Integrated Crop Management

Soybean aphids: What's happening?

It was reported in an earlier ICM Newsletter article that the Soybean Aphid Task Force has been formed to collect information on soybean aphid presence and densities this summer, and then make forecasts and recommendations concerning aphid management. This is an update on how the season has been developing.

To date, 2005 has not been a repeat of 2003. Aphids appeared early, but their numbers have been slow to build and may have declined in some areas during the hotter weather at the end of July. Most important, aphid infestations are spotty both within fields and between fields. It is true that some fields have exceeded the economic threshold of 250 aphids per plant and have been treated, but most fields have not reached economic levels. Within fields aphid populations also have been very spotty. Brian Lang, extension field crops specialist in Decorah, reports that, "You may find a plant with 2,000 aphids on it, but in the adjacent row, or 10 plants down the same row, plants might only have 30 aphids."

The take-home message from the reported aphid infestations is that it continues to be very important to scout aphids, at least for the next week or two. If a field has been treated, this doesn't mean that your adjacent field will need an insecticide treatment. On the other hand, just because no one is treating for aphids doesn't mean that you couldn't have a field that would benefit. Check your fields! Also, you will have to be conscientious in your scouting because the infestations will vary considerably among areas of a field and from plant to plant. Don't let up yet, the picture could change with the more recent cooler weather!

Ants tending soybean aphids [1]
Scout for aphids�five locations per 20 acres. Check the upper two or three trifoliate leaves and stem for aphids. Aphids are most likely to concentrate in the plant terminal. Look for ants or lady beetles on the soybean plant�they are good indicators of the presence of aphids. (Marlin E. Rice)
Asian lady beetle feeding on soybean aphids

This article originally appeared on page 159 of the IC-494(21) -- August 1, 2005 issue.


Source URL:
http://www.ipm.iastate.edu/ipm/icm//ipm/icm/2005/8-1/soybeanaphids.html