Natural Resources Minister Bruce Northrup announced an aerial spray program to target an outbreak of balsam fir sawflies. (CBC)

The Department of Natural Resources is planning a spray program over Crown forests to combat an unprecedented outbreak of balsam fir sawflies.

Natural Resources Minister Bruce Northrup said the biological control program will target only sawflies with a naturally occurring virus.

"Abietiv has been tested and approved by Health Canada and was used for a decade in Newfoundland," Northrup said in a statement.

"It is effective against the sawfly but research has shown it does not affect humans, other animals, birds, bees, other insects, fish or aquatic organisms, or plants.''

The provincial government said egg surveys done last fall showed the numbers of balsam fir sawflies could be capable of "causing severe defoliation in young balsam fir trees and sometimes tree mortality."

The Department of Natural Resources has identified roughly 182,000 hectares of Crown forest land that has high levels of the pests and another 30,000 hectares with moderate to high populations of sawflies.

The aerial spray program will happen in early to mid July on roughly 10,000 hectares of Crown forest about 20 kilometres south of Sussex.

The spray program will be conducted by Forest Protection Ltd., a private company, and will be overseen by the provincial government's Forest Pest Management Section.

Abietiv, the biological agent that will be used in the spray program, was designed specifically for use against sawflies.

The Canadian Forest Service developed Abietiv and used it experimentally from 2000 to 2005. It was then used operationally from 2006 to 2009 by the Government of Newfoundland and Labrador.