San Jose scale (SJS) (Comstockaspis perniciosus (Comstock)) is a species of armored scale in the family Diaspididae (Order Hemiptera). It was accidentally introduced to North America on ornamental nursery stock in the late 1800s, became an agricultural pest soon after, and was the first species in which insecticide resistance was documented in 1914. Considered an important pest of pome and stone fruit orchards, most of the feeding damage is on woody parts of the plant, and extensive feeding over time can result in blind wood and limb loss. In apple and peach orchards, when populations are high, crawlers will settle and form scales on fruit that become unmarketable. Like other scale insects, most of their life is spent under the protection of a waxy cover, with 2-3 generations of crawlers produced. Hence the main interventions for suppressing populations have been to target: 1) settled scale through suffocation and broad spectrum or systemic insecticides, or 2) crawlers with either broad spectrum insecticides or insect growth regulators. A third option is to disrupt winged males in their quest to locate mature females emitting a sex pheromone; mating disruption tools show promise in testing conducted in Michigan and Georgia. To improve the IPM of SJS in orchards, we are working on 1) refining temperature-driven developmental and phenological models for guiding crop and region-specific interventions, and 2) providing growers with strategies for selecting and timing interventions to minimize the development of insecticide resistant populations and for doing the least harm to beneficial arthropods.
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