Efficacy of Neem Tree Extract on White Cabbage Aphid, Brevicoryne Brassicae Control

Abstract

A field study was carried out to investigate the efficacy of Neem tree extracts (root, bark and leaves) to control aphids in cabbage under smallholder farming systems. The objectives were to identify the effective dose of the admixture of Neem tree extract in controlling aphids on cabbage, to establish the effective frequency in application of Neem tree extract in controlling population of aphids on cabbage and to propose a hypothetical model for general cost of production using Neem tree extract in comparison with synthetic pesticides.

Methods employed to achieve this results were; freshly harvesting of Neem tree parts (root, bark and leaves), crashing into a mortar, weighing 1000g of each part, mixing together in 10litres of water for 12-24hours and spraying from four weeks after crop emergence up to harvesting. Three treatment tests varied were 20ml, 30ml and 40mls (in 10litres of water) in different plots. Frequencies of application were also varied at once a week, twice a week and once in 2 weeks. The experimental design used was a completely Randomized Block Design with the three treatments replicated 4 times. There was a significant difference (P < 0.05) in aphid counts among all treatments at the concentration of 30mls with 40mls treatment resulting in the second least aphid count. At week 8, the least counts were recorded in the 30mls, followed by 40mls and 20mls treatments, which were significantly different from the control. Overall mean aphid counts showed a reduction in number with an increase in the concentration of Neem tree admixture extract applied. Cabbage vigour of growth increased with increase in the frequency of Neem tree admixture extract applied twice a week and once a week at significant difference of P = 0.05. High concentration (40mls) effectively controlled aphids but resulted in some mild scorched leaves. The study showed that Neem tree admixture extract effectively controls aphids, with best results obtained with 30mls/10litres of water sprayed twice a week. Recommendation was made for further research on the field study on the general cost of production using Neem tree admixture extract.

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