. Field testing of Bacillus thuringiensis for control of western hemlock looper. Hemlock looper Control; Bacillus thuringiensis. Results Analysis of Bacillus Deposit Numbers of viable spores in the undiluted Thuricide formulation averaged 18x10 per milliliter, slightly more than half that claimed by the manufacturer-- 30x10 per milliliter. Numbers of viable spores on glass plates exposed to spraying varied greatly, both within and between plots, but appeared to be gen- erally low. Average counts for individual plots ranged from 545 to 290, 000 viable spores per 35 square inches of plate; 13 pl
. Field testing of Bacillus thuringiensis for control of western hemlock looper. Hemlock looper Control; Bacillus thuringiensis. Results Analysis of Bacillus Deposit Numbers of viable spores in the undiluted Thuricide formulation averaged 18x10 per milliliter, slightly more than half that claimed by the manufacturer-- 30x10 per milliliter. Numbers of viable spores on glass plates exposed to spraying varied greatly, both within and between plots, but appeared to be gen- erally low. Average counts for individual plots ranged from 545 to 290, 000 viable spores per 35 square inches of plate; 13 plots were in the-range of 2,000 to 7, 500 viable spores per plate, or 57 to 214 spores per square inch. Deposits on salal leaves (fig. 8) showed very little loss in viable spore count during the first 4 days after spraying, even though a soaking rain occurred on the 3d day after spraying. Some decrease in spore count occurred at the end of 6 days, but the median-sized droplets still contained more than a lethal After 9 days, however, a sharp drop in spore count was found, and the average droplet on most leaves no longer contained a lethal dose. Beginning with the 9th day, great variation was found between individual samples but a few leaves still retained close to the original spore count. After 14 days, only an occa- sional leaf had droplets still containing lethal doses. The loss in spore count appeared due to a "weathering-off" of the spray material and was accompanied by a loss of fluorescence of the Calcofluor in the material. Results from feeding sprayed foliage to larvae from an unsprayed area paralleled the recovery of viable spore deposits from the salal leaves. How- ever, at room temperature, larvae fed rapidly, compared with field conditions, 9. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the orig
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