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Geraniums intoxicate Japanese beetles.

Several bites of a garden-variety geranium, and a Japanese beetle falls to the ground in a stupor that lasts some 8 hours. It's hardly a great way to avoid predators or get on with beetle business, like reproduction. Yet researchers now find that the beetles never learn. They choose geraniums over perfectly good linden leaves and get paralyzed day after day.

Researchers described the knockout effect on Japanese beetles in 1929, notes Daniel A. Potter. He and David W. Held, both of the University of Kentucky in Lexington, have studied beetle learning and the sad effects of geranium intoxication on family life. Their results will appear in an upcoming issue of the journal Entomologia Experimentalis et Applicata.

In theory, insects with wide-ranging tastes are the most likely to learn to avoid noxious foods, according to the few studies that have tested this idea, Potter says. However, Japanese beetles eat nearly 300 U.S. plant species but don't avoid geraniums.

The flower petals, especially from plants in full sunlight, seem the most narcotic, Potter reports. His most extensive tests were of red geraniums, but flowers of white, coral, and other colors also slammed the beetles. So did a water-soluble leaf extract.

A geranium "is like candy to them," Potter says. Beetle pairs offered a choice picked geranium flowers so often that they laid just half as many eggs as pairs provided only with linden leaves. Intoxication is dangerous for the beetle, but is it fun? Potter won't speculate.
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Title Annotation:Japanese beetles contunue to seek out geraniums, despite their narcotic effect
Author:Milius, Susan
Publication:Science News
Article Type:Brief Article
Date:Dec 5, 1998
Words:247
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