Factors Affecting Establishment and Recovery of <I>Sasajiscymnus tsugae</I> (Coleoptera: Coccinellidae), an Introduced Predator of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) on Eastern Hemlock (Pinales: Pinaceae)

Abstract

To reduce populations of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), >500,000 Sasajiscymnus tsugae (Sasaji and McClure) (Coleoptera: Coccinellidae) have been released in the Great Smoky Mountains National Park since 2002. To determine factors affecting establishment and recovery of these predatory beetles, 65 single release sites were sampled using beat sheets from 2008 to 2012. Several abiotic and biotic factors were evaluated for their association with establishment and recovery of S. tsugae. Information on predatory beetle releases (location, year of release, number released, and season of release), topographic features (elevation, slope, Beers transformed aspect, and topographic relative moisture index), and temperature data (minimum and maximum temperatures 1 d after release and average minimum and maximum temperatures 7 d after release) were obtained from Great Smoky Mountains National Park personnel. These factors were evaluated using stepwise logistic regression and Pearson correlation. S. tsugae was recovered from 13 sites 2 to 10 yr after release, and the greatest number was recovered from 2002 release sites. Regression indicated establishment and recovery was negatively associated with year of release and positively associated with the average maximum temperature 7 d after release and elevation (generally, recovery increased as temperatures increased). Several significant correlations were found between presence and number of S. tsugae and year of release, season of release, and temperature variables. These results indicate that releases of S. tsugae should be made in warmer (≍10-25°C) temperatures and monitored for at least 5 yr after releases to enhance establishment and recovery efforts.

Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings

“…Although chemical control has been used with great success to temporarily protect individual trees, financial costs, logistical constraints of manually treating large areas, and environmental constraints greatly limit its use as a sustainable strategy for protecting natural stands (Vose et al, 2013). Biological control shows some promise as several released predatory species are successfully establishing in eastern forests (Mausel et al, 2010;Hakeem et al, 2013;Vose et al, 2013;Mayfield et al 2015;D.R. Zietlow, unpublished data); but the time required for widespread predator proliferation and dispersal, and timing predator release effectively for outbreak species such as HWA, may limit the effectiveness of biological control as a stand-alone strategy.…”

Native parasitoids and recovery ofSpathius agrilifrom areas of release against emerald ash borer in eastern Tennessee, USA

“…In another forest ecosystem impacted by an invasive species, population densities of Sasajiscymnus tsugae (Sasaji and McClure), an introduced predatory lady beetle released against hemlock woolly adelgid, Adelges tsugae Annand, were significantly correlated with older (ca. > five years) release sites in the Great Smoky Mountains National Park (Hakeem et al, 2013). The recovery of S. agrili reported here may indicate that it will be a viable biological control agent in southern states, especially as EAB has continued to expand its distribution further south.…”

Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Management in Forest, Landscape, and Nursery Production

“…Recovery of Sas. tsugae in biocontrol release areas may take up to 5–7 y (Hakeem et al. 2010, Jones et al 2012).…”