Evaluation of Several Insecticides Against Stored-Product Insects

Abstract

Abstract All test insects were reared at 26.7±1°C and 50 to 60% RH, except Trogodermavariobile Ballion reared at 29.4 to 32.2°C and 45 to 50% RH. Young adults of the Indian meal moth and the Angoumois grain moth were not more than 2 days old, the granary weevil and the confused flour beetle ranged from 1 to 14 days in the adult stage, but most specimens were 7 days old; and young, active sawtoothed grain beetles were of undetermined age. Larvae of T. variabile had passed through 4 or 5 molts. Insects were anesthetized with CO2, then placed on filter paper in the lid of a disposable petri dish before being sprayed. Insecticide solutions were made up in a 19:1 (vol/vol) acetone-olive oil solvent mixture. These were applied to insects in a Potter laboratory spray tower in a room kept at 24±1°C. Air pressure was maintained at 5 psi for the first 15 sec of the spray operation, but the 5-ml aliquots of spray solutions used for each application were delivered within 10 sec through the “rich” nozzle of the Potter apparatus. An additional 15-sec settling period was allowed before insects were removed and placed in holding containers; 6-oz waxed paper cups vented with pinholes in the bottom were used for moths, and beetles were put in small plastic cups. The test insects were maintained at 26.7±1°C and 50 to 60% RH for 24 hr before mortalities were recorded, except 48 hr for T. variabile larvae. Insects unable to stand or move about were judged to be dead. Groups of 20 specimens were sprayed in each test, and duplicate tests were made for each species. Data were pooled to calculate mean results, and corrections were made for natural mortality, although only an occasional specimen died in control samples. Three series of tests were made. The first was concerned with organophosphates and a few other organic compounds sprayed directly on insects at concentrations of 0.01, 0.1 , 1.0, and 10.0 mg/ml (Table 1).