State officials are in the midst of a vast and expensive program to combat an infestation of leaf-munching gypsy moths.

According to the state Department of Agriculture, gypsy moths could be on track for one of the largest infestations in more than a decade. A survey last fall showed a high count of eggs for the gypsy moths, which ultimately can damage trees.

To prevent the eggs from turning into full-blown caterpillars and later moths, agriculture officials are spraying insecticides on nearly 100,000 acres, in spots stretching from Garrett County in the west to Talbot County on the Eastern Shore.

Eleven locations in...