Tomato leafminer, Tuta absoluta (Meyrick), and insecticide resistance: a new challenge for control strategies

The tomato leaf miner, Tuta absoluta (Lepidoptera), is a significant pest of tomatoes that has undergone a rapid expansion across Europe, North Africa and parts of Asia during the past six years. One of the main means of controlling this pest is through the use of chemical insecticides. In the current study leaf-dip bioassays were used to determine the susceptibility of T. absoluta strains established from field collections to several insecticides. Additionally, the para-type sodium channel and acetylcholinestaerase gene from T. absoluta were cloned and sequenced. This revealed the presence of three kdr/super-kdr-type mutations (M918T, T929I and L1014F) in the sodium channel gene and mutation (A201S) in the acetylcholinesterase gene. To assess the prevalence of these mutations in 27 field strains from 12 countries high-throughput TaqMan diagnostic assays were developed. The results showed the presence of these mutations at high frequency in T. absoluta populations world wide and suggests pyrethroids and organophosphates are likely to be ineffective for control. These results also support the idea that the rapid expansion of this species over the last six years may be in part mediated by the resistance of this insect to chemical insecticides hence adding new challenges to control strategies for this pest.