Evaluation of Selected Bio-insecticides on Tuta absoluta and Liriomyza trifolii on Tomato in Open Fields in Tharaka Nithi County, Kenya

Abstract

A field experiment to determine the effect of Azadirachtin, Bacillus thuringiensis, Pyrethrin + Garlic extract, and Petroleum mineral oil in managing the tomato leaf miner (Tuta absoluta) and serpentine leaf miner (Liriomyza trifolii) was conducted for two seasons between December 2016 and November 2017 at Chuka, Tharaka-Nithi County. Tomato variety, Kilele F1, was planted in the field to evaluate the effect of selected commercial products on T. absoluta and L. trifolii. The product included Azadirachtin 0.03%, Pyrethrin + Garlic extract, Bacillus thuringiensis var Kurstaki 5% w/w), and Petroleum mineral oil 98.8%. There were five treatments in a randomized complete block design (RCBD) in three replicates. There was an application of sterile water in the control experiment. There was a significant difference (P < 0.05) between the biocontrol products and the control. The Azadirachtin at 0.03% treatments had the least number of leaves damaged by T. absoluta (0.43; 1.67) in the control treatment (1.7; 5.27) in both seasons. In both seasons, there were significant differences (P < 0.05) between treatments in the number of leaflets damaged by L. trifolii. In season 1, the least damaged fruits per plant (1.33) were recorded in Azadirachtin at 0.03%, compared to the highest damage (5.0) in the untreated control. In the second season, the low fruit damage (0.67) was recorded in Petroleum mineral oil, and the highest (2.33) was in the untreated control. The study concluded that Azadirachtin 0.03%, Bacillus thuringiensis var Kurstaki 5% w/w, and Petroleum mineral oil were efficacious in managing T. absoluta and L. trifolii and be integrated into the existing tomato pest management strategies.