Ladybug Taint: Not Fine in Wine

Ladybugs are well known to gardeners as a great natural tool to control aphids and other pests. But a new study has shown that the spotted insects have a less-appealing side: They produce a foul-smelling liquid that is increasingly being found in wines. There's even a name for it -- "ladybug taint."

The smell, which connotes green bell peppers or roasted peanuts, is produced by ladybugs as a defense mechanism. The chemicals they release, in a class of compounds called methoxypyrazines, are found in other animals and plants, but Jacek Koziel of Iowa State University said ladybugs are loaded with them. "Even tiny amounts can be detected by the human nose," he said. His team used a gas chromatograph and a panel of volunteer "sniffers" to identify the odors from about 300 ladybugs of the species Harmonia axyridis. Batches of five bugs were sealed in test tubes and the odors were analyzed, revealing 28 distinct smells. Four chemicals were found to be associated with the ladybug odor.This type of ladybug has been spreading rapidly across the Midwest because some tasty new prey -- the invasive soybean aphid -- has also become widespread. Winemakers report greater concentrations of ladybugs in their vineyards and on harvested grapes. Apparently the bugs are being mixed into the fermenting grape juice by accident. Koziel's study was presented at last week's national meeting of the American Chemical Society