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Hawthorn Mealybug

By Carl Wilson, Horticulturist, Denver Cooperative Extension

The hawthorn mealybug feeds on the sap of twigs and small branches.Heavy infestations weaken plants and cause branch dieback. Sooty mold grows on the large amounts of honeydew produced and greatly detracts from hawthorn appearance.

White, waxy clumps scattered among the bark scales of the trunk and large branches are another sign of hawthorn mealybug infestation. Much of the insect's life is spent on the bark and only the young or nymph stage feeds on the leaves.

Predators include three species of ladybeetle and green lacewing larvae. Control efforts have proved difficult because the insect spends so much time under loose bark and in other protected sites.

The best time to attempt to control hawthorn mealybug appears to be in early May when crawlers are moving from overwintering sites in bark crevices to feeding sites in twig crotches. Contact an arborist to arrange for sprays with effective insecticides. Dormant season oil sprays in winter may provide some degree of control but should be coupled with spring crawler sprays.

Photograph courtesy of Judy Sedbrook.

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Date last revised: 01/05/2010