scholarly journals A Four-Year, Seven-State Reforestation Trial with Eastern Hemlocks (Tsuga canadensis) Resistant to Hemlock Woolly Adelgid (Adelges tsugae)

Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 312
Author(s):  
Ian G. Kinahan ◽  
Gabrielle Grandstaff ◽  
Alana Russell ◽  
Chad M. Rigsby ◽  
Richard A. Casagrande ◽  
...  
Keyword(s):  
Clonal Propagation ◽  
Tsuga Canadensis ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Additional Research ◽  
Eastern Hemlock ◽  
Lateral Growth ◽  
Mature Trees ◽  
Elongate Hemlock Scale ◽  
Fiorinia Externa

We conducted over a decade of research into individual eastern hemlock (Tsuga canadensis; hemlock) trees that are potentially resistant to hemlock woolly adelgid (Adelges tsugae; HWA), an invasive xylem-feeding insect that is capable of rapidly killing even mature trees. Following clonal propagation of these individuals, in 2015 we planted size- and age-matched HWA-resistant and HWA-susceptible hemlocks in HWA-infested forest plots in seven states. In 2019, we re-surveyed the plots; 96% of HWA-resistant hemlocks survived compared to 48% of susceptible trees. The surviving HWA-resistant trees were also taller, produced more lateral growth, retained more foliage, and supported lower densities of the elongate hemlock scale Fiorinia externa, another invasive hemlock pest, than the surviving HWA-susceptible trees. Our results suggest that HWA management may benefit from additional research exploring the identification, characterization, and use of HWA-resistant eastern hemlocks in future reforestation efforts.

Eastern hemlock (Tsuga canadensis) regeneration in the presence of hemlock woolly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa)

2011 ◽  
Vol 41 (12) ◽  
pp. 2433-2439 ◽  
Author(s):  
Evan L. Preisser ◽  
Mailea R. Miller-Pierce ◽  
Jacqueline Vansant ◽  
David A. Orwig
Keyword(s):  
New England ◽  
Tsuga Canadensis ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Eastern Hemlock ◽  
Invasive Pest ◽  
Seedling Density ◽  
Southern New England ◽  
Elongate Hemlock Scale ◽  
Fiorinia Externa

The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive hemipteran that poses a major threat to eastern hemlock (Tsuga canadensis (L.) Carrière) forests in the United States. We conducted three surveys over a five-year period that assessed the density of hemlock woolly adelgid (HWA) and a second invasive pest, the elongate hemlock scale (EHS; Fiorinia externa Ferris), overstory hemlock mortality, and hemlock regeneration in ~140 hemlock stands (mean size, 44 ha; range, 7–305 ha) within a 7500 km2 north–south transect of southern New England (USA). In each stand, we rated HWA and EHS density on 50 hemlock trees using a 0–3 scale (0, none; 1, 1–10 organisms/m branch; 2, 11–100 organisms/m branch; 3, >100 organisms/m branch). Data on the presence or absence of regeneration were taken in 2005; in 2007 and 2009, we quantitatively assessed regeneration by counting the number of hemlock seedlings in three 16 m2 plots per stand. In 2005, 81% of sampled stands had HWA, 72% had EHS, and 66% had hemlock regeneration. In 2007, 86% of sampled stands had HWA, 79% had EHS, and 46% had hemlock regeneration. In 2009, 91% of stands had HWA, 87% had EHS, and 37% had hemlock regeneration. The proportion of stands with hemlock regeneration declined 46% between 2005 and 2009, and hemlock seedling density declined 71% between 2007 and 2009. A best-fit model selection algorithm found that this decrease was inversely correlated with stand-level adelgid density. There was no correlation between the change in seedling density and stand-level density of the elongate hemlock scale. The apparent decline in regeneration suggests that the ecosystem-level changes currently occurring in southern New England may be difficult to reverse.

Combined Effects of Hemlock Woolly Adelgid (Adelges tsugae) Infestation and Treatment with Imidacloprid on Eastern Hemlock (Tsuga canadensis) Leaf Radiometry

2019 ◽  
Vol 117 (4) ◽  
pp. 340-350 ◽  
Author(s):  
Heath W Garris ◽  
Thomas H Settle ◽  
Jonathan E Crossman ◽  
Stephen J Grider ◽  
Shawnté L Michaels
Keyword(s):  
Optical Properties ◽  
Tsuga Canadensis ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Eastern Hemlock ◽  
Abiotic Stressors ◽  
Leaf Optical Properties ◽  
Photosynthetic Potential ◽  
And Control ◽  
Potential Efficiency

Abstract The neonicotinoid systemic insecticide imidacloprid has proven to be an effective treatment for the prevention and control of hemlock woolly adelgid (Adelges tsugae Annand) in southeastern populations of eastern hemlock (Tsuga canadensis L.). Recent studies have demonstrated that imidacloprid and A. tsugae both stimulate salicylic acid-dependent physiological responses in plant tissues responsible for plant defenses against pathogens, timing of developmental outcomes including flowering and leaf senescence, and resilience to abiotic stressors. We evaluated the interacting effects of A. tsugae presence/absence and treatment with imidacloprid on leaf optical properties indicative of photosynthetic potential, photosynthetic efficiency, and tissue senescence. Our results indicated that A. tsugae changes lower canopy leaf optical properties indicative of reduced photosynthetic potential/efficiency and accelerated senescence in mature leaves. Imidacloprid was associated with declines in photosynthetic potential and showed a largely similar, though less pronounced, effect on leaf spectral properties to that of A. tsugae.

