Effectiveness of selected insecticides against the South American invasive tomato Leafminer (Tuta absoluta) in Wakiso district, Uganda

Abstract

The importance of tomato in Uganda in contributing to food security and household income cannot be underrated. However, its production in Uganda is challenged with numerous abiotic and biotic stresses including arthropod pests which cause severe yield losses. The pest complex in the country was recently compounded by the outbreak of Tuta absoluta, a species of South American origin. Tuta absoluta has spread rapidly since its invasion of Europe in 2006 and within just a few years, its global status has changed completely, from a South American tomato pest into a major threat to world tomato production. In Uganda, Tuta absoluta was reported in 2016 in Mukono and since then, it has spread to all tomato production areas in entire country .The lack of information by farmers about this particular pest with no locally tested management tactic has exacerbated the ravaging effects of this voracious pest. Furthermore, lack of proper sanitary practices with no national quarantine practices to restrict free movement of tomato planting materials and fruits through trade have accelerated its spread throughout the country. Being an alien species in Uganda, the possible quick action to effectively combat and mitigate the effects of Tuta absoluta is to use chemicals with novel modes of action. Consequently, the objective of this study was to evaluate selected insecticides with novel modes of action against Tuta absoluta in Uganda. Five insecticides were evaluated in the field in Wakiso (Namulonge- NaCRRI) for two seasons in Randomized complete Block design. Damage caused by the leaf miner on the leaves was assessed before and after application of the treatments. Marketable yield was assessed at crop maturity. All the compounds performed better than the untreated control. Flubendiamide and Emamectin benzoate + Abamectin recorded the best efficacy against Tuta absoluta with 15% mines per plant, However they were not significantly different from each other. Chlorpyrifos and Azadirachtin showed moderate effect in reducing the damage caused by Tuta absoluta with 50% mines per plant and could be incorporated in the integrated pest management strategies against Tuta absoluta. The fourth pesticide, Alphacypermethrin + Teflubenzuron had minimal effects (75% mines per plant) against Tuta absoluta and was not statistically significant from the Control which had almost 100% mines per plant Flubendiamide and Emamectin benzoate + Abamectin treatments are therefore recommended for further evaluation for appropriate dosage to use