Cooperative
Extension
Service


University of Illinois
at
Urbana-Champaign


No. 19/July 29, 1998

Three Strikes and You're Out?

With apparent disregard for the potential negative impacts, at least one pesticide manufacturing company is promoting control of corn rootworm adults this year and control of corn rootworm larvae in the same fields next year. FMC Corporation has established the "Two Strike Program" for growers and dealers who want to "manage" western corn rootworms in corn planted after soybeans. Their recommendation is to treat soybean fields this year with Furadan 4F to control corn rootworm adults and then treat the corn next year with Furadan 4F to control rootworm larvae.

We have been quite clear about our opinion of this approach for managing rootworms in corn after soybeans: We strongly recommend against it, and we believe this is an irresponsible approach for addressing the problem. Although we understand that some growers and dealers are frustrated with the problem with rootworms in corn planted after soybeans, we cannot support an approach that is a recipe for disaster. Virtually every expert on insecticide resistance indicates that treating two life-cycle stages of an insect is one of the quickest ways to expedite the development of resistance to insecticides. As most of you are aware, corn rootworms have developed resistance to aerially applied insecticides (methyl parathion and carbaryl) in Nebraska, and we should be concerned about the potential development of resistance to insecticides in Illinois. Treating both rootworm adults and larvae with insecticides is one of the quickest ways to create a problem with insecticide resistance.

In FMC's "Two Strike Program," one of the most significant offenses is their use of our rootworm adult thresholds to "trigger" application of Furadan 4F to control adults this summer. We have stated emphatically that our thresholds were not developed for this purpose. Our thresholds are to be used by growers to determine whether or not they need to use a soil insecticide next season when they plant corn after soybeans. Consequently, we are quite distressed by the blatant misuse of our thresholds.

We are quite concerned that other pesticide manufacturing companies will promote a similar approach for rootworm "management." Spraying adult rootworms with insecticides this year and treating rootworm larvae next year with a soil insecticide is a bad idea. And we ask this question to growers: Why is it that the soil insecticides suddenly are not effective enough to protect your corn roots? Based upon all of the sales literature we have seen over the years, we assumed, like you, that soil insecticides would handle rootworms with ease. And now they won't? Apparently Furadan 4F applied for control of rootworm larvae in the spring is not sufficient.

Growers should be asking questions of all pesticide manufacturers who recommend a "Two Strike Program" or something similar. They should not buy into blatant disregard for all the pest management principles we (Illinois agriculture) embrace.

Kevin Steffey (ksteffey@uiuc.edu) and Mike Gray (m-gray4@uiuc.edu), Extension Entomology, (217)333-6652