Fenpropathrin resistance in Asian citrus psyllid, Diaphorina citri Kuwayama: risk assessment and changes in expression of CYP and GST genes associated with resistance

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Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), populations exhibit varying levels of resistance to several insecticide classes, including pyrethroids. Artificial laboratory selection was conducted to investigate mechanisms underlying fenpropathrin resistance. After ten generations of selection, the LC50 for fenpropathrin increased from 0.18 to 11.60 ng/μL, and the associated resistance ratio increased by 96.67-fold. The realized heritability of resistance (h2) to fenpropathrin changed from 0.17 to 0.44 during the first and second round of selection, respectively. We did not find high cross-resistance to imidacloprid (RR = 3.58) or dimethoate (RR = 1.77) in the fenpropathrin-selected strain, but found cross-resistance to bifenthrin (RR = 28.21). RT-qPCR analysis showed that expression of CYP6A2-1 was significantly increased in the selected population relative to the laboratory susceptible population. Our data indicate that D. citri has the capacity to develop a high level of fenpropathrin resistance following persistent selection and that cytochrome P450 (CYP) and glutathione S-transferase (GST) metabolic detoxification may be contributing mechanisms. Rotation programs that include neonicotinoids and organophosphates should manage resistance to fenpropathrin for D. citri.