Screening of plant extracts as repellent against stored-product insects


Abstract: Use of phytochemicals as natural insecticides to control stored product insects is an important area of work. Studies were conducted to test the repellency of Trichilia connaroides and Clerodendron inerme methanol extract of leaf against three stored-product insects, the lesser grain borer Rhyzopertha dominica, the red flour beetle Tribolium castaneum and the cowpea weevil Callosobruchus chinensis. The area preference method was used to determine the response of insects to the repellents by measuring their movement from the treated region on filter paper strip. The average repellency of 100, 250, 500, 750 and 1000 ppm concentrates from T. connaroides and C. inerme leaves totally achieved class lll (60.1-80% repellency) and class V (80.1-100% repellency) respectively after 24 h observation. The order of repellent activity was C. chinensis < T. castaneum < R. dominica. The concentrate of methanol-extract of C. inerme leaves was found to be more effective than T. connaroides. These plant extracts can be exploited as promising stored product insect control agents.

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