Hemlock Trees

Asked April 27, 2013, 9:41 AM EDT

My entire acre of property is surrounded by hemlock trees. I planted them 25 years ago for privacy from my neighbors. These trees are gorgeous. I have been reading that the Asian bug that destroys these trees has been found 90 miles north of my home in the Allegheny National Forest. Is there anything I can use on my trees to prevent their destruction? How do I prepare for this invasion? Thanks for your help.

Allegheny County Pennsylvania

1 Response

Few options are available for control of this pest. The adelgids can be physically removed from the tree, either by vigorous washing or by cutting off infected branches. Various petrochemical pesticides are available for home use or by a licensed arborist, including diazinon, fluvalinate, imidacloprid and malathion. The use of pesticides is limited because hemlocks tend to grow within close proximity to aquatic environments such as rivers or streams, and the risk of contaminating these vulnerable ecosystems is great. Furthermore, the large-scale use of pesticides is often denounced in forest settings. Horticultural oil and insecticidal soap are another option. Since 1997, the main approach has turned to biological control. The use of entomopathogenic fungi and certain insects as predators specific to the adelgid have potential. Several species of the coleopteran genus Laricobius, a kind of winged insect, are being tested, and the coccinellid Pseudoscymnus tsugae (a beetle) an effective predator of the Hemlock woolly adelgid in Honshū, Japan. Pseudoscymnus has been released in several states in the northeastern US. There is also evidence that another beetle, Harmonia axyridis, may be a predator of adelgids.