By Laura Jesse
Extension Entomologist
Iowa State University
The question on every ones mind appears to be, “Will this be a bad year for the multicolored Asian lady beetle?” And the answer is “I don’t know.” To be honest, entomologists are pretty bad at predicting the future. Many factors will influence how many Asian lady beetles are out there to invade our homes this year. Insects suffer from diseases, just like humans, so outbreaks of viral, bacterial and fungal infections among the insects will the affect numbers of lady beetles.
The amount of food is also important. When food is plentiful more insects survive and reproduce. Asian lady beetles eat aphids and other plant pests, so when those insects have good years, so does the Asian lady beetle.
Finally, the weather will also influence the number of lady beetles, and we all know how unpredictable the weather is. Weather will indirectly affect lady beetles by determining how much food is available. Weather also influences how many Asian lady beetles survive, and when and how they many will migrate to the exposed sunny side of the house.
As you can see, with so many variables in the big complex world, there is no simple answer.
How did the multicolored Asian lay beetle get to Iowa?
The Asian lady beetle was never released in Iowa. It traveled here by flying from other states. How the Asian lady beetle got into the U.S. is controversial. Intentional releases of this species were conducted in southern and eastern states for many decades starting in the 1920s. All these releases were carefully monitored and after the releases no Asian lady beetles were found. It was believed that the Asian lady beetle did not establish in the U.S.
Then, in 1988 a population was found near New Orleans, Louisiana. No releases of the Asian lady beetle had been made in Louisiana, so it is believed the beetles arrived accidentally off of a ship.
It is hard to believe that an insect that is so plentiful now only arrived in 1988, but other insects have demonstrated the ability to increase population size and move rapidly, so it is possible.
Is the Asian lady beetle a ladybug?
Yes. Entomologists usually call ladybugs lady beetles because they are beetles, not bugs. We have a specific group of insects called the True Bugs. The True Bugs include the boxelder bug and stink bug.
Do we have native ladybugs/lady beetles?
Yes, we may have as many as 100 species of lady beetles native to Iowa. They are very common in gardens and crop fields. Or native species of lady beetles do not gather on homes to overwinter, so we do not see them as often, nor in as large a quantity as Asian lady beetles.
Does the Asian lady beetle come from soybean fields?
The soybean aphid is commonly blamed for high Asian lady beetle numbers. In fact, the first year we had soybean aphids in Iowa coincided with a good year for the Asian lady beetles. However, we had already had Asian lady beetles in Iowa for 6 years before the soybean aphid arrived.
The Asian lady beetle migrates to overwintering spots (often our homes) on the first warm day after the first frost. This is usually sometime in mid to late October. Soybeans are also being harvested at this time. However, by the time soybeans are harvested the plants are very dry and there is no food in the soybean fields for lady beetles. The Asian lady beetles have probably moved out of the soybean fields long before harvest, but we don’t see them until their migration is triggered by weather and shortening day lengths.
How do I prevent the Asian lady beetles from getting into my house?
If you have had a problem with Asian lady beetles being attracted to your house for the past several years, it is likely you will have a problem this year.
To prevent the lady beetles from getting indoors, start by sealing cracks around windows, doors and where utilities enter the house. Screen can be placed over attic vents. If you have consistently had a severe problem you might consider using an insecticide on the outside of your house. Ohio State University researches have found that lamda-cyhalothrin, deltamethrin and bifenthrin work the best. You can find them at your local garden centers. Read and follow label directions when you apply pesticides.
Sealing cracks and insecticide treatments must be done before the lady beetles migrate. Once the lady beetles get indoors the practical thing to do is vacuum them up.
Do the multicolored Asian lady beetles lay eggs in my walls?
No. They do not lay eggs or reproduce at all in your house. The beetles that accidentally crawl into your house all winter and spring are the same individuals that arrived in October.
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