Bioassay and field trial of pesticides against spotted lanternfly (Hemiptera: Fulgoridae) egg masses at different overwintering application timings.

Spotted lanternfly (SLF; Lycorma delicatula [White]) overwinters in egg masses for approximately eight months a year, representing its longest individual life stage. Therefore, this life stage constitutes a good candidate for management practices. Egg masses were collected from various locations in Winchester, VA, and stored in climate-controlled incubators (10 °C, 65% relative humidity, and a 16:8 light-to-dark ratio). The egg masses were treated during one of three periods during the overwintering phase: winter, early spring, or late spring. Bioassays were conducted across 3 years (2021 to 2023) utilizing 13 insecticides, across multiple modes of action, along with an untreated and water check. Furthermore, in 2023, a field trial of malathion against an untreated check was investigated. Egg mass hatch reduction was analyzed to determine the efficacy of the various treatments and application timings. In all bioassays, we found strong reductions in survivorship from malathion and chlorpyrifos. Other pesticides tested in laboratory bioassays demonstrated varying, lesser hatch reductions across application timings and years. In the field trial, we found strong evidence that malathion provides ovicidal efficacy against hatching SLF nymphs.