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Corn Newsletter : 2019-27
Frogeye Leaf Spot - Is It Worth Spraying in 2019?Author(s): Anne Dorrance
Several reports over the last two weeks of heavy frogeye leaf spot pressure in some fields as well as low to moderate pressure in others. This disease will continue to increase and infect new foliage as it develops on these late planted soybeans. Based on our previous research, only once (2018) in 14 years of studies did applications at the soybean growth stage R5 contribute to preserved yield. At the R5, the leaf at the terminal is fully developed and the pods at any one of the top four nodes is fully expanded, but the seeds are just beginning to expand.
Soybeans that have frogeye and have just begun to flower, are at full flower, or have just reached the R3 growth stage, these decisions are going to be challenging. In full disclosure, we don’t have data or examples to rely on here. This late planting and late development is all new territory for all of us. But there are some sound principles to rely on.
For soybeans that are in the R3 growth stage, pods are tiny, 3/16 of an inch at one of the four uppermost nodes of the plant. This is the time if frogeye leaf spot can easily be found in the canopy, a lesion on one plant every 40’ has in our studies, preserved yield in a normal growing season. This growth stage in Ohio typically occurs in mid to late July on May planted soybeans.
So here are the questions to address for 2019 and in the order of importance.
- The value of the crop – are these soybeans grown for seed, then yes error on the side of caution and apply the fungicide and make a second application 14 days later.
- Are these soybeans under contract, and will you actually be able to sell them? If the answer is no, then adding more inputs into the crop may not be a sound investment.
- Will the soybean finish making grain before harvest? This question will most likely affect soybeans that are just now in full flower, we are hoping for a very long fall, but this will impact the return on applying the fungicide.
- How susceptible is the variety? For some resistant varieties, the frogeye leaf spots are small and only a few will form on each leaf. So double check with your seed supplier to look at the ratings. In any event your seed dealer will want to watch this variety and work with their breeders.
If you do decide to spray, please leave unsprayed check strips – at least 3 separate locations in the field and collect the yield off each of these separately, the same is true for the fungicides sprayed strips, collect the data from these as well. The yield maps will be especially important this year. Secondly, choose the cheapest triazole fungicide that you can find. This is going to be very important for the economic viability of this year’s crop. Also remember, we have detected QoI resistance in Ohio, and it is not advisable to spray these types of fungicides at these late dates on crops that are further behind in development.
If you don’t spray, and it is a highly susceptible variety, the disease will continue to increase on the plants, but only if periodic rains and heavy dews or fogs continue through the remainder of this crazy field season. Mark this field and this variety. These are important considerations for 2020 field season as this disease does now overwinter in Ohio. Replanting in the same field with the same variety or one that is susceptible to this disease is a recipe for further yield loss in the future.
Corn Earworm in Field Corn; Watch for Molds
There have been recent reports of high corn earworm populations in certain grain corn fields. Corn earworm is a pest with many hosts including corn, tomatoes and certain legumes. In Ohio it is typically considered a pest of sweet corn rather than field corn, but this past week substantial populations have been found in certain field corn sites. Corn earworm moths are most attracted to fields in the early green silk stage as a place to lay their eggs. These eggs hatch into the caterpillars that cause ear-feeding damage, open the ear to molds, and attract birds. With a wide range of planting dates this year, different fields may be at greater risk at different times.
It is open to debate how well corn earworm can overwinter in most parts of Ohio, and the majority of our population probably immigrates each summer from more southern states. Weather fronts from the south can help carry influxes of moths our way. Compounding the problem, many of these southern moths are resistant to some of the Bt hybrids used against them in the past. Dr. Celeste Welty, OSU vegetable entomologist, maintains a trapping network for corn earworm in sweet corn which can be found here:
Corn earworms are damaging as caterpillars laid by moths in the silks near the developing ear tip, and are all but impossible to find by scouting. They vary quite a bit in color – with individuals that are dark brown, brown, tan, green, or even pinkish. Typically only one caterpillar is found per ear but in heavy infestations more may be found. They enter corn ears at the tips where the majority of feeding occurs. This also opens the corn ear up to the potential development of ear rots. Unlike western bean cutworm caterpillars, corn earworm caterpillars do not spend any time out on the plant surface before migrating to the ears – they are protected in the ear structure from the beginning and so insecticide application does little good against the caterpillars. When corn earworm moths are immigrating, sweet corn growers rely on frequent sprays to kill adult moths, which is not economical in field corn.
