Fumigation of Pecans with Methyl Bromide and Phosphine to Control the Pecan Weevil13

A 24-h fumigation of inshell pecans with methyl bromide applied at a dosage of 32 mg/liter killed 100% of larvae of Curculio caryae (Horn) inside nuts with exit holes; however, dosages of 80 and 112 mg/liter (5 and 7 lb/100 f3) at 27° and 15°C, respectively, were required to kill larvae inside nuts without exit holes. A 96-h fumigation of inshell pecans with phosphine applied at concentrations as high as 2000 ppm gave no control of the larvae. Sorption of both fumigants by the pecans was rapid (≥95 and ≥60% in 24 h for phosphine and methyl brolarvae mide, respectively) and was probably a major factor in the failure of phosphine to control the larvae and in the need for such high dosages of methyl bromide to kill larvae in intact pecans.