Downstate, homeowners have been battling the hemlock woolly adelgid (HWA) for more than 20 years. We have avoided any major infestations by this pest…until now. Sure, a few have popped up once or twice on nursery stock, but these were easily controlled. Recently, however, we were called to inspect and treat a group of about 30 hemlock trees in Irondequoit that were suffering from a significant HWA infestation.
If you have hemlock trees, we recommend that you inspect them immediately. If you see white cottony masses on the branches, the HWA has found your hemlock(s). These cottony masses, which look like the ends of cotton swabs, hold, or held, HWA eggs. We don’t know the exact timing of their life cycle in our area yet. However, they hatch between February and June downstate.
The immature insects, called crawlers, have hatched, or are still hatching. They then crawl to the base of new growth needles, molt and lose their legs, and begin to feed. You can see them with a hand lens. They appear as black, flat, oval spots. In mid to late summer, they will build new cottony masses, mature and deposit their eggs.
The HWA life cycle is very complex and may involve two generations a year. The lifecycle described here involves reproduction by females only. According to Cornell Cooperative Extension of Suffolk County on Long Island, other mature adults grow wings and fly to other trees, including spruce trees, and reproduce sexually.
Needles change from dark green to grayish green to yellow as feeding damages them. This is followed by premature needle drop and loss of vitality. Within two years, limbs begin to die back, beginning at the bottom of the tree. It takes four to eight years, depending on tree size, environmental stresses and the tree location, for a tree to die.
HWA is a pest that has been plaguing hemlock owners downstate for decades. They have been able to control it but not eradicate it. At certain times of the year, dormant oil and horticultural soap are effective controls. Chemical pesticides, applied by licensed, commercial pesticide applicators either as sprays or systemic soil drenches, are also effective.
If you have hemlock trees, don’t let the hemlock wooly adelgid get a foothold, call us now for a professional inspection and, if necessary, treatment.