Enlist One (2,4-D) or a three way mix of Reflex + Dual + Enlist One (Table 1). The entire study area received 1 pt/A Dual Magnum within 24 hours of soybean planting Enlist E3 soybeans on June 4, 2024. Early postemergence (EPOST) applications were made 2 weeks after planting and late postemergence (LPOST) applications 4 weeks after planting.

Table 1. Postemergence herbicide treatments for resistant weed mitigation and control in soybean.

Herbicide(s)RateTiminga
Reflex1.5 ptEPOST or LPOST
Reflex + Dual1.5 pt + 1.5 ptEPOST or LPOST
Reflex + Enlist1.5 pt + 2 ptEPOST or LPOST
Reflex + Enlist + Dual1.5 pt + 2 pt + 1.5 ptEPOST or LPOST
a Herbicide treatments were applied early postemergence (EPOST) 2 weeks after planting or late postemergence (LPOST) 4 weeks after planting soybeans on June 4, 2024.

Broadleaf Weed Control

Application timing did not affect common lambsquarters or morningglory control. Reflex + Enlist or Reflex + Enlist + Dual controlled common lambsquarters better compared to Reflex alone, and morningglory species better than Reflex or Reflex + Dual (Fig. 2).

Figure 2. Control of common lambsquarters and morningglory species 7 weeks after soybean planting. Bars of the same color with the same letter are not significantly different according to Tukey’s HSD (α = 0.05).

Giant Foxtail Control

Applications made EPOST provided better control compared to applications made LPOST (Fig. 2), but giant foxtail control varied from 38% to 78%, with no significant differences among herbicide treatments (Fig. 3). It should be noted that Enlist One does not control grasses. Both Dual Magnum and Reflex can provide some grass activity, but only if applied PRE. Better foxtail control with EPOST treatments could be attributed to overlapping residual control with these treatments. Overlapping herbicides is a tactic that involves sequential applications of herbicides with soil-residual activity to lengthen herbicidal activity before the first herbicide dissipates. As Dual Magnum was included in both PRE and POST applications, the EPOST applications likely provided better overlapping residual control due a shorter application window between the PRE and POST applications (2 weeks for EPOST and 4 weeks for LPOST).

Figure 3. Giant foxtail control following early and late postemergence applications 7 weeks after soybean planting. Bars of the same color with the same letter are not significantly different according to Tukey’s HSD (α = 0.05). 

This research highlights the value of adding multiple herbicide groups to the tank at the time of POST applications (Fig. 4). While additional work is needed to confirm the results of this study, the following factors should be considered when deciding which herbicides to include in the tank:

  • The types of weeds are prevalent in the field. Should the spray program focus primarily on broadleaf weeds, grasses, or both?
  • The emergence period for the weeds being controlled. Will a single POST application negate the need for additional treatment, or should an herbicide with residual activity be included?
  • Each herbicide must be effective alone on the target weed. Including multiple herbicides will not be as effective if a weed already has significant resistance to one of the herbicides in the mix.
Figure 4. Weed control with early postemergence applications of a) Reflex + Dual and b) Reflex + Enlist + Dual 7 weeks after planting. Photo credit: Logan Bledsoe.

Acknowledgements

Support for this project was made possible by funding from the Maryland Soybean Board as well as technical support from Jadon Cook, Logan Bledsoe, Sam Denherder, and the University of Maryland Wye Research and Education Center.

Commercial products are mentioned in this article solely for the purpose of providing specific information. Mention of a product does not constitute a guarantee or warranty of products. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.

Preventing Combine Fires

Reprinted from University of Maryland fact sheet (FS-845): Nottingham, J. Richard. (2008). Preventing Combine Fires (FS-845). University of Maryland Extension. go.umd.edu/FS-845.

Dry field conditions that are ideal for a successful fall harvest also bring the danger of combine fires. Dry crop residue provides the tinder, and a small spark or heat source is all that is necessary for a combine fire to start. Combine fires can lead not only to lost time but substantial property damage and even injury or loss of life.

Keep Your Equipment Clean

What can you do to lessen your risk of a combine fire? First and foremost, prevention is essential. Remember the old saying, “an ounce of prevention is worth a pound of cure.” Cleanliness and maintenance are essential for combine fire prevention. Use a pressure washer or a compressed air blowgun to thoroughly clean and remove dust, dirt, grease, and crop residues from your equipment. Many farmers also find a hand-held leaf blower useful for cleaning equipment in the field. Not only will you have eliminated the “tinder” from which a fire can start, but you will have equipment that will run cooler and more efficiently. Regardless of how busy you may be, take the time to keep your equipment clean.

