San Jose scale, Quadraspidiotus perniciosus (Comstock): San Jose scale was an important pest of apple in West Virginia as late as the 1980s, however, pest status of this insect has declined with the increased planting of smaller sized trees which facilitate more thorough spray coverage. Isolated outbreaks still occur in large, poorly pruned standard-sized trees that do not receive adequate spray coverage.

Chemical control: Control is achieved with a single insecticide application at the green tip to 2-inch green stage against the overwintering immature scale and multiple applications (1 to 3) against the nymphal (crawler) stage during the postbloom period.

Amount used

Insecticide

% of acres treated

lb a.i./acre/application

lb a.i./acre/year

Chlorpyrifos

1

1.0

1.0

Methyl parathion

2

0.375 - 0.75

0.375 - 1.50

Petroleum distillate

6

3 - 6 gallons

3 - 6 gallons