C.O.R.N. Newsletter: 2021-22
Soybean Defoliation: It Takes a lot to Really Matter!
The mid-season defoliators are beginning to show up in soybean fields across Ohio. These defoliators include first generation bean leaf beetles, Japanese beetles, grasshopper nymphs and several different caterpillars such as silver-spotted skippers, painted-lady butterflies and green cloverworms. Since all of these insects collectively add to the defoliation of soybeans, their collective feeding is used in the threshold to determine the need for an insecticide treatment, but it takes a lot of feeding to add up to significant damage. It often looks worse than what it truly is.
When scouting soybean fields to assess levels of damage, it is important not to let one’s eye and mind over estimate what is truly there. Japanese beetles and grasshoppers tend to hit edges of fields first before they start moving farther into the centers of the fields. And Japanese beetles tend to feed in aggregations and at the tops of plants producing a startling appearance that easily catches one’s eye standing at the edge of a field looking in. It is imperative to assess the whole field and the entire plant from top to bottom to get a true picture of defoliation levels. It is very rare that we reach economic levels of defoliation here in Ohio.
A rescue treatment is advised when defoliation levels reach 40% in pre-bloom stages, 15% in bloom, and 25% during pod fill to harvest. These defoliation levels apply to the plant as a whole, not just certain leaves. Damage is often worst at the top of the canopy but on closer examination most of the plant is relatively unharmed. Make your decision based on the average condition of whole plants, not a scan of the top canopy. Also, defoliation tends to be worse on field edges, so make your assessment based on the field as a whole, including interior.
Later in the growing season, we will have to watch for pod injury from bean leaf beetle and grasshoppers. A different set of rules apply when dealing with pod injury.
A visual guide to defoliation is useful because it is very easy to over-estimate defoliation in soybean. Whether it is one species of foliage-feeding insect or several foliage-feeding insects present in soybean the same percent defoliation guidelines can be used for all of them collectively.
For more information about soybean defoliating insects visit our OSU Extension Entomology factsheet at:
To help train yourself about estimating soybean defoliation, look at the following soybean defoliation estimation exercise:
Tar Spot Showing Early this Year: a Note on DiagnosisAuthor(s): Pierce Paul
I have so far only received one confirmed report of Tar Spot in the state, but the fact that the disease has been reported in a few neighboring states has some stakeholders asking questions about diagnosis and management. Tar Spot is a relatively easy disease to diagnose. As the name suggests, it usually shows up as raised, black spots, primarily on the leaf blast. The size of the spots may vary, but they all have a very similar appearance – raised, circular-to-irregularly shaped, black spots. However, is you do have trouble with diagnosis, please feel free to send me images and samples (1680 Madison Ave, Wooster, OH 44691).
This is the earliest we have seen Tar Spot in the state since it was first reported in 2018. Results from studies out west suggest that yield losses due to Tar Spot tends to be highest when it develops and spreads before tasseling (VT) on susceptible hybrids. Warm, wet, and humid conditions seem to favor the development and spread of Tar Spot, so keep your eyes on the weather, and watch the progress of the disease. If it continues to spread, a fungicide application may be warranted, but efficacy of fungicides against Tar Spot is still being investigated. Find more details on Tar Spot at: https://crop-protection-network.s3.amazonaws.com/publications/tar-spot-filename-2019-03-25-120313.pdf.
Pre-harvest Sprouting and Falling Number
Persistent rainfall over the last several days has prevented some wheat fields from being harvested. This could lead to pre-harvest sprouting and other grain quality issues. However, the extent to which sprouting occurs will depend on the variety and how long the grain is exposed to warm, wet conditions before it is harvested. For instance, white wheats tend to be more susceptible to pre-harvest sprouting than the red wheats commonly grown here in Ohio. As a result, the level of sprouting will vary from one field to another. Sprouting is a trail that negatively affects grain quality. It actually is premature germination of the grain while it is still in the heads in the field. This process is driven by enzymes, including α amylase, and the activity of this enzyme can be measured to determine how bad pre-harvest sprouting it. See: https://agcrops.osu.edu/newsletter/corn-newsletter/22-2021/late-wheat-harvest-and-grain-quality-concerns for more on delayed grain harvest and grain quality.
