Neonicotinoid resistance in populations of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) in Cotton Plantation Areas of Turkey

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is a polyphagous pest that could cause economic crop losses in various crops. Cotton production areas are under insecticide application pressure, and the possibility of insecticide resistance development is higher than in other crops. Chemical insecticides, especially neonicotinoids, are the most common instruments of Integrated Pest Management (IPM) strategies against A. gossypii. In this study, the resistance status of A. gossypii populations from the largest cotton plantation areas of Turkiye was analyzed. Nine field-collected aphid populations and a susceptible strain were examined in leaf-dip bioassays with three neonicotinoid insecticides. The resistance ratios of bioassays ranged from 22.6 to 82.6 for acetamiprid, 23.5 to 67.3 for imidacloprid, and 1.1 to 20.8 for thiamethoxam. Comparative sequence analysis between susceptible and resistant strains was analyzed to identify known mutations to confer resistance to neonicotinoids. The mean enzyme activity in some populations was significantly higher than in the susceptible strain. The enzyme activity ratios ranged from 1.9 to 3.9 for CarE and 1.5 to 3.1 for GST. The bioassay data revealed moderate to high resistance levels in acetamiprid and imidacloprid and low to medium levels in thiamethoxam. A partial sequence of the beta 1 subunit of the nAChR in specimens of the populations examined did not reveal any of the V62I, L80S, and R81T and point mutations. The lack of any correlation between the carboxylesterase or glutathione-S-transferase activity and the LC50 values of three insecticides suggested that these two detoxification enzymes were not involved in the resistance levels observed. However, the resistance levels observed in the present study could be attributed to metabolic resistance mechanisms. Another important point is the cross-resistance observed between the neonicotinoids in the present study. Their extensive use, especially in cotton, might select aphid genotypes resistant to more than one neonicotinoid.