The spider mite Tetranychus urticae sitting on a leaf. Image credit: Cao et al. (CC BY 4.0)
Chemical pesticides have been widely used for over a century to manage crop pests and disease vectors. However, pests can rapidly evolve resistance to these chemicals, enabling them to survive exposures that would otherwise be lethal.
Since the first documented case of pesticide resistance in 1914, instances of insecticide resistance have grown rapidly, posing serious threats to agriculture, human health and the environment. Despite a lengthy history of resistance and related research, most studies have been carried out only after resistance became widespread. Consequently, our understanding of how resistance develops under field conditions remains limited.
Cao et al. studied the two-spotted spider mite, Tetranychus urticae, to understand how pesticide resistance can emerge. T. urticae is considered the most resistant invertebrate pest worldwide due to its ability to develop resistance to a wide range of pesticides. The researchers investigated how resistance to the new pesticide cyetpyrafen emerges in field populations by comparing samples collected before and after cyetpyrafen use. To test the mites’ susceptibility to pesticides, they conducted bioassays on 46 mite population samples collected from various regions in China between 2020 and 2024 and compared the results to previously reported data of earlier collections between 2017 and 2018 during the early release stage of cyetpyrafen.
The experiments revealed that high levels of resistance to cyetpyrafen emerged and spread across geographically distant populations within just three years of its introduction. Genomic analysis identified 15 distinct mutations in the target protein of cyetpyrafen, which consisted of an unprecedented number of amino acid changes associated with resistance to a single pesticide in a single species. Mutations arising after the release of cyetpyrafen were absent in samples collected before cyetpyrafen use, suggesting they arose only following the pesticide's introduction. Identical mutations appeared independently in multiple populations, indicating that resistance can evolve repeatedly and rapidly. Even a single mutation was sufficient to lead to high levels of resistance.
Cao et al. provide a rare longitudinal view of resistance development in field populations of an invertebrate pest by demonstrating that resistance in T. urticae can arise through multiple genetic pathways rather than solely through the spread of a single rare mutation. These findings underscore the challenges of managing pesticide resistance and highlight the urgent need for alternative pest control strategies and more considered pesticide use.