The Bt protein Vip3A (in Viptera) is still deemed effective against corn earworm. For a current infestation in field corn, because chemical control is ineffective, the scouting emphasis should be on assessing mold and disease levels in infested corn.
Feeding sites or exit holes when the caterpillar matures and leaves the ear leave holes in the corn husk, which provide a potential entry wound for pathogens like Fusarium and Gibberella. Some of these organisms can then be a further source for mycotoxins, including Fumonisins and deoxynivalenol, also known as vomitoxin. In some cases, damaged kernels will likely be colonized by opportunistic molds, meaning that the mold-causing fungi are just there because they gain easy access to the grain. However, in other cases, damaged ears may be colonized by fungi such as Fusarium, Gibberella and Aspergillus that produce harmful mycotoxins. Some molds that are associated with mycotoxins are easy to detect based on the color of the damaged areas. For instance reddish or pinkish molds are often cause by Gibberella zeae, a fungus know to be associated with several toxins, including vomitoxin. On the other hand, greenish molds may be caused by Aspergillus, which is known to be associated with aflatoxins, but not all green molds are caused by Aspergillus. The same can be said for whitish mold growth, some, but not all are caused by mycotoxin-producing fungi.
So, since it is not always easy to tell which mold is associated with which fungus or which fungus produces mycotoxins, the safe thing to do is to avoid feeding moldy grain to livestock. Mycotoxins are harmful to animals – some animals are more sensitive to vomitoxin while others are more sensitive to Fumonisins, but it is quite possible for multiple toxins to be present in those damaged ears. If you have damaged ears and moldy grain, get it tested for mycotoxins before feeding to livestock, and if you absolutely have to use moldy grain, make sure it does not make up more than the recommended limit for the toxin detected and the animal being fed. These links provides more information on ear molds and mycotoxin contamination and identification:
Assessing The Risk of Frost Injury to Late Planted CornAuthor(s): Peter Thomison
Lately I have received questions as to whether corn at various stages of development, especially the blister (R2) and dough stage (R3) stages, will mature before the 50% average frost date. According to the National Agricultural Statistics Service, as of August 18, 37 percent of Ohio’s corn acreage was in the dough stage (R4) compared to 70 percent for the five year average, and three percent of the corn acreage was in the dent stage (R5) compared to 21 percent for the five-year average. Many areas of the state corn are considerably behind the five-year average because of late planting. Late maturation of the corn crop had led to questions about the likelihood for frost damage and whether more fuel will be needed to dry corn.
Physiological maturity (R6), when kernels have obtained maximum dry weight and black layer has formed, typically occurs about 65 days after silking. At physiological maturity (kernel moisture approximately 30-35%), frosts have little or no effect on the yield potential of the corn crop.
Dr. Bob Nielsen has summarized research findings from Purdue University and Ohio State University that provide insight into both the calendar days and thermal time (growing degree days, GDDs) typically required for grain at various stages of development to achieve physiological maturity (kernel black layer, R6). This research was conducted at two locations in Indiana (west central and southeast) and two locations in Ohio (northwest and southwest) with three hybrids representing 97, 105, and 111-day relative maturities planted in early May, late May, and mid-June. The calendar days and thermal time from silking to black layer for the 111-day hybrid maturity are shown in Table 1 from http://www.agry.purdue.edu/ext/corn/news/timeless/RStagePrediction.html. The calendar days and thermal time from silking to black layer for the 97-day hybrid and 105 maturity are also available from this Purdue webpage.
