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L. Jones and R.A. Criley

The most popular Ficus for interior conditions is F. benjamina, which has many clonal selections but still drops its foliage too readily. We compared 4- to 5-foot-tall, shade-grown plants of F. nemoralis, F celebensis, F. binnendykii `Alii,' F. oblongifolia (?), and a selection of F. benjamina thought to be `Gulfstream' with F. benjamina `Exotica' that were transferred to the Hamilton Library of the Univ. Hawaii after 14 weeks under 50%, 65%, or 85% Saran shade. During a 9-week evaluation period, new growth, leaf drop, and photosynthesis were determined. Little new growth developed on any plants during the evaluation period in the library. Leaf loss was greatest for F. benjamina `Exotica,' followed by F. celebensis, while the other four species suffered little leaf loss. Leaf loss was greater for plants grown under 50% shade than for 80% shade, while leaf loss from plants produced under 65% shade was either greater or less than 80% shade, depending on species. Leaf loss was greater in low light sites (13.6 μM/m2 per s) than in medium conditions (20 μM/m2 per s) or near windows (29 μM/m2 pers). After the observation period, the plants were to be removed, but library staff asked to retain many plants as they liked the improved atmosphere the plants gave their office and library settings. Most popular for retention were F. binnendykii`Alii,' F. benjamina `Gulfstream,' and F. benjamina `Exotica,' which still looked good despite its high foliage loss initially. The weeping habits of F. nemoralis and F. oblongifolia (?) were not as desirable because of the space they required, although they are performing well after nearly 12 months in the library. F. celebensis, despite its attractive growth habit and foliage, was a disappointment as it lost many leaves and, over 12 months, developed chlorosis and exudation problems.

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Keizo Yonemori, Ayako Ikegami, Sai Eguchi, Akira Kitajima, Shinya Kanzaki, Akihiko Sato, and Masahiko Yamada

There is a non-astringent type of persimmon that loses its astringency naturally on trees, despite the absence of seeds. This type is called pollination-constant and non-astringent (PCNA)-type. PCNA-type was thought to have originated in Japan as a mutant that terminates tannin accumulation at an early stage of fruit development. This trait is confirmed to be recessive and the PCNA-type must be homozygous in all alleles. In fact, crossing among PCNA-type individuals yields only the PCNA-type in F1, while crossing between PCNA-type and non-PCNA-type yields only the non-PCNA-type. However, a new PCNA cultivar, `Luo Tian Tian Shi', was reported in 1982 to exist in Luo Tian County, China, and this PCNA-type seemed to have different mechanisms to be PCNA-type. Our previous report showed that a crossing between `Luo Tian Tian Shi' and Japanese PCNA `Taishu' yielded both PCNA-type and astringent-type in F1, indicating that the trait of PCNA in `Luo Tian Tian Shi' may be dominant. To confirm this hypothesis, we made crossings between `Luo Tian Tian Shi' and Japanese astringent-type `Yotsumizo' or `Iwasedo', and top-grafted these seedlings for earlier fruiting. As we had some fruits in a total of 25 F1 individuals last year, we investigated segregation of astringency among these individuals. We also confirmed the parental relationships of these progenies by analyzing several SSR markers. We confirmed the segregation of PCNA-type and astringent-type in F1. No mistake of artificial pollination was shown in all individuals by SSR markers. Thus, we concluded that the trait of astringency-loss in `Luo Tian Tian Shi' is dominant and the use of this cultivar as a parent will open a new window for breeding PCNA-type persimmon.

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Matthew D. Kleinhenz, Sonia Walker, John Cardina, Marvin Batte, Parwinder Grewal, Brian McSpadden-Gardener, Sally Miller, and Deborah Stinner

