As you watch your trees grow or relax under their shade on sunny afternoons, it’s hard to imagine that something small like an insect could take one of those giant structures down.

Yet even very small pests can do quite a number on your trees if you don’t catch them early and manage them.

Take scale insects, for instance, which are common pests of landscape trees and shrubs that can easily be overlooked. Yet they can be responsible for many worrisome symptoms.

Let’s learn more about scale insects on trees, what common symptoms of an infestation look like, and how to manage them.

What Is A Scale Insect?

You might be wondering what tree scale are and what they look like to ensure your trees are safe.

Scales are sap-sucking insects that feed on plants, including trees shrubs, and perennials. They don’t move much and if you look closely they seem to appear as warts or bumps rather than creepy-crawly insects. They often are colored so that they blend into the bark or leaf tissue of your trees, making them hard to spot.

There are generally two types of scale insects: soft and armored.

Soft scales, such as magnolia scale, are small (¼ to ½ inch long) around with a waxy covering that is attached to the body. These insects extract sap from the tree and then excrete a sticky waste product, called “honeydew.”.

Armored scales, such as pine needle scale, on the other hand, have waxy armor over their bodies giving them a harder exterior appearance.

You can find scale in all areas in the U.S.

Visible Symptoms Of Tree Scale

While you may not notice tree scale at first, you may see some of the signs and symptoms they leave behind.

With soft scale, the honeydew they excrete can be a nuisance. It can drip on patios, parked cars, walkways, and benches, becoming a sticky mess. It also attracts other pests like ants, flies, and wasps. Also, a fungus called sooty mold, can grow on this honeydew, prevent leaves from absorbing as much sunlight, and result in an unsightly appearance.

Armored scale doesn’t produce honeydew, but you might see these other signs and symptoms that both types of scale can cause:

Branches covered with small bumps, which are actually the insects themselves

  • Yellowing or brownish leaves
  • Premature leaf drop
  • Twig or branch dieback
  • Slower overall growth

Similar Tree Pests That Excrete ‘Honeydew’

Unfortunately, honeydew isn’t unique to tree scale.

If you see a sticky substance that resembles honeydew, it might be scale, but it could also be one of the following:

This is why a tree inspection by a certified arborist can help confirm which insect is causing the symptoms you’re seeing, so the control method can be more targeted and effective.

Tree Scale Management & Control

Tree scale are difficult to control, which is why catching the problem early can help optimize the timing of treatment for best pest management.

Both soft and armored scale are most susceptible when the nymphs first hatch from their eggs. Dormant oil applications can be a good first step in mitigating scale insect populations. Monitoring is key to optimally hit the appropriate treatment windows.

Additional steps as part of a year-round management program are usually necessary. For example, systemic insecticides can deliver lethal doses straight to the insects’ mouthparts through the very vascular system they feed within. Insect growth regulators (IGR) can also prevent new hatchlings from developing into their reproductive stage. Depending on the scale species and host plant, a certified arborist will prescribe different treatments in combination, and at precise times of year, to best manage the particular pest.


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