Kudzu Bugs

We've had two reports (Scotland County and Union County) that kudzu bugs are moving out of soybean fields and congregating on structures, including schools and school buses. This move out of host plants was anticipated but perhaps not this soon. As to why it's happening now is pure speculation, but favorable weather, particularly early this year, likely contributed to this early exodus as the adult bugs head into reproductive diapause.

The kudzu bug's fall movement indoors is very similar to what we've experienced since the 1990’s with the Asian lady beetle. The major difference between the two insects is that the Asian lady beetle is actually beneficial as a biological control agent, chomping down on aphids and other plant-feeding insects. By contrast, the kudzu bug's primary food source (aside from kudzu) happens to be field crops, such as soybeans, where they can significantly impact yield. So, this pest packs a double-whammy for North Carolinians.

The kudzu bugs’ fondness of soybeans is one reason why we could see significant numbers of them invading schools and other buildings, even in rural areas. In more urban areas, there are plenty of other hosts such as wisteria and privet. The insects are quite mobile; they are capable of catching rides on wind currents, automobiles, trucks, trains and planes. This helps explain why this pest has managed to spread in from north-central Georgia and through most of South Carolina, North Carolina, and Virginia (plus west into Mississippi) in just about 3 years time.

At this point, we still do not have anything new to report in terms of recommendations as to how you might address this problem. Kudzu bugs are attracted to light-colored surfaces but that certainly doesn't mean that brick buildings or those with dark-colored siding will escape the bug invasion. While people are going to want shortcuts and easy solutions, there simply aren't any. The emphasis still has to be on exclusion because chemical control is still only partially effective and relies primarily on directly targeting the insects that are aggregating on surfaces. Preventive sprays are not recommended - because they simply won't be durable enough to last the weeks during which these insects will be actively seeking overwintering sites.

If the problem is severe and you decide that pesticides are warranted, focus your applications around window frames and doorframes. If you use a pyrethroid for your treatment, don’t forget about the new label restrictions. The new label restrictions specify that other than applications to building foundations (which may be treated up to a maximum height of 3 feet), all outdoor applications to impervious surfaces (i.e., windows, doors, siding, sidewalks, patios, etc.) are limited to spot and crack-and-crevice applications only. Remember, a crack-and-crevice treatment is defined as the application of small amounts of insecticide to cracks and crevices in which insects hide or through which they may enter a building. Because crack-and-crevice applications are considered exempt, notification would not be required. A spot treatment is defined as pesticide application to limited areas (an area not exceeding 2 square feet) on which insects are likely to occur. Spot treatments are not considered exempt – so be sure to follow proper notification guidelines if you decide that spot treatments are needed. Under the new pyrethroid labeling, you are allowed to treat the underside of eaves, or the soffit, but again, because this would not be considered a crack-and-crevice treatment, notification would be required.

If large numbers of kudzu bugs make it indoors, simply vacuum them up. The use of pesticides indoors is not warranted and will be largely ineffective in this case.