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  • Author or Editor: Andrea McKern x
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Iowa was the sixth largest producer of grapes in the United States in the early 1900s, with 24,000 ha under production. The rapid expansion of petrochemicals post-World War II and grape's sensitivity to 2,4-D herbicides reduced vineyard size in Iowa to 28 ha in 2001. Recent state governmental support for organic fruit research and viticulture in general has led to the expansion of the grape and wine industry in Iowa. As of 2001, 5883 ha of organic grapes were produced in the United States. Challenges to organic grape production in the Midwest include diseases and weeds. The cultivation of American grape cultivars is essential in organic viticulture in the Midwest, including cultivars that are relatively cold hardy and disease tolerant. From 2003 to 2004, we experimented on-farm at Kirkland Vineyards, Norwalk, Iowa, with methods of organically approved weed management. Three replications of plots consisting of five vines each of `Marechal Foch' were laid out in 2003 in a completely randomized design in a 1-year-old vineyard. Treatments consisted of wood chips, wood chips plus vinegar herbicide (All-Down™, Summer Set Co., Chaska, Minn.), and mowing when weeds and groundcover reached 15 cm. Wood chips decreased weed load significantly over mowing alone, but wood chips plus vinegar herbicide provided the most control over 2 years of the experiment. There was a trend toward greater plant height in the wood chip treatment, but no significant differences in plant height were observed among treatments.

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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% O2 and 2% CO2 at 0.5 °C 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.

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The global market for total organic product sales was $20 billion in 2005, continuing an annual growth rate of 20% to 35%. In the United States, there were 937,000 ha of certified organic land in 2003 with 5626 ha of organic apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.]. Increases in organic fruit production have been associated with improved pest management methods, the use of disease-resistant cultivars, and organic-focused marketing schemes. Often constrained by lower apple yields and smaller fruit size compared with conventional counterparts, key challenges for organic growers include regulation of nutrient cycling processes to maintain crop yields while minimizing the need for external inputs. In local or regional organic markets, disease-resistant apple cultivars, such as ‘Enterprise’, ‘Liberty’, ‘Redfree’, and ‘Gold Rush’, have gained increased acceptance, whereas exporting countries have continued their use of cultivars susceptible to scab [Venturia inaequalis (Cooke)]. Integrated insect pest management approaches, including the use of kaolin clay, codling moth granulosis virus, and spinosad-based insecticides, have been successfully developed to comply with export standards and quarantines, and to meet market demand. Key pests, such as codling moth [Cydia pomonella (L.)], have been managed at damage levels less than 5% using these approaches. Future pest management strategies in organic apple production will focus on development of scab-resistant cultivars with enhanced storage capability and reduction in inputs associated with negative environmental and health effects.

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