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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2009-11

Dates Covered: 
April 28, 2009 - May 4, 2009
Steve Prochaska

Successful Corn Establishment in Late April and Early May

Authors: Peter Thomison

Mistakes made during the planting operation are usually irreversible, and can put a "ceiling" on the crop's yield potential before the plants have even emerged. The following are some tips that will help get a corn crop off to a good start.

1. Adjust Seeding Depth According to Soil Conditions

Plant corn seed from 1-1/2 to 2 inches deep so as to facilitate adequate root development. In late April and early May, when the soil is usually moist and evaporation rate is low, seed should be planted no deeper than 1-1/2 inches. As the season progresses and evaporation rates increase, deeper planting may be advisable. When soils are warm and dry, corn may be seeded more deeply up to 2 inches on non-crusting soils. One risk associated with shallower planting depths is the possibility of poor development of the permanent (also referred to as secondary or nodal) root system if the crown is at or near the soil surface. Permanent roots may not grow under hot, dry conditions (resulting in the "rootless" and "floppy" corn syndromes). Another potential risk from planting less than 1-1/2 inches is shoot uptake of soil-applied herbicides. Seeding depth should be monitored periodically during the planting operation and adjusted for varying soil conditions. Irregular planting depths contribute to uneven plant emergence, which can reduce yields.

2. Adjust Seeding Rates on a Field-by-Field Basis.

Adjust planting rates by using the yield potential of a site as a major criterion for determining the appropriate plant population. Higher seeding rates are recommended for sites with high-yield potential with high soil-fertility levels and water-holding capacity. On productive soils, with long term average yields of 160 bu/acre or more, final stands of 30,000-33,000 plants/acre or more may be required to maximize yields. Some recent studies conducted under favorable growing conditions on high yielding soils have indicated that final stands as high as 36,000/A were required for optimal yield. However at these higher plant densities the risk for major stalk lodging increases considerably.

Lower seeding rates are preferable when droughty soils or late planting (after June 1) limit yield potential. On soils that average 120 bu/acre or less, final stands of 20,000 to 22,000 plants/acre are adequate for optimal yields. On soils that average about 150 bu/acre, a final stand of 28,000 plants per acre may be needed to optimize yields. Seeding rate can be cut to lower seed costs but this approach typically costs more than it saves. Most research suggests that planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates (unless lodging becomes more severe at higher population levels) and harvest delays occur. Under moderate drought stress, high plant populations usually do not cause significant yield reduction on most Ohio soils. When planting occurs in cold soils, usually early planting dates, the seeding rate should be 10-15% higher than the desired harvest population. Follow seed company recommendations to adjust plant population for specific hybrids.

3. Perform Tillage Operations Only When Necessary and Under the Proper Soil Conditions.

Avoid working wet soil and reduce secondary tillage passes. Perform secondary tillage operations only when necessary to prepare an adequate seedbed. Shallow compaction created by excessive secondary tillage can reduce crop yields. Deep tillage should only be used when a compacted zone has been identified and soil is relatively dry. Late summer and fall are the best times of year for deep tillage.

Wheat Approaching Feekes 8, an Important Stage for Foliar Disease Management

Authors: Pierce Paul, Dennis Mills

The wheat crop is already a Feekes 8, flag leaf emergence, in some parts of southern and central Ohio and will reach this growth stage within the next 7 to 10 days in northern counties. This is am important growth stage for making fungicide use decisions for foliar disease management. Scout wheat fields to determine which disease is present and at what level before making a decision to apply a fungicide. Although several fungicides are available to control foliar diseases in Ohio, the decision to use these products should be based on the susceptibility of the variety planted, the level of disease in the field, weather conditions, the yield potential of the field, fungicide cost, and the market price of wheat.

The first diseases to be detected are usually Septoria leaf blotch and powdery mildew. Septoria usually shows up in late April on the lower leaves and will develops up the plant if frequent rains occur. Powdery mildew is important during the month of May and early June in mild seasons with high relative humidity. Randomly collect 30 to 50 tillers from throughout the field and look for the small white pustules on the lower leaves and leaf sheaths. If powdery mildew is present in a field planted to a susceptible variety you should watch its development over the next week or so and decide whether fungicides should be applied. Fungicides should be applied for powdery mildew control (on susceptive varieties) when 2 to 3 pustules are detected on the leaf (leaf two, counting from the top) below the flag leaf (the top-most leaf) anytime between growth stage 8 (flag leaf emergence) and 10 (boot). Stagonospora leaf and glume blotch is most severe when frequent rains occur during the months of May and June. Scout fields between growth stages 8 (flag leaf emergence) and 10.5 (full head emergence) and if 1 to 2 lesions are detected on the leaf below the flag leaf on a susceptible variety, fungicide should be applied.

Remember, for foliar disease management (powdery mildew, Septoria, Stagonospora and Rust) fungicides are usually not needed when resistant varieties are grown. An updated list of fungicides registered for wheat disease management can be found on the field crops disease web site at

Wheat Row Spacing May Vary in Modified Relay Intercrop Systems

Authors: Steve Prochaska

Modified Relay Intercropping is the planting of soybeans into wheat usually from late May to mid June in North Central Ohio. To accommodate soybean planting equipment, wheat row width is modified. Various wheat row width combinations have been utilized successfully. The following are examples in use in North Central Ohio: 10 inch row wheat and soybeans; 15 inch row wheat and soybeans; two 6 inch rows of wheat followed by two 7 inch rows of soybeans; two seven inch rows of wheat followed by one 6 inch row of soybeans and various combinations of the above. All of the above row systems have produced acceptable wheat and soybean yields.

