Issue No. 21, Article 9/August 12, 2005
Wheat Seed Treatments for Fall 2005
Treatment of wheat seed before planting with fungicides, or in some cases insecticides, can be an important part of an overall disease and wheat management plan. Many variables come into play when deciding whether seed treatments pay off: seed cost, seed treatment cost, crop value, seed condition, seed-bed condition, time of planting, anticipated disease and insect pressure, intended crop use, and options for disposal of excess treated seed. Because many of these variables are difficult to predict with much accuracy before planting, many folks looking for insurance either plant wheat a little heavier or use a seed treatment. Just like with car insurance, you buy the protection you need based on product performance and your particular situation and risk tolerance.
Many different seed treatments are registered for use on wheat. Each active ingredient has strengths and weaknesses, which is why premixed fungicide products are so common. In addition, an insecticide may be included or used alone to control insect pests. Typically, seed treatments last only about 10 to 14 days beyond planting. However, some products can protect the seedlings considerably longer when applied at the highest labeled rate. For example, difenoconazole and triadimenol can protect against fall-season foliar disease such as powdery mildew and rust. In addition, imidacloprid or thiamethoxam may be included or used alone to help manage aphids that transmit the barley yellow dwarf virus. Although these long-lasting systemic compounds offer a good deal of protection, they are relatively expensive.
Common active ingredients used for seed treatment and the fungi they control are listed in Table 3. Table 4 provides a current, but likely incomplete, list of seed treatment pesticides labeled for treating wheat seed. Check with local dealers to determine which products are available in your area and at what cost. Also consult the current edition of the Illinois Agricultural Pest Management Handbook for more information. Several of these products are available only to commercial seed treaters. Although there are many convenient premix products on the market, should you decide to create your own combination, be sure to read and follow the label of each product and contact the manufacturer if you need clarification.
To learn more about seed and seedling pests, consider purchasing the current Field Crop Scouting Manual (X880d), available at your local University of Illinois Extension office or at http://www.PublicationsPlus.uiuc.edu. For a comprehensive seed treatment resource, consider purchasing Illinois Pesticide Applicator Training Manual: Seed Treatment (SP 39-4), available from the same sources. The seed treatment manual, revised in November 2001, addresses common seed and seedling pests, seed treatment active ingredients, safety issues, and seed treating equipment and calibration.--Bruce E. Paulsrud