Beware those tiny cotton balls: They can be serious hemlock pest

Backyard Q&A

May 19, 2002|By Dennis Bishop | By Dennis Bishop,Special to the Sun; Universal Press Syndicate

Q. The branches of my hemlock tree are covered with what looks like tiny cotton balls. Also, some of the branches are losing color. Do you know what would cause this is and are they related?

A. Yes, they are related and are caused by a very serious insect pest of hemlock trees, the hemlock woolly adelgid. The woolly adelgid is an aphid-like insect that sucks sap from trees and may inject a damaging toxin while it is feeding. It causes the needles to discolor and may kill branches or entire trees.

The cottony substance that you see is actually a fluffy wax that the adelgids cover themselves with. If you pulled the wax away, you would see a small black insect underneath. They can be controlled with horticultural oil or other registered insecticides; however, timing of the treatments is important and the foliage must be thoroughly covered. Please call the Home and Garden Information Center for more information.

Q. I would like to cover a trellis with a quick-growing vine and have considered planting some morning glory seed. Do you know if the 'Heavenly Blue' morning glory is invasive like other morning glories?

A. Morning glories are in the Convolvulus family that contains a number of noxious weeds. This includes the dreaded bindweed and the "wild" purple morning glory that invades both gardens and farm fields. However, this family also includes the sweet potato and other less invasive flowering vines.

Most people consider the 'Heavenly Blue' morning glory to be a good, somewhat well-behaved ornamental vine. It can spread by seed, but it grows as an annual here and is killed each winter. This helps to limit its spread.

Dennis Bishop is an urban horticulture educator for the Baltimore office of the Maryland Cooperative Extension Services. If you have a gardening or pest problem, you can call the Home and Garden Information Center hot line (Monday through Friday, 8 a.m. to 1-p.m.) at 800-342-2507. You can also e-mail questions, order publications and diagnose plant problems by visiting the Web site, / users / hgic.


1. Be sure that all of your pots and containers are able to freely drain excess water. Heavy spring rains can flood containers and suffocate plants.

2. Watch for curled, knurly leaves on your plants. This is often a sign of aphid infestation. Aphids multiply rapidly, but are easy to control.

3. Cultivation is a beneficial form of weed control in new flower and vegetable gardens. While keeping weeds in check, it aerates the soil and returns organic matter to the soil.

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