The risk: reward for a transition to organic vegetable farming near urban areas and changes in soil, crop, and economic parameters during transition are poorly understood. A 4-year study was initiated in 2003 at the Ohio State Univ.–OARDC to document the relative advantages of four transition strategies and their effects on major cropping system variables. Soil previously in a vegetable-agronomic crop rotation has been maintained fallow, planted to a mixed-species hay, used in open field vegetable production, or used in vegetable production under high tunnels, transition strategies with a range of management intensity and expected financial return. Each strategy was replicated four times within the overall experimental area. Half of the soil in each strategy unit was amended with composted dairy manure while the remaining soil was unamended. Field vegetable plots have been planted to potato, butternut squash, and green bean. High tunnels have been planted to potato, zucchini, and a fall–spring rotation of beet, swiss chard, mixed lettuce, radish, and spinach. Data describing the outcomes of the strategies in terms of farm economics, crop yield and quality, weed ecology, plant pest and disease levels, and soil characteristics (physical, chemical, biological) have been recorded. Inputs in the high tunnels have exceeded inputs in all other strategies; however, high tunnel production has widened planting and harvesting windows and increased potato yield, relative to open field production. To date, compost application has increased crop yield 30% to 230% and influenced crop quality, based on analytical and human panelist measures. Weed (emerged seedlings, seedbank) and nematode populations also continue to vary among the transition strategies.

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Kitren Glozer and Janine Hasey

Production of extra-early cling peach varieties in California typically results in a $988 per hectare loss for Sacramento Valley growers, based on a 2004 University of California cost analysis study. This net loss is due to a number of factors, including lower yields than late-harvested peaches; and pruning, thinning, and harvest labor. The estimated cost per hectare to hand-thin extra-early varieties is $1515, which is 31% of all cultural costs. A conservative estimate for machine thinning with transportation costs would be $136 per hectare, a cost savings of about 90%. Machine thinning operates at about 200 trees per hour with two persons (operator and supervisor), compared to four to six trees per hour with two hand-thinners. In recent years, equipment to mechanically thin and harvest has become more sophisticated. We evaluated different types of equipment and settings in two experimental orchards trained in two pruning systems in 2005. We compared effects of crop load and variability in fruit development at time of shaking, as well as the timing of shaking with respect to fruit growth after bloom and compared mechanical and hand thinning. We found an optimum “window” for mechanical thinning based on fruit size and crop load, with tree architecture less important than these factors. Machine-thinning with follow-up hand-thinning reduced the thinning time by 30% to 41%. When machine thinning without follow-up hand-thinning was compared to hand-thinning alone, total yield was improved by 22% and salable yield was improved by 18% in the machine-thinned trees. The net increase in undersized yield in the machine-thinned only treatment was less than 6%.

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Patricia Garriz, Graciela Colavita, Hugo Alvarez, and Valeria Blackhall

Apple fruit abscission shortly before harvest is a frequent, recurring problem, thereby reducing potential yield. The synthetic auxin 2 (2,4-dichlorophenoxy) propionic acid (2,4-DP) was evaluated for its effect on reducing fruit drop and influencing ripening of `Braeburn' apples, in the High Valley region of Río Negro, Argentina (38°56'S, 67°59'W). Thirteen-year-old apple trees grafted on MM 111 rootstock were sprayed on 4 Mar. 2005, at 162 days after full bloom (DAFB) with 2,4-DP at doses of 0.05% and 0.10% (v/v), applied with an airblast sprayer, until runoff. Each tree was trained to palmette and planted in a single row from north to south with spacing of 2.3–4.0 m. The following measurements were performed: a) accumulated fruit drop, twice per week and b) maturity indices, weekly. Samples of uniform-size fruits were assessed for maturity (n = 20 per date and treatment), from 167 (commercial harvest) to 195 DAFB. On 23 Mar. (at 181 DAFB), cumulative fruit drop for control treatment was 19.9%, whereas 2,4-DP significantly reduced it to 4.90% and 2.94% at 0.05% and 0.10% (v/v), respectively. Reduction in the drop was also significant later, and 2,4-DP at both doses controlled drop comparably. The synthetic auxin did not affect fruit quality and maturation, based upon flesh firmness, starch degradation, and soluble solids concentration. We conclude that 2,4-DP is an effective drop control compound and it is useful as a management tool to increase yield by reducing fruit abscission and to extend the harvesting window of `Braeburn' apples, since it does not affect ripening. Delaying harvest may provide flexibility for scheduling of labor, fruit processing and packaging, cold storage, and marketing.

