Recent studies have revealed that the cotton aphid, Aphis gossypii, when exposed to sublethal doses of insecticides, can increase its reproduction rate. This can cause significant outbreaks of this pest in crops.
Four-generation experiment with A. gossypii showed that treatment with sulfoxaflor at sublethal doses (LC20) in the initial generation (G0) significantly increased the net reproductive rate (R0) and fecundity in subsequent generations (G1 and G2). However, it did not significantly affect the fertility of the G3 and G4 generations. Transcriptomic analyzes revealed that insecticide treatment induced the upregulation of pathways related to the ribosome, energy metabolism and DNA replication and repair, which may explain the increase in fecundity in the G1 and G2 generations.
The study also noted that initial exposure to sulfoxaflor followed by exposure to deltamethrin resulted in stronger reproductive stimulation than exposure to each insecticide alone. These results are important for optimizing integrated pest management strategies.
Hormesis is an evolutionary adaptation of organisms to environmental stress, including chemical stress. It can occur as a direct or compensatory response to initial stimuli of low insecticide concentration. In case of A. gossypii, it has been shown that hormesis induced by several insecticides at sublethal doses leads to excessive compensation of fecundity in surviving individuals.
Sulfoxaflor is a globally important sulfoximine insecticide widely used to control phloem-sucking insects such as A. gossypii. However, excessive use can cause pest resistance and resurgence. Previous studies indicate that interactions between insects, insecticide resistance, and symbionts play a crucial role in producing hormesis, promoting pest resurgence and outbreaks following treatment with sublethal doses of insecticides.
Treatment with sulfoxaflor at sublethal doses (LC20) significantly inhibited the population parameters of the G0 generation of A. gossypii, but stimulated the reproduction of the G1 and G2 generations. Transcriptomic data showed that insecticide treatment upregulated pathways related to the ribosome and energy metabolism in the G1 generation and DNA replication and repair in the G2 generation, potentially increasing the fecundity of A. gossypii.
According to the study authors, for the first time, it was found that multiple hormetic responses induced by sulfoxaflor and deltamethrin exposures led to stronger reproductive stimulation, which may be an important reason for severe aphid outbreaks under multiple chemical control measures.
The full analysis can be read at doi.org/10.1016/j.pestbp.2024.106061
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