Heat treatments to kill eggs of two invasive forest insects: <i>Lycorma delicatula</i> (Hemiptera: Fulgoridae) and <i>Lymantria dispar</i> (Lepidoptera: Erebidae)

The spotted lanternfly (Lycorma delicatula) and spongy moth (Lymantria dispar) are notorious invasive forest pests that are spread through human-mediated transport to invade new habitats. In this study, spotted lanternfly and spongy moth eggs were exposed to various temperature-exposure time (35 to 70 °C and 15 to 135 min) treatments in the laboratory. Spotted lanternfly egg masses were collected from various sites in 2022 and 2023, while the spongy moth egg masses were obtained from lab-reared colonies. Heat treatments were applied using an Isotemp microbiological incubator in the spring of 2023 and the spring and fall of 2024. No eggs of either species hatched when exposed to temperatures ≥ 60 °C for durations longer than 15 min. Spotted lanternfly egg hatch declined at temperatures ≥ 45 °C, while reduced hatch of spongy moth eggs was not observed until temperatures reached ≥ 50 °C. The season (spring or fall) in which the eggs were heat treated did not affect the hatch rate of spotted lanternfly eggs; however, spongy moth eggs were more vulnerable in the fall than in the spring. These findings suggest that heat treatment regimes that are already being used to kill insects in wood may effectively kill the eggs of both species on various substrates and that protocols for killing eggs at lower temperatures on more sensitive substrates may be possible by using longer-duration exposures.