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The Ladybugs Return!

With somewhat of a late start due to the wet fall, chaff swirls in the air. As Minnesota farmers harvest their soybeans, legions of critters scurry off from the field, evicted once again by those dang humans.  One of the most aggravating of these vagrants is Harmonia axyridis, the Multicolored Asian Ladybeetle. Identified by their University of Minnesota “M” on their little heads, these insects—while key in helping our local farmers control aphids—plague us in our homes.  What you may not know, is that these beetles are not just a biting, stinking nuisance, but have real negative effects on our environment and even our wine!

Asian Ladybeetles were introduced by the USDA off and on since the early 1910’s, brought in to control aphids from various crops. These creatures were thought to not be able to overwinter successfully in the USA. However, in the early 90’s, reports suggested these ladybugs found a foothold in the South, perhaps through shipping containers. Soon, these adaptable insects spread far and wide, squeezing in the food web of a variety of ecosystems.

Ladybugs are considered “generalist” predators, that is, they are not picky about what they stuff in their mouth parts. While known for munching on aphids, they also have quite a taste for insect eggs. Unfortunately, these eggs can belong to beneficial insects such as the Monarch Butterfly or other native ladybeetles. For reasons not entirely explained by scientists, certain conditions can also cause these ladybugs to try out a vegetarian diet. While rare, there are documented studies finding Asian Ladybeetles gnawing (and actually damaging) soft fruits such as raspberries.

While not able to pierce the skin of grapes, vineyard growers have discovered these ladybugs can still cause severe financial damage, not in the field, but in the cask. During the winemaking process, Asian Ladybugs can be squished alongside the grapes. Known for their bitter, foul smelling liquid they love to leak on us, this chemical (an alkaloid) can be tasted with as few as 2 beetles per kilo of grapes.

If these insects are an issue for you in your home, start sealing cracks (larger than 1/8”) where the ladybeetles can enter. Small cracks can often be sealed with simple caulk or silicone, and larger ones with steel/copper wool. Insecticides can be effective with ladybugs, but must be applied before they invade. Common ones used against them are bifenthrin or permethrin. As always please follow the label when applying any insecticide. If these insects have already made themselves at home, physical removal with a vacuum is best. Be sure to switch out vacuum bags frequently, as just being sucked up into the bag is not enough to kill them.

Works Cited:

Koch, R. L., & Galvan, T. L. (2008). Bad side of a good beetle: the North American experience with Harmonia axyridis. BioControl, 53(1), 23-35.


Shane Bugeja
Extension Educator, Ag Production Systems
(507) 304-4325
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