Have you noticed your beautiful maple trees looking shabby and lackluster? Maybe you’ve observed the canopy is thinning, early leaf loss, black sooty mold covered bark, or branch dieback. You may be dealing with one of the most serious scale insects in the eastern United States: Gloomy Scale. Even the name sounds depressing, and for good reason. Left unchecked Gloomy Scale is capable of killing large landscape maples within a few years.
What is Gloomy Scale?
Gloomy Scale is a type of armored scale insect native to North America. It primarily attacks Red Maples, Silver Maples and Sugar Maples. It is very common and active in the Mid-Atlantic region including Virginia.
Unlike soft shell scales that produce copious quantities of honeydew, Gloomy Scale is stealthier. The adults are small, less than 1/8 inch, circular, and dark gray-brown. This allows them to blend well into the bark of a maple tree. Their gray/black coloring gives the “gloomy” look you may have noticed on your maple tree.
Life Cycle
Gloomy Scale completes one generation per year, progressing through the following stages in a predictable life cycle:
- Gloomy Scale overwinters as fertilized adult females on the bark.
- In late April to early June the eggs hatch underneath the female scale’s covering into tiny yellow crawlers.
- Crawlers quickly settle on the bark of the tree and insert their piercing/sucking mouthparts, cover themselves with the protective waxy coating, and never move again.
Symptoms and Damage
There are key signs to look for to identify if your maple trees have been impacted, look for:
- Thinning canopy with small sparse leaves
- Black bark on the trunk and limbs, sooty mold
- Early leaf drop and fall leaf color
- Heavy populations can have complete covering of bark by the scale as generation after generation accumulates on the bark
Though armored scale like Gloomy Scale can be difficult to control, through proper and timely application of approved pesticides this pest can be managed. Plant health is a significant part of this management plan which includes soil analysis, soil amendments, proper mulching, and water management. All of these are essential for the long term health of your tree. When correctly diagnosed and with early treatment, Gloomy Scale does not have to be a death sentence for your maple, but ignoring it always is. Catch it early, act decisively, and your tree can bounce back beautifully.