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Issue No. 2, Article 4/April 7, 2006

Controlling Corn Soil Insect Pests

The recent wet weather may have slowed down corn planting plans, but only temporarily. As soon as the soils are ready, producers will begin planting corn, and our season will be under way. By this time of year, decisions about controlling corn soil insect pests have already been made (months ago), so last-second recommendations carry little weight. However, we believe it is important to provide a few reminders associated with managing corn soil insect pests as the corn planting season commences.

Three types of products are available for control of subterranean insect pests of corn--soil insecticides (granular and liquid formulations), seed-applied insecticides, and transgenic Bt corn for rootworm control (YieldGard Rootworm and Herculex RW hybrids). Each product type has its advantages and limitations, which have been shared in countless articles and meetings in Illinois and elsewhere in the Midwest. So now probably is not the time to reiterate such observations. However, some overarching statements and reminders are in order about properly using each type of insect control product.

We believe that every producer who uses an insect control product has an obligation to understand what the product will and will not do. Therefore, a producer should have reasonable expectations for the performance of an insect control product and understand that performance may fall short of expectations for a number of reasons. In written and spoken words, we have stated that no insect-control product is "bulletproof," and producers should not use products with an expectation that insect damage will never occur. Also, producers should seriously consider leaving untreated check rows in each field in which an insect control product is used. Untreated check rows can reveal essential information--the presence or absence of soil insect pests, or injury and yield comparisons between treated and untreated rows. The need for or performance of an insect control product can be measured only against an untreated check. One or more untreated check areas provide a producer with an understanding of the "background noise" of insect pressure in a field.

As corn planting gets under way, we offer these reminders of proper use of products to control corn soil insect pests:

  • Apply soil insecticides at the labeled rates. Applying insecticides at greater-than-labeled rates is illegal, and less-than-labeled rates may not provide the level of protection expected.
  • Place granular or liquid insecticides in a band over the row or in furrow, depending on label guidelines and advice from company representatives.
  • Incorporate granular and liquid soil insecticides into the surface soil. We believe that this has become even more important as corn planting commences early.
  • Use seed-applied insecticides at the rate indicated for the target insect(s).
  • Plant a non-Bt (i.e., non-YieldGard Rootworm or non-Herculex RW) corn refuge (20%) within or adjacent to a field of YieldGard Rootworm or Herculex RW corn. (This also holds true for YieldGard Corn Borer corn and Herculex 1 Insect Protection corn for control of Lepidoptera pests, although the topic of this article is control of corn soil insects.) The non-Bt refuge is an insect resistance management practice that is required by the U.S. Environmental Protection Agency (EPA) and encouraged by the National Corn Growers Association and the Illinois Corn Growers Association.

As always, please contact us if you have observations or questions. --Kevin Steffey

Kevin Steffey

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