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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, C.R. Rom and J.B. Murphy

Two experiments were conducted to determine the effects of leaf age and shading on the phenolic content and composition of apple foliage. In the first study, it was determined that the phenolic content of `Liberty', at increasing leaf developmental stages, was leaf age—dependent. Early during leaf development, there was an increase in the phloridzin (the primary glycoside identified) and in total phenolics, reaching a maximum when the leaf is 6 days from 20-mm blade length. After this stage, the phenolic content decreased with increasing leaf age. In the second study, the leaves of two cultivars, `Liberty' and `Starkspur Law Rome', were tagged weekly when the leaf was two-thirds unfolded. Three weeks after budbreak, the trees were placed under three shade cloth treatments (0%, 60%, and 90% shade). After 4 weeks under the shade treatments, the tagged leaves were collected to determine their phenolic content. Shade significantly affected the foliar phenolic content. Leaves in 0% shade had the highest phenolic content, whereas the lowest content was found in leaves exposed to 90% shade. There was a significant leaf age × shade interaction. The phenolic content decreased with increasing leaf age except for those leaves whose development occurred before the experiment was started. The results indicate that light and leaf developmental stage are important factors in determining the phenolic content of apple leaves, but shading appears to have a stronger influence than leaf developmental stage. E-mail mgarcia@zoo.uvm.edu; phone (802) 656-2824.

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Alisha L. Ruple, John R. Clark and M. Elena Garcia

Floral fertility of five primocane-fruiting (PF) blackberry (Rubus L. subgenus Rubus Watson) genotypes (‘Prime-Jim’®, APF-31, ‘Prime-Ark® 45’, APF-59, and APF-77) and three floricane-fruiting (FF) genotypes (‘Navaho’, ‘Natchez’, and ‘Ouachita’) were tested under field conditions using floricane flowers with four pollination treatments: undisturbed open-pollinated, emasculated self-pollinated, emasculated and cross-pollinated with pollen from a similar fruiting type (PF × PF or FF × FF), and emasculated and cross-pollinated with pollen from a different fruiting type (PF × FF or FF × PF). During primocane flowering, three pollination treatments (undisturbed open-pollinated, emasculated selfed, and emasculated cross-pollinated) were used to further test the fertility of the five PF genotypes. Significant differences between cross-pollination treatments and self-pollination were seldom noted with more differences seen in ‘Prime-Jim’® than any other genotype. Cross-pollinating primocane flowers on ‘Prime-Jim’® resulted in significantly higher fruit set, drupelet set, and average berry weight compared with self-pollination. Fruit set among genotypes ranged from 68.5 to 96.7%, and drupelet set rating ranged from 4.3 to 6.9 for floricane flowers. For open-pollinated primocane flowers, fruit set ranged from 63.9 to 92.1%, and drupelet set rating ranged from 4.3 to 7.2. The genotypes APF-31, APF-59, and APF-77 showed a marked improvement over ‘Prime-Jim’® in both percent fruit set and drupelet set of floricane and primocane flowers. The results indicated that fertility appears to be sufficient in all the genotypes evaluated and that the later-generation PF genotypes show improvement in fertility over ‘Prime-Jim’®. Pollen viability (using both chemical viability testing and in vitro germination testing), stigma receptivity, and pollen tube growth (using florescence) were evaluated in a controlled environment to determine if any improvements could be noticed when comparing a selection of later-generation PF genotypes (APF-31,' Prime-Ark® 45', APF-59, and APF-77) with ‘Prime-Jim’® and ‘Prime-Jan’®. Genotypes APF-31, APF-59, and APF-77 had significantly more viable pollen and pollen germination than ‘Prime-Jan’®. Stigma receptivity was observed in all genotypes. Pollen tube growth did not appear to be inhibited after self-pollination in any genotype studied, although significantly greater florescence resulting from pollen tube growth was seen after cross-pollination compared with self-pollination for APF-59. There were no significant differences in pollen tube growth between cross- and self-pollination for any other genotype.