Pay Special Attention to Routine Maintenance

Check lubricant levels often, and grease fittings regularly. Fix leaking oil, fuel, or hydraulic lines promptly. Check belts for proper tension and wear to reduce friction. Carefully check bearings for excessive heat- overheated bearings are a major cause of combine fires. Pay particular attention to the exhaust system, checking for leaks, damage, or an accumulation of crop residue. High heat or a spark from the exhaust can easily ignite dry crop residue. Take a close look at the wiring system, checking for exposed wiring or insulation deterioration. Remember, a blown fuse indicates an electrical problem-never replace a blown fuse with a new fuse of higher amperage.

Special Precautions for Refueling

When refueling becomes necessary, always shut off the engine and let the equipment cool for 15 minutes before you refuel. Extinguish all sources of flame and smoking materials before refueling. If fuel spills on the engine, wipe off any excess and allow the fumes to dissipate. Never store flammable liquids in glass or non approved containers. The few minutes that you spend safely refueling are insignificant compared to the property damage or injury that can be caused by a fire.

What If, Despite Our Best Efforts at Prevention, a Fire Does Occur?

Being prepared can prevent substantial loss. Experts recommend that at least one fully charged 10-lb ABC fire extinguisher be carried on all equipment. Better yet, carry two: one in the cab and one where it can be reached from the ground. The cost of fire extinguishers is insignificant when compared with the cost of your equipment. Remember that any partial discharge from an extinguisher requires it to be recharged. Visually check your extinguishers monthly, looking for cracks in the hose and inspecting the gauge to see if the extinguisher is fully charged. Have a professional fire extinguisher company inspect your fire extinguishers annually. Carry your cell phone or 2- way radio with you at all times so you can summon help. If a fire does occur, CALL 911 FIRST, and then attempt to extinguish the fire by pulling the pin on the fire extinguisher and squeezing the handles together. Aim the nozzle at the base of the fire and sweep from side to side. Remember P.A.S.S., which stands for Pull, Aim, Squeeze, Sweep.

By exercising proper fire prevention and preparedness and keeping your equipment well maintained and clean, you can help ensure a safe harvest season.

References

National Ag Safety Database Preventing Farm Equipment Fires Nebraska Forest Service, Lincoln, NE. http://www.cdc.gove/nasd/

2024 Corn Hybrid Performance Trials Results

Nicole Fiorellino | nfiorell@umd.edu
Assistant Professor & Extension Specialist, Agronomy

The 2024 Maryland Corn Hybrid Trials results can be found at https://psla.umd.edu/extension/md-crops or downloaded at the link below. Many thanks to Louis Thorne, Gene Hahn, and Audrey Sultenfuss for their time spent preparing, establishing, collecting data, and preparing the report. These trials could not be completed without them. I greatly appreciate the Center managers and personnel who assist our team with executing these trials.

We are grateful for the funding provided by Maryland Grain Producers Utilization Board to support these trials. MGPUB provides our program with checkoff funding to support applied agricultural research and so we may generate results that directly benefit Maryland producers.

Download the 2024 Corn Hybrid Trials Report here

Maryland Regional Crop Reports: September 2024

Reports are for crop conditions up to September 5, 2024.

Western Maryland

August brought us more rain than June and July combined. The hay and pasture fields responded, and there is hope for continued grazing and another cutting. The soybeans are probably the greatest beneficiary of the moisture. They are looking great as their pods fill. Modern varieties are a wonder to behold. Corn silage harvest began earlier this year thanks to the heat and drought. Many folks are glad they planted a little extra corn, primarily due to the need for forage and the low grain price forecast. Running it through livestock will add value. Triticale and oats are going in the ground for both fall and spring forage. Cool mornings and mild days have raised our countenance here in Western Maryland.—Jeff Semler, Washington Co.

Central Maryland 

August has finally brought some much needed rain; although amounts have been scattered throughout the region. A storm last week caused crop damage in some areas of the region. While it won’t be a year for record-breaking yields, most of the corn and soybeans are looking fairly good. The majority of corn is in the dent stage and is starting to dry down. Silage chopping has begun. Full season soybeans are in the beginning seed stage (R5).—Kelly Nichols, Montgomery Co.

Northern Maryland

About 6” of rain fell in August, which really woke up soybeans, especially later planted beans and double crops. Unfortunately, the rains have ceased, with the last measurable rainfall coming over two weeks ago. Rain is predicted for this weekend, so fingers crossed for good rainfall to finish out what could be a strong late season bean crop. Corn is rapidly drying down and a few acres have been harvested but the majority of corn is still 25% moisture or better. We are about another 10-14 days before the combines are rolling hard. Tar spot was also confirmed in the region at the end of August, consistent with the two years prior. A lot of good dry hay was put up over the last two weeks.—Andy Kness, Harford Co.

