Sheath mite on white pine
Editor’s note: This article is from the archives of the MSU Crop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
I had a white pine sample come into my office this week where the needles were yellow with brown tips and some needles had a blotched appearance. Looking closer, I found Eriophyid mites feeding at the base of the needles. The damage of this mite can mimic abiotic problems, such as air pollution injury or drought, and needs to be taken into consideration when diagnosing the problem.
To check if you are having a problem with these mites, you need to pull the needles apart in order to see the mites. They are very small and you will need a hand lens or microscope to see them. They are creamy white and about 1/125 of an inch (0.2 mm) in length. Their bodies gradually taper toward the end and somewhat shaped like a carrot. Most trees usually support small populations that cause no visible damage. Flare ups often occur on stressed trees or after applications of broad spectrum insecticides that kill mite predators.