Gloomy Scale Crawlers Are Active
The below information was taken from the NC Pest News, a weekly pest update from April to September.
Gloomy scale, Melanaspis tenebricosa, is an armored scale that is found on maples and other tree species. It becomes very abundant on landscape maples and can cause branch dieback and tree death in some cases. It is not unusual to find trees with nearly 100% of their trunk covered in scale. Street trees are particularly prone to gloomy scale. I have never found one that didn’t have it! Crawlers of this scale are active now and can be seen on bark and under scale covers. Control of this scale is complicated because crawlers emerge over 6 to 8 weeks so it is impossible to treat all the crawlers at once with horticultural oil or other contact insecticide. This is as opposed to scale such as euonymus scale in which all crawlers are produced within a narrow window of 2 weeks or so. However, horticultural oil can still be applied to kill gloomy scale because it will kill some adults also. We have found even a single application dramatically reduces scale abundance. Several systemic products are available to provide longer control of even late stage scales. These include Safari, TriStar, and Distance though it is impor-tant to note that imidacloprid (Merit) is not effective on armored scale. More information on armored scale control can be found https://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note157/note157.html.
To see an overview of gloomy scale on urban trees watch our short video: