Comparative Bioefficacy of Different Citrus Peel Extracts as Grain Protectant Against Callosobruchus chinensis, Trogoderma granarium and Tribolium castaneum

Efficacy of essential oils extracted from peel of various citrus species; Citrus reticulata, Citrus sinensis, Citrus paradisi and Citrus grandis were determined against the adults of Callosobruchus chinensis and Tribolium castaneum as well as against the larvae of Trogoderma granarium in order to find out safe alternatives of high toxics. Four concentrations of each oil; 2%, 4%, 6% and 8% were assayed for their insecticidal activity after exposure durations of 24, 48, 120 and 168 h. The results revealed that the essential oil vapors showed variable toxicity to insects depending on concentration and exposure duration. Efficacy increased as the exposure time and concentration were increased for all insects. All the oils were found to be very successful against adults of C. chinensis. Out of which, the oil of C. sinensis was the best against C. chinensis even at lower concentrations; LD , LD and LD values were 3.49%, 4.70% and 5.91% after 72-h 50 70 90 exposure duration followed by the oil of C. paradisi that exhibited LD , LD and LD values 2.39%, 4.61% and 50 70 90 6.30%, respectively after 168-h exposure duration. However, the other citrus oils were effective at higher concentrations and required more exposure time. The order of decrease in efficacy was C. sinensis>C. paradise>C. reticulata>C. grandis. The oil of C. sinensis found to be the most effective at LD =6% after 16850 h among all the oils against T. castaneum and the order of efficacy was the same. In case of T. granarium, the Citrus oils were found comparatively less effective than other insects.