Insecticide resistance management in Florida citrus production.

Insecticide resistance management in Florida citrus production.

Report Date: 03/14/2019
Project: 17-001C   Year: 2019
Category: ACP Vector
Author: Lukasz Stelinski
Sponsor: Citrus Research and Development Foundation

A study was designed to investigate the capacity of field collected Asian citrus psyllid (ACP) Diaphorina citri Kuwayama (Hemiptera: Liviidae) to develop resistance to the pyrethroid insecticide, fenpropathrin and determine the biochemical and genetic mechanisms of resistance to this popularly used chemistry for ACP management. We established an insecticide resistant strain of ACP in the greenhouse. The selected adult ACP population was originally collected from commercial citrus groves from Wachula, FL on July 15, 2018. They were treated with the LC50 concentration of fenpropathrin for nine generations of continuous rearing and then for a subsequent seven generations at a higher insecticide concentration. Bioassays were conducted using the bottle bioassay to assess the resistance of adults during each successive generation. Insecticides were dissolved to make 5-7 concentrations in acetone that gave 0 to 100% mortality. Control ACP were treated with acetone. Selection was performed by exposing adults to treated glass vials at the LC50 concentration. The ACP that survived were released in rearing cages to serve as parents of the next generation. The value of LC50 was increased from 0.12 to 3.71 ng/´┐ŻL after nine generations. The resistance ratio was 30.91 fold. Biochemical assays were performed with detoxifying enzymes, namely esterase (EST), glutathione S-transferase (GST) and cytochrome P450 monooxygenase (P450). These were quantified every two generations and compared with the laboratory susceptible population. The activity ratio of EST enzymes was 1.530 fold higher for the selected population compared with the laboratory population at eight generations and there were significant differences between the two populations (p < 0.001). The activity of GST enzyme was 1.486 fold higher, and for P450 the activity ratio was 1.10 fold higher for the selected population compared to the laboratory population. There were significant differences between the two populations for GST activity (p = 0.038) and for P450 activity (p = 0.045). Future experiments are planned to better understand the genetic basis of resistance by determining the expression levels of genes involved in the detoxification of pyrethorid insecticides. The results of this study provide insight into the development of insecticide resistance and designing appropriate resistance management strategies for ACP.


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