LIFE TABLE PARAMETERS OF THE COTTON LEAFWORM, Spodoptera littoralis (BOISD.)(LEPIDOPTERA:NOCTUIDAE) ON DIFFERENT HOST PLANTS.

Abstract

Present work is carried out to study the effect of different hot plants on life table parameters of the cotton leafworm Spodoptera littoralis (Boisd.) under laboratory conditions. In this study, development rate, age-specific survival and age and age-specific fecundity for cotton leafworm larvae reared on six host plants: (turnip, bean , corn , castor bean , cowpea and siris ) under laboratory conditions were studied for two successive generations. Results obtained revealed that the cotton leafworm larvae survived on four host plants, but on the fifth host (cowpea), most moths died during first two days after emergence, in the same time on the sixth host (siris), young larvae failed to survive. The remaining four host plants could be arranged according to their suitability for insect development in the following descending order castor bean, bean, corn and turnip. The lowest percentage of natural mortality values occurred 6.01, 5.9, 5.54 and 0.61% when the larvae fed on castor bean leaves for AM, RM, IM and MSR% mortality respectively. Meanwhile, the highest mortality rates were 62.56, 36.1, 32.09 and 10.84% for AM, RM, IM and MSR% mortality respectively when larvae fed on turnip leaves. On the same time, castor bean leaves harbored the highest net reproductive rate (Ro) 687.97 females/female. While the shortest reproductive rate 99.36 females/female were obtained when larvae fed on turnip leaves. Also, the longest mean generation duration (Gt) was 31.92 days when larvae were fed on corn leaves, while, moderate duration was 29.94 and 28.31 days when larvae were fed on castor bean and turnip respectively. The population intrinsic rate (rm) decreases from 0.2182, 0.1792 to 0.1736 individuals/female/day and the finite rate of increase (λ) yield 1.244, 1.196, 1.91, and 1.189 individuals /female/ day when larvae fed on castor bean leaves, bean leaves, corn leaves and turnip leaves respectively. The highest intrinsic and finite rates of increase of S. littoralis were obtained when larvae fed on castor bean leaves. The population of cotton leafworm moth doubled once every 3.98, 4.85, 4.96 and 5.0 days when larvae fed on castor bean leaves, bean leaves, corn leaves and turnip leaves respectively.