Inhibition effects of ethyl acetate extracts of Momordica charantia leaves on the experimental population of Spodoptera litura

Bitter gourd, Momordica charantia L. belongs to the Cucurbitaceae family and is widely cultivated in China as a vegetable crop. Among cucurbitaceous plants, bitter gourd is rarely attacked by phytophagous insects during the growing period. We aimed at evaluating the biological activity of the ethyl acetate extracts of M. charantia leaves on Spodoptera litura, and providing scientific basis for the exploration of the anti-insect mode and mechanism and field applications of the ethyl acetate extracts from M. charantia leaves against the pest. We fed the 3rd-instar larvae of S. litura with artificial diet, which was treated with ethyl acetate extracts of M. charantia leaves for three days and then switched to normal artificial diet. The life table and indices control population trend were used to evaluate the control effects of ethyl acetate extracts of M. charantia leaves on the experimental population of S. litura. The results showed that the ethyl acetate extracts had significant inhibition to the development of the larvae of S. litura. The higher the concentration of extracts of M. charantia leaves was, the slower of the body weight increased, the longer the larvae developmental duration was and the higher the mortality of the larvae was. After treating with M. charantia leaves extracts at 0.032%, 0.04%, 0.08% and 0.16% for two days, the inhibition rates of weight growth were 76.3%, 79.9%, 97.6% and 111.2% respectively. After treating for three days, the inhibition rates of weight growth were 77.96%, 76.42%, 94.92% and 100.85% respectively. After six days, the inhibition rates of weight growth were 61.47%, 60.68%, 80.00% and 84.35% respectively. After eight days, the inhibition rates, which were still very high, were 67.43%, 66.75%, 81.62% and 86.36% respectively. Larvae duration of each instar of S. litura that fed on ethyl acetate extracts of M. charantia leaves treated artificial diet were significantly longer then control. The whole larva stage of S. litura after treating with M. charantia leaves extracts at 0.032%, 0.04%, 0.08% and 0.16% were prolonged for 1.87 days, 1.96 days, 3.39 days and 4.62 days compared with control. Not only mortality obviously was increased, but also the pupation rate, emergence rate and fecundity were markedly reduced at a high concentration (0.16%), which mortality was increased 81.49%, the pupation rate was reduced 19.47% and emergence rate and fecundity were markedly reduced 53.18% and 50.16% respectively compared with c