Microwave assisted disinfestation of green gram (Vigna radiata L.) infested with pulse beetle, Callasobruchus maculatus (F.)

Pulse beetle (Callasobruchus maculatus) is a common infestation during storage of legumes in India, and presently being managed by chemical fumigation. In the present investigation, a non-chemical method based on dielectric heating by microwaves (900 W, 2450 MHz) was studied for disinfestation of green gram at different grain layer thickness (5, 10, 15 and 20 mm) and exposure durations (0-60 s). The susceptibility (LT95) of different stages was in the order of egg (31.668 s) > grub (40.388 s) > pupa (44.176 s) > adult (49.018 s). The adult was tolerant up to 50 s (R2-0.799, P < 0.01) to microwave exposure duration without green gram, and up to 30 s (R2-0.804, P < 0.01) with green gram. Hundred percent mortality was observed at 10 mm (30 s, R2-0.969, P < 0.01) and 15 mm (30 s, R2-0.972, P < 0.01) grain layer thickness without significantly affecting grain quality. Cooking time and germination did not vary significantly up to 30 s of exposure, thereafter, reduced significantly. However, water uptake did not vary significantly up to 60 s of exposure. The microwave radiations are found effective for disinfestations of green gram without significantly affecting the grain quality.