An investigation of number of larval in stars of Spodoptera litura (Fabricus) (Lepidoptera : Noctuidae) and Sylepta derogata (Fabricus) (Lepidoptera : Noctuidae) with an emphasis to the effect of Chloropyrifos? neem seed extract and microsporidian pathogen on these larvae

Abstract

Spodoptera litura and Sylepta derogata are pests of most vegetables. However, their biology and the effect of controlling methods have not been fully investigated. Therefore, the objectives of this study were to investigate the number of larval instars of .S. litura and S. derogata with an emphasis on the several controlling methods of these pests. S. litura and S. derogata larvae were collected from the infested leaves of various vegetable fields. Larvae were reared in the laboratory and fed them with Okra leaves, which is the common host plant for both insects. Male and female adults were kept separately in order to obtain eggs and subsequent larval generations. This study indicates that both 5. litura and S. derogata spend 5 larval instars on Okra leaves. Total larval duration were 25 days and 30 days in S. derogata and for .S. litura, respectively. Most farmers use Chloropyrifos to control pests in vegetable fields. Third instar larval group of both insects were topically treated in the laboratory with Chlorpyrifos the commercial insecticide. LD50 value has indicated that S. derogata larvae were more susceptible to the given insecticide compared to that of the S. litura larvae. Effects of botanicals on both insect groups were studied using aqueous extractions of neem seed powder. Third instar larvae were fed with Okra leaves treated with various concentrations of neem seed extractions. It has indicated that S. derogata larvae were more susceptible to the neem seed extractions than that of the S. litura larvae. Heavy larval mortality was observed in S. litura affected by a microsporidian pathogen. Crude extract of the affected S. litura larvae applied to the S. derogata. S. derogata larvae were also affected by above microsporiadian pathogen.