Comparative Study of Artificial Diet and Soybean Leaves on Growth, Development and Fecundity of Beet Armyworm, Spodoptera exigua (Hubner) (Lepidoptera : Noctuidae)

Abstract

An artificial diet and soybean leaves were used in rearing the larvae of beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera : Noctuidae) in laboratory condition. The artificial diet was composed of soaked mungbean, baking yeast, methyl paraben, sorbic acid, ascorbic acid, casein, choline chloride, agar, vitamin, formalin and distilled water. Survival of larvae on artificial diet (96.67%) was higher than those reared on soybean leaf (63.64%). Weight of larvae and pupae reared on artificial diet were significantly higher than those of the larvae and pupae fed with soybean leaves. The larval and pupal periods of those fed with artificial diet were 15.7 ± 0.84 and 6.73 ± 0.51 days respectively, whereas, those fed with soybean leaf were 18.65 ± 0.83 and 8.5 ± 0.52 days respectively. The average number of eggs laid was 577.9, when the larvae were reared on artificial diet. However, it was 472.5 when the larvae were reared with soybean leaf. The female and male life spans were 14.6 and 11.4 days on artificial diet and were 13.1 and 10.2 days with soybean leaf. Without feeding, the adult showed a life span of 6.29 ± 1.42 and 5.3 ± 0.66 days in artificial diet and soybean leaf respectively. Three consecutive generations were reared on artificial diet. Pupal ratio from larvae was found closer among the generations. The sex ratio was more or less similar in the first and second generations but in the third generation males number increased considerably (1:1.72).