September 06, 2007
Thursday

An explosion of insects that attack quaking aspen trees has left the leaves so silvery that it is hard to remember when they were dark green, but the damaged leaves might not hurt the trees as much as people think.

Caterpillars known as aspen leaf miners have hit almost every tree in the Interior and many throughout Alaska during a recent outbreak, cutting mazes beneath the surfaces of leaves.

When biologists checked out a sample of 90 aspens last year, 99 percent of the trees had at least some leaf-miner damage. Seeing those numbers, and by looking around at the silvery aspens in Alaska for the past three or four years, a person might assume that the trees are goners. How could they take such hits to their solar panels year after year and still grow?

"Working with Linda DeFoliart and Jenny Schneiderheinze, we found that mining by the aspen leaf miner on the tops of aspen leaves has little or no effect on photosynthesis," said Diane Wagner, a University of Alaska insect and plant ecologist who, with fellow UAF professor Pat Doak, has studied the leaf-miners' effects on the aspen.

"The caterpillar eats only the cells of the epidermis, the outer layer of the leaf, not the photosynthetic cells of the interior. "When leaf miners work the bottoms of aspen leaves, they do reduce photosynthesis, because leaf mining on the underside damages stomata, pores through which plants take in carbon dioxide.

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Ketchikan, Alaska