Efficacy of Selected Insecticides Against the South American Tomato Moth, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) on Tomato in the Central Rift Valley of Ethiopia

Occurrence of the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in Ethiopia was confirmed following heavy infestation of tomato, Solanum lycopersicum L., in the Central Rift Valley (CRV) region of Ethiopia in February 2013. The pest wiped out tomato plantations, causing 100 % crop loss for some producers. This was despite the use of a variety of insecticides locally available to manage other vegetable insect pests. In this study, 10 insecticides from different insecticide classes including pyrethroids, organophosphates, spinosyns, insect growth regulators and diamides were screened for their efficacy against T. absoluta using a randomized complete block design with two different planting dates in 2013. The mean fruit infestation in the untreated control plot ranged between 54 and 76 %. In plots treated with diamide insecticides (chlorantraniliprole) fruit infestation was significantly lower with 2–6 % fruit damage followed by spinosyns (spinetoram and spinosad) with 30–35 % damage. A similar trend was observed in leaf damage severity. Mean marketable and total yield from the best performing treatment, Ampligo (a mixture of a diamide and a pyrethroid), were 18.4 and 31.9 t/ha, respectively. The corresponding marketable and total yields from the untreated plot were 3.2 and 13.5 t/ha. This corresponds to yield losses of 82.6 and 57.7 % in marketable and total yield, respectively. T. absoluta has the potential to develop pesticide resistance very quickly due to short generation time and high reproductive potential. Insecticides found effective need to be used judiciously including the rotation of effective insecticides from different classes. Future research on the management of this pest should focus on developing a biocontrol based integrated pest management system.