Cold tolerance strategy and lower temperature thresholds of Lycorma delicatula (Hemiptera: Fulgoridae) egg masses

The spotted lanternfly (Lycorma delicatula, Hemiptera: Fulgoridae) is a planthopper native to China and southeastern Asia invasive in North America. To inform the risk assessment of northward spread, we determined the cold tolerance strategy and lower lethal limits of overwintering eggs. We used field-collected egg masses from Pennsylvania, USA, and treated them with short (1 or 12 h) and long (10 or 15 d) low temperature exposures (0 °C to -25 °C). We determined that eggs were chill susceptible, and their supercooling points ranged from -17.4 °C to -27.7°C. We observed successful hatch after short- and long-term exposure to temperatures below -20 °C. Hatch rates were lower at or below -20 °C in the short exposures, or -15 °C in our long exposures experiments than hatch rate in egg masses not exposed to any treatment. Because L. delicatula eggs survived temperatures near their supercooling points, -27.7 °C could be used as an estimate of the lower lethal temperature. Our findings suggest that L. delicatula may be able to survive in colder climates than initially thought. Of the locations where L. delicatula has been intercepted in Canada-central and eastern provinces-Winnipeg is the only location where frequent or intense cold spells are likely to prevent hatch. Thus, low winter temperatures may not limit L. delicatula overwinter survival in many regions of Canada or other parts of the world that experience similar winter conditions.