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 produced to protect their eggs in late summer. 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. Gently open up the woolly mass and use your hand lens to look for small, yellow brown nymphs 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 are listed as being 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 there is a chance of frost.
Some landscapers and arborists will pressure wash beech scale from the trunks this time of year. This simple cultural management practice can really help reduce the number of viable nymphs that would re-infest our beautiful beech next year.
Beech scale is quite often the precursor to Beech Bark Disease (Neonectria faginata and N. ditissima), as this scale insect feeding creates wound sites for the fungal disease to enter (photo above). The continuous formation of fungal cankers around the tree trunk eventually girdles the tree, leading to mortality.
Management of beech scale in the early stages may help suppress beech bark disease.
Leaves are nearly finished shunting nutrients back into stems and roots and there are still a few examples of the spectacular fall colour display we’ve enjoyed in many parts of the province. Think back to June, do you remember seeing discoloured, pimple-like spots on the foliage of pear trees? This is the Pear Leaf Blister mite (Eriophyes pyri). The mites overwinter under the outer bud scales where they are feed on the developing buds when the plant is dormant. By petal fall next spring, the mites will lay eggs on emerging leaves and the next generation mites will remain protected from predators within the leaf blisters. The mite is difficult to manage once it moves into the blister-like domiciles it creates by feeding on the leaf tissue in the early spring. This mite pest does not usually threaten plant health, but we’ve been seeing a lot more of it in southern Ontario.
Management of pear leaf blister mite is most effective when applied in the fall, to treat the mites while they trying to find shelter in the outer bud scales. As pear trees retain their leaves later in autumn, sometimes we have to wait a little bit longer for more leaves to drop to maximize coverage on buds for next year.
In the spring, delayed dormant applications of horticultural oil may also target any residual mites hiding in the bud scales after petal fall, but it is not as effective as fall-timed dormant oil applications.