The study indicated that corn planted in mid-June compared to early May requires 200 to 300 fewer GDDs to achieve physiological maturity. According to Dr. Nielsen, while slightly different responses among the four locations of the trial existed, there did not seem to be a consistent north/south relationship. Therefore, growers can use the results summarized in the following table to "guesstimate" the number of calendar days or heat units necessary for a late-planted field at a given grain fill stage to mature safely prior to that killing fall freeze.
How many GDDs can be expected from now until an average date of a killing
frost for a 111-day hybrid planted in mid-June? To answer this question, estimate the expected GDD accumulation from Aug. 19 until the average frost date (50% probability) for different regions of the state (Table 2). These GDD expectations are based on 30-year historical normals reported by the Ohio Agricultural Statistics Service. The GDD accumulation was calculated using the 86/50 cutoff, base 50 method.
If you want to determine the "youngest stage of corn development" that can
safely reach black layer before the average frost date at a given weather
station, use the information in Table 2 on remaining GDDs in conjunction with
Table 1 which indicates GDDs needed to reach black layer at various
stages of grain fill. Compare "GDDs remaining" for the site with the GDDs
required to achieve black layer depending on the corn's developmental stage.
Table 2. Estimated GDDs remaining from Aug. 9 to the first fall frost for Ohio.
Median Frost Date
Estimated GDDs Remaining
From Aug. 19 to Fall Frost
Oct 10 – Oct 20
673 – 723
Oct 10 – Oct 25
656 – 741
Sept 30 – Oct 25
603 – 749
Oct 10 – Oct 15
716 – 773
Oct 5 – Oct 15
670 – 796
Sept 30 – Oct 15
645 – 763
Oct 10 – Oct 15
752 – 815
Oct 15 – Oct 20
841 – 893
Oct 5 – Oct 15
651 - 774
If your corn is in the milk stage (R3) as of Aug. 19, will it be safe from frost? Table 1 indicates that corn planted in mid - June required about 681 GDDs to reach black layer from R3 and Table 2 indicates that all regions of the state can accumulate that number of GDDs before the 50% frost date.
However, if your corn is in the blister stage (R2) as of Aug. 19, it might be a different story. The kernel development - GDD accumulation relationships in Table 1 indicate that corn planted in mid-June that is at R2 needs about 781 GDDs to reach black layer. Table 2 indicates that three regions of the state, South Central, Central, and Southwest, accumulate that number of GDDs before the 50% frost date. Several other regions, West Central, and Southeast, come close to accumulating this number whereas, the Northeast, Northwest, and North Central regions are least likely to accumulate the GDDs required to achieve physiological maturity.
The research results in Table 1 demonstrate that late-planted corn has the ability to adjust its maturity requirements, and most of this adjustment occurs during the late kernel development stages. In previous growing seasons when GDD accumulation was markedly less than normal, corn planted by mid-June has usually achieved physiological maturity before the first frost occurred.
Nielsen, R.L. 2011. Predicting Corn Grain Maturity Dates for Delayed Plantings
Corny News Network, Purdue Univ. [On-Line]. Available at
(url verified 8/18/2019)
Hot Night Temperatures Can Decrease Corn Yield
Night time temperatures can affect corn yield potential. High night temperatures (in the 70s or 80s degrees F) can result in wasteful respiration and a lower net amount of dry matter accumulation in plants. Past studies reveal that above-average night temperatures during grainfill can reduce corn yield by reducing kernel number and kernel weight. The rate of respiration of plants increases rapidly as the temperature increases, approximately doubling for each 13 degree F increase. With high night temperatures more of the sugars produced by photosynthesis during the day are lost; less is available to fill developing kernels, thereby lowering potential grain yield. High night time temperatures result in faster heat unit or growing degree day (GDD) accumulation that can lead to earlier corn maturation, whereas cool night temperatures result in slower GDD accumulation that can lengthen grain filling and promote greater dry matter accumulation and grain yields.
The Pioneer Insight article referenced below concludes….
“Although higher night temperatures undoubtedly increase the rate of respiration in corn, research generally suggests that accelerated phenological development is likely the primary mechanism affecting corn yield.”
