Effect of Ultraviolet (UV) Light on Cowpea Beetle Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae) under Laboratory Conditions

Callosobruchus maculatus is a cosmopolitan and severe pest of pulses throughout the world with significant damage potential.Mostly synthetic fumigants are used to reduce population and losses of C. maculatus, but their use causes serious health and environmental problems, hence necessitating the use of alternate safe control measures for its management, including ultraviolet light radiation (UVL).Therefore, laboratory studies were conducted to determine the effect of different powers i.e., 15, 30, and 45 watts of UVL against eggs and adults of C. maculatus applied for 1, 2, 3, 4, and 5-h exposure times.UVL tube-lights of 15 watt power and 1.5 feet long were installed in 2-feet 3 insect rearing cages, covered with black cloth.The experiment was arranged in a completely randomized design with five replications.The data on adult mortality of C. maculatus was taken after 24, 48, and 72-h of treatment, whereas hatching of eggs was monitored daily for ten days.Results indicate a highly significant difference among various UVL powers and exposure timings on the mortality of C. maculatus adults as the mortality percentage increases with increasing exposure timings and powers with no significant difference between 30-and 45-watt UVL powers.After 72-h of the experiment, the highest adult mortality (74.80±2.80%)was observed with 45-watt UVL, followed by 30-watt UVL (65.20±1.92%),both applied for 5-h.Moreover, the highest adult mortality rate of C. maculatus adults was recorded when they were exposed to various UVL power for 5-h.Like adult mortality, the lowest hatching success of C. maculatus eggs was recorded in 45-watt UVL power (27.40±2.71%),whereas the maximum eggs hatched in control treatment (88.00±0.90%),whereas 5-h exposure of C. maculatus eggs with different UVL powers resulted in the minimum hatching success.Therefore, it is recommended that UVL irradiation should be included in the management of C. maculatus in warehouses, whereas further studies should be conducted to optimize appropriate power and exposure timings of UVL for the large-scale use on commercial basis. Novelty Statement | Laboratory evaluations of UVL different exposures and timings againstCallosobruchus maculatus confirmed that UVL can cause significant mortality of adults and reduce the hatchability of the eggs.As a result, UVL resulted in low population of C. maculatus that resulted in low damage to cowpea grains without using synthetic insecticides.