Integrated Crop Management

Grasshoppers confirm mild winter

If we use grasshoppers as a gauge of winter severity then the winter of 2001-2002 was certainly an insect-friendly winter. I noted [1] in the December 2001 Integrated Crop Management newsletter that a few differential grasshoppers had survived around Ames until at least December 8. Typically, many of these grasshoppers are dead by early November. Then, on February 23 of this year, which was an unseasonably warm day, I found grasshopper nymphs in my garden. The time span between the last grasshopper of 2001 and the first grasshopper of 2002 was only 77 days.

This young grasshopper was found on February 23, 2002 in Ames, Iowa.

The Des Moines Register (February 23, Winter That Wasn't) also commented on the mild winter and noted that "this winter is on track to be the second warmest" and "things unheard of have happened all winter around Iowa."

So what do these grasshoppers portend for insect pest problems in 2002? The survival of many crop insect pests that overwinter in Iowa is strongly influenced by winter weather. Both the intensity and duration of low temperatures can substantially reduce insect populations. But this past winter was very mild so I would expect larger than average populations of corn rootworms, European corn borer, alfalfa weevils, white grubs, bean leaf beetles, and soybean aphids. Other insect pests, especially those that migrate into Iowa each spring, such as black cutworm and potato leafhopper would not be influenced by the winter in Iowa. However, weather during the spring and summer also can affect insects, making their populations go up or down. It will be interesting to see what happens this summer.

This article originally appeared on page 62 of the IC-488 (7) -- May 6, 2002 issue.

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