Posted on Jan 12, 2023
Hemlock Woolly Adelgid (HWA) is a tiny, invasive insect that is killing hemlock trees across the eastern United States. The insect, which is native to Asia, was first discovered in the United States in 1951 and has since spread to infest hemlock trees in more than half of the states in the eastern US, including Virginia, West Virginia, North Carolina, Tennessee, and Pennsylvania.
Hemlock trees are a vital component of eastern forests and play an important role in the ecosystem. They provide habitat for wildlife, help regulate stream flow, and protect soil from erosion. Unfortunately, HWA is causing widespread damage to these important trees, and it is critical that steps are taken to protect and preserve hemlocks.
The HWA is a small, aphid-like insect that feeds on the sap of hemlock trees. It is about the size of a grain of rice and can be difficult to detect. The insects are usually found on the base of hemlock needles, where they form a fuzzy, white mass. This is where they lay their eggs and feed on the sap of the tree.
When an infestation of HWA is present, the needles of the hemlock tree will begin to turn yellow and then brown. The tree will also begin to lose its needles, and the branches will become stunted. In severe cases, the tree will die within 4 to 10 years of the initial infestation.
There are several ways to control HWA infestations. The most common method is the use of insecticides. Imidacloprid, a neonicotinoid insecticide, is the most widely used insecticide for controlling HWA. It is applied to the soil around the base of the tree, where it is taken up by the roots and transported to the needles, where it kills the HWA.
Another method of control is the use of biological control. This involves the release of predators or parasites that feed on HWA. For example, the predator beetle Laricobius nigrinus, which is native to the Pacific Northwest, has been shown to be effective in controlling HWA populations.
In addition to chemical and biological control, there are also cultural practices that can be used to help protect hemlock trees from HWA. One such practice is the use of hemlock woolly adelgid-resistant varieties. Some hemlock varieties, such as the Carolina hemlock, have been found to be resistant to HWA and can be used to replace infested trees.
Another cultural practice that can help protect hemlock trees is the use of proper planting and care techniques. This includes proper planting spacing, adequate water and fertilization, and proper pruning. Proper care will help to ensure that the tree is healthy and more able to resist HWA infestations.
Hemlock woolly adelgid (HWA) is a serious threat to hemlock trees across the eastern United States. It is important that steps are taken to protect and preserve these important trees. offers a range of tree services to help control HWA infestations and protect hemlock trees. We have the expertise and equipment necessary to properly diagnose, treat, and maintain hemlock trees to ensure their health and longevity.
If you suspect that your hemlock trees may be infested with HWA, or if you have any other concerns about the health of your trees, we encourage you to contact us. Our team of certified arborists will be happy to provide you with a comprehensive assessment of your trees and recommend the best course of action to protect and preserve them. Don't wait until it's too late, contact Collins Tree Service Inc today and let us help you keep your hemlock trees healthy and strong.