Park Rangers started a full-on assault of something devouring plants inside the Shenandoah National Park Thursday.

The Gypsy Moth population in the park has exploded for the first time in 13 years.

In the early morning hours Thursday, Rangers started spraying a bacteria over 2,500 acres along Skyline Dr. in the northern district. The bacteria kills the moths by getting into their digestive systems. It is not harmful to people or animals.

Gypsy moths ate more than 7,000 acres of trees and plants in the park last year. The government calls it one of the most destructive forest pests in America.