Tree scale sounds like a horrible tree disease, but it’s an infestation caused by scale insects. Scale insects are small flat-bodied insects that feed on the sap of woody-stemmed plants and trees. To the untrained eye, they resemble a harmless growth on the tree, but these tiny insects can cause a great deal of damage to your trees.
Scale insects come in two forms: armored and soft scale. However, here in Utah, soft scales are the bigger threat. Soft scale insects are flat, oval-shaped, and are protected by a waxy substance they secrete over themselves. They excrete honeydew, a form of waste, which attracts ants and can develop sooty mold. Soft scale insects can infest hundreds of species of trees in Utah including: 
- Elm
- Beech
- Linden
- Maple
- Oak
- Pine
- Yew
Life Cycle of Soft Scale
Soft scales are notoriously hard to control because of their protective waxy covering and their high birth rate. Females overwinter on tree trunks or branches. In the spring, they begin to feed and mate. Some species can even reproduce asexually. One female can also produce anywhere from 200 to 1,000 eggs at a time.
Eggs hatch into “crawlers,” which are so small they would look like specks of black dust to the naked eye. The crawlers spread around the tree by crawling on tiny legs or being blown or splashed to other plants. Eventually, crawlers begin to develop a waxy covering, find a spot to settle down, and lose their legs. Tree scale is tricky to treat because their wax coating protects them from most pesticides.
Symptoms of Tree Scale
Most trees can handle a small amount of scale insect inhabitants, but an infestation can weaken the plant and make it susceptible to other pests and disease. If you notice your trees exhibiting the following symptoms, you should check for a tree scale infestation.
- Yellowing of leaves
- Early defoliation
- Stunted growth
- Bumps or growths (insects) on branches
Most plants can handle small scale populations, but plants with a large scale infestation will show a visible reduction in vigor, yellowing of leaves, premature leaf drop, and branch dieback. Scales generally drink more sap than they need and will excrete copious amounts of honeydew. Honeydew is a sugary substance that can attract ants, wasps, and serves as a substrate for the fungus that causes sooty mold, which can turn limbs, leaves, and nearby objects like patio furniture and decks a black color.
How to Treat Tree Scale
Tree scale is tricky to treat, but you can minimize the effects of their feeding by keeping your plants and trees healthy. There are many things you can do, as the homeowner, to keep your trees strong and healthy enough to withstand small to moderate infestations.
- Attach double-sided sticky tape to trunks and limbs where scales occur and examine the tape for crawlers or adults.
- Prune infected branches and leaves to protect new growth.
- Scrub infested limbs with a mesh dish sponge to remove capped adults.
- Rake, bag, and discard infested debris.
- Spray crawlers off limbs with a high-pressure water hose.
- Keep trees in a healthy condition with optimal watering, fertilizing, and mulching.
- Apply dormant oils before bud burst in the spring to eliminate capped scales and emerging crawlers
Trust Your Trees to the Experts at Ferta-Lawn
At Ferta-Lawn we know the value of your trees and shrubs. That’s why we offer our customers tree and shrub care services to make sure your ornamentals stay strong and healthy all year.
Call us at 801-295-3057 or quickly contact us here. Check out our blog for more tips on lawn care, tree care, pest control, and more. Follow us on Facebook to stay updated on the latest news and deals from Ferta-Lawn.
