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Ohio State University Extension


C.O.R.N. Newsletter 2008-26

Dates Covered: 
August 11, 2008 - August 18, 2008
Andy Kleinschmidt

Field Crop Insect Update

Authors: Ron Hammond, Andy Michel, Bruce Eisley

Insect activity has slowed down somewhat, but growers should not become complacent about continued scouting in both corn and soybean. Soybean aphids continue to be in low numbers in Ohio, although they can be found in many soybean fields. Growers should continue to scout for them, but keep in mind that the threshold for treatment remains at an average of 250 aphids per plant. As we get into mid and late August, and R5 and R6 soybean growth stages (seed fill), the chances for economic populations greatly lesson. Defoliation by various soybean leaf feeders continues, but remember that the level needed for treatment rises to 20-25% as we get into the R5 and R6 growth stages. In dry areas of the state, growers should maintain a watch for twospotted spider mite problems, especially along field edges.

On corn, western bean cutworm adults are no longer being collected. However, we are advising growers in western and central Ohio to pay attention to corn ears for possible larval infestations. If any are found, please contact your county extension educator so they can inform us. In our sampling for the western corn rootworm variant in soybean fields, we are currently catching very few adults. We are not sure if this is representative of overall low numbers because of larval mortality, or a late population. Other states are also reporting fewer adults than normal at this time. However, because it could just reflect late population development, we do recommend continued sampling throughout August before ending the scouting program.

Get Ready for Harvest and Late Season Soybean Diseases

Authors: Anne Dorrance

Last year China found colored seeds in shiploads of soybeans from the US. This year it will be critical to clean the system of any potential contaminants from colored soybeans from field harvest (for example, pokeweed) or from remnant seed that was treated with fungicide. This is a good time to clean out weigh wagons, barns and grain bins – any place where treated seed may have been stored.

Phytophthora stem rot is quite prevalent in some fields that I walked last week. Unfortunately these were not my research plots. Fields that had flood damage earlier are now showing the secondary effects of the saturated soil conditions, with lots of Phytophthora. Soybeans, with pods on them, were wilting and turning yellow and had the characteristic chocolate brown canker moving up the stem. Check your fields, areas where large spotty stands are good places to look. It is clear in these cases that the Rps gene is not effective in all areas of the field, it is much more important to look at the partial resistance part of the resistance package. Rps1c is equal to Rps1k, in Ohio for effectiveness – in most of our fields it is the partial resistance that is doing the lion’s share of the work.

Sclerotinia stem rot has also started in some fields. About the R6 growth stage, soybeans will begin to wilt and turn a gray-green color. Look on the main stem to see the white, fluffy, mycelial growth with hard black sclerotia. This disease is favored by wet soil conditions during flowering, look in areas where fogs tend to hang longer in the morning. This disease needs a long wet or dew period in order to infect the blossoms, we mist for 3 hours in the evening and another 3 hours in the morning in inoculation trials.

SCN is also present. Now is a good time to dig plants up and look at the roots to see the tiny white females. When you dig these plants up, hold them for a minute to let the soil dry, then gently shake or crack it off of the roots. The first thing you will notice are the irregular shaped balls on the roots about 1/8 inch in diameter. Then look for bright white dots on the roots, these will be the SCN females filled with eggs. Places to look in fields are entrances in and out of the field, places in the field where plants are stunted or places where you remember from harvest that the soybeans did not yield as well. Go to the fields which are your problem fields – they never yield as well as the other fields in the area. Management for SCN is still rotation, rotation, and rotation.

Another Low Corn Disease Year In Ohio

Authors: Pierce Paul, Dennis Mills

Most of the corn in Ohio is well beyond pollination and reports coming in from across the state suggest that the 2008 crop went through this critical growth stage without major disease concerns. Barring a few lesions of gray leaf spot on the lower leaves in some fields and a few rust pustules in other fields, Ohio’s corn fields are generally disease-free.

Most of the commonly cultivated hybrids have very good resistance to foliar diseases such as gray leaf spot, northern corn leaf blight and eye spot, so even when conditions are wet like they were during silk emergence in some fields or even when corn is planted after corn, disease levels still tend to be low on resistant hybrids. Remember, for disease to develop and reach high levels, the weather must be favorable for an extended period (wet, humid, and warm), the pathogen must be available, and the crop must be susceptible. In the weeks following pollination, conditions were dry across most of the state, further contributing to low disease development.

The crop is now well into grain fill and is less likely to suffer substantial yield losses in the event of late-season foliar disease development. Our research shows that yield losses tend to be greatest when foliar diseases reach high levels before grain fill is complete.

2008 Wheat Performance Trials Available

Authors: Jim Beuerlein, Rich Minyo, Pierce Paul, Clay Sneller

The 2008 Ohio Wheat Performance Trials are now available online at

The purpose of the Ohio Wheat Performance Trial is to evaluate wheat varieties, blends, brands and breeding lines for yield, grain quality and other important performance characteristics. Depending on variety and test site, yields varied between 62.7 and 112.5 bushels per acre, and test weight ranged from 53.1 to 59.4 pounds per bushel.

Southwest Ohio Corn Grower/Fayette County Agronomy Club Field Day

Authors: John Yost

The Southwest Ohio Corn Grower/Fayette County Agronomy Club Field Day will be held on August 13th at the Fayette County Demonstration Farm on State Route 38. The day will begin at 9:30 AM. This year's program is focused on grain storage. Topics will cover grain bin pest management, grain storage system design and management, economics of storage, and grain marketing. In addition, there will be presentations on emerging corn pests, manure contracts and availability, and a commercial pesticide applicators recertification. The recertification program will offer a hour of CORE and a half hour of 2A. There will also be CCA credits offered (2 PM, 1 PD, 0.5 NM, 0.5 CM). As always we will have corn and soybean show plots, trade show, antique tractor displays, health screenings, and the ODA pesticide pickup. The program is free (there will be a $30 fee for the pesticide recertification), and includes lunch provided by the SWOCGA. Our lunch time program will feature Dr. Carl Zulauf. Dr. Zulauf was a major contributor to the new farm bill. He will be presenting the details of the plan following lunch. Dwayne Siekman, OCGA Executive Director, will provide a legislative update on the organizations activities. For more information contact John Yost at 740-335-1150.

Weather Update

Authors: Jim Noel

No changes this week. The overall pattern has shifted to near normal temperatures and below normal rainfall and this is expected to continue for the rest of August and possibly into September now. This week we will see below normal temperatures and rainfall. After this week, temperatures will return to near normal, but rainfall should continue below normal though a few areas may get normal rainfall.

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), and James Noel (NOAA/NWS/OHRFC). Extension Associates and Educators: Bruce Clevenger (Defiance), Steve Bartels (Butler), Steve Prochaska (Crawford), Wesley Haun (Logan), Harold Watters (Champaign), Glen Arnold (Putnam), Howard Siegrist (Licking), Mike Gastier (Huron), Mark Koenig (Sandusky/Ottawa), Steve Foster (Darke), Tim Fine (Miami), Les Ober (Geauga), Suzanne Mills-Wasniak (Montgomery).

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.