Establishment of a pesticide resistance monitoring tool for the two-spotted spider mite, Tetranychus urticae
Abstract
Two-spotted spider mite (TSSM), or Tetranychus urticae (Koch), is a major agriculture pest known for its rapid development of resistance to pesticides. The analysis of spider mites’ pesticide resistance demonstrated that resistance patterns and frequencies vary between T. urticae strains collected from different geographic locations and host plants. This research aims at characterization of pesticide resistance patterns in mite populations present in greenhouses in the Southwestern Ontario by identifying genetic and metabolic markers of their pesticide resistance. The establishment of these markers lays the basis for development of a pesticide resistance diagnostic tool that will enable prediction of population resistance status based on the resistance-associated markers. The ultimate aim of the project is to enable identification of genetic patterns to be used for recommendations on pesticide use to growers.
In the Fall of 2018, 19 TSSM populations from different Ontario greenhouses and different crops (tomato, eggplant, cucumber, pepper) were collected. First, the bioassay protocols were optimized and then applied to the collected populations to determine their resistance status. Following that, genotyping and RT-QPCR were performed to check for known genetic markers: single nucleotide polymorphisms associated with abamectin, bifenazate, and etoxazole resistance and metabolic markers of detoxification associated with abamectin resistance, respectively. Lastly, the correlation between the genetic/metabolic markers and resistance status was analyzed, and multiple pesticide resistance was assessed. As a result, the pesticide resistance diagnostic tool was developed for abamectin. More informative markers are needed for bifenazate diagnostic tool, and further research is needed for etoxazole. Cross-resistance to abamectin and bifenazate was also observed in three out of 19 greenhouse populations. This work demonstrates that Canadian populations differ greatly from the populations found in other countries. In addition, the high frequency of resistance-associated alleles in tested populations alerts on a need to develop pesticide resistance diagnostic tools to help growers in mite pesticide resistance management.