You are here
Corn Newsletter : 2018-28
HARVEST SEASON OUTLOOKAuthor(s): Jim Noel
Hot weather, possibly close to the hottest weather of the season is on tap over the next two weeks. This should help make corn stalks brown up fast. However, with that heat, high dewpoints or moisture will also accompany the hot weather. This means soil drying will be slower than you would normally expect with high temperatures due to a limit on the evapotranspiration rate. The hot weather will be fueled in part by tropical activity in the Pacific Ocean driving storms into the Pacific Northwest into western Canada and a big high pressure over the eastern U.S. Rainfall will likely continue at or above normal into the start of September before some drying occurs. We do not see any early freeze conditions this year.
September Harvest Outlook:
Temperatures: 2-4F above normal
Rainfall: Near normal (-0.5 to +0.5 inches)
Humidity levels: Above normal
Freeze Outlook: None
Field Conditions/Soil Moisture: 1-2 inches of extra moisture in soils so expect okay conditions for harvest except in lower areas that will likely remain wet.
October Harvest Outlook:
Temperatures: 1-3F above normal
Rainfall: Above (+0.5-+1.0 inches)
Humidity levels: Above normal
Freeze Outlook: About normal timing from Oct. 10-20 range
Field Conditions/Soil Moisture: 1-2 inches of extra moisture in the soils and with some rainy weather some challenges can be expected in harvest. Wettest conditions will be western half and northern areas driest east and southeast.
The next two weeks of rainfall can be seen on attached image. Normal is about 0.75 inches per week. Normal for two weeks is about 1.5 inches and the weather models suggest the rainfall will average 1.25 to 3+ inches over Ohio for the next two weeks. The biggest rain threats the next two weeks will be over parts of Minnesota, Wisconsin and Iowa where rainfall could top a half foot and create real wet soil conditions in those areas.
Ear Rots of Corn: Telling them Apart
Over the last few weeks, we have received samples with at least four different types of ear rots – Diplodia, Gibberella, Fusarium, and Trichoderma. Of these, Diplodia ear rot seems to be the most prevalent. Ear rots differ from each other in terms of the damage they cause (their symptoms), the toxins they produce, and the specific conditions under which they develop. Most are favored by wet, humid conditions during silk emergence (R1) and just prior to harvest. But they vary in their temperature requirements, with most being restricted my excessively warm conditions such as the 90+ F forecasted for the next several days. However, it should be noted that even when conditions are not optimum for ear rot development, mycotoxins may accumulate in infected ears.
A good first step for determining whether you have an ear rot problem is to walk fields between dough and black-layer, before plants start drying down, and observe the ears. The husks of affected ears usually appear partially or completely dead (dry and bleached), often with tinges of the color of the mycelium, spores, or spore-bearing structures of fungus causing the disease. Depending on the severity of the disease, the leaf attached to the base of the diseased ear (the ear leaf) may also die and droop, causing affected plants to stick out between healthy plants with normal, green ear leaves. Peel back the husk and examine suspect ears for typical ear rot symptoms. You can count the number of moldy ears out of ever 50 ears examined, at multiple locations across the field to determine the severity of the problem.
DIPLODIA EAR ROT: This is one of the most common ear diseases of corn in Ohio. The most characteristic symptom and the easiest way to tell Diplodia ear rot apart from other ear diseases such as Gibberella and Fusarium ear rots is the presence of white mycelium of the fungus growing over and between kernels, usually starting from the base of the ear. Under highly favorable weather conditions, entire ears may become colonized, turn grayish-brown in color and lightweight (mummified), with kernels, cobs, and ear leaves that are rotted and soft. Rotted kernels may germinate prematurely, particularly if the ears remain upright after physiological maturity. Corn is most susceptible to infection at and up to three weeks after R1. Wet conditions and moderate temperatures during this period favor infection and disease development, and the disease tends to be most severe in no-till or reduce-till fields of corn planted after corn. The greatest impact of this disease is grain yield and quality reduction. Mycotoxins have not been associated with this disease in US, although animals often refuse to consume moldy grain.
