Beech Tree Pests

Updated November 21, 2016

The American beech tree, Fagus grandifolia, grows to an average height of 60 to 80 feet and may live as long as 400 years. Beech trees have thin bark, which makes them vulnerable to attack from insects.


Beech trees are susceptible to attack from the Cryptococcus fagisuga---or woolly beech scale---and the beech blight aphid, Grylloprociphilus imbricator, as well as the giant bark aphid, Longistigma caryae. They are also vulnerable to damage from the saddled prominent caterpillar, Heterocampa guttivitta, and Lymantria dispar, the gypsy moth caterpillar.


Woolly beech scale insects are the main carrier for beech bark disease. They infect beech trees with a fungus called Nectria galligena, which kills the bark and causes tree death. Beech blight aphids, which are light blue in colour, feed on beech trees in large numbers and produce large amounts of sticky honeydew. Giant bark aphids suck tree sap through small branches. Saddled prominent caterpillars and older gypsy moth larvae defoliate beech trees by feeding on foliage.


Woolly beech scale insects may be treated with insecticides when they are still in the crawling larval stage, according to the Pennsylvania Flora Project. Horticultural sprays and insecticidal soaps are effective against beech blight aphids. Giant bark aphid populations, saddled prominent caterpillars and gypsy moths are controlled with insecticides and cultural practices that promote tree health.

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