365 Urban species. #348: Hemlock Woolly Adelgid

[urbpan]

Photo by urbpan. Location: Forest Park, Springfield, Mass.

Urban species #348: Hemlock Woolly Adelgid Adelges tsugae

This insect spends most of its life hidden in a fluffy white shelter. It sucks the fluid from the needles of hemlock trees, and it is believed that as it feeds it introduces a toxic substance into the tree. Every plant has sap-sucking pests that feed on them, and most are not seriously damaging. An infestation of these hemlock woolly adelgid can cut the lifespan of an eastern hemlock down from hundreds of years to less than ten. The Asian hemlocks that the insect feeds on in its native range developed resistances that allow the trees and adelgids to coexist.

Adelgids are close relatives of aphids. Like some aphids, hemlock woolly adelgids are all female, and several generations are born in a single year. In the short time that the insects are mobile, they are carried from tree to tree by animals or by the wind. Adelgids have fully infested the hemlocks in all counties of southern New England, as well as the areas around New York CIty, Philadelphia, Washington D.C. and New Jersey. It's possible that the adelgid affects urban trees more severely because they are already weakened by pollution and other stresses. Methods to control the infestation include saturation of individual trees with pesticide, and the introduction of predatory beetles.

Comments

[phlogiston-5.livejournal.com]

The raging disasters were the result of poor science in the early days of biological control. Things were introduced willy nilly without much regard for non-target effects. These days there is a barrage of testing that goes on for several years in the lab, then in field enclosures, to make sure that potential bio controls are very specific. As a result, a lot of the programs have been successful, particularly in agricultural settings. In nature, one of the biggest success stories is control of purple loosestrife (at least in NJ). We had a release program using Galerucella calmariensis, a Chrysomelid beetle that is doing a great job of controlling (but not eradicating) purple loosestrife density in wetlands.

[hai-kah-uhk.livejournal.com]

Purple loosestrife, the bane of my existence! (Actually it's Oriental bittersweet. I haven't even gotten around to touching the loosestrife yet. Worse, I do it all by hand. I know firsthand why hungry beetles are an appealing solution.)

It's reassuring that we're approaching it with more responsibility now. Thanks for letting me know that. I respected my botany professor, but I'm glad to know his angry tirades missed some information. And he was, after all, a politician. :)