GIBBERELLA EAR ROT - When natural early-season infections occur via the silk, Gibberella ear rot typically develops as white to pink mold covering the tip to the upper half of the ear. However, infections may also occur at the base of the ear, causing the whitish-pink diseased kernels to develop from the base of the ear upwards. This is particularly true if ears dry down in an upright position and it rains during the weeks leading up to harvest. The Gibberella ear rot fungus may also infect via wounds made by birds or insects, which leads to the mold developing wherever the damage occurs. When severe, Gibberella ear rot is a major concern because the fungus produces several mycotoxins, including deoxynivalenol (vomitoxin), that are harmful to livestock. Once the ear is infected by the fungus, these mycotoxins may be present even if no visual symptoms of the disease are detected. Hogs are particularly sensitive to vomitoxin. Therefore the FDA advisory level for vomitoxin in corn to be fed to hogs is 5 ppm and this is not to exceed 20% of the diet.
FUSARIUM EAR ROT. Fusarium ear rot is especially common in fields with bird or insect damage to the ears. Affected ears usually have individual diseased kernels scattered over the ear or in small clusters (associated with insect damage) among healthy-looking kernels. The fungus appears as a whitish mold and infected kernels sometimes develop a brownish discoloration with light-colored streaks (called starburst). Several different Fusarium species are associated with Fusarium ear rot, some of which produce toxins called Fumonisins. Horses are particularly sensitive to Fumonisins, but cattle and sheep are relatively insensitive.
TRICHODERMA EAR ROT – Abundant, thick, greenish mold growing on and between the kernels make Trichoderma ear rot very easy to distinguish from Diplodia, Fusarium, and Gibberella ear rots. However, other greenish ear rots such as Cladosporium, Penicillium and Aspergillus may sometimes be mistaken for Trichoderma ear rot. Like several of the other ear rots, diseased ears are commonly associated with bird, insect, or other types of damage. Another very characteristic feature of Trichoderma ear rots is sprouting (premature germination of the grain on the ear in the field). Although some species of Trichoderma may produce mycotoxins, these toxins are usually not found in Trichoderma-affected ears under our growing conditions.
Mexican Bean Beetles Make an Appearance
Mexican Bean Beetle adult (left) and larva (right). Photo by R. Hammond.
Though less common than it once was, the Mexican bean beetle still maintains a presence in Ohio, and we have been getting a few reports of economic populations in soybean this month, largely in the east-central part of the state. The Mexican bean beetle adult is a small, copper-colored beetle with numerous black spots, while the larva (immature) is yellow with black spines. The adult beetle resembles a ladybeetle because they are members of the same insect family, Coccinellidae. Mexican bean beetles are one of the few members of this family that are plant pests.
Mexican bean beetle overwinters in the adult stage in wooded areas near fields, entering soybean fields as they emerge from their overwintering sites. This insect has two generations per year in Ohio and the larvae we are seeing in August are members of the second generation. Both adults and larvae will feed on soybean leaves and other legumes. Thus, when scouting, growers need to be aware of both stages of this pest. Going into September, fields most at risk will be late-planted or double-cropped soybeans that are still green when other fields are yellowing – not only Mexican bean beetles, but also late-season bean leaf beetles, grasshoppers, and Japanese beetles will be attracted to these still-green fields. Also, Mexican bean beetles may be attracted to alfalfa as soybeans senesce, and fall-planted alfalfa near recently infested soybean fields may be at risk.
The treatment threshold for all of these defoliators in soybeans in the R1-R6 stages is 20% overall defoliation. It is important to evaluate the field as a whole, because many of these pests are worse at the field edge which may give a skewed impression of the problem. At this time of year, it is particularly important to be aware of the pre-harvest interval (PHI) of any insecticide chosen. Some PHIs are several weeks and could interfere with harvest schedules if applied too late.
For more everything you might like to know about Mexican bean beetle, visit https://doi.org/10.1093/jipm/pmv023
Observations Noted by Clifton Martin Larvae and pupae of Mexican Bean Beetle (Epilachna varivestis Mulsant)
A visit to one field revealed larvae, pupae and adults all present and defoliation was occurring throughout. Second generation larvae were abundant and the population was large. This field was planted in early April and was a likely target for overwintering adults emerging from nearby woods and treelines. Indeed, it was possible to look at an early planting directly adjacent to a later planting and see a visible decrease in the health of the plants in the early field. A little scouting revealed an abundant amount of larvae on the pods low on the plant. Of further consideration, this field would likely be ready for harvest in the second half of September. Key information about this pest includes:
- Earlier planted fields will tend to receive the majority of the overwintered adults.
