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M. Elena Garcia*, Lorraine P. Berkett and Terry Bradshaw

A new biopesticide has been commercially available to apple growers since 2001 in the kaolin clay-based product. This material meets Federal standards for use in organic crop production as a potential replacement for some insecticides that manage key apple insect pests. Initial research indicated that kaolin might have non-target impacts such a reduction in canopy temperature. However, most of the research on non-target effects, such as impacts on fruit quality, has been conducted in warmer, semi-arid environments. These potential impacts may not be beneficial in cooler orchard environments. The objectives of this 3-year study are to determine potential non-target effects of Surround WP application in the relatively cool and moist climate of the Northeast on `McIntosh'/M.26 apple tree productivity, and fruit quality. In 2001, preliminary data were collected and are included in these results. Treatments include: (1) Surround beginning at green tip plus fungicides; (2) Surround beginning at green tip without fungicides; (3) Surround beginning at petal fall plus fungicides; (4) IPM; and (5) Nontreated control. In 2001, the control treatment received fungicides. For 2002 and beyond, the protocol was amended to remove fungicides treatments. Data analysis indicate significant differences in treatments for several of the variables measured (fruit weight, percent drop, yield efficiency, starch index, soluble solids, fruit packout, and insect and disease damage). However, some of these differences might be due to the high incidence of scab in the treatments that received no fungicides and not due to the effect of Surround. There were no significant differences in other variables measured such as thinning, fruit color, and spur diameter.

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M. Elena Garcia, Lorraine P. Berkett and Terry Bradshaw

Surround WP, a kaolin clay-based biopesticide product, is a potential alternative to some organophosphates used in apple orchards for the management of pests, such as codling moth. In addition, Surround has been reported to have important nontarget horticultural impacts because of its effect on canopy temperature reduction. The label for use of Surround states: “When applied at recommended rates and frequencies, benefits such as increased plant vigor and improved yields may occur in certain apple cultivars.” However, most of the research on nontarget effects has been conducted in warmer, semiarid environments. The objectives of this 3-year (2002–04) interdisciplinary research project were to determine potential nontarget effects of Surround WP application on apple tree vigor, productivity, and fruit quality in the relatively cool and moist climate of the Northeast. The research was conducted at the UVM Horticultural Research Center in South Burlington, Vt., on `McIntosh'/M26 trees. The experiment used a completely randomized design with five treatments replicated six times. Each replicate consisted of single tree plots. Treatments included: 1) Surround beginning at green tip plus fungicides; 2) Surround beginning at green tip without fungicides; 3) Surround beginning at petal fall plus fungicides; 4) standard IPM; and 5) nontreated control. Results indicate no significant differences among treatments 1, 3, and 4 (treatments that included fungicide applications) in vegetative shoot length, spur characteristics, blossom number, fruit weight, firmness, soluble solids, and fruit calcium levels. Trees treated with Surround had significantly lower yield efficiencies in 2003 and 2004 than trees under IPM treatment.

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Joseph F. Costante, Wesley R. Autio and Lorraine P. Berkett

`Rogers Red McIntosh' apple (Malus domestica Borkh.) trees on MM. 111, MM. 106, M.7a, or M.26 were planted in 1984 on an old orchard site, diagnosed with an apple replant disease (ARD) problem. Soil treatments included Telone c-17, Vorlex, Nemacur 3, or not treated. After six years, tree performance problems usually associated with severe ARD did not develop. Lesion nematode [Pratylenchus penetrans (Cobb) Filipjev and Schuurmans-Stekhoven] populations feeding within or on the surface of roots were not affected by nematicide treatments nor rootstocks, even though slightly damaging levels were found in 1986. At the end of the sixth growing season, trunk cross-sectional areas were similar for trees in treated and in untreated soils. Trees on MM. 111 and MM. 106 were the largest, and those on M.26 were the smallest. Cumulative yield was not influenced by soil treatments, but trees on MM. 111 produced the greatest cumulative yields, whereas trees on M.26 were the most yield efficient.

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Joseph F. Costante, Wesley R. Autio and Lorraine P. Berkett

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Morgan L. Cromwell, Lorraine P. Berkett, Heather M. Darby and Takamaru Ashikaga

A major challenge in organic apple production in humid production regions is the available fungicide options for apple scab [Venturia inaequalis (Cooke) Wint.] management. The standard sulfur/lime sulfur fungicide program can be injurious to the applicator, the apple ecosystem, and the apple tree itself. The objectives of this study were to compare the efficacy of three potential alternative fungicides [potassium bicarbonate (PB), neem oil (NO), and Bacillus subtilis (Bs)] with a standard organic sulfur/lime sulfur (SLS) fungicide program and a non-treated control (NTC) for management of apple scab and to evaluate potential non-target impacts on pest and beneficial arthropod populations. The five treatments were applied to ‘Empire’ trees arranged in a completely randomized design with five single-tree replications at the University of Vermont Horticultural Research Center in South Burlington, VT. Fungicides were applied with a handgun to drip using maximum label rates. Applications began on 26 Apr. 2007 and 23 Apr. 2008 and continued on approximately a weekly schedule through the end of June and then every 2 weeks through 23 July 2007 and 17 July 2008, respectively. The standard SLS treatment resulted in the best scab control in both years. The NO treatment reduced foliar and fruit scab compared with the NTC and the other alternatives at the end of the 2008 growing season and had insecticidal activity. However, both the SLS and NO treatments had disadvantages, including phytotoxic burning on the fruit and/or significantly more russeting on the fruit at harvest. In each year of the study, one or more of the alternative treatments, particularly Bs, resulted in higher insect damage than the non-fungicide-treated control. This research showed that PB, Bs, and NO do not offer advantages over the standard SLS fungicide program in organic apple production and in some cases offer distinct disadvantages in terms of non-target impacts. Chemical names used: potassium bicarbonate (Armicarb “O”), Bacillus subtilis (Serenade MAX), neem oil (Trilogy), sulfur (Microthiol Sulfur)/lime sulfur (Miller Lime Sulfur)