Upper and Mid Shore

July’s much-needed rains tapered off, leaving August with sporadic showers that varied significantly depending on your neck of the woods. This inconsistency has led to some challenging conditions for crops. Signs of water stress have become apparent; soybean leaves are cupping and corn leaves are curling from lack of moisture. In response, center pivots on irrigated fields have been fired up again, helping to maximize yield potential after a brief respite in July. Corn is drying down, with some early-planted fields already harvested. Soybeans are also moving along, with early maturing varieties starting to turn and double crop beans filling out their pods. The dry conditions earlier in the season provided the perfect environment for Palmer amaranth to thrive and compete with the crops. They can clearly be seen towering over the soybean and even corn in both conventional and organic fields. The region has also noticed more spotted lanternfly activity as these pests hit their final growth stage and take to the air. While they’re mostly just a nuisance in agronomic crops, controlling them can really help out your local fruit and vegetable grower, who would surely appreciate the effort.—Dwayne Joseph, Kent Co.

Lower Shore

Corn is drying down, but harvest has not yet begun. Due to low grain prices, farmers are inclined to let corn completely dry in the field, rather than take a moisture price hit at the mills. Drought stress during vegetative and early reproductive phases hurt corn. Yield is anticipated to be poor, and ears look small. Soybean is looking better than corn, especially double-crop soybean planted after wheat. There have not been reports of serious pest or weed damage. Cover crops are being flown into some corn fields via airplane.—Sarah Hirsh, Somerset Co.

Southern Maryland

Conditions remain very dry across the majority of Southern Maryland. Corn harvest is in full swing with reports of average to well below average yields. Yields vary greatly within and between fields depending on soil type and where isolated showers happened to fall. Grain quality is a major concern this year. Growers are encouraged to get corn off as early as possible. Beans continue to put up the good fight. Many full season beans are yellowing and drying down. Double crop beans will need some more help to fill out pods. Farmers have been scouting for pod worms and stink bugs. Thankfully, only a few fields have reached threshold and required a treatment so far. Weeds continue to require attention as fields have taken longer to canopy if at all, allowing greater opportunity for weeds to gain their share of the limelight. We continue to see ragweed, pigweeds of all types, and morning glory present. Deer damage is readily apparent in later planted beans that are failing to re-grow or canopy following deer feeding. Forages have struggled this summer with many fields of cool season grasses requiring replanting this fall or next spring.—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

Tar Spot Update: First Reports for 2024

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

Figure 1. Map of tar spot of corn for 2024 growing season as of September 5.

Our first official reports of tar spot have been confirmed in Maryland for 2024; almost exactly on pace for when we first detected tar spot in 2023 and 2022. The first report came from a dent corn field in Baltimore County on August 22 and subsequent reports were made from fields in Harford County on August 27 and September 4. All of these fields are near black layer and yield loss due to tar spot infection is not likely unless infection occurred earlier in grain fill or during pollination. It is not likely that we had tar spot infections occurring in July due to the extreme heat this year. Tar spot infections require lower temperatures than other common fungal diseases of corn such as gray leaf spot.

As average daily temperatures begin to dip into the mid 70s and mid 60s, tar spot symptoms will likely start to flare up in corn. Tar spot can spread as long as there is green tissue on the plant, which means symptoms can worsen even past black layer, making for a field that could look far worse than it actually is. For reference, last fall I did yield checks in two corn fields and one research plot that had fairly moderate levels of tar spot infection (Figure 2) but still yielded very well (220-300 bu/a), with the field with the worst symptoms topping 300 bushels. What likely happened is tar spot infected corn close to R5-R6 and it continued to spread after black layer since the plants stayed green beyond physiological maturity due to the stay green effect of foliar fungicides that were applied to these fields. Even though tar spot spores can blow short distances in the wind, if you are harvesting a field infected with tar spot, it would be a good practice to try to clean as much corn fodder off of equipment prior to moving to a new farm; a blower or air compressor will do the trick.

Figure 2. Tar spot symptoms on a senesced corn leaf.

As you are scouting your corn fields, be on the lookout for tar spot. With funding from the Maryland Grain Producers Utilization Board, we are conducting a survey of the distribution of tar spot in Maryland. If you have tar spot, or think you might, please report it to corn.ipmpipe.org or reach out to me at akness@umd.edu or (410) 638-3255. Reports are kept anonymous and individuals and/or farms are not identified in any reports, publications, or communications.

