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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2008-07

Dates Covered: 
April 1, 2008 - April 8, 2008
Harold Watters

Minimizing pollen contamination of non-GMO Corn

Authors: Peter Thomison

In 2007, 41 percent of Ohio’s corn acreage was planted to transgenic (GMO) corn, i.e. Roundup Ready/Liberty Link and Bt hybrids. With GMO corn plantings likely to jump significantly in 2008, corn growers interested in obtaining non-GMO corn premiums need to develop plans to minimize pollen contamination of non-GMO corn. Pollen from corn containing transgenic traits may contaminate (by cross-pollination) nearby non-GMO corn. Ohio growers of identity preserved (IP) non-GMO corn should become more familiar with planting practices that limit pollen drift from nearby GMO corn fields. Several methods, including isolation and border rows, planting dates, and hybrid maturity, are effective in limiting exposure of non-GMO corn fields from pollen of GMO fields. For more details concerning these methods, consult Extension Fact Sheet AGF-135, Managing "Pollen Drift" to Minimize Contamination of Non-GMO Corn; it’s available online at

Once released from the anthers into the atmosphere, pollen grains can travel as far as one-half mile with a 15 mph wind in a couple of minutes (Nielsen, 2003). However, most of a corn field's pollen is deposited within a short distance of the field. Past studies have shown that at a distance of 200 feet from a source of pollen, the concentration of pollen averaged only 1 percent compared with the pollen samples collected about 3 feet from the pollen source (Burris, 2002). The number of outcrosses is reduced in half at a distance of 12 feet from a pollen source, and at a distance of 40 to 50 feet, the number of outcrosses is reduced by 99 percent. Other research has indicated that cross-pollination between corn fields could be limited to 1 percent or less on a whole field basis by a separation distance of 660 ft., and limited to 0.5 percent or less on a whole field basis by a separation distance of 984 ft. However, cross-pollination could not be limited to 0.1 percent consistently even with isolation distances of 1640 ft.

Burris, J. 2002. Adventitious Pollen Intrusion into Hybrid Maize Seed Production Fields. American Seed Trade Assoc. Online at [URL verified 3/31/08].
Nielsen, Bob. 2003. Tassel Emergence & Pollen Shed. Purdue Univ. Online at [URL verified 3/31/08]

Not the Year to Mud-in Soys

Authors: Anne Dorrance, Jim Beuerlein

In 2007 many soybean seed production fields were harvested when the seed was very dry resulting in mechanical damage to the seed. In spite of record yields the harvest damage has resulted in a severe shortage of high quality seed. Many seed lots have germination rates lower than normal along with reduced vigor and quality. Because the seed is so fragile, any handling further reduces germination and quality, leading seed companies to question whether or not to apply fungicides to the seed.

Most seed lots have been evaluated using two tests. One is the standard warm germination test that tells us the percentage of seeds that are alive and that will germinate under ideal field conditions. That percent is printed on the seed tag. The second test is the Cold Test that evaluates the seed vigor under extremely stressful conditions and these results are only available from your seed dealer. For this test, seeds are planted in a mixture of soil and sand, watered and placed in a cold chamber at 50 degrees for seven days before being moved to a 77 degree germination chamber for four days. The exposure to cold wet conditions with disease organisms present allows only the most vigorous seeds to survive and be disease free. This test is often conducted on the seed with and without a fungicide seed treatment to evaluate the benefit of seed treatment. A cold test result of 70 percent or greater indicates the seed is highly vigorous and will provide good emergence under severe field conditions.

Seed with reduced vigor is much more susceptible to seedling damping-off caused by Pythium spp. as well as Phytophthora. As the seed imbibes water it begins to swell, with the thin seed coats, this cracks and leaks plant exudates. These exudates get the pathogens “excited” and they can find the seed that much faster. Fungicide seed treatments will protect this type of seed. Especially if it is planted into fields that have a long history of stand establishment issues.

The seed we will plant in 2008 can be characterized as having:
1) High warm germination percent (90+percent) and high seed vigor (70+percent),
2) Seed with a high warm germination percent (90+percent and a medium vigor test (60-69 percent), and
3) Seed with a medium warm germination (85-89 percent) and a medium vigor test (60-69percent).