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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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M. Elena Garcia, C.R. Rom, J.B. Murphy and K. Kugler

Light is important in the production of phenolic compounds because key enzymes in phenolic biosynthesis are induced by light, and because products of photosynthesis are used in the synthesis of phenolic compounds. It is known that light intensity decreases with increasing depth in apple tree canopies. The objective of this experiment was to determine how leaf position on a limb affects the total foliar phenolic content. Leaves from `Stark Spur Supreme Red Delicious' on C6 and M26 rootstocks were collected on 28 July and 2 Aug. 1996. Each tree was divided into two sides, east and west. Each side was divided into 3 areas; exterior, middle, and interior. From each area, leaves were collected and PAR, SLW, assimilation, total N, and total phenolics were measured. Leaf position on a limb was a significant parameter for all of the measured variables. PAR, SLW, assimilation, total N, and total phenolics were highest in leaves at the exterior of the canopy. The total foliar phenolic content of the exterior canopy leaves was 20% higher than that found in the interior canopy leaves. There was a significant correlation between SLW and total phenolic content/cm2(r 2 = 0.77; P < 0.05). Assimilation may be a limiting factor in phenolics production in apple trees because of the correlation between assimilation and total phenolic content/cm2 (r2=0.56, P < 0.05).

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Neal Mays, Curt Richard Rom, Kristofor R. Brye, Mary C. Savin and M. Elena Garcia

The highly weathered, mineral, and often eroded and acidic soils of the Ozark Highlands region of northwest Arkansas generally have low soil organic matter (SOM) concentrations as a result of rapid organic matter turnover rates in the warm, moist climate. Orchard management practices that can improve SOM may also improve other soil quality-related variables for sustained production, which is an explicit goal for the National Organic Program (NOP). Therefore, beginning in Mar. 2006 and continuing for seven seasons, annual applications of municipal green compost, shredded office paper, wood chips, and mow-blow grass mulch groundcover management systems (GMS) in combination with composted poultry litter, commercial organic fertilizer, or a non-fertilized control as a nutrient source were implemented to evaluate their ability to alter near-surface soil quality in a newly established, organically managed apple orchard in the Ozark Highlands region of northwest Arkansas. The SOM concentration in the top 10 cm averaged 1.5% across all treatments at orchard establishment in 2006, but by 2012, SOM concentration had increased in all GMS and more than doubled to 5.6% under green compost. Similarly, soil bulk density in the top 6 cm, which averaged 1.34 g·cm−3 among treatment combinations in 2006, decreased in all GMS by 2012. Either green compost or shredded paper had the largest concentration of total water-stable aggregates across all aggregate size classes in the top 7.5 cm, whereas no differences among GMS were observed in the 7.5- to 15-cm soil depth. Green compost applied alone or in combination with commercial fertilizer had the largest estimated plant-available water (17.9% v/v) among all treatment combinations. Many soil quality-related variables measured in the various organic GMS had numerically greater values compared with an adjacent conventionally managed orchard on the same soils. Implementation of these GMS appears to provide apple producers in the Ozark Highlands and similar regions a tangible means of meeting NOP requirements for improving soil quality concurrent with production of certified organic crops. The findings also have implications for conventionally managed orchards, which have maintaining or improving soil quality as a management goal.

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Christopher I. Vincent, M. Elena García, Donn T. Johnson and Curt R. Rom

The broad mite (Polyphagotarsonemus latus) was found in association with leaf-curling symptoms on primocane-fruiting blackberry (Rubus rubus) in Arkansas in 2007–2009. Broad mite had not been previously reported on blackberry. The plots sampled in this study were part of a study comparing harvesting in the fall versus harvest in spring and fall, high tunnels versus ambient conditions, and three genotypes, all under organic production. Leaves were sampled, broad mites per leaf counted, and leaf area and trichome density measured. Results indicated that broad mite is capable of overwintering in a moderate temperate climate and that it reduces leaf area of primocane-fruiting blackberry. The fall-only harvest system had fewer broad mites than fall and spring harvest. There were a range of genotype effects on broad mite populations, including one genotype, ‘Prime-Jan®’, on which broad mite populations remained low, and one genotype, APF-46, on which mite populations grew significantly. Observations indicate that the broad mite may be a pest of ‘Prime-Ark® 45’, another primocane-fruiting cultivar.