Entomotoxic potential of paddy husk silica powders against Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) in stored chickpea

Abstract

The indiscriminate use of insecticides has directly contributed to the development of resistance in stored product insect pests, raising grave concerns about food contamination from toxic residues. This alarming situation has necessitated the exigency of exploring alternative, eco-friendly pest management strategies. Consequently, this study aimed to exploit paddy husk, an abundant agricultural waste product, for synthesizing silica powders and subsequently to evaluate their insecticidal potential as a seed protectant against the notorious pulse beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae), in chickpea. Amorphous silica gel, Amorphous silica precipitate and diatomaceous earth were individually applied at two different concentrations to chickpea seeds. Mortality assessments of C. chinensis adults were conducted at regular intervals after exposure to treated seeds, immediately and up to six months after storage (MAS). Data on adult emergence of C. chinensis, its damage and weight loss of chickpea seeds were recorded bi-monthly for a storage period of six months. The results revealed that seeds treated with 500 ppm of amorphous silica gel resulted in 100% mortality of C. chinensis adults by fifth day after exposure, even after extended storage periods of four months and six months. Remarkably, no adult emergence, seed damage, weight loss, lowest beetle perforation index and inhibition rate of 100 % pertaining to adult emergence was observed in treated seeds for six months storage period under ambient conditions. The paddy husk silica powders and diatomaceous earth effectively protected the seeds. The findings demonstrated the promising insecticidal potential of amorphous silica gel at 500 ppm against C. chinensis, presenting a viable alternative to conventional synthetic insecticides for controlling stored product insect pests.