P.C. Nigam, S.E. Holmes
Two dilution rates of Mimic representing applied field dosages of 17.5 and 70 grams/ha were tested for stomach and contact toxicity against spruce budworm larvae. Spray drops of varying sizes were generated with a spinning disk drop generator, and collected on silk strands then transferred to needles and fed to various instar budworm larvae or applied topically to the dorsal surface of the larvae. In all, five series of experiments were conducted. Ten or 20% glycerine was added to each mixture to increase the stability of formulation and the generation of uniform droplets.
The results show that the 70g/ha concentration was significantly more toxic to budworm larvae than the 17.5 g/ha formulation. ED50 for stomach toxicity against fifth instar of the 70 g/ha mix with 10% glycerine was 52 um drop and ED,, was 135um. Mimic has both stomach and contact toxicity. Stomach toxicity is 15 times greater than contact toxicity. Contact toxicity in these tests is similar to fenitrothion, although Helson has found Mimic@ 5.20 times more toxic than fenitrothion as a contact insecticide.