Alaska Scientists Release Sawfly's Enemy
ANCHORAGE, Alaska A wasp from Canada could cut the numbers of billions of leaf-munching sawflies that for years have been attacking birch trees across Anchorage and other parts of the state, scientists said.
For the second summer in a row, bug experts have released a small batch of the sawfly's natural enemy, a parasitic wasp gathered by scientists in the Northwest Territories of Canada.
The quarter-inch wasps use their stingerlike appendage to insert eggs into leaf-miner larvae. Over winter, the wasps consume their hosts from the inside out, bursting from their bodies in spring.
But with only 158 wasps released this summer, plus 55 set free in 2004, the project remains a minuscule beachhead at a single West Anchorage park.
"It may take four or five or six years to get the parasite established," said Duane Nelson, assistant director for the U.S. Forest Service's forest health protection program in Anchorage.
Sawflies, known to most Alaskans as leaf miners, have been attacking birch trees across Anchorage for the last few weeks, turning local parks and yards yellow long before fall.
The infestation arrived in Anchorage about 10 years ago on imported nursery stock and by 2004 had exploded across 138,000 acres.
The amber-marked leaf miner has no natural enemies in Alaska to temper its spread. The pests have moved down Turnagain Arm, hit the Kenai Peninsula and the Matanuska Valley, and even infested trees in Fairbanks, Skagway and Haines.
The wasp project, which costs about $50,000 per year, was launched four years ago with help from state, federal and Canadian agencies.
The scientists originally hoped to set loose more wasps. But no one had ever tried to transplant the wasp to fight this species of leaf miner before, said Entomologist Chris MacQuarrie, a doctoral student from the University of Alberta at Edmonton.
Scientists are still figuring out the best techniques for shipping the insects to Anchorage and keeping them alive during the winter.
Next summer, the scientists hope to monitor birch stands near the release site to see whether wasps have started to spread.
Until wasp populations expand, experts say people should keep the birch trees watered and undamaged.
"Aside from a preventative insect treatment, the best thing you can do is take good care of trees, keep from damaging them and, most important, water them during the drought periods earlier in the summer," said Corlene Rose, a pest management expert with the University of Alaska Fairbanks Cooperative Extension Service in Anchorage.
Source: Associated Press