Assessing the susceptibility of field-collected adults of Systena frontalis (Coleoptera: Chrysomelidae) to bifenthrin across eastern Virginia

Systena frontalis (Coleoptera: Chrysomelidae), commonly known as the red-headed flea beetle, is a key pest of nursery crops across Virginia. This defoliator render infested plants unsalable when present in high numbers. Affected growers might spray insecticides twice a week to control a significant population of this pest in susceptible plant taxa, such as panicled hydrangeas, sweet spire iteas and hollies. The overuse of certain insecticides may result in building resistance in individuals constantly exposed to these chemicals. One concern for nursery growers inside a quarantine area for imported fire ants is the effect of bifenthrin mixed with the potting media to fulfill the quarantine compliance requirement. Based on anecdotal observations, S. frontalis are still eclosing from pots that have the granular bifenthrin in the media. Information from this project helps to understand the susceptibility of S. frontalis to bifenthrin. Laboratory assays, following the IRAC glass vial method included treatments: a) acetone only - control, b) 2 ug, c) 6 ug, d) 20 ug, e) 60 ug and f) 120 ug of bifenthrin per vial. Mortality rates were assessed at 24 h after adult placement. Alive adults (4-20% survivorship) were documented from vials coated with 120 ug of bifenthrin. It is imperative to conduct surveillance of the onset of any potential insecticide resistance for key pests in nurseries. Results from this study will aid to inform the future use of the insecticides within the pyrethroid class for controlling S. frontalis in nursery settings.