Falling number (FN in seconds) is a widely accepted measure of pre-harvest sprouting damage. The higher the FN, the lower the level of sprouting. As a guide an FN ≥ 300 sec would indicate that the grain is not sprouted, 200 ≤ FN < 300 sec would be indicative of some sprouting, 62 < FN < 200 would indicate that the grain is severely sprouted, and FN = 62 would mean that the grain is extremely sprouted. However, PLEASE NOTE that the specific numbers and ranges will depend on the equipment used to measure FN, and what the numbers mean in terms of utilization of the grain, depends on the intended end use. So, a grain buyer has some freedom to determine what he or she would consider to be an acceptable FN.
Falling number measures the time (in seconds) it takes for a weighted plunger to fall through a suspension of heated flour paste. In other words, it measures the thickness (viscosity) of the heated flour paste made from the grain being tested. Flour paste made from badly sprouted grain is thinner (less viscous) than paste made from healthy, unsprouted grain. As a result, the plunger taking less time to fall through the flour paste from sprouted grain, hence the lower falling number.
Nutrient Value of Wheat Straw
Before removing straw from the field, it is important farmers understand the nutrient value. The nutrient value of wheat straw is influenced by several factors including weather, variety, and cultural practices. Thus, the most accurate values require sending a sample of the straw to an analytical laboratory. However, “book values” can be used to estimate the nutrient values of wheat straw. In previous newsletters, we reported that typically a ton of wheat straw would provide approximately 11 pounds of N, 3 pounds of P2O5, and 20 pounds of K2O.
The nitrogen in wheat straw will not immediately be available for plant uptake. The nitrogen will need to be converted by microorganisms to ammonium and nitrate (a process called “mineralization”). Once the nitrogen is in the ammonium or nitrate form, it is available for plant uptake. The rate of which mineralization occurs depends on the amount of carbon and nitrogen in the straw (C:N ratio). The USDA reports a C:N ratio of 80:1 for wheat straw which means there are 80 units of carbon for every unit of nitrogen. Mineralization rapidly occurs when the C:N ratio is ≤ 20:1. At a C:N ratio of 80:1, mineralization will be much slower. (For comparison, corn stover is reported to have a C:N ratio of 57:1.) Rate of mineralization is also influenced by soil moisture and temperature. Since mineralization is a microbial-driven process, mineralization will be slowed (halted) in the winter when temperatures are cold. Thus, no N credit is given for wheat straw since it is not known when the N will mineralize and become available to the following crop.
In addition to nitrogen, removal of straw does lower soil potassium levels. If straw is removed after heavy rainfall, some of the potassium may have leached out of the straw, lowering the nutrient value. However, a soil test should be done to accurately estimate nutrient availability for future crops. Besides providing nutrients, straw has value as organic matter, but it is difficult to determine the dollar value for it.
Steps to Speed up Field Curing of Hay Crops
The rainy weather in many regions of Ohio and surrounding states is making it difficult to harvest hay crops. We usually wait for a clear forecast before cutting hay, and with good reason because hay does not dry in the rain! Cutting hay is certainly a gamble but waiting for the perfect stretch of weather can end up costing us through large reductions in forage quality as the crop matures.
As we keep waiting for perfect haymaking weather, we will reach the point where the drop in quality becomes so great that the hay has little feeding value left. In such cases, it may be better to gamble more on the weather just to get the old crop off and a new one started. Some rain damage is not going to reduce the value much in that very mature forage.
Before cutting though, keep in mind that the soil should be firm enough to support equipment. Compaction damage has long-lasting effects on hay crops. We’ve seen many fields where stand loss in wheel tracks led to lower forage yields, weed invasion, and frustrating attempts to “fill in” the stand later.
This article summarizes proven techniques that can help speed up the process involved in storing good quality forage. While the weather limits how far we can push the limits, these techniques can help us improve the chances of success in those short windows of opportunity between rains, and hopefully avoid overly mature stored forages.
Haylage vs. Hay
Consider making haylage/silage or baleage instead of dry hay. Haylage is preserved at higher moisture contents, so it is a lot easier and quicker to get it to a proper dry matter content for safe preservation compared with dry hay. Proper dry matter content for chopping haylage or wrapping baleage can often be achieved within 24 hours or less as compared with 3 to 5 days for dry hay.
“Hay in a day” is possible when making hay crop silage. The forage is mowed first thing in the morning and laid in wide swaths to be raked in the late afternoon and chopped as haylage starting in early evening. Proper dry matter content for haylage ranges from 30 to 50% (50 to 70% moisture) depending on the structure used.
