Invasive Plants, Animals and Diseases in the Big Laurel-Whitetop Laurel Creek Watershed

 

The invasive plants, animals and diseases that are of most concern in the Big Laurel Creek – Whitetop Laurel Creek watershed are major concerns across southwest Virginia and northeast Tennessee, USA. 

 These non-native invasive species (NNIS) are:

Plants

• ·         Kudzu
• ·         Autumn Olive
• ·         Tree-of-Heaven

Animals and Diseases

• ·         Wooly Adelgid
• ·         Chestnut Blight

 

Plants.  The three plant NNIS are mainly found in the developed (urbanized) and agricultural floodplain (middle section) of the Big Laurel Creek – Whitetop Laurel Creek watershed but are a concern because of the high probability of further spread due to human activity, and the ability of each NNIS to outcompete native species in almost all the watershed plant communities and ecosystems.  All three plant NNIS are difficult to eradicate once they are established.

The ecology, history and use descriptions and all pictures are copied from, and are courtesy of the reference “Miller, J. H., Chambliss, E. B., & Loewenstein, N. J. (2010). A field guide for the identification of invasive plants in southern forests, https://www.srs.fs.usda.gov/pubs/gtr/gtr_srs119.pdf

 

Kudzu  “Pueraria montana (Lour.) Merr. PUMOL Fabaceae

Synonyms: P. lobata (Willd.) Ohwi, P. montana var. lobata (Willd.) Maesen & S. Almeida

 Ecology. Can grow 1 foot (30 cm) per day in spring and 60 feet (18 m) per year. Occurs
in old infestations, along right-of-ways, forest edges, and stream banks. Forms dense
mats over the ground, debris, shrubs, and mature trees forming dense patches by
twining on objects less than 4 inches (10 cm) in diameter. Colonizes by vines rooting
at nodes and spreads by wind-, animal-, and water-dispersed seeds. Seed viability
variable by habitat and across the region. Leguminous nitrogen fixer.

 History and use. Introduced from Japan and China in the early 1900s with continued
seed importation ending in the 1990s. Limited use for erosion control, livestock feed,

and folk art.”

 

Kudzu spreads laterally and vertically once it is established.  Kudzu will climb and cover trees and scrubs, and road signs, completely altering the ecosystem, forming a kudzu monoculture.  The vegetation that it climbs and covers (the host) will eventually be killed because the kudzu blocks the host plants’ access to sunlight, and the host plants’ ability to photosynthesize.

 Additional references available at:

1.       https://www.invasive.org/south/subject.html?sub=2425

2.       https://www.tnipc.org/invasive-plants/plant-details/?id=33

3.       https://www.aces.edu/blog/topics/forestry-wildlife/the-history-and-use-of-kudzu-in-the-southeastern-united-states/

 

 Autumn Olive  “Elaeagnus umbellata Thunb. ELUM Elaeagnaceae

Other common names: Russian olive, oleaster

 Ecology. Prefers drier sites. Shade tolerant. Spreads by animal-dispersed seeds and found as scattered plants in forest openings and open forests, eventually forming dense stands. A nonleguminous nitrogen fixer.  Resembles silverthorn or thorny olive (E. pungens Thunb.) and Russian olive (E. angustifolia L.). Silverthorn is an evergreen that has brown scaly and hairy twigs, flowers in late fall, and oval reddish-silver, scaly drupes in spring. Russian olive rarely occurs and has silver scaly twigs and leaves, leaves longer and more linear, flowers in early summer, and many yellow olives in fall and winter. Also resembles plum (Prunus spp.) when fruit is present, although plum leaves are not silvery beneath and fruit is much larger.

History and use. Introduced from China and Japan in 1830. Planted for wildlife food and surface-mine reclamation.”
 

In the Big Laurel Creek – Whitetop Laurel Creek watershed, Autumn Olive can often be found under electrical transmission lines, tree branches, and other bird roosting tall structures.  Autumn Olive is being dispersed throughout the Big Laurel Creek – Whitetop Laurel Creek watershed by bird droppings.  The birds will eat the ripened fruit and the seeds pass through the birds’ digestion tracts and remain viable, resulting in significant spread of this NNIS.

 Additional references available at:

1.       https://www.tnipc.org/invasive-plants/plant-details/?id=29

 

Tree-of-Heaven “Ailanthus altissima (P. Mill.) Swingle AIAL Simaroubaceae
Other common names: ailanthus, Chinese sumac, stinking sumac, paradise-tree, copal-tree

 

Ecology. Rapid growing, forming thickets and dense stands. Both shade and flood intolerant and allelopathic. Colonizes by root sprouts and spreads by prolific wind- and water-dispersed seeds. Viable seed can be produced by 2- and 3-year-old plants. A mature female tree can produce up to 300,000 wind-dispersed seeds per year that can be distributed up to 330 feet (100 m) away. Resembles hickories (Carya spp.), butternut (Juglans cinerea L.), black walnut (J. nigra L.), and sumacs (Rhus spp.), which have pinnately compound leaves but noglands at leaflet bases. Hickories distinguished by braided bark, butternut and black walnut by their ridged mature barks, and all have large nuts. Sumacs often in a shrub shape, red or winged leaf stalks, and terminal conical flower and seed clusters.

