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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2009-20

Dates Covered: 
June 30, 2009 - July 7, 2009
Jonah T. Johnson

Summer Seeded Cover Crops

Authors: Alan Sundermeier

Now is the time to prepare for planting cover crops after wheat or oats harvest this summer. Your local seed dealer may not stock supplies and need to make a special order. Control of summer annual weeds and volunteer wheat may be needed before planting cover crops.

Cover crops offer many benefits to producers that increase farm profitability and environmental sustainability. Each cover crop has a niche or special purpose. Legume cover crops are typically used to produce homegrown nitrogen. Grass cover crops are used to increase soil organic matter, recycle excess nutrients, and reduce soil compaction. Brassica crops are grown to loosen the soil, recycle nutrients, and suppress weeds. Some other cover crops are grown to suppress insects, disease, weeds, or attract beneficial insects. Therefore, cover crops should be considered an integral part of any farming system that wants to efficiently utilize nutrients, improve soil quality, and increase farm profitability. Refer to this factsheet for more about cover crops in cropping rotations:

Decisions on which cover crop to plant need to consider the following:

Homegrown Nitrogen
Summer planted legumes may contribute nitrogen to the following grain crop. The availability and amount of the nitrogen produced can vary widely depending on cover crop growth and nutrient content. Soybeans that are treated and will not carryover can be used as an economical cover crop. Cowpea is better adapted to hot, dry weather and will grow rapidly until a killing frost in the fall. Austrian Winter Pea is a legume that may or may not survive the winter when summer planted. If winter pea is planted in mid-September, fall growth will be limited but winter survival is improved, and spring growth will contribute nitrogen. Summer planted clovers usually do not establish well in hot, dry weather.

Oilseed radish has the ability to recycle soil nutrients, suppress weeds and pathogens, break up compaction, re¬duce soil erosion, and produce large amounts of biomass. Freezing temperatures of 20 to 25 degrees will kill oilseed radish which allows for successful no-till spring planting of subsequent crops. As a fast growing, cool season cover crop, oilseed radish is best utilized when planted after small grain (e.g. wheat) or corn silage harvest. Excess nutrients in manure amended soil are rapidly absorbed by this cover crop, thus preventing leaching or runoff of nutrients into water systems. Without a source of nitrogen, oilseed radish growth will be limited, therefore its use is recommended after a manure application. Refer to this factsheet for more information:

Grass Cover Crops
Cereal rye or winter rye can be planted from summer to late fall. Cereal rye is hardy and will survive the winter. A fall forage cutting is possible if planted soon after wheat. Cereal rye does an excellent job of capturing manure nutrients into biomass growth. Oats is another economical choice for summer seeded cover crops. It also can grow rapidly, absorb excess soil nutrients, and provide a fall forage harvest. Oats will winterkill and work well with no-till corn planting the following year.

The Midwest Cover Crops Council website contains more information

Harvest aids for Wheat

Authors: Mark Loux

Several herbicides are approved for application to mature wheat to prevent weeds from interfering with harvest. Ragweeds, thistle, and lambsquarters are some of the weeds most likely to be a problem at the time of harvest, especially where wheat stands were not of uniform density. Take precautions to reduce spray drift when applying harvest aids, since sensitive crops and other desirable plants are likely to be growing in adjacent areas. Some specifics on the application of harvest aids follow (consult labels and the “2009 Weed Control Guide for Ohio and Indiana” for more information).

- Various 2,4-D products are labeled as harvest aids at rates of 0.5 to 1.5 lbs ai/A, depending upon the product. 2,4-D can be applied with ground or aerial equipment after wheat has reached the hard dough stage. Some labels advise that crop injury can occur, and spot treatments should be used to minimize the extent of injury. Do not feed wheat straw to livestock where 2,4-D is applied as a harvest aid. Amine formulations have less potential than ester formulations to volatilize and move off-target, but spray particle drift is possible with either.

- Many glyphosate products can be applied as a preharvest treatment in wheat for control of annual and perennial weeds. Application rate is 0.75 lb ae/A, which corresponds to 22 oz of PowerMax, 24 oz of Durango and Touchdown products, and 32 oz of products that contain 3 lbs of glyphosate acid per gallon (Buccaneer, Credit Extra, Glyfos, etc). Apply at least 7 days prior to harvest, and after the hard dough stage when grain moisture is 30% or less. Glyphosate can be applied with ground or aerial equipment, and some glyphosate products can be mixed with 2,4-D. Wheat grown for seed should not be treated with glyphosate.