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Ed Stover, Michael J. Fargione, Christopher B. Watkins, and Kevin A. Iungerman

`McIntosh' apples (Malus ×domestica Borkh.) display a rapid increase in ethylene production as they ripen, resulting in more preharvest drop and accelerated softening compared with other major cultivars. Economic considerations often dictate a choice between delaying harvest to achieve color development or harvesting earlier to avoid excessive fruit softening and drop. We have evaluated the effects of plant growth regulators (PGRs) and summer pruning on this balance. Treatments were applied to trees in the Mid-Hudson region in New York state in 1995 and 1996, and a subset of treatments was applied in the Champlain Valley region in 1996. NAA, applied at 10 mg·L-1 in 1995 and 20 mg·L-1 in 1996, reduced drop on only one sample date in only one of the three trials. Ethephon at 150 mg·L-1 plus 10 mg·L-1 NAA, accelerated ripening and permitted harvest before substantial drop occurred. However, earlier harvest resulted in smaller fruit size, and if ethephon-treated fruit were not picked within a narrow window, rapid drop ensued, and fruit developed a high senescent breakdown incidence during storage. ReTain, containing AVG, at 124 g·ha-1 a.i. delayed drop in all three trials, but its use resulted in firmer fruit after storage in only two of seven comparisons. Use of ethephon on AVG-treated trees enhanced red color but accelerated drop, although it was reduced less than when ethephon was used alone. Severe late summer pruning accelerated red color development, drop and ripening in both years of the study. AVG was more effective for management of `McIntosh' harvest in the cooler Champlain Valley region than in the Mid-Hudson Valley region. Chemical names used: naphthalene acetic acid (NAA); 2-chloroethylphosphonic acid (ethephon); aminoethoxyvinylglycine (AVG).

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Christine Meyer, Ellen T. Paparozzi*, Scott J. Josiah, and Erin M. Blankenship

Woody floral stems are an emerging specialty crop within the floral industry, and stem color is a key to marketability. This study was conducted to assess stem color change over time in order to determine the optimum window for stem harvest. Plants of `Scarlet curls', `Flame' willow, `Bailey', `Cardinal' and `Yellow twig' dogwood were planted in a randomized complete block design in rows parallel to a windbreak.. Each experimental unit consisted of a group of five plants, each of the same cultivar. Plants were initially tagged at a set height and stem diameter and measured for color. Each stem was also tagged with one of three colored tapes, according to initial color: green for green colored stems, red for stems already showing color change, and pink for intermediate colored stems. Color was assessed initially and on a weekly basis for 10 weeks, starting at the end of September, using the Royal Horticultural Society color chart. Data were analyzed using a repeated measures procedure. `Scarlet curls' and `Flame' stems, already displaying color, attained the darkest color value for their cultivar at an early stage and were at the point of harvest in early November, while stems that were initially green never attained a similar dark color value. `Yellow twig' dogwood stems already displaying color and those beginning to color attained the darkest color value in late November. `Cardinal' stems attained a darker color value more quickly than other dogwood stems. In most cases, stems of `Cardinal' dogwood could be harvested from early October until early December, while early November was the optimum time to harvest `Bailey' dogwood stems. Woody florals planted closest to the windbreak were more variable in color development and, in some cases, appeared to be more vigorous.

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Gerard Krewer, Danny Stanaland, Oscar Liburd, Jerry Larson, Roosevelt McWilliams, D. Scott NeSmith, Ruperto Hepp, and Ben Mullinix

Georgia has an excellent window for organic blueberry production since much of the crop ripens ahead of production in the northern U.S. Major challenges facing Georgia organic blueberry growers are weed control, organic fertilization, insect control and disease control. A team of Georgia growers, extension agents and scientists are working together to solve these production problems. Since 2002 a series of experiments have been conducted on blueberry establishment and maintenance. Various mulch materials were tested. On young plants, pine straw produced the highest yields, but pine bark and landscape fabric were also successful. With the pine straw treatment, a respectable yield of 0.97 kg/plant occurred 24 months after planting. In addition, a bed shaper–plastic mulch layer was modified by developing a removable center. Using this system, beds are formed, plants are mechanically transplanted, plants are pruned to 75 mm, and plastic is then pulled over the stem. This produces a fairly tight fit around the stem and a nearly weed free system except for weeds growing from the edges. On mature plants, pine bark and wheat straw were tested. Wheat straw produced excellent weed control and improved blueberry growth in year one and two. However, pine bark mulch provided the best weed control in year three. Various organic burn down compounds such as vinegar, Xpress, Alldown, and Matran 2 were tested for winter weed control efficacy. In these trials Matran 2 was the most effective, and the product also performed well on woody weeds that were winter pruned, allowed to resprout and then treated. A propane torch was also tested, but discarded because of the fire hazard. Entrust insecticide was tested for thrips control and gibberellic acid for fruit set. Thrips populations were low, so no effect on fruit set was noted from Entrust. Gibberellic acid significantly improved fruit set.

