Archive for Sunday, October 31, 2004

Lady beetles can be difficult to control

October 31, 2004


A common and welcome visitor to local gardens is the ladybug.

Generally, they are beneficial predators that consume large quantities of aphids, scale insects and many other pests that injure plants. However, an Asian native of these savvy hunters are giving their domestic cousins a bad reputation. Homeowners across the area are being overrun by these otherwise friendly allies.

Here are some suggestions for dealing with multicolored Asian lady beetles.

In their native habitat, the beetles are an important predator of aphids and other soft-bodied insects that live high-up in trees. They are quite different from our native species that tend to hunt close to the ground in flowers, shrubs and vegetable gardens. Also, the beetles prefer to overwinter in cracks and crevices of huge cliff faces. Unfortunately, in parts of the United States where cliffs are not prevalent, they seek overwintering sites in and around buildings.

The beetles came to America two ways. There are several reports that they were accidentally brought on ships to various ports in New Orleans and Seattle. But more importantly, they were intentionally released in the United States as part of a federal effort to naturally control insect pests in trees. The federal government and the United States Agriculture Research Service released them in California as early as 1916. They also were released in the mid-1960s, '70s, and '80s. By the mid-1990s, they became well established.

It is difficult to control beetles. Although not very common, beetles will nip or "bite" humans. They are not looking for a blood meal; they are simply examining an unfamiliar surface or looking for moisture. Likewise, when disturbed, they defend themselves by exuding a yellow-orange body fluid, which is their blood -- a defense mechanism termed reflex bleeding. The blood has a foul odor and can permanently stain walls, drapes, carpeting and other surfaces. Do not crush or swat lady beetles to minimize their defensive behavior. You can safely trap them on strips of tape secured to hiding areas with the sticky side out. When the tape is full, discard it and start again. Also, use a vacuum to suck them up.

The best management strategy is to prevent beetles from entering the home or building. Seal up any crack or crevice 1/8 inch or larger. Do the work before the beetles have found their way in. Less effective prevention methods are chemical treatments. Pesticides can be applied to outside walls and siding, as well as around eaves, attic vents, roof overhangs, and doors and windows. Wettable powder and microencapsulated formulations of residual pyrethroids do the best job.

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