Upon hatching, crawlers immediately move to new sites. Female crawlers are generally more active and disperse throughout the tree. Photo by G. Krawczyk.
Some chemical strategies for controlling brown marmorated stink bug have led to infestations by white peach scale.
Description and life cycle
The female scale is 1 to 2.5 mm in diameter, oval in shape and white to yellowish in color. The female is immobile on the host plant, with a protective shell which is created by incorporating the cast skins from her previous molts with newly secreted wax. The male adult scale is a small, two winged insect that looks similar to a gnat but has two tail filaments. Male white peach scale coverings are elongate, snowy white, commonly found in clusters.
Eggs are deposited under the scale covering, on the surface of plants, ranging in color from orange (female) to white (male). Each female deposits up to 150 eggs, which hatch within five days. Upon hatching, crawlers immediately move to new sites. Female crawlers are generally more active and disperse throughout the tree. Within seven to nine days crawlers molt and begin forming their own scale covering. After multiple molts (3 to 5), adult males emerge from under the covering and mate. Usually two to three generations of white peach scale are observed per season. White peach scale overwinters as fertilized females beneath scale coverings.
To monitor crawler emergence, double sided sticky tape or black electrician tape covered with petroleum jelly should be wrapped around a limb heavily infested with scale. After crawler emergence begins, migrating crawlers can be observed on the tape as small oval whitish to orangish insects with six legs.
Several parasites and predators attack white peach scale, but in commercially managed orchards, natural enemies are seldom effective. Insecticidal control is difficult as scales protect themselves very effectively with hard, waxy armor. The most effective control can be provided in the spring during first generation crawler migration. One or two oil applications during crawler emergence, are very effective in controlling soft bodied crawlers. In-season control treatments also need to be directed against crawlers, as it is extremely difficult to penetrate female coverings. Specific chemical recommendations for home gardeners are in Fruit Production for the Home Gardener, and recommendations for commercial growers are in the Penn State Tree Fruit Production Guide.