Evaluation of common cocklebur X anthium strumarium leaf extract as post‐harvest grain protectant of black gram against pulse beetle C allosobruchus chinensis ( C oleoptera: B ruchidae) and isolation of crude compound

The pulse beetle C allosobruchus chinensis   L . is considered the most important stored grain pest of black gram V igna mungo   H epper in B angladesh and other tropical and subtropical countries. Bioactive compounds derived from plants can be used to control of the pulse beetle as a potential alternative to synthetic insecticides. Therefore, aqueous extracts of common cocklebur X anthium strumarium   L . leaf was examined for insecticidal properties against C . chinensis. The extracts showed toxicity, repellent properties, inhibited fecundity and adult emergence of the insects, and protected grains. Insect mortality was accounted highest (72.6%) with 4% extract at 4 days after treatment. The beetles showed highest repellency rate (58.0%) with 4% concentration at 1 hour exposure; however insect repellency decreased with time. The beetles exerted the lowest fecundity and grain damage and produced the lowest number of offspring when they were reared on grains treated with 4% extract. The insecticidal compounds present in common cocklebur leaf were extracted in chloroform and ethanol, and isolated by thin layer chromatography ( TLC ) and spectral studies ( 1 H ‐ NMR and IR ), which identified the presence of aromatic ester, n ‐hexyl salicylate or o ‐hydroxy‐ n ‐hexyl‐benzoate and a long‐chain ketone. Therefore, naturally occurring X . strumarium and its derivatives may be potential components for integrated management of C . chinensis .