The State : Moth Targeted for Spraying

Forest managers plan to spray bacteria on up to 105,000 acres of Plumas and Lassen national forests to combat the largest infestation of tussock moths in Northern California history. In June, airplanes will release droplets of Bacillus thuringiensis , a naturally occurring bacterium known as Bt, on the forests where the moths threaten to destroy 300 million board-feet of timber. Lawrence Crabtree, a U.S. Forest Service silviculturist who is coordinating the project, said the spraying will cost about $1.5 million. The moth, native to forests west of the Mississippi, typically experiences a population explosion every 10 to 12 years, Crabtree said. Tussock moths already have turned more than 50,000 acres of forest into a ghostly gray by nibbling the needles of white fir trees. Crabtree said larvae from millions of eggs laid last fall could spread the damage. Environmental groups said they may appeal, contending Bt also will kill other insects.