Ear and Stalk Rots May be an Issue in Corn

Andrew Kness, Senior Agriculture Agent | akness@umd.edu
University of Maryland Extension, Harford County

stalk and ear rot of corn
Stalk rot (left) and ear rot (right) of corn.

With the dry then wet (then dry again) weather pattern we had this year, corn went through a lot of stress. Stressed corn is much more susceptible to ear rots and stalk rots. The degree of severity is dependent on a variety of factors, so it is wise to scout fields prior to harvesting in order to identify problematic fields and give them harvest priority.

Several different pathogens can cause ear rots in Maryland; the main contenders are listed in the table below. Although they typically do not affect yield, they can cause grain quality issues through the production of mycotoxins. Furthermore, if infected grain is not dried quickly or to a low enough moisture content, infection can spread, even when in the bin. Therefore, it is important to scout and identify fields that are infected with ear rots and harvest those first. It is better to pay a few cents in propane to dry the wet grain than to wait and risk infection levels getting worse, and the potential for elevated mycotoxin concentration in the grain. Quickly dry infected grain to 15% for short-term storage and to below 13% for long term storage and it is not recommended to store infected grain for longer than a year. It is important to note that not all ear rotting fungi produce mycotoxins, so I would recommend working with your Extension agent or crop advisor to get proper identification so that you know the species in question and thus if mycotoxin contamination is a concern.

Table 1. Common ear rots of corn.

Disease Pathogen Symptoms (see next page for pictures) Mycotoxin
Fusarium ear rot Fusarium verticillioides “Starburst” kernels, white kernels, infected kernels may be scattered on ear Fumosin
Gibberella ear rot Fusarium graminearum Ear covered in white mat often with pink hue, infection starts at tip and can progress to butt end of ear Vomitoxin (DON)
Diplodia ear rot Stenocarpella maydis and S. macrospora White fungal mat on ear, may cover the entire ear None
Penicillium ear rot Several Penicillium species Blue-grey spores on kernels developing on damaged ears (hail, deer feeding, insects, birds, etc.), may infect the germ of the kernel Some species may produce mycotoxins
Trichoderma ear rot Trichoderma viride Green spores in between kernels None
Aspergillus ear rot Aspergillus flavus Olive green spores on ear, usually starting at tip, associated with damaged ears (feeding from insects, deer, birds, etc.) Aflatoxin

Stalk rots are also a harvest concern. Like ear rots, stalk rots are also caused by many different pathogens, several of which are listed in Table 2 below. No single factor causes stalk rots; they are rather the end result of a host of factors that contribute to a net deficit in plant carbohydrates needed for grain fill. The grain fill process is a major carbohydrate sink for the plant. As the plant produces carbohydrates through photosynthesis, it allocates almost all of it’s carbohydrate production to filling the kernels. A healthy plant will have sufficient leaf area to maximize photosynthesis and can therefore produce enough carbohydrates to fill the grain. However, when photosynthetic leaf area is compromised, the plant cannot make enough food to fill the kernels. In order to compensate for the deficit, the plant cannibalizes carbohydrates from existing tissues. The first tissues to go are the stalks, which are then easily compromised by stalk-rotting pathogens. Stalk rot is a byproduct of stressed plants during the growing season, particularly during grain fill.

Table 2. Common stalk rots of corn.

Disease Pathogen
Anthracnose stalk rot Colletotrichum graminicola
Diplodia stalk rot Stenocarpella maydis
Charcoal rot Macrophpmina phaseolina
Gibberella stalk rot Fusarium graminearum
Fusarium stalk rot Multiple Fusarium species

Any factor that reduces leaf area or reduces photosynthesis after pollination will predispose plants to stalk rots. These include reduced leaf area through insect feeding, lesions from foliar diseases, or mechanical damage (such as hail). Other factors include inadequate fertility, water stress, and excessive plant populations. Another significant factor is hybrid genetics; both resistance ratings to stalk rotting pathogens as well as ear and kernel size. High-yielding, large kernel hybrids are more susceptible to stalk rots if they are not kept healthy through grain fill.

Scout fields for stalk rots as early as black layer. The “pinch test” is one way to scout for stalk rots. Pinch the stalk in between the nodes at one of the lower two nodes. You should not be able to pinch healthy stalks, but rotted stalks will fairly easily collapse. Do this at several random locations to assess the field. Alternatively, you can do a “push test,” which involves pushing the corn stalks approximately 30 degrees from horizontal (8 inches laterally) at a height of about eye level. Healthy stalks will return to vertical while infected plants will not. If more than 10% of plants tested exhibit stalk rot symptoms, you may want to harvest as soon as possible or risk a not-so-fun harvest of lodged corn.