Virginia soybean growers are almost certainly going to have some problems with kudzu bug (KB) in soybean fields this summer.

Why? We have been getting very early reports of adults from several southeastern counties for the past several weeks (including Suffolk, Isle of Wight, Sussex, Dinwiddie, Greensville and Prince George). Likely they are much more widespread.

Adults are good fliers and land on clothing, vehicles, houses and other plants.

KBs can be numerous on fig trees. Although they are undoubtedly feeding to some extent, we do not think they are an issue on fig trees. We are recommending they be sprayed with soapy water or insecticidal soap on these transient hosts in yards as they cause a nuisance. Dish washing detergent will kill or run them off.

As you may recall, last summer in our Virginia soybean field surveillance program we observed adult KBs in soybean fields in 16 or so counties but not until well into the season.

We reckoned those adults had migrated from the south.

A few nymphs were also found in a couple of locations. No fields became infested at treatable levels.

By contrast, this years very early adult activity means fields are at much greater risk. According to the folks in South Carolina and Georgia who have been working with kudzu bug since its first occurrence in soybeans in 2009, this very early adult activity means a couple of significant things.

One, the adults we are seeing now over-wintered (in the adult stage) locally. This is a much different picture than what we had last summer and likely means we are at the beginning of having to manage them in fields.

Flowering stage

And two, they will begin to invade soybean fields as soon as the crop starts flowering.

Most alarming is the report and image I received (May 22) from Jim Oliver (Monsanto) that shows a volunteer soybean plant from the South Boston area covered with KB nymphs.

This is the first record of a heavy nymphal infestation on soybeans in Virginia. The nymphs are congregating on some of the 8-10 inch tall volunteer soybeans, but not (yet) on the newly planted beans in that field that are about 3 inches tall.

 

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My advice was to wait to see if they move to the planted crop before making a control decision.

Fortunately, we do not have to reinvent the wheel in terms of management recommendations: Just stick with what has been developed in Georgia and South Carolina where they have had a couple of years of experience and research.

First, infestations are most likely to be encountered in the earliest planted, full season, earliest maturity group soybean fields as those will be the first to flower.

Second, the threshold is based on numbers of nymphs, NOT adult activity. Basically, we need to key on the nymphal stage of this insect in soybeans.

Fields should be treated when the average reaches one nymph per sweep net sweep or if nymphs are easily found on stems, leaf petioles or leaves.

Because there are only two complete generations per year, we should be able to control the nymphs for each generation and control population development.

Third, there are several good insecticide options for controlling KB. We will provide more detail on these in future Advisories. These recommendations as well as good images of the different insect stages (egg, nymph, adult) are located in a kudzu bug field guide produced by Clemson University, University of Georgia and the United Soybean Board available online at: http://digital.turn-page.com/i/87846.

Our advice: Begin checking any soybean fields where plants have emerged, especially if you are located in the south central part of the state.

 

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