 

History and use. Introduced in 1784 from Europe, although originally from Eastern

China. Ornamental widely planted in cities due to pollution and drought tolerance.”

 

In the Big Laurel Creek – Whitetop Laurel Creek watershed, Tree-of-Heaven extensively along roadsides and adjoining open spaces.  It has no commercial timber value and prevents the native tree species from becoming established.  

Additional references available at:

1.       https://www.invasive.org/south/subject.html?sub=3003

2.       https://www.tnipc.org/invasive-plants/plant-details/?id=13

 

Animals and Diseases.  Both the NNIS animals and diseases identified as of most concern have each in its own way, permanently altered the Big Laurel Creek – Whitetop Laurel Creek watershed, and have created a situation where the ability of humans to restore the ecological form and function of the watershed to its original, pre-European settlement condition is impossible, unless methods are developed beyond what is available today.  Efforts are underway to restore both impacted species, the eastern and Carolina hemlocks, and the American chestnut.

 

·         Woolly Adelgid (aka hemlock woolly adelgid (HWA))

From the reference, https://www.invasive.org/south/subject.html?sub=289

 “Hemlock woolly adelgid, Adelges tsugae, Annand, 1924

 Origin.  Hemlock woolly adelgid, Adelges tsugae, is an invasive insect in eastern North America. DNA evidence suggests that the invasive eastern U.S. population came from Japan and not the western United States, where the species feeds on western hemlock (Tsuga heterophylla [Raf.] Sarg.) but is believed to be native and is not a pest.

Life Cycle.  Hemlock woolly adelgids are small in size and to the naked eye only their woolly coverings are easily visible. The insect has two generations per year and growth occurs from fall through late spring. Insects in summer are inactive and scarcely visible at the bases of needles as black dots. Woolly masses (the sign allowing the species to be recognized) develop in October and are present thereafter through June of the following year.

 Distribution.  In the eastern USA, Adelges tsugae is killing eastern hemlocks (Tsuga canadensis [L.] Carrière) and Carolina (Tsuga caroliniana Engelm.) in large numbers from Connecticut south along the Appalachian Mountains. From Massachusetts north, or at high elevations, tree mortality has been restrained by higher rates of mortality of adelgids in winter due to low temperatures.

Control Efforts.  A biological control program is in progress against this pest, based on specialized predatory beetles that feed only on adelgids, collected in western North America (Laricobius nigrinus Fender) or China/Japan (species of Laricobius and various Scymnus ladybird beetles). To date, releases have not demonstrated any reductions in adelgid densities from predators. Populations of L. nigrinus have become well established and abundant in some areas of western North Carolina.”

 The impact of the hemlock woolly adelgid in the Big Laurel Creek – Whitetop Laurel Creek watershed has been the destruction of vibrant riparian ecosystems along the mountainous streams.  The woolly adelgids feed on the leaves of the mature hemlocks, gradually causing the tree to die due to the inability to photosynthesis.  Once a hemlock is killed in the riparian ecosystem, the ground surface under the tree is rapidly colonized by rhododendron resulting in a monoculture where other native forest trees and shrubs cannot compete due to lack of sunlight under the thick rhododendron cover.

 Additional references available at:

1.       https://savehemlocksnc.org/hemlocks-hwa/the-importance-of-hemlocks/

2.       https://www.nwf.org/Educational-Resources/Wildlife-Guide/Threats-to-Wildlife/Climate-Change/Habitats/Eastern-Hemlock-Forests

3.       https://www.epa.gov/climateimpacts/climate-change-connections-pennsylvania-eastern-hemlock

  

·         Chestnut Blight

From the reference, https://forestpathology.org/canker/chestnut-blight/
 
” The pathogen is Cryphonectria parasitica. … Chestnut blight is a canker disease. Perhaps it is called blight because infected branches and stems die quickly, as in a shoot blight. But it doesn’t just infect shoots; it infects branches and stems of any size.
 
… Chestnut blight is a different story. What it did to American forests is no joking matter. It’s the greatest tragedy in American forest history. No one who loves forests can think about the decimation of such a fantastic and abundant tree species as anything else. An informal article by George Hepting ​[ 10.2307/3983346 ]​gives some insight into the role of chestnut in American life as well as the chaos that ensued in scientific and political circles as society struggled to deal with the new disease.”
 
The American chestnut was an unrivaled and irreplaceable keystone species of the Appalachian highland hardwood forests, which is the majority of the Big Laurel Creek – Whitetop Laurel Creek watershed.  The trees provided lumber that was sustainable, long lasting, rot resistant.  The chestnuts provided forage food for humans and livestock and were a cash crop for the watershed inhabitants prior to the arrival of the blight.  The species that have naturally replaced the American chestnut in the forest ecosystem do not provide the same high-quality lumber and almost all nuts and acorns from these species are poisonous to both humans and livestock.

 

Additional references available at:

1.       https://tacf.org/why-american-chestnuts/

2.       https://appalachiantrail.org/news-stories/the-american-chestnut-tree/

3.       https://tacf.org/american-chestnut-range-map/