The helmock wooly adelgid (HWA) is among the most devasting pests in the eastern United States. Native to Asia, HWA was orginally introduced to the Pacific Northwest in the 1920's and into the eastern US in the 1950's. Since its introduction to the East, HWA has killed millions of native hemlock trees and threatens to change the ecosytem there forever.

Affecting healthy trees, old growth trees, and small, weakened trees alike, HWA is major concern for park managers and property owners as an HWA infestation can require treatment of a large number of trees.

Hosts
HWA develops and reproduces on all hemlock spp.
   o only eastern and Carolina are susceptible when attacked
* Eastern hemlock (Tsuga canadensis)
      o Eastern hemlock range is Nova Scotia to N. AL and W. to NE MN and E. KY.
        o Eastern hemlock is a common landscape species that is planted as tree, shrub, hedge

* Carolina hemlock (Tsuga caroliniana)
       o Carolina hemlock occurs on dry mountain slopes in the southern Appalachians of WV, NC, SC, GA, TN.

Symptoms
Symptoms include needle yellowing, needle drop, followed by branch drying of the branches and a thinning crown.
* Limb dieback will occur within two years of infestation on younger trees.
* Decline and death of tree can occur over a period of 4-10 years in Northern Range of HWA and 3-6 years in southern range of HWA.
* Other factors can accelerate the rate and severity of hemlock mortality
    o Drought, construction injury
    o elongate hemlock scale (Fiorinia externa), spruce spider mite
    o root rot disease (Armillaria mellea), and needlerust (Melampsora parlowii)
* High populations of HWA/twig will decrease the production of buds and new growth the following year.  As new growth is reduce the adelgids begin feeding on older growth will contributes to decline and mortality
* As of 2005, HWA found in 16 states (Maine to Georgia)

Signs
* HWA is less than 1/16-inch
    o Color varies from dark reddish-brown to purplish-black in color
* HWA has only female stages and has six stages of development: the egg, four nymphal instars, and the adult.
* Two generations a year on hemlock.
     o The winter generation, the sistens, develops from early summer to mid-spring of the following year (June–March).
     o The spring generation, the progrediens, develops from spring to early summer (March–June).
     o Disseminated by wind, birds and mammals and by long distances via nursery stock
* HWA enters a period of dormancy during the summer months (aestivation period)
* During cooler periods (October) HWA starts feeding again during cooler temperatures (October) and continue throughout the winter months as it turns into an adult
     o December to March Adults can lay up to 300 eggs each
* Reddish brown crawlers hatch and first instar nymphs attach their piercing sucking mouth parts to new growth at the base of the needles begin feeding on stored starch
* Eventually they begin secreting white fluffy wool (ovisac)
     o Ovisacs can be readily observed from late fall to early summer on the underside of the outermost branch tips of hemlock trees
     o Cottony wool can be 3mm long

HWA can be managed using Xytect applied at the base of the tree. Ideal timing for Xytect applications are fall time or early spring. If an infestation is heavy or if the application is to be made during the summer growing season, consider a Transtect treatment. 

For remote trees or trees where a soil application is not feesible, consider a tree injection with Xytect Infusible.

Expectations
Xytect 2F and Xytect WSP
i. Up to 85 % mortality of HWA 9-12 months after application
ii. 100 % mortality of HWA 24 months after application

Xytect Infusible
i. May not provide a quick knockdown of HWA populations
ii. Treatments require time to suppress HWA populations (At least one year).
iii. Retreat once every 2 years