Kudzu Bugs Numerous in MS Soybeans This Year

This year we have seen tremendous population growth and expansion of Kudzu bugs from previous years. We have treated  some acres already that were at threshold and I am confident that there will be many more to come based on what we are seeing around the state including the Delta region. We began seeing overwintering populations emerging around the end of March this year and with steady migration into Wisteria, Kudzu, and early planted soybeans for at least 8 weeks. We started picking up the first nymphs about 2 weeks ago in south MS. This week we can easily find nymphs in many soybean fields where adults were found early.

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Kudzu bugs on Wisteria 3/31/15 by E. Flint

Research at North Carolina State by Dominic Reisig and his group indicated that it took on average 42 days from egg to adult. With this in mind we will likely start seeing the next big push into soybeans at the end of July into August as we did last year. At this time we are expecting to see much higher numbers than we are experiencing now after they have had time to complete another generation.

What to do? Fortunately we have a lot of research from our colleagues in the southeast to draw from but it will be critical to determine what tweaks we will have to make in our production system here in Mississippi because it is much different. We are already experiencing a few things that they have not encountered in the southeast. For now we have simply adopted their threshold of 5 bugs/plant during the vegetative stages and 1 nymph/sweep during the reproductive stages.

One thing that is much different here than in the southeast is the fact that we had soybeans in the reproductive stages in some areas when the overwintering bugs moved into soybeans from overwintering because we plant much earlier than the Southeast.

Remember that kudzu bugs have piercing/sucking mouthparts so they will not make holes in the leaves. They feed on the stems and petioles of the plant. They do not feed on the fruit like stink bugs. Because of the way they feed, yield loss occurs when they suck the general vigor of the plants down similar to false chinch bugs. With this in mind, it takes high numbers to be a problem so don’t get alarmed when you start finding 20 or 3o adults per 25 sweeps. The likelihood of low numbers causing any yield loss is extremely low. Hopefully by utilizing the nymph threshold, we can minimize the number of treatments required to control this pest. When nymphs show up, it is a sign the adult migration is over and one spray should be sufficient. The problem may be in our system here in the Mid-South unlike the Southeast, that this may occur in June and again in August. However, this is yet to be determined.

The figure below is a compilation of trials from 2010-2012 from the entomologist in the Southeast that shows average efficacy for various products on Kudzu Bugs. It appears that several things work well but products containing bifenthrin continue to float to the top.

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The following presentation “Observations and Biology of Kudzu Bugs and Their Management in Southeastern Soybeans” provides some fantastic photos and information from the University of Georgia and Clemson University.