'Alien' Wasp Kills Whole Forests

March 8, 2006 -- -- An invader has entered the United States and it could devastate pine trees across the country, especially throughout the lush forests of the Southeast.

The wood wasp -- Sirex noctilio Fabricius -- has wiped out huge stands of trees in the Southern Hemisphere, killing 80 percent of the trees in affected forests in New Zealand, Australia, South America and South Africa.

Scientists have dreaded the day when the alien wasp might make its way into the United States, but the wait is now over. It ended last year when Richard Hoebeke, an expert taxonomist at Cornell University, opened an insect trap in New York State.

Inside the trap he identified the first Sirex woodwasp ever found in the wild in the United States. Since that discovery, entomologists have scattered out across New York, finding wasps over a wide area. And farther north, Canadian officials have found the wasp there, raising questions about just how widespread it already is.

It's already too late to eradicate the wasp, Hoebeke says.

"We are looking at long-term management and control," he says. "We've found the wasp in too many places."

Once the wasp penetrates a tree to lay eggs and produce the next generation, the tree begins to die. Not because of the wasps, or the resulting larvae, but because of a symbiotic fungus that the female wasp also introduces into the bark of the tree to provide food for the larvae to survive.

The fungus attacks the tree, and it can kill it in less than a year.

Government officials and the North American Plant Protection Organization recently issued dire warnings about the danger. The wasp likes all sorts of conifers, but it has a particular taste for pines.

Death comes fairly quickly to the trees, although that may not be obvious at the time.

"When the wasp attacks a tree, the tree within that season will start to die," Hoebeke says. "You'll start seeing wilting of some of the upper branches, discoloration and yellowing, and eventually death."