A common denominator in all MRI systems is a tram line (normally fitted to tractor tires) that is utilized to accurately guide soybean planting equipment through the headed wheat. Do not attempt to intercrop soybeans into wheat where there is not any tram line and wheat row spacing configured to accommodate the soybean planting equipment.

Wheat is a flexible, adaptable plant that may allow farmers with good management to capture some 66% of the traditional growing season in Ohio — May 25 to September 30 — to produce a second crop through the inter-planting of soybeans into wheat. In years with adequate and well distributed rain, soybean yields of over 40 bushels per acre and wheat yields of over 80 bushels per acre have been measured. To learn more about this system go to: .

Armyworm and Black Cutworm Watch

Authors: Ron Hammond, Andy Michel, Bruce Eisley

Adults of both the black cutworm and armyworm are being collecting in Ohio, as well as in states to our south and west. So far, none of the states are reporting exceptionally heavy armyworm flights, at least compared to those seen in outbreak years such as 2006 or 2008. However, the arrival of these moths in Ohio suggests that problems could occur in Ohio in the coming months.

Wheat should be checked over the next few months to prevent unnecessary defoliation from armyworm. This scouting should begin in early to mid May in southern Ohio to mid and late May as you get to the north and continue into June. Also remember that corn planted into a rye cover crop is especially at risk from armyworm. For information on armyworm biology and how to scout, see our revised fact sheet For a list of insecticides labeled for armyworm on wheat, see

As corn begins to emerge and grow, scouting should be initiated for black cutworm, especially in fields that had larger amounts of annual winter weeds present, especially chickweed. Black cutworms go through seven instars, with only the last four producing the greatest amount of injury. See our revised fact sheet on black cutworm, , for information its biology, scouting, and when to treat. See for insecticides labeled for cutworms on corn.

An additional worry related to corn is that much of the crop is going to be planted relatively late this spring. Only a small percentage of intended corn acres have been planted as of this C.O.R.N. newsletter issue (with most of those being planted the past 2-3 days), and with the forecast for rain over the next week, a good portion of the corn will not be planted for a while. Corn will be rather small when larvae of these pests begin their heavier feeding. Thus, the potential for plant injury and subsequent economic losses will be much higher than normal because of the size of the corn.

Alfalfa Weevil Update

Authors: Ron Hammond, Andy Michel, Bruce Eisley

With the recent warm weather, heat unit accumulations necessary for initiating scouting for alfalfa weevil larvae have been reached for all parts of Ohio. Accumulations in southern and central Ohio suggest that scouting should be a priority because of the potential size and feeding of weevil larvae. Heat units in north central and northwestern Ohio also would indicate that larval feeding might now be noticeable. Although heat unit accumulations in northeastern Ohio are not as far along, they are to the point where scouting for alfalfa weevil should begin. With reports of excellent alfalfa growth, growers should take care that the weevil does not cause problems. See the C.O.R.N. newsletter from April 14, #9, for detailed information on how to scout for alfalfa weevil. See the OSU Alfalfa Weevil Fact Sheet for more on alfalfa weevil scouting and thresholds. For insecticides that are labeled for alfalfa weevil, see .

OSU On-Farm Research Evaluates Early Fungicide Use on Wheat

Authors: Bruce Clevenger

OSU on-farm research evaluates agronomic practices and products on a field-scale setting with a local farm operation. In 2008, two replicated studies were completed on early (prior to flag leaf emergence) fungicide applications on wheat. Fungicides were applied in one study at Feekes growth stage 5-6 (leaf strongly erected to first node visible) and the other study at Feekes growth stage 7 (second node visible). Both studies found no significant yield difference as a result of the fungicide application. No significant differences were observed in disease presence in any treatments or control plots. Fungicide application decisions should be based on susceptibility of the variety planted, the level of disease in the field, weather conditions, the yield potential of the field, and the market price of wheat. The direct link to these on-farm reports is:

Evaluation of a ½ Rate of a Foliar Fungicide on Wheat (Defiance County):

Evaluation of Foliar Fungicides on Wheat (Van Wert County):

Additional OSU on-farm research reports can be found at:

Early May Weather Forecast

Authors: Jim Noel

The warm weather will end after today. We will return to a more normal temperature period for the next 2-3 weeks. The main change as we talked about last week was the warm and dry period would end early this week and would be followed by a wet period. This looks to be the case the next 2-3 weeks with periods of showers and thunderstorms. It looks active Tuesday through Friday then a nice cooler and dry weekend with more wet weather next week. There will be some breaks but some locally heavy rain is expected the next 2-3 weeks. The probability of >2" of rain the next 2 weeks is >90% for most of the state. Some of our models indicate some flooding is even possible.

Archive Issue Contributors: 

State Specialists: Pierce Paul and Anne Dorrance (Plant Pathology), Ron Hammond, Bruce Eisley and Andy Michel (Entomology), Peter Thomison (Corn Production). Jim Noel (NOAA). County Extension professionals: Roger Bender (Shelby), Harold Watters (Champaign), Greg LaBarge (Fulton), Les Ober (Geauga), Mike Gastier (Huron), Wesley Hahn (Logan), Bruce Clevenger (Defiance), Howard Siegrist (Licking), Suzanne Mills-Wasniak (Montgomery), Tim Fine (Miami), Glen Arnold (Putnam), Jonah Johnson (Clark), Mark Koening (Sandusky 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.