• What is hemlock woolly adelgid?
• Where did HWA come from?
• What makes HWA different from other pests/diseases?
• What is the life cycle of HWA?

• How does HWA affect hemlock trees?
• How serious is the threat of HWA?
• Could hemlock become extinct?

• What is the best time of year to look for HWA infestations?
• Who do I contact if I think I see hemlock woolly adelgid?
• Can hikers carry HWA?
• What can I do to prevent the spread of HWA while hiking, riding ATV’s, or enjoying other recreational activities?

• What are the treatment options?
• Can you treat hemlock trees near water?
• What can I do on my property?
• Should I plant a hemlock tree in my yard?
• Should I use fertilizer on my hemlock trees?
• Should I cut my hemlocks down and plant something else?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

What is hemlock woolly adelgid?
Hemlock woolly adelgid (Adelges tsugae) or HWA is an invasive insect that develops, reproduces and feeds on all species of hemlock trees. Both Carolina hemlock (Tsuga caroliniana) and eastern hemlock (Tsuga canadensis) are vulnerable to infestation and are currently suffering widespread mortality in the eastern United States. Unfortunately, hemlock woolly adelgid was discovered in Kentucky during the spring of 2006.
[back to top]

Where did HWA come from?
Hemlock woolly adelgid is an insect species native to Asia that was introduced first in the 1920’s to the Pacific Northwest region of the United States, and introduced again in the early 1950’s to the Washington DC and Richmond, Virginia areas. States such as Virginia, New Jersey and Connecticut have reported devastating mortality rates between 42 and 90 percent of the hemlock species.
[back to top]

What makes HWA different from other pests/diseases?
Most pests can be classified as either and economic or ecological threat. HWA is an ecological threat. Hemlocks occupy a unique ecological niche in the southern Appalachians. Its association with aquatic habitats, wildlife and native plants cannot be replaced by any other native evergreen tree. The ‘holes’ left after its demise will be filled in by opportunistic undesirable plant species like Tree of Heaven or maple, which are not conducive to a hardwood forest ecosystem.
[back to top]

What is the life cycle of HWA?
• HWA has two generations per year.
• In early spring, nymphs or crawlers emerge from egg masses and within a few weeks mature and produce another generation of crawlers. These crawlers migrate to a favorable feeding site and pass through the summer in a resting state.
• Once cool weather begins in the fall these crawlers mature into adults by winter and begin laying eggs in January.
• The shorter life cycle of the two generations is referred to as the ‘progradiens’ and the longer cycle is called the ‘sistens’.
• Once crawlers find a suitable feeding site, they insert their mouthparts into the stem and begin to feed on tree sap. Crawlers do not move again once they begin to feed.
• The interesting facet of their life is that all the insects are female. Reproduction without the aid of a male is called parthenogenesis.
• Females in the progradiens generation may lay up to 125 eggs, while in the sistens generation they may lay up to 300 eggs. Populations typically explode after the initial infestation, in part due to parthenogenesis.
[back to top]

How does HWA affect hemlock trees?
It reduces new shoot growth, and causes premature needle drop and eventual tree death within 2-7 years.
[back to top]

How serious is the threat of HWA?
The threat is quite serious. HWA has killed 80% or more of the hemlocks in states where it has been found. Besides the ecological ramifications from the loss of hemlock, the resultant fuel load increase from the dead trees will increase the likelihood and intensity of woodland fires.
[back to top]

Could hemlock become extinct?
Although their numbers will be greatly reduced, they will not become extinct. There will be chemically treated trees in home landscapes and arboreta that will survive. Too, there will be some trees in the forests that will survive because of some resistance factor to HWA though their numbers will be quite small.
[back to top]

What is the best time of year to look for HWA infestations?
Hemlock woolly adelgid begins to feed on the hemlock and reproduce exponentially throughout the warm seasons. As summer passes and the temperature drops the adelgid prepares itself for the next winter season by producing small little cocoons that resemble small cotton balls about the size of a bb that protect it from the cold. Hemlock woolly adelgid is not visible to the human eye, but these white woolly masses are visible year round.
[back to top]

Who do I contact if I think I see hemlock woolly adelgid?
If you see hemlocks infested with white wooly masses, please contact:
• University of Kentucky’s Department of Entomology at (859)-257-7450
• Kentucky Division of Forestry: (800)-866-0555
[back to top]

Can hikers carry HWA?
• HWA is primarily transported by birds that land on one hemlock tree and carry it to the next, however, hikers, ATV’s, and other recreational users have the potential to carry hemlock woolly adelgid.
• HWA can become caught in the tread of shoes, ATV tires, or any other surface that may come in contact with infected hemlock trees or the soil around these trees, and carried to areas that have not yet been infected by the insect.
[back to top]

What can I do to prevent the spread of HWA while hiking, riding ATV’s, or enjoying other recreational activities?
• Avoid hiking, or riding through areas with high densities of hemlock trees.
• Take care not to walk or drive through areas were the soil is moist and has the ability to catch a ride on shoes, tires, or other surfaces.
• Immediately wash and rinse off shoes, tires, or other surfaces that have collected soil or mud.
[back to top]

What are the treatment options?
• Trees can be sprayed with insecticidal soaps and horticultural oils during March through April and from September to October. This type of treatment may be needed during both the spring and fall or at least annually. If trees are not thoroughly covered or trees are too tall for available equipment, the surviving HWA will soon reinfest the trees. This method will kill any beneficial insects on your tree and is not guaranteed to protect it from HWA.
• Trees can also be systemically treated with an insecticide containing the active ingredient Imidacloprid. Systemic treatments allow the insecticide to move with the tree sap and are consumed by HWA as they feed. These types of treatments may remain effective for 2-5 years.
• There are three methods for applying systemic insecticides: 1.) soil drenching, 2.) soil injection, 3.) trunk injection. Trunk injections can kill your tree and are not recommended.
[back to top]

Can you treat hemlock trees near water?
• Extreme caution must be taken near water and Imidacloprid insecticides should never be applied directly to water.
• Data has shown that Imidacloprid binds too organic soil and moves very little from its origin.
• Trunk injection is the safest method for trees very close to water. However, soil injections have proven to be more successful at controlling HWA and may be used on portions of the tree roots that are located within 20 feet of the water source. The soil should not be sandy or rocky.
• Other application methods should not be used near water.
[back to top]

What can I do on my property?
• Keep a watch out for white woolly masses on your hemlock trees and report any findings of HWA to the proper agencies listed above.
• In urban settings avoid placing bird feeders in areas close to hemlock trees.
• Examine nursery stock for HWA before planting hemlocks in your yard.
[back to top]

Should I plant a hemlock tree in my yard?
• Yes, it is safe to plant hemlocks in your yard.
• Hemlock woolly adelgid has the ability to infect hemlock trees in urban areas, however infection is less common in urban landscapes versus forests or timberland.
• In addition, there are relatively inexpensive treatment options available to individual landowners when treating trees in there yard for HWA.
[back to top]

Should I use fertilizer on my hemlock trees?
Hemlock trees that are infested with HWA should not be fertilized. It has been found that fertilizing trees during infestation actually aids in HWA production.
[back to top]

Should I cut my hemlocks down and plant something else?
• If your hemlocks show no sign of infection or dieback then there is no reason to cut down your hemlocks to plant another tree.
• Trees that show signs of infection should be treated if feasible. Please consult with a professional forester or certified arborist to decide if a tree should be removed and what to plant in its place.
• Trees that are dead may present a serious hazard. Please contact a professional forester or certified arborist for removal.
[back to top]