Adelgids are small, soft bodied aphids that feed exclusively on coniferous plants using piercing-sucking mouth parts. They are an invasive insect and thought to be of Asian origin.
The hemlock Wooly Adelgid
and balsam wooly adelgid attack hemlock and firs respectively by feeding on the sap.
Wooly adelgids use piercing-sucking mouth parts and feed only on coniferous tree sap. Immature nymphs and adults damage trees by sucking sap from the twigs and at the base of the needles. The tree loses vigor and prematurely drops needles. This loss of vigor and loss of foliage can eventually cause the tree to die. If left uncontrolled, the adelgid can kill a tree in a single year.
Good tree care can go a long way toward prevention. Avoid crowding plantings too closely. Thin out branches to open up the tree crown, but don't top or dehorn. Keep trees wound free. Fertilize trees in the spring with a complete fertilizer. Water trees deeply during dry spells.
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Wooly adelgids can be controlled during late October as the second generation begins to develop. Insecticidal soaps and horticultural oils are effective. Horticultural oil can be applied during winter and before new growth emerges in the spring. Several biological control agents are being tested but it is too early to make any conclusions