Toxicity of Long Pepper, Piper longum L. (Piperaceae) Leaf Extracts to the Red Flour Beetle, Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae)

Numerous species of beetle attack agricultural storage items, causing significant economic losses in terms of quantity and quality. The most harmful pest infesting dry stored produce is the red flour beetle, Tribolium castaneum, which is a well-known secondary pest of stored products. This insect pest show resistance to chemical insecticides, making it difficult to control this pest species with conventional pesticides. Search for non-chemical alternatives for managing this beetle pest has drawn attention for phyto derivatives, many of which are potent as insecticide and yet environmentally friendly. In this study Piper longum leaf extracts in ethyl acetate and methanol were used against eggs of different age, and fourth and fifth instar larvae of Tribolium castaneum. In petri dish bioassay method, ethyl acetate and methanol extracts showed significant ovicidal action with 100% mortality on ‘0’, ‘2’, and ‘4’ days old eggs at concentrations ranging from 300 to 500 µg/dL after 72 and 96 h. The ethyl acetate extract caused 100% mortality of fourth instar larvae at 10, 9 and 8 µg/dL; and on the fifth instar at 10, 8 and 7 µg/dL after 48, 72 and 96 h, respectively. The methanol extract exhibited a similar pattern to that shown in the ethyl acetate extract on the fourth instar larvae after 48, 72 and 96 h of exposure, while for the fifth instar larvae, 100% mortality was recorded at concentrations of 9, 8 and 7 µg/dL, respectively. The results of the study showed that Piper longum leaf extracts is a promising toxic agent to Tribolium castaneum. According to the existence literature survey, this is the first research report on the ovicidal and larvicidal activity of Piper longum leaf extracts against Tribolium castaneum.