Eggs: The eggs are oval, ca. 0.3 mm long, and lemon yellow in color. Eggs are laid in ovisacs or nests consisting of dense cottony material covering a mass of separate eggs. The nests are 4-9 mm long, 1-3 mm wide, and can be found on the trunk, twigs, or leaves of apple. The ovisacs contain up to several hundred eggs. Apple mealybug nests can be distinguished from grape mealybug nests by their appearance: the grape mealybug is a loose, cottony mass, whereas the apple mealybug's nest is a well-defined cottony cylinder.
Nymphs: The first instar nymph is lemon yellow like the egg, and about the same size (0.3-0.4 mm), but with bright red eyes. Nymphs remain in the nest for a while, and gradually disperse to nearby plant tissues. Soon after they begin feeding, they develop the "mealy" coating (a granular white waxy covering) waxy filaments at the caudal end that is typical of mealybugs. This is well developed in later instars.
Adults: The adult female is 3-4 mm long, with a sage green body color visible through the white waxy coating. The "tails" on the caudal end of the mealybug are shorter than those of grape mealybug, and the body color (green vs pale purple) distinguishes it from grape mealybug, the most common mealybug pest in Washington tree fruits. The male is a typical of the Coccoidea, winged and relatively delicate.
Life History. All reports in the literature specify one generation per year. The information from the Pacific Northwest is scarce, thus much of the information is taken from other areas. The apple mealybug overwinters as a second instar nymph in a cocoon under bark scales or in cracks in the bark. Feeding is done by inserting the proboscis into plant tissues (bark or leaves) and sucking plant sap. They emerge from overwintering sites very early in the spring, feed on twigs, mature to the adult stage (male and female) and mate. Egglaying begins in early May in central Washington.
The mealybugs appear to be quite indiscriminate about their oviposition sites; many of the nests are on twigs, especially in the crotches; some are in pruning scars on heavy wood, and some are on the leaves (underside is common, but they can also be found on the upper surface). In heavy infestations, nests can be found on twine used for tree training, or dead leaves. Multiple nests are frequently laid overlapping each other, especially in the crotches of twigs. Just before laying her eggs, the female becomes sedentary, and develops a loose, fluffy covering of waxy filaments. Eggs are laid, and the ovisac constructed as she moves along. The female may construct more than one ovisac, but most frequently, the female can be found at one end of the ovisac, where she eventually dies. Initially the female in the nest will retain the sage green color, but becomes progressively more yellow as she begins to dessicate. Eggs begin to hatch in early June, although crawlers may not emerge from the nests immediately. Gradually, they disperse to nearby tissues (leaves, especially near the midribs; twigs; leaf axils, and fruit) and begin feeding. Nymphs grow slowly over the course of the summer, and partially grown nymphs seek overwintering quarters in the fall.
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