develop. Matured fruit were harvested at 0800 hr each day, and the duration from anthesis to full-slip was recorded for each fruit together with fruit size and fresh weight. After harvest, a group of fruit (10 replicates per treatment) was stored for 3 d
Gene E. Lester, Robert A. Saftner and D. Mark Hodges
Stephen M. Southwick, Kitren G. Weis, James T. Yeager and Hong Zhou
Whole-tree sprays of Release LC [predominantly gibberellic acid] (GA,) were applied in a commercial peach [Prunus perisca (L.) Batsch.] orchard in the California Central Valley on three dates from mid-June (about 90 days after full bloom = 28 days before harvest) to late July (14 days postharvest) 1993 at 50, 75, 100, and 120 mg·liter-1. Gibberellin (GA) reduced the number of flowers differentiated in 1993, thereby reducing fruit density in 1994, when sprays were applied by early July 1993. Sprays in late July did not reduce flowering and fruiting density in the following year. In 1994, there were fewer fruit located on the proximal third of the shoot after GA sprays of 75,100, and 120 mg-liter' applied on 15 June compared to hand-thinned controls, and reduction was linear with increase in GA rate. Fruit numbers in the middle and distal sections of shoots were reduced by all 15 June and some 9 July GA sprays, with fewer fruit as concentration increased. However, the distribution of fruit within shoot sections, after GA treatments during floral differentiation, expressed as a percentage of the total number of fruit along fruiting shoots, showed even fruiting compared with hand thinning. Due to reduced flowering in response to GA treatments in June and early July 1993, the hand-thinning requirement was significantly reduced, with no thinning required in 1994 from 15 June 1993 GA sprays. All sprays applied in early July resulted in 40% to 60% fewer fruit removed during thinning than the nontreated controls. Sprays in late July were ineffective. Sprays of GA applied in mid-June at 50,75, 100, and 120 mg·liter and sprays of 120 mg·liter-1 GA applied in early July (4 days preharvest) increased the firmness of `Loadel' cling peach (about 26% improvement in June sprays) in 1993. The salable yield of fruit (after removal of the undersized fruit) was the same on hand thinned and on non-hand thinned trees treated with GA on 15 June at 50 mg·liter-1. The salable yield of fruit was increased by GA sprays of 50 and 75 mg·liter applied on 9 July 1993 compared to controls. There were no differences in fruit size (by weight or diameter) among the aforementioned treatments and hand thinning. GA sprays of 75,100, and 120 mg-liter' applied on 15 June 1993 tended to reduce salable yield, but fruit size increased with decreased yield. Based on the results obtained in 1993 and 1994, we believe that Release LC has good potential for chemically thinning peaches in California.
Stephen S. Miller
To control excessive growth, vigorous `Smoothee Golden Delicious', `Jonagold', `Empire', and `Gala' apple (Malus domestica Borkh.) cultivars on Malling 7A (M.7A) rootstock planted at close in-row spacing (2.5 or 1.8 m) were mechanically root-pruned (RP), trunk-scored (TS; ringing), or both, annually for 3 to 5 years beginning in the fourth leaf. Trees were grown in a deep, well-drained, fertile soil and supplied with trickle irrigation. RP reduced terminal shoot length in 2 of 5 years on `Smoothee Golden Delicious'; trunk cross-sectional area (TCSA) was not affected by RP. TS reduced terminal length in 3 years and TCSA in each of 5 years of treatment on `Smoothee Golden Delicious'. Bloom density was not affected by RP on `Smoothee Golden Delicious' but was increased by TS in two of the three years measured. RP reduced terminal shoot length in `Gala', `Empire', and `Jonagold' in most years and TCSA in 1993 for all cultivars. TS had no effect on shoot length or TCSA in these three cultivars. Effects of RP and TS on yield and fruit size varied with year and cultivar. In general, the effects of RP and TS were inconsistent and often failed to reduce shoot growth or canopy spread. No practical advantage was recognized from these techniques for young apple trees growing on a fertile site with trickle irrigation.
T.G. Thorp and B. Stowell
Avocado (Persea americana Mill. cv. Hass) trees were pruned over 3 years at either 4 or 6 m in height by removing or heading back selected limbs. Yields were compared with those from control trees with no pruning in the upper canopy. All trees had similar crop loads before pruning. Trees were at 9 × 10-m spacing and were 8 years old when first pruned. Fruit yields were recorded for 2 years before the first pruning and then in each year of pruning. In the final year, trees were harvested in four height zones: 0-2m; 2-4 m; 4-6 m; and >6 m. Cumulative yields over 3 years were similar on 6-m and control trees, but were less on 4-m trees due to the large volume of fruiting canopy removed in the first pruning. The height of the main fruiting zone was lowered on the 4-m trees, with yields in the 2-4-m zone similar to those in the 4-6-m zone of the control trees. Pruning to reduce the number and length of scaffold branches increased fruit yields on the remaining scaffolds without reducing fruit size. Results are discussed in terms of harvest efficiency and the benefits of small tree orchard systems.
