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  • Author or Editor: James Schupp x
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In 1984 trees of `Starkspur Supreme Delicious' apple (Malus domestica Borkh) on 16 rootstocks were planted at 30 sites in North America according to guidelines established for cooperative testing by the North Central Regional Cooperative Project (NC-140). Tree loss and root suckering in the Maine planting have been low, similar to that of other sites. Tree size in Maine is smallest amoung all sites after seven seasons. Trees on Budagovsky 9 (B.9) rootstock were the most precocious, producing significantly higher flower numbers and yield in the third year. Other precocious root-stocks in this planting included C.6, M.26EMLA, M.7EMLA and P.1. After seven years, B.9, C.6 and M.26EMLA were the most productive amoung the dwarf trees, and consequently are the most efficient. P.1 and M.7EMLA were the most productive amoung the more vigorous stocks. This trial will be conducted for 3 more seasons, however it appears that B.9, C.6 and P.1 may have potential as rootstocks for commercial apple orchards in New England.

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To evaluate the interactions between cultivar and rootstock, four apple (Malus domestica Borkh.) cultivars, `Pioneer Mac', `Marshall McIntosh', `Ginger Gold', and `Empire' on two rootstocks, M.26 and Mark, were planted in a split-plot design. After 5 years, `Pioneer Mac' and `Ginger Gold' had larger trunk cross-sectional area (TCSA) on M.26 than on Mark. `Marshall McIntosh' and `Empire' had larger TCSA on Mark than on M.26. Precocity, expressed as both number of flower clusters and yield, was greater for trees on Mark for all cultivars except `Ginger Gold', which had greater flower cluster numbers and yield on M.26. Fruit size was variable from year to year, depending on crop load; however, `Pioneer Mac' and `Ginger Gold' usually produced the largest fruit, while `Empire' consistently produced the smallest fruit—'Ginger Gold' appears to be incompatible on Mark. The results of this study demonstrate that cultivar × rootstock interactions can be significant and need to be considered when rootstock and planting density recommendations are made.

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In 1984 trees of `Starkspur Supreme Delicious' apple (Malus domestica, Borkh) on 16 rootstocks were planted at 32 sites In Morth America according to guidelines established for cooperative testing by the North Central Regional Cooperative Project (NC--140). Tree loss and root suckering in the Maine planting have been low, similar to that of other sites. Tree size in Maine is smallest amoung all sites after eight seasons. Trees on Budagovsky 9 (B.9) rootstock were the most precocious, producing significantly higher flower numbers and yield in the third year. Other precocious rootstocks in this planting included C.6, M.26EMLA, M.7EMLA and P.l. After eight years, B.9, C.6 and M.26EMLA were the most productive amoung the dwarf trees. P.l and M.7EMLA were the most productive amoung the more vigorous stocks. Heavy croping trees on dwarf rootstocks leaned more due to hurricane winds than larger better anchored trees which lost a larger proportion of their crop. B.9, C.6 and P.1 may have potential as rootstocks for commercial apple orchards in New England.

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A trial was established in 1989 to evaluate the performance of `McIntosh'/M.26 apple trees trained to central leader, Y-trellis or vertical axe training systems. In-row tree spacings were 1.2, 1.8 or 2.4m with the vertical axe and 1.8, 2.4 and 3.0m with the central leader and Y-trellis trees. Treatments were arranged as a split-plot design with system as the main plot treatment, in-row spacing as the sub-plot treatment, and six replications. In 1991, the vertical axe trees had higher yields than the other two systems. System had no effect on yield in 1992. Trees at 1.8m produced greater yield/ha than trees at 2.4m. Y-trellis trees produced more large fruit than central leader trees, while vertical axe trees produced the fewest large fruit. Trees at 1.2m produced fewer large fruit than at 1.8 or 2.4m in the vertical axe systems. In-row light interception increased as tree spacing dropped from 2.4 to 1.8m. Vertical axe trees intercepted more light within the row than the other two systems.

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To compare the effects of growth regulators on preharvest fruit drop and fruit maturity, aminoethoxyvinylglycine (AVG) was applied to `McIntosh' apple trees at 75, 150, or 225 mg·L-1, at 8, 4, or 2 weeks before harvest (WBH). These treatments were compared to NAA, daminozide, and to an untreated control. All AVG treatments and timings except 75 mg·L-1 applied 8 WBH delayed preharvest drop and fruit maturity. AVG applied at 225 mg·L-1was more effective in delaying drop and development of maturity than other rates when applied 8 or 2 WBH, but at 4 WBH, 150 mg·L-1 gave equivalent results to 225 mg·L-1. AVG at 150 mg·L-1 was superior to NAA or daminozide as a stop-drop agent. No concentration, or time of application of AVG influenced fruit size at harvest. AVG reduced internal ethylene concentration (IEC) in `McIntosh' apples linearly with increasing AVG concentration. There was a linear relationship between time of AVG application (8, 4, or 2 WBH) and IEC in the fruit after harvest, and the time required for harvested fruit to enter the ethylene climacteric. Development of red color was delayed by AVG. This was attributed to a delay in ripening as determined by a slower increase in IEC and starch hydrolysis. In general, earlier application of AVG resulted in reduced effectiveness of lowering IEC following harvest. Chemical names used: aminoethoxyvinylglycine (AVG), naphthaleneacetic acid (NAA), succinic acid-2,2-dimethylhydrazide (daminozide).

