Often mistaken for a disease, the leucanium scale is an insect pest that’s appearing in landscapes this spring.

You can easily rub them off the stem and when you do, a white powdery substance may appear, which is why many people think it’s a disease. The powdery substance can also be uncovered and seen on the stems.

These are the young scale insects, called the crawler stage. This is the stage at which they can be blown by the wind to nearby trees.

Leucanium scale insects tend to appear in masses after a dry year, then moisture arrives the following spring. This is because scale insects, like most insects, thrive on trees that are under stress. The dry hot weather the year prior will stress even the most established mature trees.

Scale insects are normally an aesthetic nuisance, and no control should be taken, mostly because their natural predators will take care of them. Natural predators of the scale insects are lady beetles (ladybugs) and microscopic wasps, for example.

However, if you are dealing with masses of scale insects, so much that the tree’s leaves are discoloring or stems are dying back, there are some control measures you can try.

First and foremost, get the insect identified correctly. Take a sample of the insects in a sealed clear container to your local Extension office or take a clear closeup picture and send it to gotbugs@okstate.edu.

This email goes straight to OSU Stillwater’s Plant Disease and Insect Diagnostic Laboratory, where a diagnostic entomologist can identify insects for you. Correctly identifying an insect will lead you to the most effective form of control, and sometimes it will tell you that those bugs are beneficial and should be left alone.

If it is leucanium scale you’re dealing with, make sure your trees are getting the water and care they need to thrive.

A slow, long watering is going to get deeper to those tree roots than a sprinkler running for 30 minutes a day can do. Mulching with some wood chips, fallen leaves, pine straw or some other organic substance that’s going to break down will help the tree conserve moisture during dry and/or hot weather.

Just make sure the mulch isn’t sitting up against the trunk of the tree, which holds moisture against the trunk and encourages rot.

Next, know the time of year an insecticide might work and use one that doesn’t affect beneficial insects that may be on the tree. Often, you’ll find the word selective on the label. Broad spectrum insecticides, on the other hand, will damage or kill any insect they touch.

Timing of application is important because insecticides won’t penetrate the scale’s armor very well, but they do work on the crawlers. If you know when those crawlers are active, that’s the time of year you’ll apply the recommended pesticide.

You can apply insecticidal soap or ultra fine oil to smother them at that time of year. This will be a spray, so it may only be feasible for you to apply it if the tree is small.

Otherwise, hire a professional tree care company to spray the tree.

In addition, apply imidacloprid as a soil drench in the fall, which is feasible for a homeowner to do. The tree will absorb the product through the roots, and it will travel up and throughout the tree. The scale insects that are feeding on the tree will also ingest the imidacloprid when it is absorbed by the tree.

When applying a soil drench, it helps if you can pull away any mulch or leaf litter before you pour it on the root zone.

Contact Canadian County OSU Extension at 405-262-0155 for more information on controlling scale insects.

In addition to scale insects, you’re probably seeing an abundance of galls, like oak apple gall and pocket vein gall. Galls are also nuisance pests, meaning they won’t kill the tree, but they are a sign that the tree is stressed.

You can help by making sure your tree gets 1 inch of water per week at a slow drip, removing any grass or weeds in the root zone to eliminate competition for water and nutrients, getting the tree selectively pruned so the tree can use less resources to keep itself alive, and most importantly, encouraging natural enemies of pests to the landscape by planting pollinator plants and shelter plants, providing water in the landscape for those natural enemies, and leaving the leaves that blow into your garden spaces.

In time, you’ll have plenty of natural enemies in your landscape to take care of the nuisance and harmful pests.