ABSTRACT
Apples originated from wild species endemic to Asia (van de Vrie 1985). When apple trees were domesticated, they were moved throughout Europe and subsequently to the other continents. Insects, mites, and pathogens such as scab, mildew, and canker attack the cultivars grown today. Apple orchards are a stable agroecosystem, offering overwintering sites and habitats for both pests and natural enemies for many years. Trees begin to produce a crop within 2 to 6 years after planting and may live for 20 to 30 years. Because blemish-free, large fruits are desired, apples historically have required multiple pesticide applications to manage the arthropod pests and diseases. Chemical or mechanical fruit thinning is used to enhance the size of the fruits (Hoyt and Burts 1974); however, intensive use of pesticides is expensive, harmful to the environment, and disruptive to natural enemies. Furthermore, consumers are demanding fruits of high quality that lack spray residues. As a result, the development of integrated pest management (IPM) programs for apples has been a high priority (van de Vrie 1985, Prokopy and Croft 1994, Jones et al. 2006, 2009, Martinez-Rocha et al. 2008). It long has been recognized that spider mites are induced pests in apple orchards because their natural enemies have been disrupted by pesticides (MacPhee and Sanford 1954, Morgan and Anderson 1958, van de Vrie 1962, Sanford 1967, Hoyt and Burts 1974). The tetranychid species found on apples vary by geographic location, which may be due to both climatic differences and cultural practices (van de Vrie 1985). Some consider spider mites to be induced pests caused by the increased use of fertilizers and pruning, as well as the use of pesticides that disrupt their natural enemies.
