scholarly journals Susceptibility of Chinese Hemlock (Tsuga chinensis) to Injury from Autumn Horticultural Oil Applications

2013 ◽  
Vol 39 (1) ◽  
Author(s):  
Richard Harper ◽  
Richard Cowles
Keyword(s):  
Spider Mite ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Elongate Hemlock Scale ◽  
Fiorinia Externa ◽  
Spruce Spider Mite

Chinese hemlock (Tsuga chinensis) has been suggested as a possible replacement in landscape plantings for eastern hemlocks (T. canadensis), which are being lost due to infestations of hemlock woolly adelgid (Adelges tsugae). Chinese hemlock is highly resistant to hemlock woolly adelgid, but is a host for elongate hemlock scale (Fiorinia externa). Horticultural oil is a popular insecticide commonly used by professionals to manage various insect and mite pests of hemlock in landscapes, including hemlock woolly adelgid, spruce spider mite, and armored scales. In tests, horticultural oil applied in two separate autumn sprays was not phytotoxic to Chinese hemlocks. Therefore, 1% or 2% horticultural oil may be used to maintain Chinese hemlocks in landscape plantings.

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.

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.

Vegetation dynamics in declining eastern hemlock stands: 9 years of forest response to hemlock woolly adelgid infestation

2006 ◽  
Vol 36 (6) ◽  
pp. 1435-1450 ◽  
Author(s):  
Anne K Eschtruth ◽  
Natalie L Cleavitt ◽  
John J Battles ◽  
Richard A Evans ◽  
Timothy J Fahey
Keyword(s):  
Invasive Plants ◽  
Light Availability ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Eastern Hemlock ◽  
Percent Cover ◽  
Eastern United States ◽  
Transmitted Radiation ◽  
Exotic Invasive ◽  
Exotic Invasive Plants

Hemlock woolly adelgid (HWA; Adelges tsugae Annand) infestations have resulted in the continuing decline of eastern hemlock (Tsuga canadensis (L.) Carrière) throughout much of the eastern United States. In 1994 and 2003, we quantified the vegetation composition and structure of two hemlock ravines in the Delaware Water Gap National Recreation Area. This is the first study to use pre-adelgid disturbance data, annual monitoring of infestation severity, and annual records of hemlock health to assess forest response to HWA infestation. In 2003, 25% of monitored hemlock trees were either dead or in severe decline. Measures of hemlock decline (crown vigor, transparency, density, and dieback) were correlated with HWA infestation severity and changes in light availability over the study period. Average percent total transmitted radiation more than doubled at these sites from 5.0% in 1994 to 11.7% in 2003. The total percent cover of vascular plants increased from 3.1% in 1994 to 11.3% in 2003. Species richness increased significantly, and more species were gained (53) than lost (19) from both ravine floras over the 9-year study period. Though exotic invasive plants were absent from these ravines in 1994, our 2003 resurvey found invasive plants in 35% of the permanent vegetation plots.

scholarly journals The Past, Present, and Future of the Hemlock Woolly Adelgid (Adelges tsugae) and Its Ecological Interactions with Eastern Hemlock (Tsuga canadensis) Forests

Insects ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 172 ◽  
Author(s):  
Aaron Ellison ◽  
David Orwig ◽  
Matthew Fitzpatrick ◽  
Evan Preisser
Keyword(s):  
Biological Diversity ◽  
Carbon Sources ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Ecosystem Dynamics ◽  
Eastern Hemlock ◽  
Carbon Sinks ◽  
The North ◽  
Spread Dynamics ◽  
Landscape Scales

The nonnative hemlock woolly adelgid is steadily killing eastern hemlock trees in many parts of eastern North America. We summarize impacts of the adelgid on these forest foundation species; review previous models and analyses of adelgid spread dynamics; and examine how previous forecasts of adelgid spread and ecosystem dynamics compare with current conditions. The adelgid has reset successional sequences, homogenized biological diversity at landscape scales, altered hydrological dynamics, and changed forest stands from carbon sinks into carbon sources. A new model better predicts spread of the adelgid in the south and west of the range of hemlock, but still under-predicts its spread in the north and east. Whether these underpredictions result from inadequately modeling accelerating climate change or accounting for people inadvertently moving the adelgid into new locales needs further study. Ecosystem models of adelgid-driven hemlock dynamics have consistently forecast that forest carbon stocks will be little affected by the shift from hemlock to early-successional mixed hardwood stands, but these forecasts have assumed that the intermediate stages will remain carbon sinks. New forecasting models of adelgid-driven hemlock decline should account for observed abrupt changes in carbon flux and ongoing and accelerating human-driven land-use and climatic changes.

Diversity of proteobacterial endosymbionts in hemlock woolly adelgid (Adelges tsugae) (Hemiptera: Adelgidae) from its native and introduced range

2013 ◽  
Vol 15 (7) ◽  
pp. 2043-2062 ◽  
Author(s):  
Carol D. von Dohlen ◽  
Usha Spaulding ◽  
Kathleen Shields ◽  
Nathan P. Havill ◽  
Cristina Rosa ◽  
...  
Keyword(s):  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Introduced Range

scholarly journals Impact of Imidacloprid for Control of Hemlock Woolly Adelgid on Nearby Aquatic Macroinvertebrate Assemblages

2011 ◽  
Vol 35 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Melissa A. Churchel ◽  
James L. Hanula ◽  
C. Wayne Berisford ◽  
James M. Vose ◽  
Mark J. Dalusky
Keyword(s):  
North Carolina ◽  
Aquatic Invertebrates ◽  
Organic Matter Content ◽  
Adult Emergence ◽  
Hemlock Woolly Adelgid ◽  
Adelges Tsugae ◽  
Matter Content ◽  
Systemic Insecticide ◽  
Aquatic Macroinvertebrate ◽  
Southern Appalachian

Abstract Imidacloprid, a systemic insecticide that acts on the nervous system, is currently being used to control hemlock woolly adelgid (Adelges tsugae Annand), which is damaging hemlock trees. The objective of this study was to determine whether soil injection with imidacloprid for hemlock woolly adelgid control near streams adversely affects aquatic invertebrates. Eastern hemlocks (Tsuga canadensis) in the watersheds surrounding four streams in the southern Appalachian region of Georgia and North Carolina were treated with imidacloprid. Addie Branch was the only stream that exhibited a possible effect from imidacloprid treatment. However, the data followed the same pattern as the other treatment streams, but with a more pronounced decrease in taxa due to adult emergence. Only a trace amount of imidacloprid was detected in one water sample from Holcomb Tributary over a period of 2 years, and no effect was observed on the aquatic macroinvertebrates in that stream. However, caution should be used when applying these results to other areas with different soil types (e.g., low organic matter content) that may not bind imidacloprid as tightly. Our results indicate that soil injections of imidacloprid can safely be used in the southern Appalachian area to control hemlock woolly adelgid.

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.

Stethorus punctillum 1 Associated with Spruce Spider Mite 2 on Ornamentals

1973 ◽  
Vol 2 (4) ◽  
pp. 718-720 ◽  
Author(s):  
A. G. Wheeler ◽  
R. B. Colburn ◽  
R. D. Lehman
Keyword(s):  
Spider Mite ◽  
Spruce Spider Mite ◽  
Stethorus Punctillum
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