- Both the larvae and adult feed on soybean leaves.
- Severe defoliation generally occurs in late summer when late instar larvae of the 2nd generation reach peak activity.
- MBB feed between the veins on a leaf creating a skeletonized appearance
- Economic thresholds for spraying are 15% defoliation at pod fill and 25% at full pod to harvest
- Pod feeding is rarely a problem in soybeans, but it can happen. In the case of pod feeding, it is even more rare for the beetle to pierce all the way to a seed, but damage to the pod can create opportunity for disease to take hold.
- Several insecticides are labeled for control.
Foliar soybean defoliation caused by Mexican Bean Beetle (Epilachna varivestis Mulsant)
Mexican Bean Beetle larvae on soybean pods
Corn, Soybean, Wheat and Alfalfa Field Guide. Bulletin 827. The Ohio State University. Page 81.
Defoliators on Soybean, OSU Factsheet ENT-39, https://ohioline.osu.edu/factsheet/ENT-39
Tip Dieback and Zipper Ears in Corn
Alyssa Lamb, and Alison Peart
Although ear and kernel development appears excellent in many Ohio cornfields, there are reports of incomplete ear fill that are related to poor pollination and kernel abortion. Several factors may have caused this problem. The ovules at the tip of the ear are the last to be pollinated, and under stress, only a limited amount of pollen may be available to germinate late emerging silks. Pollen shed was complete or nearly complete before the silks associated with the tip ovules emerge. As a result, no kernels may be evident on the last two or more inches of the ear tip. Uneven soil conditions and plant development within fields may have magnified this problem. Pollen feeding and silk clipping by corn rootworm beetles and Japanese beetles can also contribute to pollination problems resulting in poorly filled tips and ears.
If plant nutrients (sugars and proteins) are limited during the early stages of kernel development, then kernels at the tip of the ear may abort. Kernels at the tip of the ear are the last to be pollinated and cannot compete as effectively for nutrients as kernels formed earlier. Although we usually associate this problem with drought conditions, the stress conditions that occurred this year, such as N deficiency, excessive soil moisture and foliar disease damage, may cause a shortage of nutrients that lead to kernel abortion. Periods of cloudy weather following pollination, or the mutual shading from high plant populations can also contribute to kernel abortion. Agronomists and farmers characterize the poor pollination and kernel abortion that occurs at the tip of the ear as “tip dieback”, “tip-back”, or “nosing back”, although poor pollination is usually the factor affecting poor kernel set at the tip. Kernel abortion may be distinguished from poor pollination of tip kernels by color. Aborted kernels and ovules not fertilized will both appear dried up and shrunken; however aborted kernels often have a slight yellowish color.
“Zipper ears” are another ear development problem evident in some fields. Zipper ears exhibit missing kernel rows (often on the side of the cob away from the stalk that give sort of “a zippering look on the ears”). The zippering is due to kernels that are poorly developed and/or ovules that have aborted and/or not pollinated. Zippering often extends most of the cob’s length and is often associated with a curvature of the cob, to such an extent that zipper ears are also referred to as "banana ears". Zipper ears are often associated with corn plants that have experienced drought stress during early grain fill. Ohio studies indicate that some hybrids are more susceptible to zippering than others are and that zippering among such hybrids is more pronounced at higher seeding rates. Zippering has also been observed in corn plants subject to severe defoliation during the late silk and early blister stages.
For a 3D model showing a zipper ear, see the following
Use the cursor to view the zipper ear model from different perspectives.
