Specializing in the care and treatment of Western North Carolina hemlocks afflicted with woolly adelgid
The following article was written by our very own Ian Bailey as a guest columnist for the Asheville Citizen-Times. It ran in the Home and Garden section of the 2/22/08 edition.
Spring an ideal time to treat hemlocks for woolly adelgids
By Ian Bailey
There has been lots of buzz lately about the destructive effects of the hemlock woolly adelgid on our hemlocks, and the need to save the trees. Since spring is quickly approaching, and is an ideal time to treat infected trees, I thought a quick review would be helpful.
The hemlock wooly adelgid is an aphid-like insect that only survives on hemlock trees. This insect is tiny (approximately 1/32 inch), reddish purple, and covers itself with a fluffy white secretion. They settle on twigs and at the base of needles and suck the hemlock sap to feed. This feeding retards new growth, and causes the needles to turn grayish green and drop early. Infested hemlocks become covered with globs of cottony white puffs. These trees often defoliate prematurely, and eventually die.
Every hemlock in our area is at risk of getting infested by this pest. It is really only a matter of time before they all are. The infestation spreads to new trees by winged nymphs, wind, animals and human activity.
But hemlocks in urban landscapes and developed areas stand a good chance of survival, with proper treatment of systemic insecticides, such as Imidacloprid, that eliminate the insect population and prevent re-infestation for up to four years. There are also some biological controls emerging that show promising control results.
Any visual sign of this pest on your hemlock indicates a need for treatment, although all hemlocks in this area would benefit from treatment as a preventative measure.
Approved insecticides can be applied by several different methods, depending on the level of infestation, soil condition, and proximity of the tree or trees to surface water. The state of North Carolina allows consumers to purchase and apply Imidacloprid (often found at home and garden centers) as directed by product labeling (usually by soil-drench method around the base of the tree). Application rates are based on the diameter of the tree trunk measured chest height (circumference at chest height divided by 3).
Trees in close proximity to surface water will need to be treated using a trunk-injection method. This prevents the chemical from coming into contact with the water, as it is toxic to marine life. This method must be done by a professional arborist certified by the state of NC to apply pesticides commercially.
As a certified arborist, I recommend hiring a skilled professional to correctly diagnose hemlock woolly adelgid, and administer the preferred treatment program for optimum control. A good arborist will safely handle and apply the chemical to minimize environmental hazard and exposure to people and pets.
Diagnosis and treatment cost estimates provided by a professional are usually free, and you can expect to pay between $3 to $10 per diameter inch of tree stem for professional application (depending on application method).
I also advise that you check the credentials and reputation of a tree specialist before you hire one. The International Society of Arboriculture certifies professional arborists. For more information on the certification process and a list of certified arborists in the area, visit www.treesaregood.org
Ian Bailey owns Bailey Tree Preservation (www.baileytreepreservation.com) and is a member of the International Society of Arboriculture.
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