Our suggestions for managing your seed supply are:
1) All your seed should be treated with fungicides for protection from root rot diseases. Treating may reduce the germination a bit but should increase final stands and root system health.
2) Work with your seed dealer to classify the seed you will plant into one of the three categories above.
3) Plant the highest quality seed first and in the most adverse environments. You may want to reduce the seeding rate 10-15 percent to extend this seed over more acres.
4) Plant the lowest quality seed in fields with excellent soil drainage, good soil tilth, and when the soil is warm and moist.
5) Handle the seed as gently as possible and the least amount possible.
6) Slow the planter down so that each seed is planted 1 inch to 1.5 inch deep and spaced uniformly in the row. If you must reduce seeding rates, it is much better to have low populations in narrow rows than wide rows.

On-farm soybean seed treatment

Authors: Dennis Mills, Anne Dorrance

Much of the soybean seed supply in the eastern Midwest is of lower than normal quality. For most areas of the state, the seed will need a fungicide treatment to protect it from disease. Studies have shown that fungicide seed treatments provide substantial protection and can increase yields.

The seed treating process can damage seed and reduce the germination rate, if the seed coat is thin or cracked. Therefore some companies have opted not to treat some seed lots. If this seed is planted early into cold, wet, soil conditions a seed treatment will be necessary, but precautions should be taken to reduce further damage due to treating and handling.

There are two on-farm treatments that can help with this untreated seed situation. For those with untreated bagged seed, Enhance is a hopper box treatment containing Vitavax and Captan. Vitavax and Captan will protect seed against Fusarium, Pythium and some Rihzoctonia but not Phytophthora. Another option for those with on-farm slurry or mist type treaters is Apron Maxx RTA. Apron Maxx RTA is also a broad spectrum seed treatment, but for those growers with heavy pressure from Phytophthora additional Apron XL will help. (read and follow label directions). In both cases be very gentle with the seed as you are treating and be extra careful with handling. This seed is prone to breakage that further reduces germination.

Poorly drained fields under no-till production, continuous soybeans or fields with a history of stand problems will benefit from a seed treatment. To reiterate what was stated in the previous article, plant soybeans this year under optimum planting conditions.

Sentinel plots for soybean rust monitoring are being planted in the south

Authors: Anne Dorrance

The efforts to monitor soybean rust have continued through the winter. Kudzu, which is another host of this fungal pathogen, has been monitored in Georgia, Florida, Alabama, Mississippi, Louisiana, and Texas. In addition, Mexico is now part of the IPM Pipe website, Rust is present on kudzu in Florida, Alabama, Louisiana and Texas as of March 31, 2008. There are three main events that need to happen before rust could impact Ohio soybeans.

The first is that soybean rust needs to overwinter at sizeable levels in the southeast and deep south. This appears to have happened so far this year, although as of last week, sporulation of the rust on kudzu in the Florida panhandle was low. Last year, there was an April freeze followed by an exceedingly dry spring that knocked rust back.

The second thing that needs to happen is a rapid build-up of soybean rust in the south for sizeable inoculum. As soybean sentinel plots are planted throughout the southern US, you will see green boxes begin to appear on the soybean rust web site. These indicate locations where soybean rust is monitored on a weekly basis – in the south, kudzu, soybeans and other beans are monitored. If rust builds up, these green boxes will turn red, once the first rust pustule is found. Based on last years’ movement, we saw rust move with every storm front from August through October until all of the leaves were gone on the soybeans. The question for 2008 is will rust build up early enough to begin its northward movement to impact the crop. We may be able to tell this by the July 4th holiday.

The third thing that needs to happen is to have rain storms follow a northerly tract, up the Mississippi and Ohio Rivers or up through North Carolina which follows the tobacco blue mold pathway. We have sentinel plots well positioned throughout the state to accommodate all of these pathways, including a kudzu patch in Lawrence county. Ohio’s sentinel plots will be planted at the end of this month and monitored weekly from the end of June through the end of August. If you see anything suspicious, please submit it to the C.Wayne Ellett Plant Diagnostic Clinic (, 110 Kottman Hall, 2021 Coffey Rd., Columbus, OH 43210-1087, . Ohio’s sentinel plot network is funded through the soybean check-off and USDA.

