C.O.R.N. Newsletter: 2022-21
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Tar Spot Q&A
Q: Is tar spot a late-season disease in Ohio?
A: No, tar spot can develop at any time during the growing season. For the first few years after it was first reported in Ohio in 2018, tar spot was detected primarily towards the end of the season, giving the impression that it would likely be a late-season disease in the state. However, in 2021, symptoms were seen at the R1 growth state in some fields, suggesting that under the right set of conditions (moderate temperatures and extended wet periods), tar spot could develop much earlier than previously observed, if the hybrid is susceptible and spores are available. This is similar to what is being observed in neighboring states where the disease is established and considered to be endemic. So far in 2022, tar spot has been reported on V5-V6 plants in multiple Corn Belt states. This is not at all surprising, given that plants of any age are susceptible to infection by the tar spot fungus.
Q: Is tar spot mainly a problem in NW Ohio?
A: No, tar spot can develop anywhere in the state. From 2018 to 2020, tar spot was most frequently detected in fields in the NW corner of the state. However, in 2021 it was reported in more than 30 counties, including a few in the southern and eastern portions of the state. During the first few years, tar spot development in Ohio was likely driven mainly by spores blowing in from neighboring states. Consequently, the location and timing of symptom development depended on where and when spores landed and whether conditions were favorable for them to infect. Since fields in NW Ohio are closer to states from which spores are likely blowing in, tar spot tends to show up first and reach higher levels in that region. In addition, in 2021, some fields in the NW had more frequent rainfall during the months of July and August than fields in other areas, contributing to more tar spot in that region of the state; rain is one of the main drivers of tar spot. However, as the disease becomes established and widespread, fields in other regions of the state will be affected and symptoms with develop early, if the hybrid is susceptible and weather conditions are favorable.
Q: Why is rain or moisture so important for tar spot development and spread?
A: Moisture is important for spore production, release, and spread, and infection of the plant. Moisture is needed for the spores to ooze out of the stromata in which they are produced and then splashed into the air and carried by wind to new plants or fields. Moisture is also needed for spores to germinate and infect leaves, and for symptoms to develop.
Q: Why do some fields under rotation with soybean and/or tillage still show symptoms of tar spot”.
A: Wind can carry spores over long distances between fields within counties and even between counties and states. So, the reason why some fields without a history of tar spot (did not have the disease previously) and some under rotation and tillage (with little or no corn stubble on the soil surface) still develop tar spot is because spores are picked up and transported from field to field within and across states. If these spores land on the leaves of a susceptible hybrid under wet, humid conditions, they will germinate and penetrate, and symptoms of tar spot will develop
Q: Can tar spot be controlled with fungicides?
A: Yes, based on data from neighboring states, fungicides do show promising results against tar spot. We continue to evaluate products and application timing for efficacy in Ohio. So far, fungicides with multiple active ingredients (AI) tend to be more consistently effective than single-AI fungicides, but no fungicide will provide 100% control of tar spot. In addition, fungicides are most effective when applied as soon as symptoms begin to develop and before the disease spreads. Applications made between R1 and R2 tend to give the best results.
For more on tar spot:
https://cropprotectionnetwork.org/resources/articles/diseases/tar-spot-of-corn
https://agcrops.osu.edu/newsletter/corn-newsletter/2020-03/tar-spot-corn
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Lep Monitoring Update CEW, WBC, FAW and ECB Updates
Corn Earworm
Corn earworm (CEW) (Figure 1) numbers have decreased over the past week. Currently only Van Wert County is reporting an average above 20 moths per trap (Figure 2). Counties with high numbers of CEW and silking corn are at the most risk for CEW, because adult moths are attracted to silking corn. For more information on corn earworm: https://agcrops.osu.edu/newsletter/corn-newsletter/2019-27/corn-earworm-field-corn-watch-mold
Figure 1. Corn earworm (CEW) moth with wings folded at rest. Photograph by Jessi Raubenolt.
Corn Earworm moth map
June 27 – July 3, 2022
Figure 2. Average corn earworm (CEW) moths captured from June 27th through July 3rd. The large number indicates the average moth count for the week and the small number in parentheses is the total traps set up in the county.
Western Bean Cutworm
We are in our second week of monitoring for Western bean cutworm (WBC) and numbers have remained low in all monitoring counties (Figure 3). Currently nine counties are reporting WBC moth catches, with all counties below an average of 2 moths per county. Western bean cutworm typically peaks in July, so we expect the averages to increase over the next 3 weeks.Western Bean Cutworm moth map
June 27 – July 3, 2022
Figure 3. Average western bean cutworm (WBC) moths captured from June 27th through July 3rd. The large number indicates the average moth count for the week and the small number in parentheses is the total traps set up in the county.
