This week the Iowa Insect Diagnostic Clinic has officially declared that the annual multicolored Asian lady beetle migration to homes has begun! The beetles spend their summers in our gardens, forests, and crop fields eating aphids and many other pest insects. In the fall, the shorter days and first frosts trigger their annual search for a good spot to spend the winter. Research has found that these insects tend to fly toward large objects that have a high amount of contrast. Unfortunately, our homes are large objects and with the afternoon light casting many shadows on the southern and western sides of the house, they also have very contrasting patterns. Normally the lady beetles would prefer to overwinter in cracks and crevices of a cliff or other rock face, but since they are lacking in most of Iowa, they tend to locate many of our homes. In general houses are not the best spot for overwintering. The beetles accumulate within the walls of homes where they would ideally stay cold and moist all winter. The cold keeps them dormant so they don't crawl about and use up their food stores, and the moisture keeps them from drying out and dying. Unfortunately for the lady beetles, we heat homes all winter so the beetles often become active and the heat also dries out the air.

If the lady beetles just stayed in our walls it wouldn't be quite so bad, however a good many find their way into the living areas of homes. Once they are indoors the only thing to do is sweep they up and throw them away. Preventing them from getting indoors in the first place is the best method of control. The first step is to seal cracks around windows and doors and where utilities enter the house. Insecticides can be of some help when applied to areas where the beetles gather (often around windows and doors on the sides of the house that are in the sun in the afternoon). The best insecticides for repelling the beetles are pyrethroids such as deltamethrin, bifenthrin, cyfluthrin, tralomethrin, or esfenvalerate. Insecticides may have to be reapplied.

There are no 100% effective methods to keep the lady beetles outdoors, but these steps can help reduce the number in your home.