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AVG was evaluated for its effect on controlling preharvest drop and influencing ripening of `McIntosh' apples in Maine and Massachusetts. AVG consistently and effectively retarded preharvest drop. AVG was superior to NAA and comparable to daminozide in drop control. Dilute or 2× applications were more effective than applications made at lower water volumes. One application of AVG made 4 weeks before anticipated normal harvest was more effective in controlling preharvest drop than split applications of the same amount made earlier or later. In general, AVG delayed ripening as assessed by a retardation in the development of red color, maintenance of flesh firmness, delayed degradation of starch, and a delayed onset of the ethylene climacteric. We conclude that AVG is an effective drop control compound that is also useful as a management tool to extend the harvest window for blocks of `McIntosh' that would otherwise ripen simultaneously. Chemical names used: aminoethoxyvinylglycine (AVG), naphthaleneacetic acid (NAA), succinic acid-2,2-dimethylhydrazide (daminozide, Alar).

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'Macoun'/Budagovsky 9 apple (Malus ×domestica Borkh.) trees were planted in May 1998 in one of four preplant treatments that were soil incorporation of: 1) control, no phosphorus (P); 2) 90 g P per tree; 3) 128 kg compost per tree; and 4) 90 g P and 128 kg compost per tree. Preplant addition of P had no effect on soil organic matter, P, magnesium (Mg), and calcium (Ca) in the first three seasons after planting, but lowered soil potassium (K) in the second season. Foliar nutrients, tree growth and flowering were also not affected by P. The addition of compost increased soil organic matter and P in the first season after planting, and pH, K, Mg, and Ca in the first three seasons. The addition of compost increased foliar nitrogen and K in all three seasons, and decreased foliar Mg in the first season. Compost incorporation increased shoot length in the first season, trunk cross-sectional area in the first two seasons, tree height and the number of growing points in third season, and flowering in the third and fourth seasons. Compost addition was more effective than P fertilization for increasing tree growth during the establishment years.

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'Macoun'/B.9 apple (Malus ×domestica Borkh.) trees were planted in May 1998 in ± compost or ± monoammonium phosphate (MAP) for a total of four preplant treatments: 1) 90 g phosphorus (P) per tree, 2) 128 kg compost per tree, 3) 90 g P and 128 kg compost per tree, and 4) and an untreated control. MAP did not increase tree growth or yield in any year of the study. Compost increased canopy width into the sixth year after planting, and increased tree height and trunk cross-sectional area (TCA) into the seventh year. Annual yield was increased by compost in the fifth and seventh years, but not fourth or sixth year after planting. Compost increased cumulative yield in the sixth and seventh years.

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Hand-thinning of fruit is among the most labor-intensive orchard practices and consequently contributes significantly to peach (Prunus persica) production costs. Prior research conducted by the authors on string blossom thinners for managing peach tree cropload demonstrated that this new technology reduces labor requirement and also improves fruit size. Studies were conducted over two seasons in peach orchards trained to perpendicular V or open-center systems to evaluate possible pruning strategies to improve tree canopy access by string thinners. The objectives were to demonstrate if modifications in fruiting shoot orientation, pruning detail, and/or scaffold accessibility improved flower removal, reduced follow-up hand-thinning requirement, and/or increased fruit size. Blossom removal was improved by either detailed pruning or partial pruning (elimination of all shoots on the side of a limb inaccessible by the thinner spindle) in both training systems. Flower density and fruit set measurements revealed greater differences among pruning treatments compared with hand-thinned control treatments with both fruiting shoot orientation pruning modifications and detail pruning resulting in improved thinning. Thinning efficacy was unaffected by scaffold angle but increased as canopy accessibility ranking increased. Follow-up hand-thinning time was reduced by all treatment, system/cultivar, and year combinations except standard pruning in an open center-trained 2009 trial. Detail pruning consistently improved fruit size compared with hand-thinned control and other pruning treatments in both perpendicular V- and open center-trained orchard plots. The best treatments resulted in a thinning savings of $120/ha to $282/ha in perpendicular V plantings and $26/ha to $46/ha in open-center plantings. Realized economic savings beyond hand-thinning alone ranged from $473/ha to $2875/ha in perpendicular V trials and $28/ha to $293/ha in open-center trials.

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Trials were conducted in 2009 and 2010 to evaluate the use of a hand-thinning gauge [Equilifruit; Institut National de la Recherche Agronomique (INRA), Montpelier, France] on three cultivars of apple (Malus ×domestica) trees trained to tall spindle. Hand-thinning treatments were applied after June drop to trees with supra-optimal crop loads. Three hand-thinning treatments were applied using the hand-thinning gauge: 1) thinning to ≈6 fruit/cm2 branch cross-sectional area (BCSA) (F value), 2) subtracting the delta value [Δ (an adjustment factor to increase or decrease the number of fruit per BCSA] from the F value (F − Δ), and 3) F − 2Δ. These treatments were compared with a control and a traditional hand-thinning heuristic of spacing a solitary fruit every 7 to 8 inches of branch length. Use of the hand-thinning gauge generally improved fruit weight and maintained whole tree yields when compared with the control. Hand-thinning based upon traditional fruit-spacing heuristics reduced crop density and increased final fruit weight of apple, but significant reductions in yield were observed in two of four studies when compared with the control. We find the hand-thinning gauge a useful tool in adjusting final crop load of apple.

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