Fall Armyworm
Fall armyworm (FAW) moths (Figure 4A) are currently being monitored in four counties in Ohio: Clark, Madison, Van Wert and Wayne. While we do not expect the majority of FAW moths to arrive in Ohio until later this summer, we do plan to actively monitor a couple of traps around to state. Currently only Van Wert is report FAW moth catches (Figure 5). However, there have been several moths reported in the bucket traps as by-catch. This moth can be identified as the Phragmites Wainscot and has a dark bar in in the scales of the forewing (Figure 4B). Monitoring for FAW in additional counties will begin in August.
Figure 4. (A) Fall armyworm (FAW) adult moth. Photo by: Lyle Buss, University of Florida, Bugwood.org. (B) By-catch, Phragmites Wainscot (Leucania phragmitidicola) being found in FAW bucket traps. Photo by Jessi Raubenolt, The Ohio State University.
Fall Armyworm moth map
June 27 – July 3, 2022
Figure 5. Average fall armyworm (FAW) moths captured from June 27th through July 3rd. The large number indicates the average moth count for the week and the small number in parentheses is the total traps set up in the county.
European Corn Borer
There are currently no reports of European corn borer in any of the monitoring counties (Figure 6).European Corn Borer moth map
June 27 – July 3, 2022
Figure 6. Average European corn borer (ECB) moths captured from June 27th to July 3rd. The first number indicates the average ECB-IA followed by a comma and then the average ECB-NY moth count for the week. The small number in parentheses is the total traps for each species set in each county.
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Weather Update: A Dry Trend, Interrupted?
Summary
After a wet spring, June took a turn toward much drier conditions. Figure 1 shows that a large swath of the state only received 50-75% of normal precipitation, despite derechos and numerous pop-up thunderstorms throughout the month. Though locations around the state set both daytime maximum and nighttime warmth records, we also experienced several cool mornings due to dry conditions. This left the state running about 1-2°F above average for the month. The recent dry conditions have led to rapid drying of soils with reports of cracking, lawns turning brown, and crop stress including rolled corn and slow growth of soybeans. For the latest up-to-date conditions, seasonal outlooks, and monthly climate summaries, please visit the State Climate Office of Ohio.
Forecast
A ridge of high pressure has set up to our southwest. This will leave Ohio in northwesterly flow on the northeast side of this high pressure. Temperatures will start out close to 90°F before cooling off into the mid-80s later in the week. Humidity will run high all week. Clusters of showers and storms will traverse the region, much like Monday, bringing repeated rounds of beneficial rain across the region. While the exact timing and location of each cluster is unknown far in advance, rainfall will add up over the course of the week. The Weather Prediction Center is forecasting a large area of 1.5-3.0”, lesser amounts in the far northeastern counties over the next 7 days (Figure 2).
The Climate Prediction Center’s 6–10-day outlook for the period of July 11 - 15, 2022 and the 16-Day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center show average temperatures and precipitation are expected (Figure 3). Climate averages are nearing their annual peak during this period include a high-temperature range of 83-87°F, a low-temperature range of 62-66°F, and average weekly total precipitation of 0.85-0.90 inches.
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Agronomy 101 Field Day
OSU Extension Darke County is proud to announce our Agronomy 101 Field Day in partnership with Rob See Co and Hatfield Seed Supply! This field day will cover Tar Spot Management with Marian Luis and Maira Rodriquez Duffeck, Postdocs in the Cereal Plant Pathology Lab, Soybean Disease Management with Horacio Lopez-Nicora, Soybean Pathology Specialist, Tillage Decisions with Stephanie Karhoff Agronomic Field Specialist, and 2022 Corn Management with Osler Ortez, our new Corn Specialist. The field day will be on July 27th from 9 a.m. to Noon on 3131 Drew Rd, Arcanum Ohio 45304, with lunch provided from our partners! Please RSVP by July 22 to the Darke County Extension office at 937-548-5215 or dill.138@osu.edu.
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Western ARS Weed and Agronomy Field Day, Wednesday July 13, 2022
The Western Agricultural Research Station Weed and Agronomy Field Day will be held July 13th. The station is planted but everything went in on the edge – as you saw it on your farm too. Hear our researchers’ thoughts and recommendations on how to manage this interesting season.
Held at the OSU Western Agricultural Research Station at 7721 South Charleston Pike, South Charleston (https://oardc.osu.edu/facility/western-agricultural-research-station)
Registration begins at 8:30 a.m. and the event will start promptly at 9:00 a.m.
Topics planned, subject to change with the concerns and problems of the growing season:
- 9:00 Alternative Crops – Alyssa Essman,
- Hemp, Sunflowers – Alyssa Essman, Jim Jasinski, and Horacio Lopez-Nicora
- 10:00 Cover Crops and Early Plant Soybeans?
- Rye Cover Crop and Soybean Plant Date Interaction – Laura Lindsey
- 11:00 Pesky Weeds!