- Several premixes of dicamba and 2,4-D (WeedMaster, Brash, etc) can be applied at least 7 days before harvest when wheat is in the hard dough stage, and after all green color has disappeared from the nodes of the wheat stem. This product can be mixed with glyphosate. Do not use treated wheat for seed unless a germination test is performed on the seed prior to planting.

- Aim can be applied as a preharvest treatment at the rate of 1 to 2 oz/A, but is likely to have a more narrow spectrum of activity compared with other products mentioned here. Apply at least 3 days before harvest with nonionic surfactant or crop oil concentrate.

- Rage D-Tech is a premix of Aim and 2,4-D that is also labeled for preharvest application. Apply at least 7 days before harvest when wheat is in the hard dough stage. Apply 16 to 32 oz/A with NIS (0.25% v/v) or COC (1.5 to 2% v/v).

Recovery and Yield Potential of Root Lodged Corn

Authors: Peter Thomison

Strong winds and heavy rains associated with severe thunderstorms can lodge or knock corn plants over, especially if the nodal root system is not fully developed. Root lodging can be directly related to severe feeding by rootworm larvae. However, Bt rootworm resistance alone will not prevent root lodging. Hybrids differ in their ability to resist root lodging. Moreover, a hybrid may exhibit outstanding stalk lodging resistance but may be very susceptible to root lodging. Hot, dry weather conditions and soil compaction may inhibit nodal root formation and predispose plants to wind injury.

Strong winds can pull corn roots part way out of the soil. The problem is more pronounced when soil are saturated by heavy rains accompanying winds. If root lodging occurs before grain fill, plants usually recover at least partly by "kneeing up." This response results in the characteristic gooseneck bend in the lower stalk with brace roots providing above ground support. If this stalk bending takes place before pollination, there may be little effect on yield. When lodging occurs later in the season, some yield decrease due to partial loss of root activity and reduced light interception may occur. If root lodging occurs shortly before or during pollen shed and pollination, it may interfere with effective fertilization thereby reducing kernel set. Several university studies have been performed to assess the impact of wind lodging on corn growth and grain yield.

Iowa state researchers forced V10 corn to “root lodge” at a 45 degree angle in plots with and without rootworms. Grain yield of root lodged corn without rootworms yielded 11 and 40 percent less than the control in the two years of the study while root lodged corn with rootworms yielded 12 and 28 percent of the control. Years were a major factor affecting the yield response. The ISU researchers concluded that “root lodging was more detrimental to biomass accumulation and grain yield than corn rootworm injury caused by larval feeding.” In another ISU study that evaluated natural root lodging, root lodged plants intercepted 28 percent less light than plants that were not root lodged.

In a University of Wisconsin study, root lodging was simulated by saturating soil with water and manually pushing corn plants over at the base, perpendicular to row direction. Wind damage was simulated at various vegetative stages through silking (V10 to R1). Compared to hand harvested grain yields of control plants, grain yield decreased by 2 to 6%, 5 to 15% and 13 to 31% when the lodging occurred at early (V10-V12), medium (V13-V15) and late (V17-R1) stages, respectively.


Elmore, R. 2005.Mid-to-late season lodging. Iowa State University Integrated Crop Management Newsletter IC-494(21)161-162.

Carter, P.R. and K.D. Hudelson. 1988. Influence of simulated wind lodging on corn growth and grain yield. J. Production Agriculture. 1:295-299.

Foliar Diseases in Soybean

Authors: Anne Dorrance

Soybean rust has been reported in Florida, Georgia, Alabama and Louisiana so far this year ( According to the “super-rust- scouters” in the Southern states, it is on kudzu but inoculum is higher than what it has been in recent years. However, it is still limited to one or a few kudzu patches in each county AND it is now HOT in these states as well (temperatures >90oF). This will slow soybean rust down. At this point, the development of soybean rust in Ohio is still low for the 2009 season. The next time that is critical is when our crop goes into R1 (first flower) and R2 (full flower). How prevalent soybean rust is at this time will be a better predictor of the potential risk in Ohio as well as the hurricane activity in the southern U.S. All sentinel plots and spore traps in Ohio were negative for soybean rust last week.

