Scale

Scale insects are often inconspicuous pests that infest a wide variety of shrubs. You can find them on twigs, branches, leaves and trunks. Since they are small and generally immobile, they can be difficult to spot. Scales resemble individual fish scales pressed tightly against the plant on which they are feeding. The name "scale" comes from their protective shell-like coating. There are two categories of scales: soft and armored. Soft scales create a soft, thin, waxy layer over themselves that cannot be separated from their bodies. They will move between branches and leaves during their lifecycle, and they produce honeydew. Armored, or hard scales create a hard, shell-like covering that can be separated from their bodies. Armored scales do not move to leaves and do not produce honeydew.
 

Damage to Plants

Scale insects can cause considerable damage to trees and shrubs by removing fluids from their hosts. Leaf stunting and yellowing, branch dieback and plant death can occur depending upon the level of infestation. In some cases, plant death can occur by secondary causes after weakening by scale attack.

Honeydew, a sticky, sweet substance secreted by soft scales, can become a nuisance problem. The stickiness and dark mold that accompanies honeydew can be a problem for anything located next to scale-infested trees.
 
 

Control

Nature usually keeps scales under control. Maintaining healthy plants through proper fertilization, pruning and watering goes a long way in fending off scale infestation. Under certain circumstances however, scale populations can increase and become harmful. Once scales begin to affect plant health adversely, control measures must be taken. Adult scales are not usually affected by insecticides, as they have a protective covering.

All-Seasons Horticulture and Dormant Spray Oil is an excellent way to control scale insects and is labeled for use on many different trees and shrubs, including fruit trees, shade trees, ornamentals and roses. Also great for houseplants and home greenhouse plants.

Thanks to Virginia Cooperative Extension for images of scale and the University of Minnesota Extension Service for information.

Privet Scale

Q:

Our hedge was carefully propagated from the hedge that lines the football field at Sanford Stadium in Athens. Now it has white powdery stuff on the stems. What could it be?

A:

Your Dawg-hedge has a bad case of peach scale (or maybe euonymous scale) insects on it, sucking the sap from your shrubs. The infestation looks pretty extensive so you need to battle it immediately. The first step is to spray horticultural oil (Sun Spray, Volck Oil, etc) thoroughly on the stems now. The oil suffocates scale insects. Repeat in March. Also in March, drench the soil around the shrubs with the systemic insecticide imidacloprid (Bayer Tree & Shrub Insecticide), following label directions exactly. In May, evaluate how much control you’ve gotten. Dead scales should be easy to rub off the bark of the shrubs. Live ones will have yellow or pink juice that becomes visible when you mash them with your thumb. If you have lots of live ones, consider pruning the shrubs down to twelve inches tall and destroying the debris to remove most of your infestation. Continue to spray with horticultural oil every couple of months until the plants regain their health. See University of Florida, IFAS Extension and Euonymous scale Control The information above is located at: www.walterreeves.com

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