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Quick Insect Update for This Week

July 31, 2003

As I write this relatively brief article, I am only an hour away from reimmersing myself in evaluations of numerous corn rootworm research efforts. Mike Gray, Sue Ratcliffe, Martin Bohn, Ron Estes, and I (all in the Department of Crop Sciences), with the help of numerous graduate students and summer employees, began digging, washing, and rating roots from several research trials in Urbana on Monday, July 28. The types of trials we are evaluating include standard insecticide efficacy trials, a time of planting/crop rotation study, and several large corn breeding trials (under the direction of Martin Bohn). At the Urbana location, we are in the midst of assessing 4,700 roots for rootworm larval damage (with 2,500 yet to be dug, washed, and rated). We hope to begin evaluation at our Monmouth location (2,240 roots) on July 31 and at our DeKalb location (2,200 roots) on August 4. Shortly thereafter we will begin our survey of root damage in fields of corn planted after soybeans. By the time it's all said and done, we will have evaluated more than 13,000 roots for rootworm damage. That's a lot of roots and mud! We're already looking forward to September.

Because of this fieldwork, we cannot offer much in the way of insect updates this week. So I'll provide a few brief comments about ongoing and pending insect problems, and then I'll head back to the field. Thanks for your patience.

Corn Rootworms. We have received many reports of significant corn rootworm larval damage, especially from counties in northern Illinois. The focus there, of course, has been on the variant western corn rootworm that laid eggs in soybeans in 2002 and is causing damage to the roots this year. As touched on in the following article, the range of this insect has expanded in Illinois (mostly to the north and west), and damage is fairly severe in fields on the "leading edge" of this expansion. We intend to expand our survey efforts into northern Illinois so that we can get a reasonable assessment (through random selection of fields) of the areas of occurrence of this very important pest. We'll share results from the survey and from some of our research efforts in future issues of the Bulletin.

Soybean aphid. Infestations of soybean aphids in Illinois are worse in 2003 than they have been since their discovery in North America in 2000. Reports of very high densities of soybean aphids continue to come into our office, and many fields have been treated with insecticides. The numbers of soybean aphids collected in our suction traps for the week ending July 25 were as follows:

  • Dixon Springs--1
  • Monmouth--59
  • DeKalb--940
  • Brownstown--3
  • Perry--4
  • Urbana--2
  • Freeport--112
  • Joliet--not reported
  • Eureka1--42

Compared with captures in these traps in previous years, the numbers being captured in northern Illinois are enormous (especially at DeKalb). Obviously a lot of winged aphids are flying about, moving from field to field as densities within fields increase. For more information about the suction trap network in Illinois, go to the IPM Website.

Despite the widespread infestations of soybean aphids in Illinois, not every field has economic levels of the pest. Monitoring continues to be extremely important. Having a field treated simply because neighbors are having their fields treated is not a sound pest management practice. As you monitor soy-bean fields for aphids, be certain to watch for natural enemies and alatoid nymphs, both of which may suggest a forthcoming "crash" in the aphid population. For more information about soybean aphids, refer to the article "Soybean Aphid Update" in issue no. 18 (July 25, 2003).

European corn borer. There's not much news to report concerning European corn borers, but folks in central and northern Illinois should be very watchful as the second generation begins. According to Ron Hines, senior research specialist at the University of Illinois Dixon Springs Agricultural Center, insecticide treatments to control second-generation corn borers, if necessary, should be applied soon in southern counties. The time for control of second-generation European corn borers is approaching elsewhere in the state. So keep your eyes peeled for moths flitting about fields, egg masses on the undersides of leaves, and small larvae in the leaf axils (if you have patience and good eyesight). Refer to Kelly Cook's article "Start Thinking About Second-Generation European Corn Borers" in issue no. 18 (July 25, 2003) for specific information about scouting, thresholds, and management.

Japanese beetle. Japanese beetles probably have done about as much as they can do to the corn crop in most areas of Illinois, and they continue to defoliate soybeans in some areas. As the season for this pest draws to a close in 2003, we will reassess what we know and what we need to know about this nuisance and direct some of our attention toward more field research in 2004. As a closing salvo, the close-up photograph of Japanese beetles, taken by Robert Bellm (Extension crop systems educator in Edwardsville), reminds us what these beetles can do when corn is pollinating.

Japanese beetles on an ear of corn at the Brownstown Agronomy Research Center. (Photograph courtesy of Robert Bellm.)

As we roll into August and some of our insect problems begin to diminish, we'll keep providing updates and management information as appropriate. Keep your reports coming. They are most welcome.--Kevin Steffey

Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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