A leaf-eating caterpillar has defoliated thousands of acres of aspens in the Santa Fe national forest and may kill a number of the trees, said a New Mexico State University forest entomologist. No control measures will be taken to eliminate the insects. Also, overcrowding will weaken the caterpillars and lead to starvation. Although the caterpillar problem has existed since 1990, this year's defoliation will be especially stressful because of the dry conditions in the forest.
Leaves often develop later in the summer, after an attack by the caterpillars.
But this year, with so little moisture, the trees will have a harder time regenerating foliage, Cain said. Weather conditions also can affect the situation. Last year's cool spring temperatures kept the trees from leafing out until mid-June, and a foliar disease in late summer caused an early leaf drop, Cain said. A fungus called Cytospora also is attacking and killing aspens this year. The insects and drought have weakened some older trees to the point that they can no longer resist the fungal disease, he said.