Issue 8, June 14, 2013

Hawthorn and Apple Mealybug

Hawthorn mealybug is being found in high numbers on cotoneaster in northeastern Illinois. Hawthorn mealybug, Phenacoccus dearnessi, is also known as two-circuli mealybug. It feeds on hawthorn, cotoneaster, pyracantha, mountain ash, amelanchier, and other rose family plants.

This mealybug is globular and red, but is covered with white wax so that the red does not show unless the wax is removed. Older nymphs overwinter in cracks in the bark. In the spring, the females move to twigs, being numerous on the undersides. They become fully grown in late May to June. At the same time, the male nymphs that stayed in the bark crevices molt into winged adults. Mating occurs, and the females retain their fertilized eggs which hatch into crawlers which then emerge from their mothers.
These nymphs crawl onto the leaves to feed. In late summer, large numbers of nymphs form aggregations in leaf folds. They move to bark crevices to overwinter in September and October.

The apple mealybug, Phenacoccus aceris, is similar in size and appearance, but it has an elevated crest running up the back of the mealybug. This crest is high enough to be easily seen despite the white wax. It feeds on rose family hosts like the hawthorn mealybug but also feeds on other trees and shrubs including honeysuckle, maple, elm, linden, dogwood, oak, and magnolia. Its life cycle is similar to hawthorn mealybug in that mature females are present and obvious at this time of year.

Control can be obtained on ornamental hosts with systemic insecticides such as imidacloprid (Merit, Xytech, Pointer, Imicide) or dinotefuran (Safari). Trees can be trunk injected and both trees and shrubs can be treated through soil injection. Sprays should also be effective, including imidacloprid, acephate (Orthene), and labeled pyrethroids. Be watchful for crawlers, control will be more effective then.

Phil Nixon
Jim Fizzell

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