Brown spot has shown up in a few fields. To my surprise it is not present in more fields with all of the rain. If you do have brown spot, monitor its development through the flowering stages. Look at other varieties to see if they are all developing the same amount and if not, then switch next year to those varieties where this is not developing.

The same is true for Frogeye leaf spot. First spot was reported in Butler County this week on a susceptible line. So again, over the next 2 weeks begin to scout for this disease as well. We’ve gotten economical control of frogeye when we had at least one frogeye leafspot every 25 foot of row during 2007.

June 29: Final Results of the 2009 Ohio Wheat Scab Survey

Authors: Alissa Kriss, Pierce Paul, Dennis Mills

Based on the results of the 2009 wheat scab survey that was completed for 21 counties in Ohio, average scab incidence was low (overall 3.64%) this year. With the cooperation of Ohio State University Extension Educators and growers, we surveyed a total of 97 fields across the state and rated the incidence of head scab. In each field, incidence was assessed by counting the number of diseased and healthy heads per foot-of-row in ten one-foot locations, spaced approximately 100 feet apart. The percentage of diseased heads per foot-of-row was calculated by dividing the number of heads with scab symptoms by the total number of heads and multiplying by 100.

The head scab forecasting model ( predicted low risk for all counties in the state throughout the flowering period in Ohio. Based on our survey, incidence ranged from 0 to 28%. Of the 97 fields inspected, 22 (23%) had incidence less than 1%, 50 (52%) had incidence between 1 and 5%, 21 (22%) had incidence between 5 and 10%, and 4 (4%) of the fields had higher than 10% incidence. All of the fields with greater than 10% incidence were in the southwestern part of the state, and two of those fields were planted after corn. Remember, the scab fungus also causes ear and stalk rot on corn and survives in corn residues that remain in the field. More corn stubble leads to a higher amount of spores available to infect the wheat.

During the survey, information was also gathered on the variety that was planted in each field and its level of resistance to wheat scab. Data on variety resistance were based on OSU’s wheat performance trials and seed company’s claims. Of the 37 fields for which variety resistance data was provided, 18 (48%) were planted with moderately resistant varieties, 8 (22%) with moderately susceptible varieties, and 11 (30%) with susceptible varieties. Average scab incidence was the lowest in fields with moderately resistant varieties, 2%, compared to 5.2% and 3.7%, respectively, in fields with moderately susceptible and susceptible varieties.

In moderate to low scab years, like this year, the difference in scab incidence between moderately resistant and susceptible cultivars was not overly apparent. However, the difference in scab incidence between fields planted after corn and those planted after soybeans was very clear. The value of planting resistant varieties and planting wheat after soybeans instead of corn or wheat is extremely important, especially in moderate to high scab years. This was very clear in some southern states were scab levels were high (


Cephalosporium Stripe of Wheat

Authors: Dennis Mills, Pierce Paul

Cephalosporium stripe has been identified in several wheat fields in Ohio this spring and summer. The disease can be especially severe when wheat is grown under limited rotations, such as continuous relay cropping of wheat and soybeans, or when wheat is preceded by a susceptible cereal crop like winter wheat, barley, or rye. Several grasses are also susceptible, but wheat is the major economic host. Yield loss results from premature death of tillers, reduced seed set and reduced seed size.

Symptoms of Cephalosporium stripe include broad yellow and brown stripes extending the length of the leaf blade which stands out in contrast to green areas of the leaf. Diseased plants may be more prevalent in wetter, lower areas of the field, or in areas with higher clay content. Frequently, affected plants appear randomly distributed.

The fungus survives between susceptible cereal crops in infested residues. Crop rotation is essential for control of Cephalosporium stripe. Normally a two to three year rotation away from wheat will prevent build up of the fungus in the soil. In fields with yield limiting levels of the disease, the field should not be planted to wheat or any other winter cereal crop for 3 to 4 years. Crop rotations with legumes are recommended. Weed control is important because the fungus also infects other grasses. Elimination of these weed species may help decrease inoculum levels.

Ohio Soybean Aphid Update

Authors: Ron Hammond, Andy Michel, Bruce Eisley

Although not yet finding large populations of soybean aphids yet, we are finding additional areas infested with early season populations, including Sandusky and Trumbull Counties in northern and northeastern Ohio. So far the levels are well below the threshold of 250 aphids per plant. We would mention that most of these fields were early planted, probably around the first week in May, and are already in the V5-V6 growth stages. These fields were not treated with a seed treatment such as Cruiser. In comparison, soybean aphids are not being found in fields that were treated with Cruiser. We would point out that locations to our north, including Michigan and the provinces of Ontario and Quebec, are also finding widespread infestations of aphids. You can check out locations with soybean aphid by going to the PIPE system at A few comments are in order at this time regarding soybean aphids and what to expect as the summer progresses.

