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Grasshoppers Hopping (07/16/20)

Nymph grasshoppers (young grasshoppers) have increased recently in field edges of wheat, soybean and other crops.

Nymph grasshoppers (young grasshoppers) have increaseent.1d recently in field edges of wheat, soybean and other crops. Field reports have come in from Benson, Ramsey, Steele Counties and other areas that were dry. Scout fields weekly for economic populations of 50-75 nymphs per square yard in field margin or 30-45 nymphs per square yard in field. Since it is difficult to estimate the number of grasshoppers per square yard when population densities are high, pest managers can use four 180-degree sweeps with a 15-inch sweep net, which is equivalent to the number of nymph grasshoppers per square yard.

It may be puzzling why grasshoppers are becoming a problem with the recent wet weather. However, most of the nymphs are in the late growth stages now, so they can survive wet weather better than newly hatched grasshoppers. The weather was fairly dry and hot during most of the grasshopper emergence from mid-May to early June, which favors grasshopper development and survival.

 If grasshopper nymphs are at threshold, it is better to management them now than to wait until they become adult grasshoppers. There are a number of advantages in treating grasshoppers early:  (1) fewer acres will have to be treated and less insecticide is necessary to obtain control, thus reducing cost; (2) grasshoppers are killed before they have had the opportunity to cause significant crop loss; (3) smaller grasshoppers are more susceptible to pesticides than larger grasshoppers; adult grasshopper also have wings and are mobile moving out of treated fields to untreated fields; (4) early treatment before grasshoppers reach maturity prevents egg deposition in fall, which may help reduce the potential grasshopper threat for the following crop year.

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Janet J. Knodel

Extension Entomologist

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