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Issue No. 20, Article 2/August 11, 2006

Insect Reminders

You may find some observations of interest about insects in field crops, and others may require your attention. Following is a brief list of reminders:

  • Keep scouting cornfields for western bean cutworms. Timing for insecticide applications likely has passed for most fields, but an assessment of the presence or absence of this new pest will give you a better handle on potential management scenarios in 2007. Jim Donnelly, crop specialist with Ag View FS in Walnut, scouted a field in Bureau County in which about 20% of the plants were infested with western bean cutworm, with as many as five larvae per ear. He admits that the situation in this field may be atypical, but his observations suggest that others should be looking more closely for western bean cutworms. The impact of this pest in Illinois probably will increase over time.
  • When looking for western bean cutworm, look also for second-generation European corn borers. As we have stated previously, numbers of European corn borers in 2006 seem to be larger than in the previous few years in some areas of the state.
  • Numbers of potato leafhoppers in some fields of alfalfa are very large, and fields have been treated with insecticides. It is important to note that the economic threshold is lower in alfalfa regrowing after a cutting than in alfalfa that is close to harvest (0.2 and 2 leafhoppers per sweep, respectively).

As the growing season begins to close in on harvest, insect problems will begin to abate. But as I stated last week, August can be a critical month for some insect species, so don't let your guard down too early.--Kevin Steffey

Kevin Steffey

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