THE CONTROL OF THE COTTON LEAFWORM, SPODOPTERA LITTORALIS BOISD. (LEPIDOPTERA: NOCTUIDAE ) USING NATURAL PLANT EXTRACTS

Abstract

The extensive and intensive use of synthetic pesticides have created several serious problems, which including insect resistance, toxicity hazards, environmental pollution and upsetting of the natural balance. •Other approaches for pest control should be considered. The use of naturally occurring insecticides of plant origins is one of these approaches which can be used as alternatives to these synthetic chemicals. Actually, these substances are environmentally safe, selective in their action and/or may promote physiological disorders during insect development resulting in its mortality or sterility. Therefore, laboratory studies were directed towards the investigation of the possible biological effects of some plant extracts on the cotton leafworm, S. littoralis. Twelve naturally growing plant species together with two plants, purchased from the local market, were selected for this study. The results could be summarized as follows:

Insecticidal activity of plant extracts to S.littoralis: Preliminary experiments were carried out, using organic solvents of variable polarities (ethyl alcohol, acetone, petroleum ether and chloroform) to prepare the plant extracts that tested against S. littorals. Of the fourteen selected tested plants only four plants showed significant toxicity towards 4th instar larvae, namely, Achillea santo/ina, Asphodelus microcarpus, Cephaelis ipecacaunha and Peganum harmala. Their toxicity data indicated the following: 1- LDso's of Cephaelis ipecacaunha against 4th instar larvae of S. littoralis were 35, 58, 77 and 120 J.Lg/larva when extracts of chloroform, acetone, ethanol and petroleum ether were used, respectively.