Older nymphs of some species are covered with fluffy, white wax. Biology Mealybugs are pests of ornamental crops indoors and outdoors across the world. They are most active in warm, dry weather. Most species of ornamental plants can be infested with mealybugs. Mealybugs damage plants by inserting their threadlike mouthparts into any part of the plant and sucking out sap.
Mealybugs excrete honeydew, a sweet, sticky liquid.
Sooty molds often grow in the honeydew causing infested plants to turn black. The citrus mealybug has a toxin in its saliva which causes its host plants to drop leaves and buds. Heavily infested plants are disfigured by the mealybugs, their ovisacs, honeydew and sooty molds. Female mealybugs have no wings and must be transported directly to or near the next host plant. They can travel short distances by crawling or the very young nymphs may be blown about by the wind or carried on the feet of birds.