Evaluation of the Efficacy of Crude Extracts of Tick Berry Lantana camara and Mexican Marigold Tagetes manuta Against Cabbage Aphids Brevicoryne brassicae

The efficacy of two plant extracts; Lantana camara, Tagetes manuta and a combination of Lanatana camara and Tagetes manuta applied to the cabbage plants at differeent concentrations against cabbage aphids were tested at St. Mary’s College Rushoroza Demonstration farm, Kabale district in 2015. The purpose of the study was to evaluate the efficacy of selected botanical plants’ crude extracts against the cabbage aphid Brevicoryne brassicae L. The specific objectives of the study were to compare the aphid populations on cabbage plants sprayed with Lantana camara , Tagetes manuta extracts and their combination, to determine the effective concentration of Lantana camara, Tagetes manuta and their combination that could protect the crop against cabbage aphids and to determine the yield of cabbage under different treatments of Lantana camara , Tagetes manuta and their combination on aphids. A field experiment was laid in a Randomized Complete Block Design (RCBD) with four blocks, three treatments replicated four times and a control experiment. Each experimental plot was 3 M by 2.5 M (7.5 M 2 area) per plot and separated by 0.9 m between plots to avoid interplot and interblock interference. Data collected were aphid infestations (adults and nymphs) per three leaves, reduction in aphid populations after application of sprays, and percentage marketable yield. Data were subjected to one way Analysis of Variance (ANOVA) in Genstat software (eleventh edition) programme to compare the aphid population means in treated groups and untreated groups of cabbage. The plant extracts treatments of Lantana camara, Tagetes manuta and their combination on cabbage plants significantly reduced the number of aphids than on the untreated plants during the trial seasons. The populations of aphids were not significantly different (p>0.05) at 5% and 10% concentrations between Lantan a camara, Tagetes  manuta , their combination, and the control experiment but showed significant difference  (P<0.05) for 15% and 20% concentrations and the control experiment due to their high dosage rates. All the treatments at higher concentrations showed  protection of cabbage against the aphids. The highest percentage aphid reduction was  given by lantana camara extract at 20% concentration.  A combination of Lantana camara and Tagetes manuta and Tagetes manuta at 20% concentration were also found effective. The cabbage plots sprayed with a 20% concentration of Lantana camara were found to have the biggest mean weight and percentage of marketable yield.  It was concluded that the extracts of Lantana camara , Tagetes manuta and their combination had both pesticide and repellent roles in the control of cabbage aphids and therefore could be good insecticidal options for Integrated Pest Management Programmes in the control of cabbage aphids. It was therefore recommended that pending further research, these extracts could be used  in pest management to minimize environmental problems resulting from use of synthetic pesticides.