Neonicotinoid toxicity and resistance in cotton aphid ( <i>Aphis gossypii</i> ) populations across Türkiye

Cotton aphid ( Aphis gossypii Glover) is an important pest adversely affecting cotton production globally. The plant-sap-sucking and virus transmission by the pests result in severe economic losses. Türkiye is a major cotton-producing country, and pesticides are frequently used for pest management. Continuous use of pesticides has led to the evolution of resistance and environmental concerns. However, few studies have examined the comparative toxicity of neonicotinoids against A. gossypii populations from various regions. This study evaluated the toxicity and resistance ratios of three neonicotinoids (acetamiprid, imidacloprid, and sulfoxaflor) against A. gossypii in Türkiye. Five populations were collected from four cotton-producing regions, including Adana, Aydın, Hatay, and Şanlıurfa. Leaf-dip bioassays were conducted to determine lethal concentrations (LC₅₀ and LC₉₀), plot dose-response curves, and evaluate inter-insecticide toxicity ratios. Sulfoxaflor caused the highest toxicity across all populations (LC₅₀ = 10.37-11.91 ppm). Nevertheless, acetamiprid (LC₅₀ 48.25–75.86 ppm) and imidacloprid (LC₅₀ 56.20–70.19 ppm) proved less toxic. Sulfoxaflor was 4.28–7.04 times more toxic than acetamiprid and 5.21–6.23 times more toxic than imidacloprid. Inter-population variability ratios for all tested insecticides remained below 2-fold, indicating that populations had not undergone substantial differential selection pressure. Hillslope values (1.17–2.11) indicated that populations responded similarly to the tested insecticides. The results provide baseline toxicity data and suggest sulfoxaflor as a candidate for pesticide rotation in an integrated pest management (IPM) program. Nevertheless, continuous monitoring, molecular resistance screening, and field-level efficacy trials are recommended to sustain effective chemical control of A. gossypii .