Phosphine Fumigation of Inshell Almonds for Insect Control, 1989

Fumigations with phosphine (PH3) were conducted to determine minimum lethal exposure times and concentrations at various temperatures for control of NOW or IMM in inshell almonds. A dosage of 30 g/ 1000 ft3 PH3 gas generated from aluminum phosphide pellets was used on infested almonds at 10, 15.6, 21.1, 26.7 or 32.2°C. Insect eggs, 0-24 h old, or early pupae were placed in screened vials which were buried within the almond load (53% v/v) contained in a fumigation chamber. The exposure time, in days, required for complete kill at each temperature was determined in preliminary tests, after which the treatments were replicated three times. Control insects were set up in the same manner as those treated, but were not exposed to PH3. Following fumigation and 2 h aeration, the eggs or pupae were removed from the almond load and placed in a holding incubator at conditions of 27°C, 60% RH for 14-21 d to determine egg hatch or adult emergence.