RICHLAND, Wash. - Millions of small, white butterflies have been fluttering around forests and yards this summer, particularly in eastern Washington. They are Pine White butterflies, and these outbreaks happen only every 30 to 50 years, according to U.S. Forest Service entomologist Dayle Bennett. The butterflies themselves are harmless, but Bennett says the eggs they're laying could mean trouble for pine and fir trees, next year.
"They lay the eggs on the needles of the pine trees, usually in the upper portions of the crown. And next spring they will hatch, and the ensuing small, green caterpillars with black heads will feed on the pine needles."
The branches of affected trees end up looking like lion's tails, with tufts of new needles only on the tips. But Bennett says the Forest Service has no plans to take action, since effective insecticides would do more harm than good.
"Pines will be putting out a new complement of needles in the spring and the caterpillars mostly feed on the older needles. So, that's a bit of a saving grace."
Some property owners may be concerned about landscape tree health, and Bennett advises contacting a local extension office for information about possible control methods.
He says Pine White butterflies are always present, although not usually in such large numbers. And even when there is an outbreak, experts don't know if it's a guarantee of trouble. Local butterfly watchers in the Tri-Cities area say they've spotted mostly males, and that females of this species are much more rare.