Get Ready for Fall Scale Management



Magnolia scale NYMPHS on the undersides of twigs (J. Llewellyn)

Many horticultural professionals are ramping up for fall applications of horticultural oil. The full rate of horticultural oil is excellent for smothering juvenile stages of insects this time of year.  Magnolia scale populations were quite high in the GTA this year, making these trees prime candidates for dormant oil applications.  Several professionals have reported that for magnolia scale especially, fall dormant-rate horticultural oil applications are very effective at managing this pest.  Be certain to aim spray on the undersides of twigs to maximize coverage.

Close up of colonies of beech scale (Chris Malumphy, The Food and Environment Research Agency,

Beech scale (Cryptococcus fagisugae) is quite prominent this time of year on our native American beech (Fagus grandifolia).

Beech ScaleNymphDC

Beech scale NYMPHS within woolly masses on trunks and large branches of American beech (D. Cheung)

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.


Beech Scale Crawlers (Photo: Melody Melzer, University of Guelph)

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 once all chance of contact with leaves is no longer the case.   Re-assess beech scale viability about 10-14 days to determine whether a second application may be necessary.  Do not apply dormant oil when temperatures are expected to dip down into lower single digits or there is a chance of frost.

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.

About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
This entry was posted in Arboriculture, Insects, Weekly Nursery Landscape Report and tagged , , . Bookmark the permalink.

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