Scots Pine, P. Cembrae Control, Washington, 1973

Infested trees in a commercial Christmas tree plantation near Oak Harbor, Washington, were so badly damaged that the grower had cut and burned several hundred. Treatments were applied at bud break Apr 23, when new shoots were 3-20 cm long May 14, or at both times. Four single-tree replicates of each treatment were arranged in randomized complete block design. Each tree was 4-5 ft (1.2-1.5m) tall and heavily infested. Applications were full coverage sprays at 2 rates via hand pumped compressed air sprayer. Effectiveness was determined on May 29 by counting the number of live adelgids per cm on 3 current-year twigs per replicate.