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Alternative Chemical Control Tactics for the Red headed Flea Beetle in Ornamentals

By Julie Brindley and Alejandro Del Pozo – Virginia Tech, Department of Entomology, Hampton Roads AREC, Virginia Beach, VA

Abstract: Systena frontalis (F.) (Coleoptera: Chrysomelidae), commonly known as the red headed flea beetle, is a key pest under contain erized nursery production, defoliating several plant taxa including hydrangeas, sweet spire iteas and hollies. Affected growers can spray both pyrethroids and neonicotinoid s u p to two times a week during the peak of seasonal activity of this pest. The main goal of this project is to propose alternative control tactics for this beetle, including the use of 1 ) individual leaf bioassays, 2) drenches and top dressed granular formulations, and 3) foliar spray applications of alternative chemicals, irrigation regimes and volume. Ultimately, this rese arc h seeks to provide additional information on effective control tactics to manage this pest while reducing operational costs, non target effects and the exposure of workers in the nursery industry.

Insecticide Efficacy Bioassays

Fig. 1. Hydrangea leaf insecticide bioassay initiation, one adult per dish, nine insecticide treatments and an untreated control.

Fig. 2. 30 second dip bioassay results shown as the proportion of adults alive at 24, 48, 72, and 168 hours after initiation.

Fig. 3. Residual bioassays where beetles were exposed to hydrangea leaves 3 days post insecticide application. Results shown as the proportion of adults dead at 24, 48, 72, and 168 hours after bioassay initiation.

Fig. 4. Residual bioassays where beetles were exposed to hydrangea leaves 7 days post insecticide application. Results are shown as the proportion of adults dead at 24, 48, and 168 hours after bioassay initiation.

Fig. 5. Red headed flea beetle larvae.

Discussion

• Container plant nursery growers continue to face challenges controlling red headed flea beetles and subsequent plant damage which results in unmarketable plant material.

• This research investigated both industry standard and alternative chemicals under controlled laboratory and field conditions, targeting both larvae and adults.

• Results highlight several points:

• Alternative chemicals such as Tetrino and XXpire may have potential as tools in chemical treatment plans for both larvae and adults.

• Targeting first generation larvae in the plant substrate with effective insecticides can potentially reduce adult emergence in spring.

• Residual effects of insecticide treatments appear to be variable and short, with mortality not occurring beyond day 3 post application. Irrigation and other environmental conditions may contribute to this issue.

• Considering these results, future research should continue investigating new and alternative chemicals, additional timing and technique of larvae substrate applications to target multiple generations, and irrigation scheduling and adjuvants to prolong post application efficacy.

Drench and Top dress Field Trials

Fig. 6. Top: 2023 drench (Arena clothianidin, Tetrino tetraniliprole, XXpire sulfoxaflor + spinetoram) and top dress (Acelepryn chlorantraniliprole, Advion indoxacarb, Meridian thiamethoxam) substrate insecticide applications targeting larvae applied at approximately 500 GDD at base 50 F. Bottom: 2022 drench only (Altus flupyradifurone, Apta tolfenpyrad, Grandevo Chromobacteria , Mainspring cyantraniliprole) substrate insecticide applications targeting larvae applied at approximately 400 GDD50

Foliar Insecticide Field Trial

Fig. 7. Foliar insecticide applications, including Flagship thiamethoxam, Talstar bifenthrin, Merit imidacloprid, Scimitar lambda cyhalothrin, on containerized hydrangeas under either industry standard overhead irrigation or manual hand watering conditions.

Acknowledgments: We would like to thank Cody Herbert of Bennett’s Creek Nursery and Joe Compton of Lancaster Farms Nursery for their support. We would also like to thank Joseph Leo, Mireya Turcios, and Alecia Fischman for their technical assistance. This work was funded by the Virginia Nursery and Landscape Association and the VA Tech Hatch Project number VA 160164.