- Cover Crops on Weed Control – Alyssa Essman
- Weed Control Strategies – Mark Loux
- 12:00 Lunch
- Rudy’s BBQ
- 1:00 Soybean Yield Robbers
- Soybean Diseases and Cyst nematode – Horacio Lopez-Nicora
- 2:00 Are Corn Diseases on the Rise This Season?
- Corn Disease Challenges – Pierce Paul
Cost is free and is open to the public; lunch provided. Please RSVP to Joe Davlin at 937-462-8016, or davlin.1@osu.edu or Mark Loux loux.1@osu.edu by July 11, 2022.
- 9:00 Alternative Crops – Alyssa Essman,
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Spray Drone Field Day Date Change!
The spray drone business started booming in Western Ohio suddenly this season and there are many new things to learn with this technology for researchers, extension, and producers. Darke County in particular has had a couple of custom application businesses start in the last few months, offering custom applications for fungicides, cover crops, and some emergency burndown. OSU Extension Darke County is hosting a short Spray Drone Field Day on July 9th from 11 a.m. to 1 p.m. at the County Farm by the Sheriff’s Office in Greenville Ohio. The spray drone demo will be done by Knapke Ag LLC. This is new local business started by a pair of brothers out of Bradford providing custom drone services. Dr. John Fulton, Precision Ag Specialist, will be speaking on this new technology. Lunch will be provided thanks to Farm Credit and will be Winner’s pork tenderloin, grilled by Dudley Lipps. To RSVP for a headcount for a meal please contact Taylor Dill at 937-569-5000 or dill.138@osu.edu.
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Application of Manure to Double Crop Soybeans to Encourage Emergence
Wheat harvest is mostly done in the state and some farmers are planting double-crop soybeans. The summer manure application window following wheat harvest is typically the 2nd largest application window each year. In recent years there has been more interest from livestock producers in applying manure to newly planted soybeans to provide moisture to help get the crop to emerge.
Both swine and dairy manure can be used to add moisture to newly planted soybean fields. It’s important that the soybeans were properly covered with soil when planted to keep a barrier between the salt and nitrogen in the manure and the germinating soybean seed. It is also important that livestock producers know their soil phosphorus levels, and the phosphorus in the manure being applied, so soil phosphorus levels are kept in an acceptable range.
An acre-inch of water is 27,154 gallons. The application of 10,000 gallons per acre of dairy manure would be about 0.37 inches of moisture. The application of 7,000 gallons of swine manure would be about 0.26 inches of moisture. While we strongly encourage the incorporation of livestock manure whenever possible, the use of manure to help with double-crop soybean emergence does not really allow for incorporation.
If soybeans are just out of the ground, swine finishing manure will kill the emerged plants. We applied swine finishing manure to early V3 soybeans at the Hoytville OARDC research farm the past three years and while the manure did not kill the soybeans, there was significant leaf burning. Swine nursery manure and sow manure are unlikely to kill emerged soybeans.
If manure is incorporated prior to planting double-crop soybeans be sure the manure salt and nitrogen is not placed in the planting zone. Placing the manure in contact with germinating seeds can result in severe emergence problems.
If red clover was frost seeded in the wheat, young clover is easy to kill with a summer manure application. Livestock producers have told me stories of accidentally killing clover stands when applying manure to wheat stubble just after wheat harvest.
As always, print out the weather forecast when surface applying manure. Remember the “not greater than 50% chance of 0.5 inches of rainfall in the next 24 hours” rule in the Western Lake Erie Basin.
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Wheat Harvest Date Reminders
While many areas of Ohio have already successfully harvested wheat, there are fields that still need to be harvested. With rainfall this week, harvest may be delayed. Late harvest coupled with excessive rainfall means more time for late-season mold growth, mycotoxin accumulation, test weight reduction, and sprouting; all of which could result in poor overall grain quality. In 2018, we evaluated wheat harvested on June 29 (at 12% moisture content) and July 8 (at 14% moisture content). Grain moisture increased between June 29 and July 8 due to 0.58 inch of rainfall between the two harvest dates. When wheat harvest was delayed until July 8, yield decreased by 9 bu/acre, test weight decreased by 2.9 bu/acre, and DON level increased by 0.86 ppm. These reductions in yield and test weight and increase in DON are likely attributed to re-wetting of dry grain.
Test weight (grain weight per unit volume or grain density) is one of the grain quality traits most likely to be affected by harvest delay and wet conditions. Low test weights usually occur if grain is prevented from filling completely or maturing and drying naturally in the field. Rewetting of grain in the field after maturity but prior to harvest is one of the main causes of reduced test weight. When grain is rewetted, the germination process begins, causing photosynthates (i.e., starch) to be digested. This leaves small voids inside the grain which decreases test weight. Additionally, grain will swell each time it is rewetted and may not return to its original size as it dries which will also reduce test weight. Thus, the enlarge kernels will take more space but weigh the same, allowing fewer kernels to pack in the measuring container, lowering the test weight.
