How to Manage Pests

Pests in Gardens and Landscapes

Mealybugs

Mealybugs are wingless, soft-bodied, insects about 1/20 to 1/5 inch long. They are usually elongate and segmented, and may have wax filaments radiating from the body, especially at the tail. Most females can move slowly and are covered with whitish, mealy or cottony wax. This waxy covering is similar to that produced by cottony cushion scales. Colonies occur as white, sticky clusters among leaves and fruit. Larvae are mobile. Mealybugs are often confused with woolly aphids.

Identification of species

Life cycle

Mealybugs overwinter as eggs or crawlers in protected places on the tree, such as crevices in the bark. The yellow to orange eggs are laid in a cottony mass called an ovisac. The young nymphs, or crawlers, are oblong, whitish, yellowish, or reddish and may or may not be covered with waxy filaments. In spring, crawlers move to the base of growing shoots or fruit clusters and stay until maturity (late May or June). As they mature, mealybugs become purple and develop a white powdery wax covering. Mature female mealybugs are about 3/16 inch long. Males are tiny two-winged insects that are rarely seen. Mature females return to protected places under the bark and lay eggs. Eggs also may be laid in the calyx end of the fruit such as apples.

Eggs hatch in June, and the new generation of crawlers moves from the bark to tender shoots or fruit to feed with those hatched on the fruit. Adults of this generation move back to the bark in August or September and lay eggs for overwintering. Some of these eggs may hatch in the fall to produce crawlers that overwinter. Most mealybugs have several generations a year.

Damage

Mealybugs tend to congregate in large numbers, forming white, cottony masses on plants. They feed on stems and leaves of fruit trees and ornamentals. High populations slow plant growth and cause premature leaf or fruit drop and twig dieback. Mealybugs can lower fruit quality by covering it with wax or sticky honeydew upon which black sooty mold grows.

Solutions

Provide proper cultural control so that plants are vigorous and can tolerate moderate mealybug feeding without being damaged. Naturally occurring predators and parasites provide good control of many mealybug species, unless these beneficials are disrupted. Manage ants, which are attracted to honeydew and inhibit the activities of natural enemies. Removal of overwintering sites, such as loose bark, can reduce mealybug numbers. Populations often drop in summer. Mealybugs are difficult to control with insecticides and systemic materials may be required. On ornamentals, insecticidal soap, narrow-range oil, or a forceful stream of water can be applied to reduce exposed populations with minimal harm to natural enemies that may migrate in later. Mealybugs are sensitive to heat and their waxy coat protects them from insecticides. Treatments are usually not justified or effective on home fruit trees.

For more information, see the Mealybugs Pest Note.

citrusmealy
Citrus mealybug adults

Mealybugs covering stems
Mealybugs covering stems

Longtailed mealybug
Longtailed mealybug

Grape mealybug crawlers
Grape mealybug crawlers


Statewide IPM Program, Agriculture and Natural Resources, University of California
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