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.
