Science: Trunk Call

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Trees battle bugs with signals

There is nothing lovely as a tree or, apparently, as garrulous. So contend two University of Washington scientists, who provided the surprising news last week that trees appear to communicate with one another. Not in words, to be sure, but by chemical signals.

Ecologists Gordon Orians and David Rhoades believe they discovered arboreal conversations while studying the depredations of western tent caterpillars and fall webworms on Sitka willows. As expected, the researchers found that the leaf chemistry of victimized trees changed to make them less palatable and even harmful to bugs. Curiously, the same natural defense was also invoked by nearby trees not under attack.

Orians and Rhoades speculate that stricken trees release chemical signals called pheromones (more commonly known as insect sex lures). Wafted through the air, these vapors apparently stimulate neighboring undamaged trees, which also alter their leaf chemistry in order to become less tasty to voracious bugs.

The scientists acknowledge that they have not yet pinpointed the signaling chemicals. But they note that a similar warning ability seems to have been found in sugar maple and poplar seedlings in New England. If the chemicals can be isolated, Orians and Rhoades say, they might serve as an alternative to pesticides in protecting forests. And that, certainly, would be something for the trees to talk about.