Longevity and potential mechanisms of fenpropathrin resistance in Asian citrus psyllid, Diaphorina citri Kuwayama

Authors: CHEN, XUE DONG - University Of Florida; Stockton, Dara; GILL, TORRENCE - Chowan College; GOSSETT, HUNTER - University Of Florida; QURESHI, JAWAD - University Of Florida; PELZ-STELINSKI, KIRSTEN - University Of Florida; STELINSKI, LUKASZ - University Of Florida

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2024
Publication Date: 4/27/2024
Citation: Chen, X., Stockton, D.G., Gill, T.A., Gossett, H., Qureshi, J.A., Pelz-Stelinski, K.S., Stelinski, L.L. 2024. Longevity and potential mechanisms of fenpropathrin resistance in Asian citrus psyllid, Diaphorina citri Kuwayama. Horticulturae. 10(5). https://doi.org/10.3390/horticulturae10050448.
DOI: https://doi.org/10.3390/horticulturae10050448

Interpretive Summary: Management of Asian citrus psyllid, the vector of citrus greening disease, has relied on calendar based insecticide application since it's detection in Florida during 2008. As a result, insecticide resistance is an ongoing issue for commercial citrus in the U.S. and abroad. This study aimed to understand how long resistance to pyrethroid insecticides would last in a population absent continued application pressure. It also aimed to investigate the changes in gene expression associated with pyrethroid resistance. The results showed that resistance to pyrethroids is not stable and rapidly decays over time if insecticides are not reapplied. This helps explain why area-wide management programs have been so effective, so quickly, with this species. The results also showed that certain CPY genes may be responsible for this recovery of susceptibility as expression was greater over time.

Technical Abstract: We studied the stability of, and mechanisms underlying, of fenpropathrin resistance in populations of Asian citrus psyllid (Diaphorina citri) differing in initial frequencies was studied under laboratory conditions. A mechanism of pyrethroid resistance and resistance stability was investigated under laboratory conditions. The stability of resistance was assessed with bimonthly toxicity bioassays in which five populations were established with initial fenpropathrin resistance ratios (RR) ranging from fully susceptible (00RR) to fully resistant (100RR). of RR100: 100RR+0SS; RR75: 75RR+25SS; 50RR: 50RR+50SS, RR25: 25RR+75SS and RR00: 00RR+SS100 of resistant individuals mixes with a laboratory susceptibility (SS) population. We assessed the gene expression of the sodium channel genes and CYP6 levels comparing the by laboratory and field-selected D. citri after eight months with no insecticide applications. There were no consistent changes in susceptibility of the susceptible strain after eight months without insecticide pressure. In the resistance population, the resistance to fenpropathrin (RR > 10.83), was maintained higher up to eight months without further exposure to fenpropathrin. The fenpropathrin resistance in D. citri declined in the absence of selection pressure in the cross RR25 (RR25+SS75) population. Real-time quantitative PCR analysis using the laboratory population revealed that levels of D. citri expression of CYP6A2-1 and F1530 were higher in resistant strain after eight months of recovery. The expression levels were not higher than those in the heterozygotes. The results suggest that fenpropathrin resistance probably is unstable under field conditions, primarily due to the immigration of susceptible individuals. There was no correlation between the target insensitivity and increased metabolic detoxification in pyrethroid resistance of D. citri was observed in the laboratory and selected strain or RR and SS cross population. Our results suggest that insecticide resistance to fenpropathrin in D. citri is more complex than previously described and implicate a much broader array of potential resistance mechanisms.