Expert to study how to kill birch-loving leaf miners

Posted: Sunday, July 27, 2003

ANCHORAGE (AP) An entomology doctoral student is spending the summer in Alaska studying the pesky birch leaf miners, or sawflies, that are infesting birches in Anchorage, the Matanuska Valley, down Turnagain Arm and up to Eielson Air Force Base.

Chris MacQuarrie, who attends the University of Alberta at Edmonton, is gathering data to help plan a biological counterassault that begins next year with the release of a parasitic wasp from northern Canada.

''We're finding some leaves with 30 to 40 eggs on them,'' MacQuarrie said Thursday as he snipped fresh samples with a pruning pole at a tree near Anchorage's Jewel Lake. ''But in a leaf there's only enough stuff to feed 10 to 20 larvae. So some of them aren't even developing.''

The warm summer weather, following a mild winter, has only helped the leaf miner, said U.S. Forest Service insect expert Ed Holsten. ''They started about a week earlier this year,'' he told the Anchorage Daily News.

Native to Europe, the leaf miner probably arrived in the city on nursery stock a decade ago. In the same insect family as bees, wasps and ants, Profenusa thomsoni are tiny sawflies whose larvae subsist entirely by eating the chlorophyll-producing layer of birch trees. As they grow inside the leaf, they shed skins five times, then drop to the ground, find a crack in the dirt and spin a cocoon for the winter, MacQuarrie said.

In summer, the emerging adults (all females) fly to the nearest birch tree. They slice open a leaf with the serrated stinger-like ovipositor that gives them their name and deposit eggs within, starting the cycle over.

With no significant natural enemies here, Anchorage has been like a ''giant salad bar'' for them, Holsten said.

Parasitic wasps of a type that lays eggs inside the larvae are now being collected in the Hay River area of Northwest Territories by a team of scientists, MacQuarrie said. For leaf miners, meeting this wasp often turns out very badly.

State entomologist Roger Burnside said he was working with federal and state agencies to line up necessary permits, and everything remains on track for the wasp release in Anchorage beginning in 2004. The three-year project will cost about $90,000, according to Holsten.

That wasp knocked back an infestation of amber-marked leaf miners in Edmonton in the mid-1990s without any unintended problems for beneficial insects, and entomologists say it has a good chance of succeeding here.

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