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Excessive tree vigor is a significant production problem for the PA apple industry. A series of experiments were conducted from 1994 to 1999, which indicated that Apogee® could effectively reduce vegetative shoot growth. Results from 1994 to 1996 have previously been reported (HortScience 31:598, 32:558). In 1997, 16 treatments composed of four rates (0, 63, 125, and 250 ppm) and four timings (22 May; 4, 11, and 24 June) in various combinations, were applied as dilute handgun sprays. These treatments were applied to sixth leaf `York Imperial' apple trees. Ten peripheral shoots, at a height of 2 m, were tagged and measured on 21 May, 9 and 30 June, 16 July, 12 Aug., and on 10 Oct. Shoots treated with 63, 125, or 250 ppm on 22 May followed by 0, 63, or 125 ppm on 4, 11, or 24 June were from 65% to 76% of the length of the controls (25.5 cm). Treated shoots were from 69% to 78% of the length of the controls following sprays with 63 ppm on 22 May followed by 0, 63, or 125 ppm on 4, 11, or 24 June. Shoots treated with 125 ppm on 22 May followed by 0 or 63 ppm on 4, 11, or 24 June were from 69% to 73% of the length of the controls. The later applications (11 and 24 June) of 250 ppm gave no growth control but the 22 May treatment gave a 30% reduction in growth. In 1999, dilute handgun sprays of 125, 125, 83, and 83 ppm were made on 22 May and on 4, 11, and 24 June, respectively. Cultivars treated were `Spartan', `Delicious', `York Imperial', `Gala', and `Mutsu'. The length of 10 peripheral shoots at 2 and 3 m were measured on 28 July and on 12 Aug. All cultivars responded and on 12 Aug. treated terminal shoot lengths ranged from 33% to 55% of the controls. With reduced vegetative tree vigor many horticultural factors will be improved. In addition, the severity of shoot fire blight can be reduced and the control of all pests that prosper on young succulent leaves will be easier, especially apple aphids and obliquebanded leafrollers. Major factors to be considered in developing an efficacious Apogee® program appear to be initial tree vigor, length of growing season, and crop load. An initial application at 1 to 3 inches of terminal growth is probably the most critical factor.

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The Mid-Atlantic region consists of the states of Pennsylvania, Maryland, West Virginia, Virginia, and New Jersey, and produces about as many apples as New York or Michigan. The climate in this region in the summer often has warm days and relatively warm nights. Light intensity can often be reduced by clouds from tropical air masses, and this is usually accompanied with high relative humidity. Most orchards are not irrigated, and rainfall can varies widely. The predominant cultivars are `Delicious', `Golden Delicious', `Rome', and `York Imperial'. With these cultivars and this set of climatic conditions, excessive vegetative growth and fluctuating return bloom are common problems. This climate and apple variety assortment are markedly different from more northerly apple production regions in the U.S. The need for an effective growth-control chemical has been obvious for years. The development of BAS-125 appears to have made this a possibility and has caused much interest among pomologists and growers that are aware of this chemical. Research was conducted from 1994 to 1995 on `York Imperial', `Delicious', and `Spartan', and was reported in HortScience (31:191). Research in 1996 dealt with `Law Rome' and `Golden Delicious'. On `Law Rome', treated shoots were ≈24 cm in length, while untreated shoots were 38 cm in length. On `Golden Delicious' this compound controlled shoots to ≈29 cm in length, while untreated shoots had about 39 cm of total shoots growth. BAS-125 can effectively reduce shoot growth, which will improve the light regime in mid-Atlantic apple tree canopies. This should result in savings in pruning, increased fruit quality, and increased cropping levels due to enhanced fruit bud production.

