No. 9 Article 5/May 20, 2005

Chatter About Soybean Insects Will Escalate

Only about 15% of the planted soybeans had emerged by May 15, according to the "Current Illinois Weather and Crop Report" released by the Illinois Agricultural Statistics Service. However, warmer temperatures will speed up soybean emergence, so we can anticipate hearing more about insect infestations soon. Bean leaf beetles will be the first insect pests on our radar screen, but soybean aphids won't be far behind. We have written more than once about the status of soybean aphids on buckthorn, so right now we are in a holding pattern, waiting to assess the movement of winged soybean aphids to soybean fields.

Early signs of injury caused by bean leaf beetles include feeding scars on cotyledons and shot holes in unifoliate and trifoliate leaves. When growing conditions are favorable for soybeans, defoliation injury usually does not result in economic losses later in the season. However, if the injury is significant and soybean seedlings are growing slowly, an insecticide application may be justified. Table 2 shows the insecticides suggested for control of bean leaf beetles infesting soybeans in Illinois.

Soybean seedlings with bean leaf beetle feeding injury.

Instead of summarizing information about soybean aphids from a couple of experts (David Voegtlin, Illinois Natural History Survey, and Robert O'Neil, Purdue University), I direct you to an article they wrote for The New Agriculture Network. The article, "Planning for the 2005 Soybean Aphid Population," covers some of the ground that we have covered in the Bulletin previously, but Dave and Bob provide additional detail.

Keep us apprised of soybean insect activity in your area, and we'll pass along information we receive.--Kevin Steffey

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