Wrapped baleage usually requires 24 hours to cure. Wrapped baleage should be dried to 40 to 55% dry matter (45 to 60% moisture).
Dry hay should be baled at 80 to 85% dry matter (15 to 20% moisture), depending on the size of the bale package. The larger and the denser the dry hay package, the drier it must be to avoid spoilage. For example, safe baling moistures for dry hay without preservatives are 18-20% for small square bales (80 to 82% dry matter), 18% or less for large round bales, and less than 17% for large square bales. See below for more information on baling with preservatives.
Mechanically Condition the Forage
Faster drying of cut forage begins with using a well-adjusted mower-conditioner to cause crimping/cracking of the stem (roller conditioners) or abrasion to the stems (impeller conditioners). Adjust roller conditioners so at least 90% of the stems are either cracked or crimped (roller conditioners) or show some mechanical abrasion (impeller conditioners).
Some excellent guidelines for adjusting these mower conditioners can be found in an article by Dr. Ronald Schuler of the University of Wisconsin, available online at https://fyi.extension.wisc.edu/forage/adjusting-the-conditioning-system-....
Desiccants are chemicals applied when mowing the crop that increase the drying rate. The most effective desiccants contain potassium carbonate or sodium carbonate. They are more effective on legumes than grasses and most useful for making hay rather than silage or baleage. Desiccants work best under good drying conditions. They do not help increase drying rate when conditions are humid, damp, and cloudy, such as we have often experienced this summer. Consider the weather conditions before applying them.
Maximize exposure to sunlight
I once heard someone say "You can’t dry your laundry in a pile, so why do you expect to dry hay that way?"
Exposure to the sun is the single most important weather factor to speed drying. The trick is to expose to sunshine as much of the cut forage as possible.
The swath width should be about 70% of the actual cut area. The mowers on the market vary in how wide a windrow they can make, but even those that make narrow windrows have been modified to spread the windrow wider. Details can be found in articles at the Univ. of Wisconsin website mentioned above (see especially “Getting the Most from the Mower Conditioner” by Kevin Shinners, https://fyi.extension.wisc.edu/forage/getting-the-most-from-the-mower-conditioner/).
Another way to spread out and aerate the crop for faster drying is with a tedder. Tedders are especially effective with grass crops. They can cause excessive leaf loss in legumes if used when the leaves are dry. Tedders can be a good option when the ground is damp, because the crop can be mowed into narrow windrows to allow more ground exposure to sunlight for a short time, and then once the soil has dried a bit the crop can be spread out with the tedder. Tedding twice may decrease drying time. Tedding shortly after mowing allows 100% ground coverage, then tedding the next day helps keep the crop off the ground. Be cautious to set tedder properly so that dirt is not incorporated into the hay but all hay is lifted off the ground.
Take precautions to follow manufacturer recommendations on ground speed and RPM’s when tedding. Many of the modern in-line “fluffer” type tedders are ground driven and operators often exceed recommended speeds, which can result in bunching and wrapping of the hay, which will increase drying time and make raking more difficult.
When making haylage, if drying conditions are good, rake multiple wide swaths into a windrow just before chopping. For hay, if drying conditions are good, merge or rake multiple wide swaths into a windrow the next morning when the forage is 40 to 60% moisture to avoid excessive leaf loss.
Research studies and experience have proven that drying forage in wide swaths can significantly speed up drying. Faster drying in wide swaths results in less chance of rain damage and studies by the University of Wisconsin showed that wide swaths (72% of the cut width) result in lower neutral detergent fiber (NDF) and higher energy in the stored forage.
Sometimes the rain just comes quicker than we have time for making dry hay. As mentioned above, making haylage helps us preserve good quality forage in those short rain-free windows. A second option is to use a preservative. The most effective preservatives are based on proprionic acid, which is caustic to equipment, but many buffered proprionic preservatives are available that minimize that problem.
Preservatives inhibit mold growth and allow safe baling at moisture contents a little higher than the normal range for dry hay. Carefully follow the preservative manufacturer’s directions and application rates for the hay moisture content at baling. Be sure the application is uniform to avoid spots that spoil. Most products are effective when hay moisture is less than 25% but become iffy between 25-30% and do not work if moisture is over 30%. When utilizing preservatives, safe baling moisture can go up to 26% on small squares and round bales, but only 23% on large squares, according to label guidelines on most proprionic acid based products. Baling at these moistures requires properly calibrated equipment to apply the correct amounts of preservative, and it does not guarantee that bales will not generate internal heat.