Description of the adult male elongate hemlock scale, Fiorinia externa Ferris (Coccoidea: Diaspididae), with notes on the seasonal development of the species on eastern hemlock, Tsuga canadensis (L.) Carrieré (Pinaceae), in the southern Appalachian region (U.S.A.)

Zootaxa ◽  
2007 ◽  
Vol 1615 (1) ◽  
pp. 29-39 ◽  
Author(s):  
PARIS LAMBDIN ◽  
CHRISTOPHER HODGSON ◽  
JEROME GRANT
Keyword(s):  
Adult Male ◽  
Overlapping Generations ◽  
Tsuga Canadensis ◽  
Eastern Hemlock ◽  
Seasonal Development ◽  
Adult Males ◽  
First Instar ◽  
Elongate Hemlock Scale ◽  
Fiorinia Externa ◽  
First Time

The adult male of Fiorinia externa Ferris is described for the first time. Its morphology agrees with that of previously described adult males in the tribe Diaspidini, and suggests a close affinity to Pseudaulacaspis. F. externa has two complete overlapping generations per year on the needles of eastern hemlock, Tsuga canadensis (L.) Carrieré, in the eastern Tennessee (USA) southern Appalachians. Adult females (both gravid and non-gravid) and first-instar nymphs were the dominant overwintering stages, although all stages apart from the adult males were present throughout the winter months. Adult males began emerging in mid March with emergence peaks in mid April to early May and again in mid to late September.

scholarly journals Hemlock woolly adelgid (Adelges tsugae) infestation affects water and carbon relations of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana)

2013 ◽  
Vol 199 (2) ◽  
pp. 452-463 ◽  
Author(s):  
Jean-Christophe Domec ◽  
Laura N. Rivera ◽  
John S. King ◽  
Ilona Peszlen ◽  
Fred Hain ◽  
...  
Keyword(s):  
Tsuga Canadensis ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Eastern Hemlock

scholarly journals Thinning effects on foliar elements in eastern hemlock: implications for managing the spread of the hemlock woolly adelgid

2017 ◽  
Vol 47 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Kathryn B. Piatek ◽  
Mary Ann Fajvan ◽  
Richard M. Turcotte
Keyword(s):  
Tsuga Canadensis ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Foliar Nutrients ◽  
Eastern Hemlock ◽  
Foliar N ◽  
Stand Thinning ◽  
Foliar Concentrations ◽  
Mn Concentrations

Stand thinning is being tested as a means to limit the impacts of the invasive hemlock woolly adelgid (HWA; Adelges tsugae Annand) on eastern hemlock (Tsuga canadensis (L.) Carriere). The efficacy of this strategy may be reduced if thinning increases hemlock foliar nutrients because HWA densities are correlated with foliar concentrations of N, P, K, Ca, and Mn. We determined foliar N, P, K, Ca, and Mn concentrations in 1-year-old and all other (older) needles prior to and for 4 years after thinning in northwestern Pennsylvania stands of eastern hemlock without HWA. Average foliar concentrations in 1-year-old needles were 1.30–1.80 g N·100 g−1, 1300–1700 mg P·kg−1, 4200–6300 mg K·kg−1, 2500–5200 mg Ca·kg−1, and 2393 μg Mn·g−1. N, P, and K decreased, Ca increased, and Mn first increased and then stabilized. Thinning by itself did not affect the tested foliar nutrients. The interaction between treatment and year was significant and evident in temporal trajectories of foliar N and K. However, the differences between thinned and unthinned plots within years averaged only 0.03 g N·100 g−1 and 340 mg K·kg−1. We concluded that even though thinning changed the temporal trajectories of foliar N and K, the nutritional shifts were minimal, brief, and unlikely to affect the efficacy of thinning in limiting the impacts of HWA.

Water use by eastern hemlock (Tsuga canadensis) and black birch (Betula lenta): implications of effects of the hemlock woolly adelgid

2007 ◽  
Vol 37 (10) ◽  
pp. 2031-2040 ◽  
Author(s):  
Michael J. Daley ◽  
Nathan G. Phillips ◽  
Cory Pettijohn ◽  
Julian L. Hadley
Keyword(s):  
Water Use ◽  
Measurement Techniques ◽  
Growing Season ◽  
Tsuga Canadensis ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Eastern Hemlock ◽  
Evergreen Species ◽  
Betula Lenta ◽  
Annual Water

Eastern hemlock ( Tsuga canadensis (L.) Carr.) is a coniferous evergreen species found across the northeastern United States that is currently threatened by the exotic pest hemlock woolly adelgid (HWA; Adelges tsugae Annand). As HWA kills eastern hemlock trees, black birch ( Betula lenta L.) has been found to be a dominant replacement species in the region. Seasonal changes in water use by eastern hemlock and black birch were investigated utilizing whole-tree transpiration measurement techniques. Annual evapotranspiration in an eastern hemlock and deciduous stand was also estimated. During the peak growing season, daily rates of transpiration were 1.6 times greater in black birch. Cumulative transpiration in black birch exceeded hemlock transpiration by 77 mm from June until October. During the dormant season, evapotranspiration rates were higher in the hemlock stand; however, estimated annual evapotranspiration was 327 mm in eastern hemlock compared with 417 mm in the deciduous stand. Our results suggest that a transition from a hemlock-dominated to a black birch-dominated stand will alter the annual water balance with the greatest impact occurring during the peak growing season. Late in the growing season, flow may be unsustainable in streams that normally have light or moderate flow because ofincreased water use by black birch.

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