Western Black-Headed Budworm Laboratory Spray Tests, 1974-75

Abstract

Abstract Laboratory spray chamber tests of 12 insecticides were conducted in 1974 and 1975. Five dosages of each insecticide were tested in each of 3 to 5 replications. These were prepared by serial dilution of stock solutions freshly re-formulated for each replication. The western black-headed budworm larvae were maintained on western hemlock foliage and were used in bioassays from 1 to 7 days after their receipt from Ketchikan, Alaska, in July of both years. The insects were second to fifrh instars when received. In 1974, they were held at 4°C pre- and post-spray, while in 1975 they were held at 18°C. For spray treatment, 1-3 flushing branch lets of western hemlock containing 5-20 insects were placed in a filter paper lined glass petri dish (20 x 100 mm). The filter paper was changed for each concentration of each insecticide to prevent pre-spray contamination of insects or foliage. The insecticides were applied in a stainless steel laboratory spray chamber using a fine Potter spray nozzle for atomization. Dosage was determined by colorimetric analysis. Approximately 1 gallon/acre was applied. After spray, the insects and foliage were placed in sterile plastic petri dishes. The filter paper was moistened to maintain foliage turgidity during the post-spray holding period. Since Orthene and TH-6040 tend to be slower acting, their effects were rallied after 10 days. No fresh foliage was provided for either holding periods. Data were subjected to probit analysis.