HWA Research
The key to implementing biocontrol as an effective pest management strategy is understanding HWA biology and behavior in New York. To that end, we conduct field and lab experiments to learn more about HWA and support our biocontrol research.
There are three main research components that we study regarding HWA: Phenology, Winter Mortality and Development.
HWA Phenology
Our lab investigates the timing of HWA’s major life cycle stages, or phenology, in order to time biocontrol releases across variable climates in New York. In the field, we’ve teamed up with the National Phenology Network to track HWA phenology using the Nature’s Notebook mobile app. We also work closely with the New York Phenology Project, which is tracks phenology for several New York plant and animal species.
The key life cycle stages that we track for biocontrol releases are aestivation break in the fall, and the beginning of HWA egg-laying in the spring. Aestivation break occurs when the first (sistens) generation of HWA begins actively feeding and developing following their period of dormancy in the summer months. Once HWA breaks aestivation in the fall, we release Laricobius beetles to feed on growing HWA nymphs and HWA adults throughout the fall and winter. HWA egg-laying occurs twice during the spring, with the first generation laying eggs in early spring and the second (progrediens) generation laying eggs at the end of the spring and early summer. Our lab releases Leucotaraxis silver flies once adelgids begin laying eggs, and those fly larvae feed on HWA eggs of both the first and second generations of HWA.
HWA Winter Mortality
Since 2014, we have tracked HWA winter mortality by comparing HWA survivorship at “cold” sites in the Catskills and “warm” sites in the Finger Lakes during the winter months. Our field team collects samples of HWA-infested foliage at each site, then compares the percentage of live and dead HWA at each site at regular intervals throughout the season. Our current understanding of HWA mortality is that sudden cold snaps following several days of milder temperatures contribute to massive HWA die-off. Although we have studied winter mortality for several years, we continue to collect data to better understand HWA population dynamics in response to winter temperatures.
In addition to field studies, we have also conducted supercooling experiments in a lab setting to investigate the ability of HWA to survive low temperatures. Data from supercooling experiments suggests that cold mortality increases following cold snaps preceded by a period of warmer temperatures. Conducting these controlled experiments allows us to better understand HWA’s sensitivity to cold, and predict HWA mortality rates based on winter temperatures.
HWA Development
Previous studies of HWA in the field have revealed that infestations are variable by year and geographic location. Temperature, in particular, appears to play a large role in HWA development and spread. In 2017, we began a study aimed at carefully tracking HWA development in four different temperature treatments ranging from 8°C (46.4°F) to 20°C (68°F) and one outdoor control. One insight from this study is the amount of variability in the timing of the HWA life cycle, even between individuals on the same twig. Data from this study, which concluded in 2018, were incorporated in a publication in the Journal for Integrated Pest Management.