University of Illinois

No. 5/April 24, 1998

Thinking About Trapping Corn Rootworm Adults
in Soybeans This Summer?

In issue no. 2 (April 3, 1998) of this Bulletin, Mike Gray wrote an article that indicated where you could purchase Pherocon AM traps if you want to monitor for western corn rootworm adults in soybeans this summer. The article generated a lot of interest, and many people are planning to engage in this activity this year. Consequently, we need to offer a couple of general guidelines.

First, although other sticky cards are available for trapping corn rootworm adults, we can recommend only Pherocon AM traps because the research we have conducted is based solely on this type of trap. If you wish to compare your results with the information we generate, don't use another type of trap. Second, if you want to use the traps for decision making, you will need to follow a specific protocol based upon numbers and arrangement of traps and trapping duration. We will develop this protocol in a fact sheet that we intend to make available reasonably soon. However, if you want to use the traps outside the affected area of 10 to 12 counties of east-central Illinois to learn whether western corn rootworm adults can be found in soybeans in your area, you can implement a less rigorous protocol. Again, we will make this protocol available in the very near future. Also, keep in mind that presence of western corn rootworm adults in soybeans does not mean the problem exists. The only way to verify that rootworm larvae are affecting corn planted after soybeans is to dig up root systems in July and examine the roots for feeding injury.

Future issues of this Bulletin will provide more on this unique problem with rootworms in corn after soybeans.

Kevin Steffey (, Extension Entomology, (217)333-6652