R.E. Mickle, E. Kettela, G. Thurston, S. Holmes, G. Cormier and P. Amirault
SERG Project # 1995/07 (1999)
New aqueous formulations of Bacillus thuringiensis ssp kurstaki (Bioprotec® - AEF Global Inc; and Thuricide® 76LV, Thuricide® 96LV - Thermo Trilogy Corporation) were tested against spruce budworm on white spruce and balsam fir. Results were compared to the registered product Thuricide® 48LV (Thermo Trilogy Corporation). All products were applied with a Cessna 188 Ag Truck equipped with DGPS guidance (AGNAV®2) and four Micronair® AU4000 atomizers set to spin at approximately 8000 RPM. Track spacing was 23 m and aircraft height was nominally 15 m above the canopy. All trials were conducted using optimization strategies to maximize deposit uniformity across the test blocks. Each product was applied undiluted at 30 BIU/ha to two 25-ha sub-plots within a 50-ha block of forest. For one Bioprotec® block, a second 30 BIU/ha application to two 25-ha blocks was completed 2.5 days after the first application.
Spray assessments included larval development index, bud development index, larval populations, and percent defoliation. Final population and defoliation estimates were conducted after larvae had ceased feeding and pupation had commenced.
For white spruce, percentage reduction in survival was calculated to be 89% in the Thuricide® 96LV block and 80% in the Thuricide® 76LV block. Survival reduction on balsam fir was 95% in the Thuricide® 96LV block and 91 % in the Thuricide® 76LV block. Bioprotec® provided similar population reduction in mixed spruce stands. One application (1 x 30 BIU/ha) provided 92% reduction in survival in white spruce while a double application of Bioprotec® (2 x 30 BIU/ha) provided 98% reduction in survival. Results for balsam fir were 98% for a single or double application. The positive check (Thuricide® 48LV at 1 x 30 BIU/ha) resulted in survival reductions of 64% in white spruce and 90% in balsam fir.
In terms of foliage protection in white spruce, percent reduction in defoliation in the 96LV block was 73% and in the Thuricide® 76LV block 46%. For Bioprotec®, percent reduction ranged from 51% (1 x 30 BIUIha) to 69% (2 x 30 BIUIha). Higher protection was achieved in balsam fir with reduction in defoliation ranging from 89% for Thuricide® 76LV and Thuricide® 96LV to 82% for Bioprotec® (1 x 30 BIUIha) and 95% for Bioprotec® (2 x 30 BIUIha). A single application of Thuricide® 48LV, the positive control, resulted in 62% reduction in defoliation in white spruce and 53% in balsam fir. The balsam fir results are for a limited sample of two trees.
The new aqueous formulations of Bacillus thuringiensis ssp kurstaki applied at 30 BIU/ha were found, in general, to result in equivalent or improved population and defoliation reduction when compared to the registered product Thuricide® 48LV.