Photo Credit: Eric Honeycutt, Bartlett Tree Experts, Bugwood.org
As the sun emerges and heats up each summer morning, a menacing presence casts a gloomy shadow over our plants – the gloomy scale. Native to the eastern United States, gloomy scale (Melanaspis tenebricosa) is an armored scale insect that preys on maple trees. These stealthy pests are masters of camouflage. They can engulf your tree and cause damage before you even get a chance to notice that they are there. In this article, we will teach you about gloomy scale and how you can treat it.
What is Scale?
First, let’s take a look at what scale is. Scales are an interesting set of insects. They are tiny sap-sucking bugs that latch onto trees and spend most of their lives immobile. To the untrained eye, they often don’t look like insects at all! There are two types of scale: hard or armored scale and soft scale.
When scale eggs hatch, they go through several nymph stages. They will crawl and travel until they find a suitable host plant. Once they find the ideal home, they latch on to the plant and remain in that spot for the rest of their lives. They use their straw-like mouths to feed in place on sap and plant cells. Even when scales have died, they often remain stuck to the plant. Scales are tricky bugs!
Photo Credit: John .A. Davidson, Univ. Md, College Pk, Bugwood.org
Gloomy Scale
While some scales, like the calico scale, have eye-catching designs, gloomy scales have a brown coating that helps them blend into their host trees. Additionally, because they are an armored scale, gloomy scales do not produce honeydew like their soft-scale counterparts, making it harder to know when they are around. It is easy to overlook a few knobs on a tree branch, and within a matter of weeks, female gloomy scales can lay dozens of eggs – most of whom will spend the rest of their lives within 10 centimeters of their birth spot.
Gloomy scales can affect maple trees, hollies, mulberries, sweetgums, and other deciduous plants. Like most scale insects, gloomy scales love the heat. They thrive in hot urban areas like right here in the Metropolitan DC area. In fact, one study found that a 30-degree Fahrenheit difference resulted in a 52% increase in egg production per female! This means that summer is the prime time for gloomy scale activity.
Why You Need to Watch Out
Scale insects feed on tree sap, extracting nutrients out of their host plant. The truth is, having a small infestation will not immediately kill your tree. That being said, untreated populations can spread over your entire tree. Left unchecked, a severe infection can weaken or eventually kill the host. It is important to be proactive about treating scales, because the severity may not be visible until the tree is damaged. Other than noticing their bumpy appearance, some signs of gloomy scale include branch dieback or yellowing leaves.
We Can Help!
- The best time to treat active gloomy scale is the crawler stage before they develop their hard outer coating. Gloomy scales are born over a 6-8 week period, meaning multiple timely treatments may be needed.
- During the dormant season when female scales overwinter, a horticultural oil can be used to suppress their reemergence in the spring.
- One preventative measure is regular Plant Health Care Inspections – which ensures a professional is inspecting your trees multiple times throughout the active season.
- Another way to avoid a scale infestation is by having strong healthy trees. Getting Bio-Stimulant treatments can help give your plants a fighting chance.
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