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Scale Pests: What are they and How to Manage

A scale is an insect that can cause serious damage to plants depending on the type. Most people do not identify scale as insects because the females and nymphs are wingless, immobile, and usually have no sign of a defined body or head. An adult male scale is tiny delicate insects with one pair of wings that are rarely seen. They only live for a few hours as they do not feed.

There are several types of scale and identification is important to determine which insecticide is the best to use and which is safest for the natural scale predators. Using the wrong insecticide could kill off the predators and increase the population of the scale colony.

Basic scale identification:

An armored scale is less than 1/8 inch in diameter and has a cover that is flattened and plate-like. A small tube-like projection stems from the middle of the armor and is surrounded by rings that get bigger as the insect grows. The insect body lies underneath the protection of the cover. The armored species of scale do not excrete honeydew.

Adult female California Red Scale (armored)

A soft scale is around ¼ inch long and can be cottony, waxy, or smooth. While armored scale are circular, smooth scale are usually more round and convex. Their outer coverings cannot be removed because they are part of the actual insect body.

Greedy Scale Colony

Other scale species include the cottony cushion scale, European elm scale, oak pit scale, and sycamore scale.

Scale are not to be confused with aphids or mealy bugs, which also cause damage to plants by eating holes through the leaves and excrete honeydew.

How do scale pests damage plants?

A scale will attach itself to the plant by inserting the straw-like mouthpart in to the plant to extract fluids. Soft scale feed from the phloem tissue, which helps the food produced in the leaves travel to the rest of the plant, and then excrete honeydew, or sugary water substance. This disrupts growth of the plant. The honeydew can also cause sooty mold and ants which can keep away the scale’s natural enemies.

Damage from armored scale is primarily aesthetic. These scales can cause the leaves to turn yellowish, look wilted, curl, or drop prematurely. They can form odd looking blemishes and form discolored halos, or small rings in fruit, twigs, or leaves. Scale can also cause bark to crack and produce gum.

How to manage scale pests:

Tree and shrub management is vital to keeping the scale population at bay. If the infestation of scale pests become too numerous, a timely tree and shrub management program is recommended using a narrow-range or horticultural oil in the early spring. It is important to apply the horticultural oil when the insects are still embedded in their self-secreted scale coverings. Complete spray coverage including underneath the leaves is necessary to maintain control of scale.


Keep a close eye on your plants and regularly look for signs of female or nymph scales, sooty mold, or honeydew. Also monitor the trunks of trees for ants. If these ants have swollen abdomens, you may have insects that are excreting honeydew.

For more information on scale, aphids, and mites click here.

Remember that all plants are susceptible to some sort of pest. Utilizing Dowco’s tree and shrub care program will ensure that you don’t have to worry about the health of your plants!

Call Dowco for a free estimate of our Tree & Shrub Program today!

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Topics: Winter Season Maintenance Seasonal Yard Maintenance Tree & Shrub Care Dowco Specific Plant Care

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