The Virginia Supreme Court yesterday dissolved an injunction that blocked pesticide spraying in agricultural officials said aerial spraying along the Blue Ridge will start at dawn today.

A group of Loudoun and Clarke County residents has opposed the federal-state spraying project designed to eradicate gypsy moth infestations, contending that the chemical to be used, Dimilin W-25, may cause cancer.

Last night almost 50 persons gathered in front of the Loudoun County Court House in Leesburg to protest the spraying. They said dozens of others from the affected area-more than 5,600 acres-were leaving their homes to spend the night on the grounds of a local church or with friends in Leesburg to avoid the spraying.

A Supreme Court panel of Judges Harry L. Carrico, Richard H. Poff and A. Christian Compton dissolved a temporary injunction granted Tuesday by a Loudoun County Circuit Court judge. Assistant that a delay in the spraying program would diminish the effectiveness of the pesticide.

The spraying was originally scheduled to start Wednesday; the injunction would have delayed it until May 16. Federal officials involved in the spraying project agreed to drop plans to spray in West Virginia as well as Northern Virginia pending the outcome of an appeal.

Virginia Agriculture Commissioner S. Mason Carbaugh said yesterday's ruling will permit the state "to protect not only the hardwood forests in Virginia from defoliation but to protect residential and recreational areas from the threat of gypsy moth infestations."

Gypsy moths, which have already defoliated more than 450,000 acres of Pennsylvania forests, were spotted along a ridge running from Bluemont, Va., to Jefferson County, W.Va., last year.

Carbaugh said, "Dimilin was the product of choice" in the project and "poses no reasonable risk or threats to humans, birds, bees, wildlife or to the environment."

Although Dimilin has been approved for the gypsy moth program by the U.S. Environmental Protection Agency, Peter Dunning, president of the Bluemont Citizens Associaton and a resident of the area to be sprayed, said that pregnant women and those with small children plan to stay out of the sprayed area for several days.