Garden Guide

Kudzu bugs are back!
Oct. 30, 2013 @ 04:58 AM

An article was written about kudzu bugs back in May; but a lot of calls are coming in about these nuisance pests again.   

Kudzu bugs are 4 to 6 mm long (about 1⁄6 inch - 1⁄4 inch), somewhat oblong in shape, and olive-green colored with brown speckles. They are “true bugs” and so they have piercing-sucking mouthparts. Aside from kudzu, these insects are known to feed on a wide variety of legumes (soybeans and other bean species, as well as wisteria and some vetches, Eger et al. 2010). Kudzu bugs have several generations per year. In the spring, they feed extensively in kudzu patches and on other legume hosts. In July-August, they will move into soybeans where they feed on stems and foliage and can have a significant impact on crop yields. The bugs continue to feed and lay eggs into the fall on kudzu and other hosts. People reported kudzu bugs showing up around houses a few weeks ago. However, the decreasing day lengths and temperatures have triggered a noticeable increase in the movement of kudzu bugs out of soybean and kudzu fields. In some cases, the bugs are finding overwintering spots in bark crevices, mulch and leaf litter, but there has been a spike in frantic calls from residents about kudzu bugs covering their house siding, cars, themselves, etc.

The answers to the questions that people will pose most frequently are not going to help their disposition:

How long will this invasion continue? That’s hard to estimate but hopefully it will stop before you’re carving the Thanksgiving turkey. Don’t be surprised if the activity continues for 2-3 weeks. Cool morning temperatures will slow the activity, but warm midday temperatures will have the bugs on the move.

What can I spray to stop them? Nothing ... Chemical control is still only partially effective and relies primarily on targeting the insects that are currently gathering on surfaces. Preventive sprays are not recommended — because a) you really don’t know whether the bugs will gather (more likely they’ll be spread out over broad areas, too), trying to treat the entire exterior of your house isn’t economically, logistically or environmentally prudent. The sprays simply won’t be durable enough to last the weeks during which these insects will be actively seeking overwintering sites. More importantly, “do-it-yourselfers” usually lack the ability (equipment and know-how) to do a thorough exterior treatment safely and effectively. Even pest control companies will rely primarily on targeted treatments of critical areas: windows and door frames, some soffits, which is the same recommendation that we make to homeowners. There are a number of products people can use under the Ortho, Spectracide and other common brand names. Most of these products contain “pyrethroids,” the pesticides with common names (not brand names) usually ending in “thrin” (permethrin, bifenthrin, lamda-cyhalothrin, etc.). An important point to remember is the need to exercise extreme caution when spraying the exterior of their homes because no matter how careful they are, chemical will splash back and drift onto them and nearby objects (barbecue grills, furniture, children’s toys, pet water bowls, bird baths, etc.) These objects need to be moved or at least covered while applying the chemical. Note that the emphasis is on exterior treatments.

Pesticides have limited ability to stop the bugs from entering homes. So, it is also important to seal gaps and openings (such as around plumbing and AC lines) to prevent the bugs from entering the home. Avoid crushing insects that do find their way indoors as this may stain surfaces and/or result in unpleasant odors. Vacuum up the insects and then place the vacuum bag (or contents) into a trash bag and freeze the bag for several days. You can also drop the bugs into soapy water to kill them. If you simply dump the live insects outdoors, they will likely end up back inside or surviving somewhere else around your property.

We do not recommend interior treatments of homes (or businesses) because these are an exercise in futility and potential harmful to occupants if pesticides are applied improperly. You can’t predict where the insects will show up indoors and so it doesn’t help to spray baseboards or around window interiors or setting off insecticidal foggers. Stick with using a vacuum cleaner but make sure to discard the bag (or clean the vacuum if it’s a bagless unit) because the bugs do emit an odor.

People have asked about spraying kudzu with an insecticide to kill the bugs before they make their move toward your home. I don’t expect this tactic to succeed because, in most cases, kudzu is covering such a wide area it is virtually impossible to make any sort of effective foliar application of an insecticide. Similarly, spraying kudzu with a herbicide earlier in the summer may not have the expected impact because you’re making the assumption that that kudzu patch is the source of your invaders which may not be the case. That doesn’t mean removing the kudzu won’t help, but just don’t count on it being the only contributing host particularly in rural areas where soybeans and other hosts are abundant. We have information for residential settings at: http://insects.ncsu.edu/Urban/kudzubug.htm