Pacific Northwest

November, 2001
Regional Report

Local Buzz

Ladybug, Ladybug, Fly Away Home
As temperatures begin to fall, people aren't the only ones heading indoors. Lady beetles have become unwelcome pests in many homes here in the Pacific Northwest.



The species found most abundantly is the multicolored Asian lady beetle, Harmonia axyridis, common in Japan, Korea, and other parts of Asia. The name "multicolored" refers to the tremendous color variations in this species, ranging from black with two red spots, to red with 19 black spots, and about every combination in between. They were introduced in eastern Washington by USDA Agricultural Research scientists in the late 1970s and early 1980s as a biological control agent for pear psylla and other soft-bodied insects. The insects didn't establish there, but moved west of the Cascade Mountains into the more temperate climate of western Washington.



Most lady beetle adults spend the winter months in clusters, protected from the weather. In their native home, Harmonia axyridis overwinters on cliffs, but in Washington, the next best thing is a house. Attracted to vertical surfaces, they often appear on walls with a south or southwest exposure. The insects enter wall voids through cracks and settle down for the winter.



Lady beetles are beneficial insects and should be preserved, if possible. Locating entry points and sealing up cracks will help reduce their numbers indoors. You can vacuum them each day and release them outdoors, but they are strong fliers and should be taken some distance away from the house before being released.



Insecticides are not recommended because lady beetle carcasses will remain in wall voids where other insects, such as carpet beetles, can use them for food. Once they've depleted their food source, the carpet beetles move in and feed on carpets, clothing, linens and stored food products. Carpet beetles are extremely difficult to eliminate from a building.



Although this particular lady beetle can be a nuisance during late winter and spring, they will eventually move out to locate their natural prey. This means a decline in aphid, mite and scale insects infesting ornamental trees and shrubs, which may result in reduced insecticide use, leading to an improved environment. Caulking and a few weeks of vacuuming on our part may turn out to be a good investment for everyone.

Favorite or New Plant

Iris unguicularis, a Mid-winter Treat
For reliable winter color in my perennial bed, I've planted winter iris (Iris unguicularis). The flower buds first appear in October and are produced throughout the winter, opening in flushes during mild spells. The soft violet colored flowers are nestled in the foliage and, like crocus, form on tubes rather than on stems. The sword-shaped foliage remains evergreen, but I cut it down in March to renew the plant. (The leaves look a little shop-worn by then!) Winter flowering iris likes moderately rich, well draining soil, and a spot that's sunny in winter but shady during the summer months. I often cut unopened flower buds and bring them indoors. When they open, they fill the room with the sweet scent of violets.

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