For more information and pictures of other ear and kernel abnormalities, check the following: “Troubleshooting Abnormal Corn Ears” available online at http://u.osu.edu/mastercorn/
Ciampitti, I. 2014. Abnormal corn ears. https://www.agronomy.k-state.edu/extension/documents/crop-production/Abnormal_Corn_Ears.pdf (URL verified 8/27/18)
Nielsen, R.L. 2017. The "Zipper" Pattern of Poor Kernel Set in Corn. Available at
URL: http://www.agry.purdue.edu/ext/corn/news/timeless/Zipper.html (URL verified 8/27/18)
Winter Malting Barley Trial Results AvailableAuthor(s): Laura Lindsey
and Raj Shrestha
Due to growing interest in winter malting barley, we conducted a nitrogen rate and seeding rate trial during the 2017-2018 growing season. The trials were conducted at the Northwest Agricultural Research Station (NWARS) in Wood County, the Ohio Agricultural Research and Development Center (OARDC) in Wayne County, and the Western Agricultural Research Station (WARS) in Clark County. The first-year research reports and Malting Barley Production Guide can be found here: https://stepupsoy.osu.edu/winter-malting-barley
Summary of Nitrogen Rate Results: We evaluated the effect of four spring N application rates: 0, 40, 80, and 120 lb N/acre. (Each field received approximately 20 lb N/acre in the fall and cultivar ‘Puffin’ was planted.) Nitrogen was applied at Feekes 5 growth stage. The agronomic optimum N rate (N rate where grain yield was greatest) ranged from 100-119 lb N/acre depending on the location.
However, protein content of the grain is extremely important, which is influenced by N application rate. For the malting industry, grain protein should be 9.5-12.5% on a dry weight basis. In our trials, grain protein content increased with increasing N application rate. At the Wood County location (NWARS), average grain protein was ≤ 12.5% regardless of spring N application rate. At the Clark County (WARS) and Wayne County location (OARDC), average grain protein content exceeded 12.5% when 80 lb N/acre or more was applied.
Summary of Seeding Rate Results: We evaluated the effect of five seeding rates: 0.75, 1.0, 1.5, 2.0, and 2.5 million seeds/acre on the cultivar ‘Puffin.’ Barley was planted Sept. 29, Oct. 7, and Oct. 19 at the Northwest Agricultural Research Station (NWARS) in Wood County, the Ohio Agricultural Research and Development Center (OARDC) in Wayne County, and Western Agricultural Research Station (WARS) in Clark County, respectively. Overall, there was a poor relationship between seeding rate and grain yield. However, the agronomic optimum seeding rate (seeding rate where grain yield was greatest) was 1.6-1.8 million seeds/acre. Barley should be planted based on the number of seeds/acre. Planting by pounds/acre or bushels/acre is inaccurate due to variability in seed size. Keep in mind, barley seed is often large (fewer seeds per pound). In our trials, ‘Puffin’ had ~10,000 seeds/pound.
This research was funded by the Ohio Small Grains Marketing Program.
Western Bean Cutworm: Final Adult Moth UpdateAuthor(s): Amy Raudenbush
John Schoenhals, Mark Badertscher, Lee Beers, Bruce Clevenger, Sam Custer, Tom Dehass, Allen Gahler, Jason Hartschuh, Ed Lentz, Cecilia Lokai-Minnich, David Marrison, Sarah Noggle, Les Ober, Eric Richer, Garth Ruff, Jeff Stachler, Alan Sundermeier, Curtis Young, Megan Zerrer, Chris Zoller, Andy Michel, Kelley Tilmon
As Western bean cutworm (WBC) adult trap monitoring comes to an end for the 2018 season, we would like to thank everyone for their participation including land owners and farm cooperators who allowed us to place traps in their fields. Week ending August 25, 2018 was our final week monitoring WBC adult moth catches in Ohio as very few adult moths are being reported in the bucket traps. Overall, 23 counties monitored 69 traps and resulted in a statewide average of 0.7 adult moths per trap (51 total captured). This is a decrease from an average of 1.2 moths per trap (76 total captured) the previous week.
Figure 1. Average WBC adult per trap in Ohio counties, followed in parentheses by total number of traps monitored in each county for the week ending August 25, 2018. Legend (bottom right) describes the color coding on map for the average WBC per county.
PAT Credits offered at Independent Ag Equipment Field DayAuthor(s): Mike Gastier, CCA
OSU Extension will offer both private and commercial Pesticide Applicator Training credits at a field day sponsored by Independent Ag Equipment, 4341 Sandhill Road, Bellevue, OH 44811. The field day will be held this Wednesday, August 29, 2018 with PAT sessions beginning at 1:30 p.m. Although this is a company field day, pesticide training is open to the public. Huron County Extension Educator Mike Gastier, working with neighboring Extension Educators Jason Hartschuh and Al Gahler will offer one hour of core training and one half hour in category 2A and 2C ( Category 1 private). Certified Crop Advisor continuing education credits will also be offered. No reservations are required. If more information is needed please call the Huron County Extension office at 419-668-8219.
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.
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.