EFFECT OF NOVEL NICOTINYL INSECTICIDES AND COMMERCIAL BIOINSECTICIDES ON THE COTTON LEAF WORM, SPODOPTERA LITTORALIS (BOISDUVAL) (LEPIDOPTERA: NOCTUIDAE)

Abstract

The cotton leafworm, Spodoptera littoralis (Biosduval) (Lepidoptera: Noctuidae), is one of the most serious cotton pests in Egypt. New control methods are needed to diminish reliance on conventional insecticides as part of (IPM) programs. In this study, the toxicity of Bacillus thuringiensis and NPV as bioinsecticides as well as two neonicotinoid compounds, imidacloprid and acetamiprid were evaluated. Imidacloprid was recommended to be used over acetamiprid for both 2nd and 4th instar larvae due to its low LC50 values, while, both profect and viruset showed the same pattern of toxicity towards 2nd and 4th instar larvae. The successive application of LC25 of profect followed by treatment with LC25 of acetamiprid was found to be superior in reducing 2nd instar larval population, while, the treatment of 4th instar larvae with viruset followed by treatment with acetamiprid was found to be superior in reducing larval population. The total protein content as well as the activity of enzymes that may play a role in insect immune response towards insecticides was determined. The insect immune responses to bioinsecticides infection were determined in terms of detecting expression level of transferrin gene (Tsf) using real time-PCR. Viruset treatment downregulated the gene, while profect treatment caused its upregulation, in comparison to non-treated control group. Key words: B. thuringiensis, Immune response, Neonicotinoids, NPV, S. littoralis, Transferrin.