Hemlock Wooly Adelgid - Identification and Control

Hemlock wooly adelgid are difficult to control because the fluffy secretions protect it from pesticides. Late October is a good time to attempt control as the second generation begins to develop. Insecticidal soaps and horticultural oils are effective for HWA control with minimal harm to natural predators. Horticultural oil can be applied during winter and before new growth emerges in the spring. Oil sprays can damage hemlock during the growing season.

Two predatory beetles, Sasajiscymnus tsugae and Laricobius nigrinus, are being mass produced and released into HWA infested hemlock forests. These beetles feed exclusively on HWA. Although they will not prevent or eradicate HWA infestation, they are good management tools. The use of chemical control can maintain hemlock stands until S. tsugae and L. nigrinus can become established or until more effective biological control agents are discovered and introduced..