Bio-efficacy of indigenous plant-based protectants against pulse beetle, Callosobruchus chinensis L. (Bruchidae: Coleoptera)

Abstract

Pulse beetle, Callosobruchus chinensis is a destructive pest of mung bean grains in storage. It starts damaging pulses in the field and is carried to the storage structures. In mung bean, 50-58% losses in seed weight have been recorded due to severe attack of this pest. The studies were done to determine aptness of ethanol extract of leaves of eight plants and extracted oils of seeds of five plants against C. chinensis in stored mung bean. Pulse beetle culture was maintained to conduct insect bioassays in the laboratory. The insecticidal effect of extracts and oils was determined by different parameters like, number of eggs per grain, number of holes per grain, percentage reduction of F₁ adults emerged, percentage inhibition rate, percent weight loss of grains and adult mortality. The results showed that all the tested plant extracts were effective against PB as compared to control. Plant extract of Withania somnifera was the best in reducing fecundity of 0.41 eggs per grain. The beetles made minimum number of holes (0.13) per grain in treated grains with extract of Tribulus terrestris. The most effective plant extract was Silybum marianum in reducing number of F₁ adults emerged of PB. The maximum inhibition (94.83%) of F₁ adults was seen in W. somnifera treated grains. The minimum weight loss of 4.62% of mung bean grains was recorded in W. somnifera treated grains. The plant seed oil of S. marianum was the best in the reduction of number of eggs (0.35per grain), number of holes (0.10 per grain), 2.1 of F₁ adults emerged, and weight loss of 6.58% of mung bean grains. This seed oil also provided the highest adult mortality of 5.66, 8.6 and 9 after 24, 48 and 72 hours, respectively and the maximum inhibition (96.76%) in emergence of F₁ adults of PB. The plant seed oils of Eclipta prostrate and Acacia modesta were the least effective against PB. The outcome of this study included safe and effective control measures and brought forward the effective IPM strategy against this economic pest.