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B.S. Wilkins, R.C. Ebel, W.A. Dozier, J. Pitts, and R. Boozer

This study was conducted to determine efficacy of Tergitol TMN-6 in thinning peach blossoms. A pretest was conducted and demonstrated no difference between TMN-6 and TMN-10 in efficacy when applied at full bloom or petal fall and at rates of 20 and 40 mL·L-1. In the main test, Tergitol TMN-6 was sprayed once at 10, 20, or 30 mL·L-1 at full bloom or petal fall and compared to an unsprayed control for 3 years. Tergitol caused widespread necrosis of flower parts including sepals, petals, pistils, stamens and peduncles. There was a difference among chemical treatments with more fruit removed at higher concentrations, although the amount of fruit removed was similar for the 20 and 30 mL·L-1 rates. There was no difference in thinning response at full bloom or petal fall, indicating a wide window of efficacy. There was also a difference among years, which was apparently not related to temperature or relative humidity during time of application. Tergitol caused some leaf yellowing and tip burn especially at the higher rates when leaves were present, but the trees did not appear to be seriously affected. Fruit weight was either not affected or larger in some years from treatment. Unlike higher concentrations, tergitol at 10 mL·L-1 did not negatively impact fruit number per tree at harvest. At harvest, fruit weight, skin blush, firmness, and soluble solids at harvest were not affected by treatment. Tergitol TMN-6 proved to be an effective thinning agent and when applied from full bloom to petal fall at 10 mL·L-1 it did not adversely affect the tree or fruit.

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Richard V. Tyson, Eric H. Simonne, Danielle D. Treadwell, James M. White, and Amarat Simonne

Integrating hydroponic and aquaculture systems (aquaponics) requires balanced pH for plants, fish, and nitrifying bacteria. Nitrification prevents accumulation of fish waste ammonia by converting it to NO3 -N. The difference in optimum pH for hydroponic cucumber (Cucumis sativa) (5.5 to 6.0) and nitrification (7.5 to 9.0) requires reconciliation to improve systems integration and sustainability. The purpose of this investigation was to: 1) determine the ammonia biofiltration rate of a perlite trickling biofilter/root growth medium in an aquaponic system, 2) predict the relative contribution of nitrifiers and plants to ammonia biofiltration, and 3) establish the reconciling pH for ammonia biofiltration and cucumber yield in recirculating aquaponics. The biofiltration rate of total ammonia nitrogen (TAN) removal was 19, 31, and 80 g·m−3·d−1 for aquaponic systems [cucumber, tilapia (Oreochromis niloticus), and nitrifying bacteria (Nitrosomonas sp. + Nitrobacter sp.)] with operating pH at 6.0, 7.0, and 8.0, respectively. With the existing aquaponic design (four plants/20 L perlite biofilter/100 L tank water), the aquaponic biofilter (with plants and nitrifiers) was three times more effective at removing TAN compared with plant uptake alone at pH 6.0. Most probable number of Nitrosomonas sp. bacteria cells sampled from biofilter cores indicated that the aquaculture control (pH 7.0) had a significantly higher (0.01% level) bacteria cell number compared with treatments containing plants in the biofilter (pH 6.0, 7.0, or 8.0). However, the highest TAN removal was with aquaponic production at pH 8.0. Thus, operating pH was more important than nitrifying bacteria population in determining the rate of ammonia biofiltration. Early marketable cucumber fruit yield decreased linearly from 1.5 to 0.7 kg/plant as pH increased from 6.0 to 8.0, but total marketable yield was not different. The reconciling pH for this system was pH 8.0, except during production for early-season cucumber market windows in which pH 7.0 would be recommended.