Research at the University of Illinois conducted back in the 1960’s indicated that corn grown at night temperatures in the mid-60s (degrees F) out yielded corn grown at temperatures in the mid-80s (degrees F). Average corn yields are generally much higher with irrigation in western states, which have low humidity and limited rainfall. While these areas are characterized by hot sunny days, night temperatures are often cooler than in the Eastern Corn Belt. Low night temperatures during grain fill (which typically occurs in July and August) have been associated with some of our highest corn yields in Ohio. The cool night temperatures may have reduced respiration losses during grain fill and lengthened the rain fill period. Cooler than average night temperatures can also mitigate water stress and slow the development of foliar diseases and insect problems.
Hoeft, R.G., E. D. Nafziger, R.R. Johnson, and S.R. Aldrich. 2000. Modern Corn and Soybean Production. MCSP Publications, Champaign, IL. [see “Climate and Corn” section]
Lutt,N. M. Jeschke M. and S. D. Strachan. 2016. High Night Temperature Effects on Corn Yield. DuPont Pioneer Agronomy Sciences. Crop Insights, Vol. 26, No.16.
Peters, D.B., J.W. Pendleton, R.H. Hageman, and C.M. Brown. 1971. Effect of night air temperature on grain yield of corn, wheat, and soybeans. Agron. J. 63:809.
Harvest Management of Sorghum Forages
Many producers in Ohio have planted summer annual grasses this year to increase their low forage inventories. These include sudangrass, sorghum-sudangrass, forage sorghum, pearl millet, and teff grass. When should these grasses be harvested or grazed?
The general guidelines for harvesting or grazing these summer annual grasses as listed in the Ohio Agronomy Guide are shown in the table below.
Table 7-12: Harvest Information for Summer-Annual Grasses.
A recent research study sheds more light on these general recommendations, particularly in relation to mid-summer planting of the sorghum grasses. We planted a trail on July 19, 2019 near South Charleston, OH to evaluate the yield and fiber quality of a conventional sudangrass variety (hereafter designated “Normal”) and a sorghum-sudangrass hybrid carrying the BMR-6 gene for reduced lignin (hereafter designated “BMR”). Forage yield, neutral detergent fiber (NDF) concentration and NDF digestibility (NDFD) were measured on four dates after planting, with the forage being cut to a 4-inch stubble height at each harvest. The NDFD was measured after 30-hours of in vitro fermentation in rumen fluid plus buffer, followed by removal of microbial contaminants with neutral detergent solution.
The results were not surprising in that yield and NDF increased while NDFD decreased fairly sharply as the plants grew and matured (see figures below). There was a distinct advantage for the BMR hybrid over the non-BMR sudangrass variety (“Normal”) in terms of NDFD.
In general, diets can be formulated for different classes of livestock based on the fiber quality of the forage. For lactating cows using these forages, the amount of forage that can be fed will be limited by the NDF level. For example, if harvest was delayed in order to obtain highest forage yield, the NDF level was near 70%. At 70% NDF, the forage would probably have to be limited to 10% of the total diet of lactating dairy cows, on a dry matter basis.
For lactating cows, forage with NDFD levels of 50% are usually acceptable, and levels as low as 40% NDFD could probably work if necessary. However, higher producing herd or groups within herds are more sensitive to NDFD and require NDFD values greater than 50%. Based on these parameters, these grasses provided acceptable forage for lactating cow diets when harvested between 40 to 60 days after planting (30 to 50 inches tall). Heifer cow diets could utilize this forage harvested at about 60 days (50 inches tall).
Harvest of the BMR hybrid provided a longer window of acceptable forage. In this case, the forage could have been harvested almost to 80 days after planting (67 inches tall) and still be acceptable in a lactating or heifer cow diets. This provides opportunity for significantly greater forage yields.
Dry matter yield and total fiber (NDF) and 30-hour fiber digestibility (NDFD) of two varieties of summer annual grasses planted on July 19, 2013 near South Charleston, OH.
Forage having NDFD levels as low as 35 to 40% with high NDF levels are acceptable for dry cows or beef cattle provided they are part of a balanced diet and their mineral concentrations are not excessive relative to requirements. Based on the results shown above, the forage harvested from 60 to 80 days after planting (50 to 67 inches tall) would have been acceptable for dry cows or beef cattle.
