Woolly Adelgid on Sebago’s Shores
December 17, 2018 -
LEA News/Summer Edition-by Colin Holme, August 2018: SEBAGO-A news invader that could negatively impact water quality is quickly making its way into our area. It is not an invasive aquatic plant like milfoil, but instead a tiny terrestrial insect called Hemlock Woolly Adelgid. This aphid-like insect can kill off whole stands of Hemlock tress, which make up an important part of our shoreline buffers. While the state is working to slow down the advancement of this noxious invader, there are several things landowners can do to help prevent its spread throughout the lake Region.
Hemlocks are a long-lived, slow growing tree and the only shade tolerant conifer in Maine. These characteristics allow the tree to wait patiently in the understory for an opportunity to take off and fill gaps created when other trees die. They can tolerate moist soils and young trees can be easily pruned into a hedge. Although the wood of the Hemlock is naturally rot resistant, it is not a commercially viable tree species.
Today, Hemlock is one of the most dominant trees in the riparian zone and groves of this beautiful species provide habitat for deer, bear and porcupine as well as many other species. But the Hemlock Woolly Adelgid can kill large swaths of these trees as it has already done in southern New England and New York. It has been on the coast of Maine for around ten years and the Maine Forest Service has been actively and aggressively trying to control the spread but it has now got a foothold around the shores of Sebago.
Last fall, the forest service treated a large patch on Frye Island near the public works with the insecticide Dinotefuran. They treated by spraying the bark of the trees with a wand sprayer. They did not work near the water and their primary goal was to help prevent the introduction of the insect by large fire trucks and other vehicles that routinely move in and out of the area.
Use of insecticides comes with risk and a thorough evaluation of the pros, cons, and alternatives should always be considered. The insecticide used on Frye Island is in a class of pesticides called neonicotinoids, which are highly toxic to many insects and moderately toxic to mammals. In the sun, it has a short half-life and quickly disappears but in ground it can last for over 3 years. It needs to be applied when the trees are actively photosynthesizing but when other insects, particularly bees, are not around. It is a tricky business and very controlled and targeted applications are best. Only licensed pesticide applicators are allowed to use these products commercially and it is illegal to use any insecticide in a way that is not described on the product's label.
What Can You Do?
Hemlock Woolly Adelgid is often spread by cars and people. If a person or vehicle brushes up against an infested tree, these little bugs can hitch a ride and easily move to another Hemlock. To prevent this, the Forest Service recommends pruning back the branches of all Hemlock trees along roads and trails. Cutting back healthy, non-infested branches is a way to reduce your property's susceptibility to the invader. If your trees already have the insect, branches should be cut and left on the ground. They should not be moved as this may spread the infestation. Once on the ground, it is unlikely the insect will climb back up into a tree. If you do have the Adelgid, tree work should be done outside of the season when the insects are actively moving (March through July in Maine). Another vector for this species is birds. To help prevent infestations from spreading via birds, bird feeders should only be used in the winter months and taken down in March. At a minimum, feeders should be far away from any Hemlock trees as birds usually grab seeds and fly back to nearby trees for cover.
To identify Hemlock Woolly Adelgid, look for small, fuzzy, whitish-grey balls on the underside of the needles where they meet the stem.
If you are interested in finding out more, stop by LEA's main office for a fact card or check out what the Maine Forest SErvice has compiled at: http://www.maine.gov/dacf/mfs/fores_health/insects/hemlock_woolly_adelgid.htm.
Lakes: Sebago Lake
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