Chemical spraying of the Mount Olympus Cove area to eradicate the gypsy moth is expected to start Thursday at daybreak if weather permits, officials of the Utah Department of Agriculture said Monday.

Van Burgess, the department's director of plant industry, said a helicopter will take off from Airport No. 2 early Thursday and set down on U.S. Forest Service land east of Mount Olympus Cove before daylight."The Salt Lake County Sheriff's Department will cordon off an area and whatever streets are necessary so the spraying can be completed with undue difficulty," Burgess said. "The helicopter pilot will probably have to set down and load his tanks with chemical spray two or three times. He should be finished with the job by 7 or 7:30 a.m."

Burgess said the weather is critical and could delay the spraying. "I know we won't spray before Thursday. If everything goes off as planned, we'll spray again the following two Thursdays. "That should take care of the problem."

The gypsy moth, which has been sighted in large concentrations in the Mount Olympus Cove area, could, if left unchecked, cause millions of dollars in damage to fruit trees, oak and other hardwood trees and watershed, Burgess said.

A quarantine of a 6,000-acre area which includes Mount Olympus Cove was started several weeks ago and will continue until the threat of the gypsy moth is over, Utah Department of Agriculture officials said.

Burgess said the chemical being used against the gypsy moth - Bacillus Thuringiensis or B.t. - will be laid down over 1,190 acres. "It is not harmful to people or pets, but I'd suggest people stay indoors if they can."