Introduced Beech scale (Cryptococcus fagisugae) is easier to see this time of year on our native American beech (Fagus grandifolia). That’s because of the white waxy coverings the females produce to protect their eggs. Look for tiny tufts of white, cottony-like masses on the main trunk and large branches.
Examine trunks and large branches for white, woolly masses. Lightly open up the woolly mass and use your hand lens to look for small, yellow brown crawlers with red eyes. You will need a hand lens to see them in detail. See more images on BugFinder.
This life stage is sensitive to horticultural oil applications. Although some horticultural oil products may be phytotoxic to beech leaf tissue, a direct trunk application may be appropriate this late in the season. Re-assess beech scale viability about 10-14 days later to determine whether a second application may be necessary. Do not apply horticultural oil at the dormant rate when temperatures are expected to dip down into lower single digits or there is a chance of frost.
Some arborists will pressure wash the scale off of the trunks this time of year and this simple cultural management step can really help reduce the number of viable nymphs that would re-infest our beautiful beech.
Beech scale is quite often the precursor to Beech Bark Disease (Neonectria faginata and N. ditissima) as the scale insect feeding creates wound sites for the fungal disease to enter. Management of beech scale in the early stages may help suppress beech bark disease.