Organic Apple Production in Two Humid Regions: Comparing Progress in Pest Management Strategies in Iowa and New Zealand Kathleen Delate 1 and Andrea McKern Department of Horticulture, Iowa State University, 106 Horticulture Hall, Ames, IA 50011-1100 Robert Turnbull Department of Entomology, Iowa State University, 110 Insectary Hall, Ames, IA 50011-3140 James T.S. Walker, Richard Volz, Allan White, Vincent Bus, Dave Rogers, Lyn Cole, Natalie How, and Sarah Guernsey The Horticulture and Food Research Institute of New Zealand, Ltd., Private Bag 1401, Havelock North, New Zealand Jason Johnston The Horticulture and Food Research Institute of New Zealand, Ltd., Private Bag 92169, Auckland 1142, New Zealand Additional index words. codling moth, controlled atmosphere, leafroller, woolly apple aphid, scab-resistant cultivars Abstract. By 2003, organic apple [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] production had increased to 5626 ha in the United States and to 2964 ha in New Zealand by 2002. Common problems facing organic apple growers in the humid regions of New Zealand and the United States include effective management strategies for apple scab [Venturia inaequalis (Cooke)] and insect pests. Experiments conducted in Iowa in 2003–2004 demonstrated the effectiveness of a kaolin clay- and spinosad-based insecticide program in maintaining codling moth [Cydia pomonella (L.)] damage levels to less than 5% in the scab-resistant cultivars Enterprise, Liberty, Redfree, and Gold Rush. Similar pest management systems have been developed in New Zealand to comply with export standards and quarantines. The use of codling moth granulosis virus and a spinosad-based insecticide have led to reduced pest pressure and to an increase in organic exports with a 41% premium price over conventional apples. However, an association between spinosad use and woolly apple aphid [Eriosoma lanigerum (Hausmann)] population increase was observed in organic orchard surveys in 2006. An alternative to spinosad applications, insect disinfestation through controlled atmosphere (CA) treatment, was investigated to control quarantined pests and to extend the storage potential of scab-resistant cultivars. A CA treatment of 9 weeks of 2% O 2 and 2% CO 2 at 0.5 8C was determined to maintain firmness ratings to export standards in CA-stored, scab-resistant ‘Pinkie’ apples and to decrease internal ethylene concentration by 84% compared with apples stored in air. In addition, new scab-resistant cultivars with ‘Pinkie’ background under development in New Zealand show promise for organic production in humid regions. Few fruit quality differences were determined between ‘Pinkie’ fruits from integrated fruit production and organic production systems, although premium prices exist only for certified organic apples. Experiencing a fivefold increase from 1997 to 2003 to 5626 ha in organic apple production in the United States (U.S. Depart- ment of Agriculture–Economic Research Service, 2003), organic apple growers have requested assistance from universities and research institutes to address key production and postharvest issues for their industry. Concerns for environmental health, food safety, and food quality have motivated consumer demand for organic products (Crawshaw, 1997; Organic Trade Associa- tion, 2005), and new organic pest and disease management strategies, improved orchard management practices, and marketing incen- tives, particularly in the European Union (EU), have increased the supply of organic apples (Weibel, 2001). Key issues for organic fruit growers include selection of cultivars that are traditionally developed (nongeneti- cally modified) in compliance with U.S. Department of Agriculture-certified organic regulations (U.S. Department of Agriculture– Agriculture Marketing Service, 2006) and that meet production area constraints and market demands. Insect pest and disease management, weed control, and plant nutri- tion are also important issues for organic apple growers (Ames and Kuepper, 2004; Swezey et al., 2000; Weibel, 2001). Manage- ment of apple scab disease (or black spot) requires intensive spray programs in humid regions (Tamm et al., 2004) or the use of scab-resistant cultivars (Bus et al., 2002; Delate et al., 2005). Challenges associated with scab-resistant cultivars include poor shipping potential (Brookfield, 1999) and poor eating quality of certain cultivars (Selby and White, 1993). The role of beneficial insects in providing biological control of fruit crop pests has been reported worldwide (Solomon et al., 2000; Wearing et al., 1995a), but when these options fail to provide adequate control, least toxic, organic-compliant insecticides are used (Swezey et al., 2000). However, non- target effects of some organic-compliant insecticides, such as mortality of beneficial insects and resurgence of secondary pests, are becoming key concerns in organic orchards. The humid regions in New Zealand and in the United States share many common prob- lems in relation to organic apple production: acceptance and improvement of scab-resis- tant cultivars, more effective methods for managing specific insect pests, and methods to extend storage life in currently available scab-resistant cultivars. The objectives of this study were 1) to compare management sys- tems in organic apple orchards in humid regions in New Zealand and in Iowa; 2) to evaluate differences in insect and disease development among scab-resistant cultivars in an organic orchard in a humid region of Iowa; 3) to evaluate tree performance and fruit quality, at harvest and after controlled atmosphere (CA) treatment, of New Zealand scab-resistant cultivars with potential for importation into the United States; 4) to determine the effect of a systems approach using pheromone technology on leafroller presence in organic apples in a humid region of New Zealand; and 5) to determine associ- ations between a new organic-compliant insecticide in use in New Zealand and in the United States and nontarget effects on secondary pests and beneficial insects. Com- parisons between the two countries’ strate- gies and effectiveness of these strategies for future use in organic apple systems are considered. Mention of commercial brand names does not constitute an endorsement of any product by Iowa State University or cooperating agencies. 1 To whom reprint requests should be addressed; e-mail kdelate@iastate.edu. 12 HORTSCIENCE VOL. 43(1) FEBRUARY 2008