Aphids and viruses

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

With the recent reports of soybean aphids being captured in suction traps throughout Michigan, vegetable growers are concerned about virus transmission. Very small numbers of soybean aphids have been caught so far in 2007, but we don’t expect large numbers until later in the year. You can track the soybean aphid flight in Michigan by checking the NCR IPM Regional Soybean Aphid Suction Trap Network.

What can be done to prevent virus transmission if and when large numbers of soybean aphids begin to fly?

For vegetable growers the answer, unfortunately, is not much. Soybean aphids do not live on vegetable crops. Any aphids you find on your vegetable are not likely to be soybean aphids. Any alate (wingless) aphids on vegetables are definitely not soybean aphids, since soybean aphids cannot reproduce on vegetables. Soybean aphids may land on melons, beans and peppers in an attempt to find their host plant (soybean), but they will not stay. Instead, they will “taste” the plant to determine if it is a soybean plant, and if it does not “taste right” they will fly off again.

During the few seconds it tastes the plant, any viruses that it is carrying can be transferred. No insecticide works fast enough to prevent this transmission. Insecticides do not prevent virus transmission in most vegetables and any application of insecticides to prevent viruses does more harm than good by killing natural enemies. The most effective way to reduce the incidence of viruses is to plant virus resistant varieties, avoid late plantings (during July and August when aphids are flying) during years of high soybean aphid populations (like 2007) and manage weeds in and around vegetable fields.

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