We have had many questions on what the threshold is for vegetative soybeans. At the present time, we do not have a definitive answer. However, early-planted fields with soybean aphids, currently in the V5-V6 growth stages, are beginning to get flowers. These fields will be in the reproductive stages, R1 and R2 or flowering, within a very short time. These are the stages where the threshold is an average of 250 aphids per plant with a rising population. Thus, for those fields with soybean aphids, the normally used threshold of 250 aphids will be reached shortly.

Another question concerns Cruiser, or any other seed treatment. These seed treatments will, and have shown good control, of early season aphids. However, the thought is that insect control will only last 45-60 days. Being that fields with aphids were most likely planted the first week in May, the seed treatments have lost or are about to lose their efficacy. In other words, seed treatments should not be counted on to provide any control from this point on, including when winged aphids begin to make their appearance in mid to late July, assumingly from locations to our north. And as mentioned, Michigan, Ontario, and Quebec are all finding aphids. Thus, all fields, including those that were treated with a seed treatment, will be at risk for economic infestations later this month and into August.

A third question is whether an insurance or prophylactic insecticide treatment, alone or added to an herbicide or fungicide spray, is worthwhile. As practitioners of IPM, we highly discourage this practice. First, there is no way to predict which fields, let alone which area of the state might have economic outbreaks of the soybean aphid. There is too great a chance for wasting money. Second, the only thing that insecticides will assuredly do at this time is to kill beneficial insects that could prove valuable in helping prevent outbreaks of aphids later in the summer. Although we do not have all the answers on the role beneficial insects have in the population dynamics of aphids, we need to let them have their chance. And removing those “good” insects early can only cause more harm than good.

As always, we recommend IPM. Keep reading this C.O.R.N. newsletter to keep abreast of the latest happenings. From this site, go to the Agronomic Crops Insects web site,, and search out newsletters from surrounding states and Canadian provinces to see what is happening in those locations. Learn how to scout for the aphids, and using the 250 aphids per plant with a rising population threshold, only spray when economic losses are anticipated.

First Western Bean Cutworm Found

Authors: Bruce Eisley, Ron Hammond, Andy Michel

As mentioned two weeks ago, The Ohio State University Extension is conducting surveys for Western Bean Cutworm (WBCW) across the state. Most of the traps were deployed last week, and we have caught our first WBC adult of 2009. It was found on Tuesday, June 23 in Northern Wood County in a trap that was placed on Friday, June 19th, 2009. That weekend, intense storms passed through the area and likely carried the moth along for a ride. While the collection of this single moth can shed no light on what to expect this season, it does provide a warning to place traps out as soon as possible. Remember, peak flight occurs around mid-July that will give a better predictor on what to expect and when to begin scouting for eggs and larvae in corn. For trapping instructions, see our article 2 weeks ago, or go to the North-Central IPM Center’s web page for WBCW ( We will provide periodic updates all through the season in the C.O.R.N. newsletter as more catches come in.

Insect Update

Authors: Ron Hammond, Andy Michel, Bruce Eisley

We have been receiving reports of heavy potato leafhoppers in alfalfa, European corn borer moths and larvae being observed in corn, and Japanese beginning to be seen in numerous crops. Alfalfa should be sampled for leafhoppers for the remainder of the summer, as well as corn for first generation corn borer. Remember that if transgenic Bt corn was planted, that the refuge area should still be checked for corn borer larvae. As soybeans reach the reproductive stages, Japanese beetles as well as other defoliators should be checked to prevent defoliation from becoming economic. See the past article on potato leafhopper in the May 26 issue of this C.O.R.N. newsletter, Issue 15, for information on leafhopper thresholds in alfalfa. For all three insects, see our new Agronomic Crops Insects web site at for information on scouting and management.

Weather Update

Authors: Jim Noel

No changes overall.

The trend toward slightly below normal rainfall and slightly above normal temperatures remains intact over the 2-3 week period.

