ESA Annual Meetings Online Program
Biotic and abiotic factors affecting establishment of introduced predators of hemlock woolly adelgid in the Great Smoky Mountains national park
Hemlock woolly adelgid (HWA), Adelges tsugae, presents a serious threat to the survival and viability of eastern hemlock. In the Great Smoky Mountains National Park, ca. 500,000 Sasajiscymnus tsugae (St) have been released at more than 200 sites to reduce populations of HWA. Of these sites, 65 St release sites were sampled using a beat sheet for four hours between 2008 and 2012. Several biotic and abotic factors (release size, year of release, slope, elevation, aspect, and four temperature variables [minimum and maximum temperature one-day after release, average minimum and maximum temperature seven-days after release]) were analyzed using stepwise logistic regression and correlation to test whether they contributed to St establishment. Larvae and/or adults of St were recovered from 13 of 65 (20%) release sites. Recovery of St from one egg release site indicates that egg releases also may be successful if released when temperatures are appropriate. Stepwise logistic regression indicated that an inverse association between year of release and establishment of St. Spearman correlation also indicated a significant inverse relationship between year of release and St establishment (coefficient = -0.447; P = 0.01) which indicates that St populations require more time to reach detectable levels. In addition, a significant positive correlation (P< 0.05) was found between St establishment and temperature at the time of release (minimum and maximum temperature one-day after release, and average minimum and maximum temperature seven-days after release). This study suggests that low temperatures near time of release may negatively effect St establishment.
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