Efficacy of vegetable oil extracts for control of insect pests of tomato in southern Benin

Abstract

Pests are a menace to production of tomato (Lycopersicon esculentum Mill.) in sub-Sahara Africa. The objective of this study was to evaluate the efficacy of oil extracts of selected common plants for control of pests of tomato in Benin. The study was carried out on the Togba market garden sites in Benin. The botanical pesticides (Tephrosia purpurea, Ricinus communis, Thevetia neriifolia and Cashew Nut Shell Cold Liquid (CNSL cold) were compared with a biological insecticide (Topbio), a synthetic insecticide (Lambda cyhalothrin) and an untreated negative control. The fish model and the generalised linear mixed or fixed effects model were used to explain the number of caterpillars per plot as a function of the products tested during the different plant phases. Tephrosia purpurea oil, cold CNSL, Topbio and lambda cyhalothrin treatments significantly reduced H. armigera, S. littoralis and T. absoluta populations. The average yields of marketable tomato ranged from 7.20 ± 0.89 t ha^-1 for the controls and 21.14 ± 3.56 and 20.46±1.98 t ha^-1 for the plots treated with Tephrosia purpurea and CNSL cold on tomato, respectively. Plots treated with the synthetic insecticide lambda cyhalothrin gave the best yields (31.15±3.20 t ha^-1). Of all the extracts tested, cold extracted CNSL and T. purpurea oil showed very high larvicidal activity at doses of 10%, compared to R. communis and T. neriifolia oil on the farm. The larvicidal activity of the extracts observed at low doses on H. armigera and S. littoralis larvae seems to offer an alternative advantage for the control of tomato pests.