EFFICIENCY OF PHOSPHINE AGAINST DIAPAUSING LARVAE OF EPHESTIA-ELUTELLA (LEPIDOPTERA) OVER A WIDE-RANGE OF CONCENTRATIONS AND EXPOSURE TIMES

Diapausing larvae of Ephestia elutella (Hübner) were fumigated at 20 C with phosphine at concentrations of 0.014-4.0 mg/l, and exposure periods of 3 1 2hr to 43 days. Phosphine achieved peak efficiency at concentrations of 0.04-0.10 mg/l, a concentration-time (CT) product of 14 mg hr/l being adequate for 100% kill. At 0.7 mg/l, nearly 10% of larvae survived 20 mg hr/l, while at 4.0 mg/l, one in eight larvae survived 56 mg hr/l. For 90 or 99% kill, concentrations less than 0.04 mg/l were not fully efficient, and CT products increased very sharply to about 100 mg hr/l for the LD99 at 0.02 mg/l. The CT products required for 50% kill, however, varied little. For concentrations between 0.04 and 0.35 mg/l, the LD50, LD90 or LD99 was constant for C0.9T. As concentrations were increased beyond this range the CT products required for the LD90 and LD99 increased more rapidly and from 0.7 mg/l the more rapid increase was also evident at the LD50 level. © 1979.