September 24, 2009

Aphids resemble gnats; swarm yards, parks and gardens

The small, greenish-yellow aphids are out in larger numbers this year, likely because their populations grew late in the season and were not treated with insecticides, said Purdue University entomologist Christian Krupke.

"In late summer and early fall, as day-length declines and soybeans begin to yellow and die, winged soybean aphids take flight in search of their overwintering host -- a common roadside shrub called buckthorn," Krupke said.

The aphids mate and lay eggs on buckthorn shrubs in the fall, and eggs hatch in spring. In April and May the winged insects fly to young, newly planted soybeans, Krupke said. Soybeans provide food for the aphids through the summer and the cycle repeats in the fall.

"The host range of the soybean aphid is restricted to buckthorn and soybeans, so homeowners and gardeners do not need to be concerned," Krupke said. "They may land on various other plants, but they won't be able to feed or develop on them. They are primarily a nuisance -- especially in areas with an abundance of soybeans or buckthorn shrubs."

Krupke said the number of aphids should subside by the end of September.

Photos of soybean aphids and a video clip of the insects flying to buckthorn trees during fall migration is available on the Purdue Extension Entomology "Hot News" Web site at https://extension.entm.purdue.edu/publications/HN-65.pdf

Writer: Jennifer Stewart, 765-494-6682, jsstewar@purdue.edu

Sources: Christian Krupke, 765-494-4912, ckrupke@purdue.edu   

Ag Communications: (765) 494-8415;
Steve Leer, sleer@purdue.edu
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