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Issue No. 24, Article 4/November 9, 2007

Suction Traps Have Captured Very Low Numbers of Soybean Aphids This Fall

The outbreak of soybean aphids in Illinois in 2007 was second in intensity (numbers of fields with densities greater than the economic threshold) only to the outbreak that occurred in 2003. Many fields were sprayed with insecticides to prevent significant yield losses. As we have learned from past experience, these summer outbreaks have been followed by low numbers of winged soybean aphids flying to their overwintering host, buckthorn, in the fall. This same phenomenon occurred in 2007. Dr. David Voegtlin, the Illinois Natural History Survey entomologist who coordinates the suction trap network, indicates that the captures of soybean aphids in suction traps in Illinois in 2007 have been the lowest recorded since the 2001 inception of the network.

You can view the captures of soybean aphids in suction traps in Illinois from 2001 through 2007. There are lots of zeroes at all nine sites since some of the larger captures in August at DeKalb, Perry, Urbana, Freeport, Morris, and Metamora. If the pattern of captures of small numbers of soybean aphids in the fall followed by few soybean aphid infestations in soybean fields the following year holds up, soybean producers should be able to breathe a sigh of relief in 2008. However, it is worth noting that multicolored Asian lady beetles have not been all that common this fall, either. They have been around, of course, but we have not heard many widespread screams about their home invasions this year. Typically numbers of these predators are quite large in the fall following a soybean aphid outbreak, so the lower numbers this fall are worth noting. We will have to see how this all plays out next year.

If you want to examine captures of soybean aphids in suction traps throughout the Midwest, visit the North Central IPM Center Web site. You can view the 2007 captures at any of the 42 sites, from as far west as Manhattan, Kansas, and Brookings, South Dakota, to as far east as southeastern Michigan and Lexington, Kentucky. You will note very low numbers of soybean aphids captured at all sites in October.

Regarding soybean aphids and their management, we will have a lot to talk about during educational programs this winter. In the meantime, we continue to compile and analyze data to share. Stay tuned to future developments.--Kevin Steffey

Kevin Steffey

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