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The Mid-Atlantic area has a long, warm growing season and a reputation for grainy or firm, yellow apple products. There is interest in varieties that are large, firm, yellow-fleshed, that store and process well. The attributes of four NY selections, grown in PA, are described. NY 179 (Loop Red Rome X Yorking) fruit firmness (FF) dropped from 9 to 8.5 kg from 270 to 300 Julian days (JD). Over this same period, soluble solids (SS) rose from 13-15%. At 270 JD dropped fruit (DF) ranged from 0-5% while at 300 JD they ranged from 0-10%. Mean fruit weight was 285 g. NY 180 (Loop Red Rome X Yorking) averaged 351 g and FF was similar to NY 179. From 270 to 300 JD SS rose from 12-15%. Dropped fruit rose from 0-10% at 270 JD to 35% by 285 JD but to 95% by 300 JD. NY 88 (Melrose X Monroe) had a FF of 8.5 kg at 255 JD which decreased to about 7.5 kg at 300 JD. Over this same period SS rose from 13 -14.5%. At 255 JD DF were 0%; they ranged from 0-10% at 300 JD and never exceeded 10%. NY 151 (Red Spy X Yorking) averaged 171 g. At 270 JD FF was 12 kg falling to 11 kg at 330 JD. Over this period SS rose from 11-16%. Drops increased from 0% at 270 JD to 10-20% at 330 JD. These selections are undergoing regular and CA storage and processing tests.

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When applied as a dilute spray (at 125 and 250 ppm), BAS 125W effectively reduced shoot extension growth on `York' Imperial (YI) and `Spartan' (S) apple trees but was less effectively on `Delicious' (D). In 1994, lateral shoot growth of YI/M.26 trees (1 to 2 m tall) from 10 May to 7 July was reduced (35 vs. 7 cm) by sprays applied on May 13. The initial surge of growth by vertical shoots was suppressed by the treatments (16 vs. 35 cm), but there was more regrowth (6.5 vs. 0.5 cm). Some leaf injury was seen on YI. The 1995 experiments were conducted on S/M.111 and D/M.111 in an orchard spaced 3.7 m by 7.3 m. On S, lateral shoot length on five dates from 7 June to 20 Sept. was reduced by the sprays (44 vs. 32 cm on 20 Sept.). The initial surge of growth by vertical shoots was suppressed by the treatments (30 vs. 85 cm), but there was more regrowth (34 vs. 4 cm). There were fewer apples that were <25% red and more that were 25% to 40% and 66% to 85% red. On D, lateral shoot length on five dates from 7 June to 20 Sept. was reduced by the sprays (51 vs. 38 cm on 20 Sept.). The growth of vertical shoots was not influenced by the treatments, possibly due to a light fruit load in the tops of the trees. Growers viewing the 1995 plots estimated enhanced income of $933/ha for D and $780/ha for S.

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Abstract

An inexpensive, versatile, and simple recirculating controlled atmosphere storage system was designed, constructed and tested. It is demonstrated that this controlled atmosphere storage system has minimal variation in O2 and CO2 composition. In addition, the system allows controlled atmosphere research to be conducted in conventional storages that are otherwise unsuited for this type of research.

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The NY 151 apple selection, a cross of Kuppens Red Spy X Yorking, was made by Roger Way of Cornell University at the NYSAES in Geneva, NY. Due to several orchard weaknesses it was deleted from the NY program but it has performed well in the hot humid mid-Atlantic area. At harvest fruit quality measurements were made over the period 280 to 310 Julian days with the following results: soluble solids rose from 12% to 14.5%; flesh color changed from greenish-white to white and taste changed from tart-balanced to balanced. Fruit firmness often exceeded the 126 newton (N) upper limit of the McCormick tester using an 11 mm tip. Fruit from the 1991 harvest tested about 84 N coming out of cold storage in Feb. but were about 106 N coming out of CA storage in July. In 1992, apples harvested on Oct. 13 and Nov. 4 measured 133 N 75% and 32% of the time respectively, which is the upper limit of the Magness-Taylor tester. In order to compare the 8 and 11 mm tips 150 apples were tested with each tip. Values for the 8 mm tip ranged from 30 - 87 N and from 52 - 133 N for the 11 mm tip. Eleven mm firmness values can be predicted from 8 mm values by the equation y = 3.17 + 1.62x (R squared =.758). Although recommended for pears the 8 mm tip should be used for measuring the at harvest firmness of NY 151 apples.

