Red pine scale (Matsucoccus matsumurae), an invasive pest native to Asia, has been causing significant damage to red pine (Pinus resinosa) stands in Maine. First identified in the United States in Connecticut during the 1940s, this pest was later detected in Maine on Mount Desert Island in 2014. It feeds on the inner bark of red pine, which can lead to crown thinning, needle loss, and eventual tree mortality, though early infestations may be difficult to detect. Further information on the species can be found in our factsheet.
Images: (left) Infestation causes discoloration of red pine needles; (right) A severe red pine scale infestation can result in the eventual death of all red pine in a stand, leaving other species such as white pine unaffected.
In 2024, the Maine Forest Service piloted a new method of detecting the red pine scale using sticky traps. The program focused on sites in the Downeast region to evaluate the effectiveness of this technique in early detection and to identify new infestation sites.
Findings
The trapping program successfully detected red pine scale at several key locations. To confirm the species’ identity, a subsample of the collected specimens was submitted to the University of Maine Cooperative Extension Diagnostic and Research Laboratory for genetic testing.
Images: (left) Sticky trap designed to passively capture airborne red pine scale crawlers; (center) the crawler stage can be very difficult to detect using the naked eye; (right) red pine scale crawler on the sticky trap collection surface.
Known infested areas in T22 MD BPP, Columbia, and Osborn served as positive controls. Red pine scale crawlers were detected at all sites in these towns. Crawlers were also collected at three locations not previously known to have the scale, including sites in T30 MD BPP, T36 MD BPP, and southern Beddington.
The site in T36 MD BPP is notable due to its location in the Machias River Corridor on publicly owned land with a large amount of mature red pine. The relatively low number of crawlers collected, combined with the lack of obvious host symptoms, suggests an early-stage infestation.
These findings highlight the potential of sticky traps as an effective tool for early detection of red pine scale infestations, particularly in areas where visible symptoms have yet to emerge.
Next Steps
Land managers with commercially important red pine resource are encouraged to proactively monitor sites for signs and symptoms of red pine scale. These include settled scales underneath bark flakes on twigs, white fluffy material associated with some stages of the insects and a progression in color change of the needles from healthy green, to olive green, to brick red, and eventually gray. This progression can be quite rapid, so frequent visits to mature stands are recommended. Please report any suspected areas of infestation to our office.
Images: (left) The settled scales are small, flat, and white-fringed; (center) adult females are mobile and dark red; (right) male cocoons and female egg ovisacs are covered in a white cottony substance.
The Maine Forest Service will continue monitoring efforts. If you own or manage red pine outside of the areas with detections and are interested in volunteering to help, please reach out to foresthealth@maine.gov. We will be looking for sites to trap as well as looking for cooperators interested in conducting trapping in cooperation with our team.
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