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Cornell University

New York State Hemlock Initiative

Keeping the legacy alive

Hemlock Stand Traits

There are several stand traits that may make a hemlock a good candidate for HWA treatment. Considering those characteristics can help determine the level of threat an HWA infestation will pose to the stand and overall forest health.

 

Current Stand Health
Does the stand experience dought conditions, or are there other forest pests present? Is there construction or development close enough to impact roots? Do the trees have healthy branches all the way down the trunk? Are there bright, lime green new shoots present in the early summer? These questions point to the overall health of the stand. If your stand has HWA but is otherwise in good condition, treatment will ensure that the stand will remain healthy.

Proximity to Other Pests
How close is the nearest HWA infestation? Are there other hemlock pests such as elongate hemlock scale present? A stand that is near infestations could be prioritized for management efforts in the future. Keeping an eye on the healthy stand and the spread of a local HWA infestation can help optimize and plan treatments when the time is right.

Proximity to Water Body
HWA often (though not always) arrives near water when infestations enter a new area. Monitoring areas near water is helpful during early detection efforts. If HWA is found on a stand that is close to water, consider a treatment method where the product is applied directly, like a basal bark application, to reduce risks to off-target organisms. Hemlocks help protect clean water ecosystems, so maintaining the health of hemlocks near water can help maintain the aquatic ecosystem in the area. 

Stand Size
How large is the hemlock population in this area? How dense is the stand? Hemlock stands that are larger and denser will have a greater impact on the local environment, and will cause a larger disruption with their loss.

Basal Area Percentage
The percent basal area is the percent of the total tree diameter in a given area that is hemlock. If the stand is more dense, the loss of hemlocks will have greater effects on the ecosystem. If a stand is more mixed, representing hemlocks and other species, it may be less of a conservation focus.

Genetic Diversity
Conserving hemlock trees also conserves their genetic diversity and adaptation to their specific location. We believe that in order to maintain viable eastern hemlock populations or be able to replace hemlocks that have succumbed to HWA it is critical to conserve hemlocks for the future. Unfortunately, there is not currently much data regarding hemlock genetic diversity, so the application of this particular metric is uncertain.

Learn about other prioritization metrics:

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Report HWA Findings

To tell us about hemlock woolly adelgid findings in your area, click here