In the short term, this week will see below normal rainfall except in the northeast section where rainfall will be near normal. A big cool pool of air aloft will spell some showers across Ohio especially Tuesday and Wednesday. Temperatures this week will be below normal with highs mostly in the 70s, but some 60s are possible in the north and east midweek. Temperatures will return to mostly 80s by Friday into the weekend.

Temperatures will relax some early next week again to upper 70s and low 80s with another cold front. There should be some rainfall ahead of the front either Sunday or Monday.

Temperatures will then warm up again later next week into the following week with some scattered storms as a big upper ridge builds to our southwest again so we get a pattern similar to last week.

Even when the heat builds in, it still looks like what we have said all spring and summer. Highs will reach around 90 but the humidity will become high, so it will feel worse to us than the crops. Low will reach around 70. This will translate to above normal temperatures, but the real heat this summer will remain off to our southwest for the most part.

We will continue to monitor El Nino.

Overall, decent crop conditions continue!

OSU Weed Science Field Day

Authors: Mark Loux

The OSU Weed Science field day will be held at the OARDC Western Agricultural Research Station on Wednesday, July 8. The tour of our research plots, which is self-directed in nature, starts at 9 am and runs until noon. OARDC Western Agricultural Station is north of South Charleston on State Route 41, approximately 5 miles south of Interstate 70.

Agronomy Field Day at Western O.A.R.D.C.

Authors: Harold Watters, Jonah Johnson

The 2009 OSU Extension “Agronomy Field Day” will be at the O.A.R.D.C. Western Agricultural Research Station on Wednesday, July 22, 2009. The morning field day will begin at 9:00am with a wagon tour of the farm; there will be multiple stops at OSU Extension Research specialist/scientist’s plots during the morning. Each Specialist will discuss their research and any topics of interest that pertain to the growing season.

At Noon, we will have lunch provided for each participant (must be pre-registered to eat lunch!).

After lunch, participants will have the option to re-visit one of the OSU Extension specialist’s plots with a specialist (the participant’s choice), for a more in-depth session where they can walk through the plot and “find & diagnose” issues that are currently occurring. There will be multiple locations across the research station with different topics of interest to walk through. A great learning opportunity for participants to obtain a more “in-depth” knowledge on selected subject matter.

O.A.R.D.C. Western Agricultural Station (7721 South Charleston Pike, South Chalreston, OH 45368) is north of South Charleston on State Route 41, approximately 5 miles south of Interstate 70.

Certified Crop Advisor - C.E.U.’s and private P.A.T. re-certification credits available!

Topics for the day include:

-“Integrated Disease Management in Ohio Corn Production,” by Pierce Paul, Cereal Grains Pathologist with OARDC and OSU Extension.

-“Alfalfa Fertility Based on Removal Rates and Fertilizer Sources,” by Mark Sulc, Forage Specialist with OARDC and OSU Extension.

-“Field Crop Insect Update for 2009: Rootworms, Western Bean Cutworm, and Aphids,” by Andrew Michel, Entomologist with OARDC and OSU Extension.

-“Mid-Season Diagnostics: What to Look for in Foliar Diseases, and Are We at Risk for Asian Soybean Rust?” by Anne Dorrance, Soybean Pathologist with OARDC and OSU Extension.

-“Cover Crops and Nitrogen Management,” by Robert Mullen, Soil Fertility Specialist with OARDC and OSU Extension.

-“Weed Control Issues for 2009,” by Mark Loux, Weed Specialist with OARDC and OSU Extension.

-“How Corn Plants Can Recover from Weather-Related Injuries,” by Peter Thomison, Corn Specialist with OARDC and OSU Extension.

Please pre-register with the Clark County Extension Office (937-328-4607) by July 15th, 2009 to be able to attend.

For more information, contact Jonah Johnson at 937-328-4607 or or Watters at 937-484-1526 or

Archive Issue Contributors: 

Pierce Paul, Anne Dorrance, and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), Peter Thomison (Corn Production), Mark Loux (Weed Science) and Jim Noel (NOAA). Extension Agents and Associates: Steve Bartels (Butler), Roger Bender (Shelby), Howard Siegrist (Licking), Greg LaBarge (Fulton), Harold Watters (Champaign), Mark Koenig (Sandusky), Wes Haun (Logan), Jonah Johnson (Clark), Steve Prochaska (Crawford), Alan Sundermeier (Wood), Suzanne Mills-Wasniak (Montgomery) and Tim Fine (Miami)

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.