Apple, Control of the Pandemis Leafroller with Bacillus Thuringiensis (Bt) Products in Summer, 1992

Three Bt products were evaluated for control PLR larvae of the summer generation. The test orchard was located at the Tree Fruit Research and Extension Center, Wenatchee. Test Trees were 15-year-old spur type ‘Red Delicious’ on dwarfing roots. The orchard was irrigated by over-tree sprinklers on a 14-day schedule. The test design consisted of seven-tree plots replicated five times in randomized complete block. All treatments were applied with a handgun sprayer at 300 psi to the point of drip, simulating a dilute spray of approximately 400 gal/acre. Dates of different treatments are shown in the table. The 9 Jun application was timed to coincide with predicted beginning of egg hatch. The 15 Jun application was timed to coincide with predicted peak of egg hatch, and the 22 Jun application was timed to coincide with the completion of egg hatch. The post-treatment evaluation was made on 20 Jul when surviving larvae could be easily found at the tips of growing shoots. Each tree was examined for 2 min and the number of active feeding sites (live leafroller larvae) was recorded.