Evaluation of neem formulations for the control of selected pests of French beans (phaseolus vulgaris. L.)

Abstract

Evaluation on efficacy of neem seed oil (NSO) and neem kernel cake powder (NKCP) as compared to synthetic pesticides against Aphis fabae, Megarulothrips sjostedti and frankliniella species and their effects on natural enemies was conducted at Jomo Kenyatta University of Agriculture and Technology (JKUAT), Thika District, Central Province of Kenya, between August 1998 and June 1999. NKCP/wannin and Gaucho (imidochloroprid) were applied as seed treatment, NKCP and Furadan (carbofuran) as soil amendment, while NSO, neem kernel cake powder water extract (NKCP/WE) and Karate (lambda-cyhalothrin) as foliar sprays, replicated four times in a Rondomixed Complete Block Design (RCBD). The parameters involved were seed germination, leaf damage, flower drop, crop yield, pod quality, thrips and aphid infestation, parasitoid and predator populations. NKCP/wannin had the highest germination and differed significantly from NKCP soil amendment. There was no significant difference (P>0.05) in leaf damage and infestation by Frankliniellla species amongst the treatments. There was significant difference in aphid, adult thrips and larvae population amongst the treatments. However, treatments with Karate resulted with the lowest infestation by thrips and aphids. There was a significant difference in the population of Megarulothrips sjostedti among the treatments during the reproductive stage, with NSO and NKCP/WE treated plots having significantly low population. The mean number of flower drops differed significantly among the treatments. The parasitoid and predator population compared within the plots sprayed with NKCP/WE and control, but different significantly from plots sprayed with Karate an indication that Karate adversely affected the population. Although there was no significant difference (P>0.05) in pod yield among the treatments, the pod quality differed significantly (P<0.05) amongst the treatments. High percentage of unblemished pods was obtained in plots sprayed with NSO, NKCP/WE and Karate. The high percentage difference in pod quality was attributed to high infestation of thrips. The amount of NKCP used, as a soil amendment is not economical due to the large quantities required. Thus seed treatment using NKCP could be used instead of the conventional pesticides as it is cheap and little amounts are required. NSO and NKCP/water extract could also be used as alternatives to Karate as they reduced thrip population thus reducing the extent of pod damage and had no adverse effects on the natural enemies.