The results from the experiment shown here agree fairly well with a study conducted by researchers at Cornell University (Kilcer et al., 2005), who concluded that BMR sorghum-sudangrass has a relatively large harvest window to produce forage for lactating cow diets. However, they recommended that BMR sorghum-sudangrass be harvested for lactating cows when stand heights are about 50 inches (2-cuts possible with early June planting) because this will occur before the shift from vegetative to reproductive growth that lowers quality and it also reduces the amount of water that must be evaporated as yields increase. They did state, however, that with delayed planting into July, a second harvest may not be feasible, and delaying harvest to heights greater than 50 inches may be advantageous if extra forage is needed on the farm and the extra moisture can be dealt with.
In our study, we also investigated whether a 2-harvest system could provide similar forage yields with higher forage nutritive value compared with a single harvest after a mid-July planting date. The only combination of harvest dates that provided reasonable forage yields occurred when the first harvest was made at an 8-inch stubble height (to encourage faster regrowth) at 35 days after planting and the second harvest was made at a 4-inch stubble 48 days later (83 days after planting). That 2-harvest combination produced a total dry matter yield of 3813 lbs/acre for the BMR and 4870 lbs/acre for the normal variety, with an average NDF concentration of 65% and 48% NDFD for the BMR and 45% NDFD for the normal variety. Therefore, we concluded the 2-harvest system showed no significant advantage over harvesting once at 60 days when planting in mid-July.
In summary, non-BMR sudangrass and sorghum-sudangrass planted in mid-July should be harvested between 40 to 60 days (30 to 50 inches tall) for lactating dairy cows, at about 60 days after planting (50 inches tall) for feeding heifers, and 60 to 80 days after planting (50 to 67 inches tall) for beef cattle or dry cows. The BMR hybrid provided a wider harvest window for lactating cows, with acceptable forage harvested nearly 80 days after planting.
Keep in mind that the sorghum grasses should be harvested or grazed prior to a frost, which can produce toxic levels of prussic acid in the forage. Details of this risk are available at https://agcrops.osu.edu/newsletter/corn-newsletter/2018-35/avoid-forage-toxicities-after-frosts.
Kilcer, T.F., Q.M. Ketterings, J.H. Cherney, P. Cerosaletti, and P. Barney. 2005. Optimum stand height for forage brown midrib sorghum x sudangrass in North-eastern USA. J. Agronomy & Crop Science 191:45-40.
Profile of Organic Corn Growers in a Four-State RegionAuthor(s): Cassandra Brown
For decades, consumer demand for organic food has grown annually by double-digits. (1) While still a comparatively small portion of overall agricultural production, organic corn acreage in the U.S. increased by more than 55% between 2011 and 2016, driven mainly by demand from organic dairy farms. (2) Despite the large increase in production, organic grain was imported to the U.S. in 2016, indicating the potential for future growth (3, 4). Currently, Ohio ranks in the top 5 states for number of certified organic corn growers, and in the top ten for acres harvested (5). However, relatively little is known about the management practices of these farms.
As part of an interdisciplinary study on soil balancing, Ohio State researchers surveyed certified organic corn growers in Ohio, Michigan, Pennsylvania, and Indiana in the spring of 2018. These four states collectively represent one-third of all U.S. organic corn growers and produce about 20% of the nation’s organic corn.
Responses showed that a little more than half of the growers of organic corn in this region were dairy farmers (Figure 1). More than half of the organic corn grown in 2017 was used as on-farm livestock feed. Most respondents harvested corn as grain (70%) and/or silage (36%). Other uses were rare. A surprisingly large number (nearly 2/3) of the growers use horse-powered equipment, indicating they were likely members of Old Order Amish or similar Plain communities.
Figure 1. Primary Source of Farm Income for Certified Organic Corn Growers in Ohio, Pennsylvania, Indiana., and Michigan
The survey gathered information on the use of soil amendments, crop rotations, cover crops, various tillage and cultivation strategies, yields, selling costs, and management priorities. Manure and compost were by far the most common soil amendments, used by 89% of all organic corn growers. Other soil amendments were used by fewer than half the growers. Tillage practices were chosen for weed management, but most other management decisions focused on soil health.
