Effect of a severe cold spell on overwintering survival of an invasive forest insect pest

Cold temperatures can play a significant role in the range and impact of pest insects. Severe cold events can reduce the size of insect outbreaks and perhaps even cause outbreaks to end. Measuring the precise impact of cold events, however, can be difficult because estimates of insect mortality are often made at the end of the winter season. In late January 2023 long-term climate models predicted a significant cold event to occur over eastern North America. We used this event to evaluate the immediate impact on hemlock woolly adelgid (Adelges tsugae Annand) overwintering mortality at four sites on the northern edge of the insects invaded range in eastern North America. We observed complete mortality, partial mortality and no effects on hemlock woolly adelgid mortality that correlated with the location of populations and strength of the cold event. Our data showed support for preconditioning of overwintering adelgids having an impact on their overwintering survival following this severe cold event. Finally, we compared the climatic conditions at our sites to historical weather data and previous observations of mortality in Nova Scotia. The cold event observed in February 2023 resulted in the coldest temperatures observed at these sites, including the period within which hemlock woolly adelgid invaded, suggesting cold conditions, especially under anthropogenic climate forcing, may not be a limiting factor in determining the ultimate northern range of hemlock woolly adelgid in eastern North America

Data from: Effect of a severe cold spell on overwintering survival of an invasive forest insect pest

<p>Data from a study of a servere cold event in February 2023 on the survival of hemlock woolly adelgid (<em>Adelges tsugae</em> Annand) from four populations in Canada. Cold temperatures can play a significant role in the range and impact of pest insects. Severe cold events can reduce the size of insect outbreaks or in some cases even cause outbreaks to end. Measuring the precise impact of cold events, however, can be difficult because estimates of insect mortality are often made at the end of the winter season. In late January, 2023 long-term climate models predicted a significant cold event to occur over eastern North America. We used this event to evaluate the immediate impact on hemlock woolly adelgid overwintering mortality at four sites on the northern edge of the insects invaded range in eastern North America. We observed complete mortality, partial mortality and no effect of the cold event that correlated with the location and strength of the cold event. Our data also showed lack of support for preconditioning of overwintering adelgids as impacting their overwintering survival following this severe cold event. Finally, we compared the climatic conditions at our sites to historical weather data. The cold event observed in February 2023 resulted in the coldest temperatures observed at these sites, including the period within which hemlock woolly adelgid invaded these sites, suggesting cold conditions, especially under anthropogenic climate forcing, may not be a limiting factor in determining the ultimate northern range of hemlock woolly adelgid in eastern North America.</p><p>Insects were collected from infested trees at 4 sites in 2 Canadian provinces immediately before and immeditely after a severe cold spell. The health and status of the insects (live/dead) was determined in a laboratory. The survival was then compared to observed temperature data extracted from Environment and Climate Change Canada weather stations. </p&gt