While the acid works to limit the production of mold and fungal spores that can lead to additional heating, any type of bale made over 20% moisture always has the potential to heat. Although mold production may be limited, discoloration and carmelization of the higher moisture stems can still occur. This heating can also degrade proteins in the hay, reducing overall feed quality despite still helping to preserving the hay from spoilage and hopefully making it safe to store indoors. Keep in mind that preservative treated hay should be fed within a year or less, as the preservative effect will wear off over time.
If baling on the wet side, watch those bales carefully! If hay is baled at higher moisture contents that are pushing the safe limits, keep a close watch on them for two to three weeks. Use a hay temperature probe and monitor the internal temperature of the hay during the first three weeks after baling. See the following article for more information on monitoring wet hay: https://agcrops.osu.edu/newsletter/corn-newsletter/15-2021/hay-barn-fires-are-real-hazard
Late Wheat Harvest and Grain Quality Concerns
Most of the winter wheat in Ohio has been harvested. However, persistent wet weather has delayed harvest in some areas of the state. 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 a previous CORN newsletter article, we summarized some of our wheat harvest date research: https://agcrops.osu.edu/newsletter/corn-newsletter/18-2021/don%E2%80%99t-delay-wheat-harvest
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 enlarged 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.
Western Bean Cutworm Numbers Begin to Increase Across OhioAuthor(s): Amy Raudenbush, Suranga Basnagala , Aaron Wilson, Olivia Lang, Kyle Akred, , Mark Badertscher, , Frank Becker, Lee Beers, CCA, Bruce Clevenger, CCA, Tom Dehaas, Taylor Dill, Nick Eckel, Allen Gahler, Jamie Hampton, Andrew Holden, James Jasinski, Stephanie Karhoff, CCA, Alan Leininger, Ed Lentz, CCA, Cecilia Lokai-Minnich, David Marrison, Jess McWatters, Sarah Noggle, Les Ober, CCA, Maggie Pollard, Eric Richer, CCA, Beth Scheckelhoff, Clint Schroeder, Mike Sunderman, Curtis Young, CCA, Chris Zoller, Andy Michel, Kelley Tilmon
Western bean cutworm (WBC) numbers for the week ending July 11 have increased to the point where scouting for egg masses is recommended in Fulton, Henry, Lorain and Lucas counties. Traps were monitored from July 5 – 11 and resulted in a statewide average of 3.9 average moths per trap, though higher in the counties noted; Figure 1).
We used growing degree day calculations to predict approximate percentage of adult WBC flight as of Sunday July 11th (Figure 2). At this time, the majority of counties in NW Ohio are seeing approximately 25% adult flight, whereas counties in central and NE Ohio remain at 10%. Once GDD numbers accumulate to 2704, approximately 50% of WBC flight will have occurred. For more information on calculating GDD and WBC please see the following article: https://cropwatch.unl.edu/2021/degree-days-prediction-western-bean-cutworm-flight
Counties with adult WBC trap counts averaging 7 or more moths per week should begin scouting for WBC egg masses in corn fields that are pre-tassel approaching tassel. Freshly laid egg masses are white and turn a purplish color as they mature (Figure 3), close to hatch. To scout, randomly choose at least 20 consecutive plants in 5 locations within a field (a total of 100 plants per field). Inspect 3–4 leaves on the uppermost portion of the corn plant. It is very useful to look at leaves with the sun behind them – often the shadow of the egg mass will reveal it without having to examine the leaf closely. Field corn should be treated with a foliar treatment if more than 5 % of inspected plants have eggs or larvae. Sweet corn should be treated if more than 4 % of inspected plants have eggs or larvae (processing market), or 1 % of plants (fresh-market). For more scouting information, view our WBC scouting video https://aginsects.osu.edu/news/western-bean-cutworm-video
If the number of egg masses/larvae exceed the threshold mentioned above, foliar applications of insecticides are available, especially those containing a pyrethroid. Timing an insecticide application is critical and must happen before the caterpillar enters the ear, but after the eggs hatch. If the eggs have hatched, applications should be made after 95% of the field has tassels. If the eggs have not hatched, monitor the egg masses for the color change. Newly laid egg masses will be white but turn purple as they mature. Hatch will occur within 24–48 hours once eggs turn purple.
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.
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