Rain and harvest delay may also lead to pre-harvest sprouting in some varieties. Sprouting is characterized by the swelling of kernels, splitting of seed coats, and germination of seeds (emergence of roots and shoots) within the wheat heads. Some varieties are more tolerant to sprouting than other, and for a given variety, sprouting may vary from one field to another depending on the duration of warm, wet conditions. Sprouting affects grain quality (test weight). Once moisture is taken up by mature grain, stored reserves (sugars especially) are converted and used up for germination, which leads to reduced test weights. Even before visual signs of sprouting are evident, sugars are converted, and grain quality is reduced. Since varieties differ in their ability to take up water, their drying rate, the rate at which sugars are used up, and embryo dormancy (resistance to germination), grain quality reduction will vary from one variety to another.
In addition to sprouting, the growth of mold is another problem that may result from rain-related harvest delay. To fungi, mature wheat heads are nothing more than dead plant tissue ready to be colonized. Under warm, wet conditions, saprophytic fungi (and even fungi known to cause diseases such as wheat scab) readily colonize wheat heads, resulting in a dark moldy cast being formed over the heads and straw. This problem is particularly severe on lodged wheat. In general, the growth of blackish saprophytic molds on the surface of the grain usually does not affect the grain. However, the growth of pathogens, usually whitish or pinkish mold, could result in low test weights and poor overall grain quality. In particular, in those fields with head scab, vomitoxin may build-up to higher levels in the grain, leading to further grain quality reduction and dockage. While vomitoxin contamination is generally higher in fields with high levels of wheat scab, it is not uncommon to find above 2 ppm vomitoxin in late-harvested fields that have been exposed to excessive moisture. Even in the absence of visual scab symptoms, the fungi that produce vomitoxin may still colonize grain and produce toxins if harvest is delayed.
To minimize grain quality losses, it is best to harvest wheat on the first dry-down. Harvesting at a slightly higher moisture level (18% for example) may also be useful for minimizing quality losses, particularly those associated sprouting and mold growth due to rainfall and harvest delay. However, if grain is harvested at moisture above 15%, it should be dried down below 15% before storage to minimize mold growth and mycotoxins in storage.
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Soybean Progress and Flowering Growth Stage
Currently, most soybean fields in Ohio are at the flowering growth stage (R1-R2). (Some late-planted or re-planted soybean may still be at a vegetative stage.) Even as soybean plants begin to flower, they may only have 3-5 trifoliolates due to late planting and wet weather followed by dry conditions. However, even if plants have flowers and only a few trifoliolates, the plant will continue to add leaf area up to the R5 growth stage, which comes 4-6 weeks later. As long as the canopy is complete by the beginning of seed filling, the plant has the potential to reach full yield potential.
What does the soybean crop need to maximize yield during the flowering growth stage? While adequate soybean flowers are needed for subsequent reproductive development, soybeans are amazingly resilient to stress during flowering due to their ability to continue to develop flowers over several weeks. Flowering marks the beginning of rapid dry weight and nutrient accumulation rates. Therefore, duration of light interception and thermal energy/heat unit accumulation provide the potential for flower and pod retention and seed fill.
Misconceptions at the R1-R2 growth stage: There are several common misconceptions about soybean plants at the flowering growth stage.
Misconception
Reality
Compared to normal-sized plants, short, compact plants often produce more pods and higher yields.
Short plants can produce high yield, but if dry soils or low plant populations limit plant height, pod numbers, and canopy cover, yields will usually be lower.
Throughout the growing season, all soybean plants in a field should be uniform in size, weight and pod number; if they aren’t, yield will be lower.
Soybean plants grown at normal plant populations always develop a great deal of variability in size and pod numbers, even if they are uniform early in the season. Reasons for this are not well-understood, but larger plants adjust to compensate for smaller ones, and there is no indication that this causes lower yields. Smaller soybean plants do not act ‘weedy’- lower yields of larger plants- in a full stand.
Flower abortion reduces yield.
Soybean naturally aborts 20-80% of its flowers. Soybean produces many more flowers over a long period of time than can be supported by the plant as a mechanism to avoid the impact of short periods of stress.
Sugar can be applied to produce more flowers.
It has been proposed in the past that foliar applications of sugar can make the plant set more flowers; however, this is not the case
For more information on soybean flowering, see this Science for Success video featuring my colleague Dr. Shaun Casteel from Purdue University: https://www.youtube.com/watch?v=oYqNNqsz_zU and also this Science for Success FactSheet: https://soybeanresearchinfo.com/wp-content/uploads/2022/01/Science-for-Success-Soybean-Growth-Stages-V3.pdf
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
Contributors
Disclaimer
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