Investigating the molecular mechanism of onsecticide resistance in the tomato leaf miner, Tuta absoluta

Tuta absoluta is an economically significant pest of tomatoes, which has undergone a rapid expansion in its range during the past six years. One of the main means of controlling this pest is through the use of chemical insecticides including pyrethroids and spinosad. However, their intensive use has led to the development of resistance. The aim of this PhD was to understand the mechanisms underlying resistance to pyrethroids and spinosad. The target site of pyrethroids, the sodium channel, was cloned and three known knockdown resistance mutations, L1014F, M918T and T929I were found. High-throughput diagnostic assays were developed and the prevalence of the three mutations was then assessed. All three mutations were found at high frequencies in populations across the range of T. absoluta. Additionally, a fourth novel mutation L925M was found in 14% of samples. Therefore, pyrethroids are unlikely to be effective at controlling T. absoluta