Effect of Host Plants on Development, Fecundity and Enzyme Activity of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)

The beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is an economically important pest of crops worldwide, attacking plants from over 20 families including trans-continental agricultural cotton, corn and citrus crops. In this study, performance and subsequent enzyme activity of beet armyworm reared on host plants from five families were investigated. Significant differences were found in development, fecundity and enzyme activity on different host plants. Survival rate was the highest (42.8%) on asparagus lettuce (Lactuca sativar var. asparagina) and the lowest (17.0%) on sweet pepper (Capsicum annuum). Larval duration was the shortest on asparagus lettuce (12.0 d), and was 43.4% longer on sweet peppers (21.2 d). The activity of acetylcholine esterase (AChE) and carboxylesterase (CarE) in 3rd instar larvae, and soluble carbohydrate and crude protein contents in different host plants were determined. AChE activity was the highest in the larvae feeding on Chinese cabbage (Brassica rapa), but declined by nearly 60% on maize (Zea mays) seedlings. The ratio of soluble carbohydrate content to crude protein content in host plants was found to have a positive effect on oviposition and a negative correlation with larval duration and life time (from larval to adult stages) of the insect.