Reported yields varied widely, ranging from 25 to 250 bushels per acre for grain and 5-34 tons per acre for silage. Selling prices averaged $9.44 per bushel for grain and $69.99 per ton for silage. Estimates based on survey responses and standard economic methods suggested that very few farmers lost money on the fields reported on for this study.
Figure 2: Distribution of Yields for Certified Organic Corn Production in Ohio, Michigan, Pennsylvania, and Indiana
Farmers with more years of experience raising crops organically tended to have higher net returns on average, suggesting that economic performance can be expected to improve over time for farms transitioning to organic production. About 40% of respondents had less than five years of experience farming organically.
Researchers received a 57% response rate (859 responses), yielding a margin of error of 2%. For full survey results, read our technical reports at go.osu.edu/orgcorn.
1. Greene, Catherine. 2017. Organic Market Overview. USDA Economic Research Service. Available online: https://www.ers.usda.gov/topics/natural-resources-environment/organic-agriculture/
2. McBride, William D, Catherine Greene, Linda Foreman, and Mir Ali. 2015. The profit potential of certified organic field crop production. ERR-188. Washington, DC: United States Department of Agriculture, Economic Research Service. Available online: https://www.ers.usda.gov/publications/pub-details/?pubid=45383
3. Greene, Catherine, and Dennis Vilorio. 2018 (June 04). “Lower Conventional Corn Prices and Strong Demand for Organic Livestock Feed Spurred Increased U.S. Organic Corn Production in 2016.” Amber Waves (June 04). United States Department of Agriculture Economic Research Service. Available online: https://www.ers.usda.gov/amber-waves/2018/june/lower-conventional-corn-prices-and-strong-demand-for-organic-livestock-feed-spurred-increased-us-organic-corn-production-in-2016/
4. Oberholtzer, Lydia, Carolyn Dimitri, and Edward C Jaenicke. 2013. "International trade of organic food: Evidence of US imports." Renewable Agriculture and Food Systems 28(3):255-262. Available online: https://www.cambridge.org/core/journals/renewable-agriculture-and-food-systems/article/international-trade-of-organic-food-evidence-of-us-imports/ABFBE6900A0B5A8E6FBCF235A5DBFFD2
5. USDA-NASS. 2017. Certified Organic Corn Survey 2016 Summary. USDA National Agricultural Statistics Service. Available online: https://downloads.usda.library.cornell.edu/usda-esmis/files/zg64tk92g/70795b52w/4m90dz33q/OrganicProduction-09-20-2017_correction.pdf
What is Your Soil Wearing?Author(s): Amanda Douridas
Join us for a hands on workshop on Cover Crops and Soil Health September 5 from 5-8pm. Speakers include Dave Brandt, no-tiller and cover cropper for over 40 years. Nathan and Carrie Brause, Crawford County farmers, have no-tilled and cover cropped for the last 6 years. They have also implemented over 50 acres of conservation practices including water ways, filter strips and quail buffers. Frank Gibbs, owner of Wetland and Soil Consulting Services and former NRCS Soil Scientist will talk about soil structure and health. Hosts Tom and Nancy Smith have a small plot where attendees will be able to see different mixes of cover crops. Todd Dallas, Dallas Ag, will talk about soil testing methods and share results from the farm.
Tom and Nancy’s farm is located at 2684 Mt. Tabor Rd., West Liberty, OH 43357. Registration is $10 ahead of the event or $15 at the door and includes dinner. This event is presented by the Logan County Land Trust, Farm Credit Services, OSU Extension, Dallas Ag, LLC, Indian Lake Watershed and Logan and Champaign SWCD/NRCS offices. To register, please complete the form found at: https://agcrops.osu.edu/events/what-your-soil-wearing. Questions can be directed to Bob Stoll with the Logan County Land Trust at 937-935-7505.
About the C.O.R.N. Newsletter
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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