A White Growth Along the Branches of an Orange Tree

Citrus Mealybug

• A white growth along the branches of an orange tree is likely to be a sign of infestation by the citrus mealybug (Planococcus citri). The adult, female mealybug is covered with a white, cottony wax and lays her eggs inside sacs that look like white cotton balls. She lays 300 to 600 eggs in groups of five to 20 eggs per sac. As a result, just one female is capable of dotting a branch with dozens of white growths.

Identification

• Below the white wax that adorns her, the female adult mealybug is pink in color and although she is mobile, the insect possesses no wings. Mealybugs crawl about from tree to tree or are transported by the wind or on the feet of birds. The eggs the female deposits are pink in color and will hatch in a little more than one week, with 30 days required for the larvae to reach adulthood. The first crawlers normally appear in April and begin feeding on twigs and fruit.

Damage

• After they crawl out from their white cotton sacs along the branches of an orange tree, the immature mealybugs inject a toxic saliva into the tree while they suck away the sap. This can result in defoliation, fruit discoloring and fruit drop from the tree. They also deposit honeydew -- waste material -- on the orange tree that leads to the development of sooty mold, a fungal problem that further contributes to defoliation and a reduction in fruit quality and tree vigor.

Management

• The citrus mealybug enjoys humid conditions and thrives among closely planted trees with a significant amount of shade. The mealybug overwinters on the tree, so gardeners can inspect the tree in late winter or early spring for signs of infestation, primarily the white, waxy material that covers the mealybug. Chemical insecticide is effective in controlling the citrus mealybug provided it is applied as soon as the crawlers begin to emerge in early spring.