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In both experiments. 20-apple samples from 6 commercial orchards were harvested and stored in 208 liter containers at 0C for 4, 6, and 8 months. Additional samples were removed from CA and held at 0C for 14 days before evaluation. Gas composition was measured and controlled 6 times per day using automatic control equipment.

In the first experiment, samples were stored at constant 0.0% CO2 and one of three O2 regimes (constant 2.0%. 0.5 rising to 3.5%. or 3.5% falling to 0.5% O2). Apples stored at 3.5% falling to 0.5% O2 during the storage period were softer than apples held at constant 2.0% or those held at 0.5% rising to 3.5% O2 during the storage period. Variable O2 concentrations did not influence weight loss during storage and insignificant scald, flesh browning, core browning, rot, and low 02 injury were observed.

In the second experiment, samples were stored at constant 2.0% O2 and one of three CO2 regimes (constant 0%, constant 5%. or 0% rising to 6% CO2). Constant 5% or rising CO2 conditions did not significantly influence flesh softening or weight loss during storage. Negligible CO2 injury was observed.

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The influence of rootstocks on the growth and productivity of `Starkspur Supreme Pagnelli Delicious' was determined in an NC-140 experiment started in 1984. The planting was supplemental to the main experiment and it contained Ottawa (Ott) 3, M.20, and Arnold Lynd (AL) 800, but did not contain Budagovsky (Bud) 490, Bud 9, Antonovka 313, or C6. Trees that apparently would not stand were given support. Data on tree size and yield were collected every year. As expected, many characteristics were strongly influenced by rootstock. Yield efficiency calculated as the total fruit weight per square cm of trunk cross-sectional area was used as a measure of production efficiency. In 1989, efficient producers of fruit (all in decreasing order) were Poland (P) 2, EMLA.26, P 16, and Michigan Apple Clone (MAC) 39. Intermediate in productivity were M.20, Cornell-Geneva (CG) 10, Pl, and AL 800. A lower efficiency group of rootstocks were EMLA.7, Ott 3, MAC 1, Seedling, M.4, P 18, and CG 24. `Golden Delicious' and `McIntosh' on EMLA.26, used as pollinizers, were ranked second and third in yield efficiency.

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In many years, apples grown in the mid-Atlantic region fail to exhibit a high percentage of the dark red color that buyers and consumers desire. In 1996, we initiated studies to examine the use of a metalized silver low-density polyethylene reflective groundcover (RGC) to improve red color on several apple cultivars under several training systems. A RGC placed in the orchard drive middle of 8-year-old `Delicious' apple trees trained to a “Y” trellis increased the percent surface red color and resulted in darker, more red-colored apples at harvest. A RGC increased surface red color on `Empire' apples on a “Y” trellis, but on central leader-trained semi-dwarf and standard size `Empire' showed no effects on color. Central leader-trained `Fuji'/EMLA.7 apples with a RGC had more red color than untreated fruit at harvest. In 1997, RGC placed under the canopy of 3-year-old `Fuji' trees trained to a “Y” trellis increased the full sunlight on the underside of the canopy by 28%. Ambient air temperatures within the RGC illuminated canopy averaged 2.1 °C higher than the non-RGC canopy. The level of percent full sunlight was increased within the canopy of well-pruned 32-year-old `Miller Spur Delicious' apple trees 4- to 8-fold with RGC placed in the row middle or under the canopy in a commercial orchard in 1998. Position of the RGC to the canopy affected fruit red color response differently between the lower and upper part of the canopy. Bins of fruit graded with a commercial color sorter showed no difference in fruit color; however, there was a strong trend toward increased red color where the RGC material was applied.

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