Evaluation of anti – aphids properties of the aqueous crude fruit sap extract of Solanum incanum
The green peach aphid, Myzus persicae is a worldwide aphid species which is responsible for important economic losses. Its feed on more than 50 plant families, causing great losses to agro industrial crops, vegetables, horticultural crops and stone fruits and it is presently categorized as one of the most important agricultural pests worldwide. Conventional insecticides used for aphids control are expensive and arguably associated with various severe adverse side effects hence the need to develop botanical pesticides that are effective as alternative. Solanum incanum is a perennial, wild shrub like herb that belongs to family Solanaceae, which grows in many regions of Africa, Middle East and Far East Asia. Though S. incanum fruits sap has been used by the local farmers to control aphids, review of the literature show no scientifically investigated report of its effectiveness and the mode of its insecticidal action. This study was therefore designed to evaluate anti-aphids properties of crude fruit sap extract of S. incanum and its possible inhibition of acetylcholinesterase enzyme in green peach aphids. A total of 180 kales plants were planted in the Plant Transformation Laboratory of Kenyatta University. They were divided into six groups with 10 plants each. Each group was subjected to routine spray with 10, 25, 50 and 75% S. incanum extract. Group five was sprayed with dimethoate and the last group was sprayed with water. The number of live and dead aphids was counted with the help of hand lens for two weeks after every spray in each group with an interval of one day to determine the deterrent and insecticidal activity. Acetylcholinesterase inhibition was determined using Ellman method. The S. incanum extracts at different concentrations tested showed insecticidal and deterrent activities against green peach aphids. The extract also inhibited the acetylcholinesterase of the green peach aphids at a dose dependent manner and IC50 of 49.9 was calculated. Further, phytochemical screening results showed that the crude fruits sap extract of S. incanum have phytochemicals associated with insecticidal and deterrent activity. The study has established that the crude fruits sap extract of S. incanum are effective in managing insects‟ pest.