Efficacy of Neem Tree (Azadirachta indica A. Jusieu) Extract on White Cabbage Aphid (Brevicoryne brassicae L. (Hem: Aphididae) Control in the Field

Abstract

Neem tree extracts from root, bark and leaves have generally been used in the control of pests. The extracts’ efficacy in the control of aphids in cabbages under smallholder farming systems formed the subject of the study. The dose of the admixture of the extract that effectively controlled aphids was determined through experimental methods that involved harvesting and crashing 0.1 × 10-4 of Neem tree parts. The extract was fermented for 18-48 hours.Treatment tests solutions varied were 20 mL, 30 mL and 40 mL of the extract respectively in 10litres of water and applied to cabbage in the field at intervals of once a week, twice a week and once in 2 weeks in a triplicated completely Randomized Block Design. The treated plants were observed for average number of live aphids, number of dead aphids, degree of leaf perforation, leaf curls, stunting, and finally the yield of the cabbage visa vis treatments. Aphid counts at the concentration of 30mL in 10L of water were significantly lower for live aphids and higher for dead aphids (P < 0.05), Although all treatments revealed significant differences from the control in terms of Aphid mortality, overall mean aphid counts showed a reduction in number (implying high mortality) with an increase in the concentration of Neem extract applied and cabbage vigour increased with increase in the frequency of admixture application, with a bi-weekly application producing significant results (P < 0.05). High concentration (40 mL) more effectively controlled aphids but resulted in mild scorched leaves. Smallholder farmers should take advantage of the naturally available Neem tree concoctions of 30 mLs in 10litres of water twice a week to keep aphid’s population below the economic injury level.