Issue No. 3, Article 2/April 8, 2005
Protecting Corn from Soil Insect Injury
The fantastic weather in late March and early April throughout much of Illinois got people all fired up for planting corn. And so it has begun. As of April 3, the Illinois Agricultural Statistics Service had reported that 1% of the corn had been planted (http://www.agstats.state.il.us/). A respected source in western Illinois estimated on April 5 that 10% of the corn in his area had been planted. And planters continue to roll as the weather and soil conditions continue to be favorable for planting.
A practice that often accompanies corn planting throughout much of the Midwest is that of applying a soil insecticide or planting transgenic seed or insecticide-treated seed for control of soil insect pests (e.g., black cutworms, corn rootworms, white grubs, and wireworms). A lot of producers use these insect-control products as insurance to protect against the potential for economic damage. Although this practice is not necessarily a tenet of integrated pest management (IPM) and is an unnecessary expense if the target insects do not occur at economic levels, applying insecticides as prophylactics has been a common practice for decades. We could debate (and have debated) the merits and negative aspects of this practice in thousands of written and spoken words, but for now, let's accept the fact that this practice is commonplace and instead discuss reasonable expectations and subsequent evaluations.
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. Throughout the winter meeting season and in many previous articles in the Bulletin, we have stated that no rootworm-control product is "bulletproof" and that producers should not use these products expecting that rootworm damage will never occur. Every product currently labeled for rootworm control has provided less than adequate protection in some fields in some years. There are no exceptions. Occasionally, performance problems are widespread. We have discussed, in some detail, the factors that may contribute to less-than-adequate control of soil insects--for example, soil too wet or too dry; windy conditions at planting; early planting (especially relevant again this year); inadequate incorporation of soil insecticides (especially when corn is planted early); and interactions among the environment, corn hybrid, and insect. So suffice it to say that we should expect performance problems again in 2005. It's almost inevitable.
We state once again that 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 for a producer--presence or absence of soil insect pests, and 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 shifts into high gear, we offer these last-second reminders:
- Apply soil insecticides at the labeled rates. Applying insecticides at greater-than-labeled rates is illegal.
- 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.
- Use seed-applied insecticides at the rate indicated for the target insect(s).
- Plant a non-Bt (i.e., non-YieldGard Rootworm) corn refuge (20%) within or adjacent to a field of YieldGard Rootworm corn. (This holds true also for YieldGard Corn Borer corn and Herculex 1 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.
Here's wishing you a safe and successful planting season, as well as satisfied expectations for control of soil insect pests in 2005.--Kevin Steffey