Carl H. Shanks

The Activity of Some Insecticides against the Garden Symphylan, Scutigerella immaculata

Laboratory techniques were developed for comparing the activity of Zinophos® O,O -diethyl O -2 pyrazinyl phosphorothioate; parathion; and Nemacide®, O -(2,4-dichlorophenyl) O,O -diethyl phosphorothioate against the garden symphylan, Scutigerlla immaculate (Newport). Bioassay of treated soil from field plots, using the garden symphylan, showed that Zinophos at 2½ and 5 lb/acre was active for 5 week while parathion at 5 lb and Nemacide at 7½ and 15 lb were active for 2 weeks or less. Zinophos at 0.5 ppm in soil killed as fast as 4 ppm of parathion while Nemacide acted more slowly than parathion. When symphylans were exposed to insecticide-treated soil and the survivors removed to clean soil, many of those survivors remained alive. When symphylans were give 20-min exposures to soil treated with Zinophos or parathion and the exposures alternated with periods of 0–12 hr in clean soil, fewer exposures were required for 90% mortality as the time in clean soil increased. The effect of the absorbed toxicant apparently lasts for at least 12 hr. Zinophos did not repel symphylans. They moved readily into treated soil and were killed. These techniques reduce the amount of field plots need for obtaining adequate data on the performance of new insecticides against and garden symphylan.