Evaluation of Resistance and Toxicity of Different Insecticides on Tuta absoluta Meyrick Populations in Major Tomato Growing States of Nigeria

Abstract

The sudden invasion of the tomato leaf miner, Tuta absoluta Meyrick into tomato crops in Nigeria in 2015 has led to the extensive use of common insecticides, together with the introduction of a new insecticide referred to as “Tuta solution”, as only control method. After two years the farmers in major tomato producing states of Nigeria (Kaduna, Kano and Katsina States) reported that most of the insecticides applied were no longer effective in controlling Tuta. This led to the investigation of the toxicities of common insecticides lambda-cyhalothrin (MoA group 3A) and deltamethrin (MoA group 3A), and of the newly introduced formulations of chlorantraniliprole + lambda-cyhalothrin (MoA group 28 + 3A) and spirotetramat + flubendiamide (MoA group 23 + 28). These insecticides were tested on larvae obtained from populations collected from major tomato-growing states (Bomo and Giwa in Kaduna State; Beriberi and Funtua in Katsina State; and Bagauda, Watari and Samawa in Kano State) and a susceptible laboratory population of the National Horticultural Research Institute (NIHORT), Ibadan, Nigeria. These populations were subjected to concentration mortality bioassays, according to susceptibility test method No. 022, devised by the Insecticide Resistance Action Committee (IRAC). Resistance to chlorantraniliprole + lambda-cyhalothrin, lambda-cyhalothrin, and deltamethrin were observed in all the populations and compared with that of the susceptible NIHORT population. The resistance ratios obtained within the 7 populations ranged from 4.09 to 16.97 for chlorantraniliprole + lambda-cyhalothrin, 2.66 to 7.88 for lambda-cyhalothrin, and 3.23 to 6.24 for deltamethrin. However, resistance to spirotetramat + flubendiamide was not observed in all the 7 populations, with resistance ratio value of 1.05 as this combination was only introduced in 2017 for the control of T. absoluta in Nigeria and differently from the others, has not yet been abused. The sole dependence on, and indiscriminate usage of insecticides by farmers due to reckless recommendations, without regard for Integrated Pest Management, resulted in the widespread, higher levels of resistance observed in chlorantraniliprole + lambda-cyhalothrin, a product recently introduced into Nigeria in 2015.