The Washington Post
03-28-07
When it comes to wine, ladybugs stink
By Marc Kaufman
The Washington Post
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 lessappealing 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
taint.
This type of ladybug has been spreading rapidly across the Midwest because
some tasty new prey — the invasive soybean aphid — also has 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 last week at a national meeting of the American
Chemical Society.