Soybean Aphid Expectations in Ohio for 2008

Authors: Ron Hammond, Andy Michel, Bruce Eisley

Since we are getting closer to the 2008 growing season, we thought it appropriate to mention our prediction for soybean aphids this year. Whereas last spring we saw large numbers of eggs followed by a big egg hatch on buckthorn (albeit we think that the early April freeze killed most of the aphids resulting in few economic problems), we saw neither aphids nor eggs last fall on its overwintering host. Combine this with the overall lack of winged aphids being caught last fall in states surrounding Ohio, we are predicting few if any soybean aphid problems this coming summer. Although there are really no preventive treatments available for aphid anyway, we still think growers can benefit by NOT having to plan on worrying about the aphid. However, as always, we recommend that growers continue to read this newsletter for future developments on the soybean aphid front just in case our prediction is wrong.

Weeds and the Potential for Insect Outbreaks 2008

Authors: Ron Hammond, Andy Michel, Bruce Eisley

With warm weather just around the corner, weeds are making their presence known. There are some insect pests, most notably the black cutworm, that are associated with the presence of weeds. In fields with winter annuals, especially chickweed, the potential for cutworm problems are high. Thus, growers should plan on monitoring their cutworm situation during the early stages of corn growth in such fields. Additionally, some growers might choose to till under heavier weed growth. As we get into later April and early May, the tillage and burial of weeds can cause an increase in seedcorn maggots. Although insect increases are usually associated with the tillage of old alfalfa fields or even wheat fields, large seedcorn maggot populations and subsequent injury have been seen with tillage of significant weed growth. In such cases, growers would be advised to consider an insecticide seed treatment on either corn or soybean.

Identifying Wheat Growth Is Important for Management Decisions

Authors: Pierce Paul, Jim Beuerlein, Dennis Mills

Due to cold, wet conditions, wheat growth throughout the state has been a bit slower this spring than during the past few years, however, the crop will start greening up within the next few weeks and growers will need to pay attention to crop growth stage in order to make adequate management decisions. Wheat growth stage identification it critical for effective timing of fungicide, insecticide and herbicide applications. In the case of diseases, insects, and weeds, management programs are based on thresholds at specific crop growth stages. Hence, crop growth stage identifications are extremely important. Failure to correctly identify these growth stages may lead to improper timing of applications, which may result in violation of pesticide label restrictions (products being applied off label), inferior control efficacy, and injury to the crop.

Cold temperatures in late March have prevented early and rapid growth of the crop. This is primarily due to soil temperatures remaining below 45 F for most of this time. However, as soon as it warms up and conditions are dry enough to handle application equipment, wheat producers throughout the state will be applying top-dress nitrogen. Plants are now ready for rapid growth as soon as consistent warmer weather occurs. As the wheat begins to green up, wheat producers should check fields in order to identify crop growth state. One of the most important growth stages for early management decision making is stem elongation or jointing growth state (Feekes' growth stage 6). Jointing growth stage can be identified by examining the larger tillers in the fields. Pull tillers and strip down the lower leaves and leaf sheaths on the stem to check for the presence of the first node at the base of the stem. Jointing is a critical stage for management reasons. Growth stage 6 signals the end of tillering and beginning stem elongation. All top dressed nitrogen should be applied by this time in order to maximize yield. This is also the growth stage when some herbicides can no longer be applied.

Some earlier planted fields in southern Ohio likely will green up and reach growth stage 6 within the next two weeks (once it warms up). Warmer weather and a shift to longer day lengths will cause the wheat crop to advance through the tillering growth stage by late April. Wheat growers in Southern and Central Ohio should check fields for growth stage before herbicides are applied. Assuming the weather will be near normal, we would predict that wheat in the more northern counties would reach growth stage 6 by the last week of April.

For more on wheat growth stage identification visit:

OARDC Research Station Weather and information websites

Authors: Harold Watters

Here’s something to bookmark. There are new web sites for the University research stations. The web site for each location also shows a graph of temperature and rainfall for the previous 24 hours. This would be a good way to see soil temperatures and rainfall in the area that contributes to crop growth.

For the major row crop areas of Ohio we have the stations Northwest, Western and North Central:

Archive Issue Contributors: 

Anne Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), Jim Beuerlein (Soybean & Small Grain Production), Peter Thomison (Corn Production), Robert Mullen (Soil Fertility) and Mark Loux (Weed Science). Extension Agents: Todd Mangen (Mercer), Roger Bender (Shelby), Howard Siecrist (Licking), Glen Arnold (Putnam), Greg LaBarge (Fulton), Steve Foster (Darke), Harold Watters (Champaign), Mike Gastier (Huron), Mark Koenig (Sandusky), Gary Wilson (Hancock), Jonah Johnson (Clark), Ed Lentz (Seneca) and Steve Prochaska (Crawford).

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.