Efficacy of Acorus calamus L. leaves and rhizome on mortality and reproduction of Callosobruchus chinensis L. (Coleoptera: Bruchidae)

Abstract

Laboratory and field experiments were conducted to investigate the bioefficacy of sweet flag (Acorus calamus) against the pulse beetle Callosobruchus chinensis, which infests stored chick pea seeds. Dried powders of the leaf and rhizome as well as their extracts in methanol (ME) and petroleum ether (PEE) were evaluated as bio-insecticides against the beetle. Rhizome powder (5 mg/g seed) was found to be more efficacious, causing 100% mortality, than leaf powder (20 mg/g seed), showing 91.1% mortality. Rhizome powders also showed 100% ovicidal activity and thus completely inhibited F1 emergence at a lower dose than that of leaf powders. The ME and PEE of leaves and rhizome showed 12 to 100% mortality. The percentage of egg laying decreased from 12.8 to 100 with increasing doses of powders and extracts. No F1 adult emerged at 0.3–0.4 mg/g ME of leaves and rhizome and PEE of rhizome. In six-month field trials, all treatments at laboratory doses proved efficacious (75–98%) over organophosphate insecticide malathion (74.4%) in terms of feeding deterrence. Powder- and extract-treated chick pea seeds did not lose their viability and germinated at 100%, similar to control seeds. It was concluded that leaf and rhizome powders and their solvent extracts showed significant mortality, and inhibition of egg laying and F1 emergence of C. chinensis at varying concentrations. Hence, the leaves and rhizome of A. calamus may be recommended as admixtures in the integrated management of beetle infestation of pulse seeds during storage.