Bug Blog

West Coast Flies Imported to Help Hemlocks

West Coast Flies Imported to Help Hemlocks

About half of hemlock groves on the east coast are infected with a pest called a wooly adelgid.  This bug, related to an aphid, arrived in the fifties from Asia.  With no natural predators here, it has flourished.  Yet a tiny fly could offer some hope in battling a serious infestation, say researchers.

The silver fly is a known predator in the western U.S., but in the east it seems to only live on pine trees.  In the west, the silver fly prefers eating what bugs it can find on hemlocks, so bringing the bugs to the east coast is the next step.

Two species of silver flies, identified by professors at University of Vermont (UVM) and Oregon State, feed on adelgids.  The two researchers are using this knowledge to lead a team of scientists in researching whether the flies can effectively reduce the infestation of adelgids.

At the very least, the researchers are hoping the flies will put enough of a dent in the population of adelgids to allow the hemlock trees to recover.  But seeing the results of the experimental introduction of these west coast variants will take time.

“Once hemlock is removed, the soil type changes, the stream dynamics change, the forest type changes — and it’s hard to recover,” said Kimberly Wallin, assistant professor and UVM scientist.