Carlos Miranda Jiménez and J. Bernardo Royo Díaz
Peach [Prunus persica (L.) Batsch, Peach Group] tree productivity is improved if trees are thinned early, either in full bloom or when the fruit is recently set. Chemical thinning reduces the high cost of manual thinning and distributes the fruit irregularly on the shoots. The effect is similar to a late spring frost that mostly affects early flower buds on the tip of the shoot. To simulate frost damage (or chemical thinning) and evaluate the effect of fruit distribution on production, fruit growth of several peach cultivars—'Catherine', `Baby Gold 6', `Baby Gold 7', `O'Henry', `Sudanell' and `Miraflores'—and the nectarine [Prunus persica (L.) Batsch, Nectarine Group] `Queen Giant' was studied in the central Ebro Valley (Spain) in 1999 and 2000. The factors investigated were the intensity of thinning and fruit distribution on the shoot (concentrated in the basal area or uniformly placed). The treatments were performed at 30 days after full bloom in 1999 and at bloom in 2000. For `Baby Gold 6' and `Miraflores' and when fruit load was high after thinning (over four fruit per shoot), a high concentration of fruit on the basal portion of the shoot had a negative influence on final yield and fruit size. The intensity of thinning (or simulated frost) greatly affected fruit diameter but was also strongly related to cultivar, tree size, and length of shoots. Thus, relationships between thinning intensity and fruit diameter varied, even among trees of the same cultivar.
María A. Pescie and Bernadine C. Strik
Five-year-old hardy kiwifruit [Actinidia arguta (Sieb. et Zucc.) Miq. `Ananasnaya'] vines in a commercial vineyard were subjected to thinning before bloom in 1999. Flowers were thinned at four severities: 0% (control), 15%, 30%, and 50% flower bud removal (2-5 June). The average yield of vines thinned 50% was significantly less than that of control vines. However, marketable yield from vines thinned 15%, 30% and 50% was not significantly different from control vines. Thinning, regardless of severity, increased average fruit volume and king fruit volume by 18% and 27%, respectively, compared to control vines. King fruit were more affected by thinning than the two adjacent lateral fruit in the cluster. Thinning before bloom had no effect on percent soluble solids, seed number or total seed weight per fruit.
Marta Alvarez Gil, Carlos Moya López, María Elena Dominí Cuadra, Jorge Arzuaga Sánchez, Benedicto Martínez Coca, Simón Pérez Martínez and Jesús Cuartero Zueco
Elizabeth T. Maynard*
In northern Indiana, jack-o-lantern pumpkins (Cucurbita pepo) can be planted from late May through June to produce mature fruit for sales associated with Halloween. Field trials were conducted to evaluate the influence of planting date on pumpkin yield and yield components. `Gold Medal' and `Magic Lantern' pumpkins were each seeded on three planting dates (PD) in 2002 (31 May, 10 and 20 June 10) and 2003 (5, 16, and 25 June). Each planting date was harvested between 100 and 110 days after planting. The weight per plant of pumpkins that were completely mature (orange) was greatest for the June 10 planting in 2002 (14.9 kg vs. 12.5 kg for 1st and 12.2 kg for 3rd PD), but did not differ among dates in 2003 (PD1: 10.9 kg, PD2: 10.4 kg, PD3: 9.0 kg). The number of orange pumpkins per plant was lowest for the 20 June 2002 planting (1.63 vs. 1.88 for 1st and 1.91 for 2nd PD) but did not differ among dates in 2003 (PD1: 1.08, PD2: 1.20, PD3: 1.19). The average weight of an orange pumpkin was lowest for the 31 May 200 planting date (7.17 kg vs. 8.35 kg for 2nd and 7.89 kg for 3rd PD) and highest for the 5 June 2003 planting date (10.6 kg vs. 9.07 kg for 2nd and 8.16 kg for 3rd PD). In both years the last planting date produced the least weight per plant, and in 2002 the fewest number, of pumpkins that had begun to turn orange plus fully orange pumpkins. The two cultivars produced similar weight per plant and responded similarly to planting date, but `Gold Medal' produced fewer and larger fruit. No planting date consistently produced the greatest yield or largest fruit.
F. Kultur, H.C. Harrison and J.E. Staub
Muskmelon (Cucumis melo L.) genotypes, Birdsnest 1 [`Qalya' (BN1)], Birdsnest 2 (BN2), and `Mission' (V) were used to determine the effects of differing plant architecture and spacing on fruit sugar concentration and yield. The BN1 and BN2 genotypes possessed a highly branched growth habit specific to birdsnest melon types, but not characteristic of standard indeterminate vining types (e.g., `Mission'). Experiments were conducted at both the Hancock and Arlington Experimental Farms in Wisconsin, where plant response to two within-row spacings [35 cm (72,600 plants/ha) and 70 cm (36,300 plants/ha)] in rows on 210-cm centers was examined. Genotypes were grown in a randomized complete-block design with four replications at each location and evaluated for primary lateral branch number, fruit number per plant and per hectare, average fruit weight, yield per plant (g), yield per hectare (t), and fruit sugar concentration. Yield, fruit number, and sugar concentration were higher for all genotypes at Arlington than at Hancock. The main effect of genotype was significant for all traits examined. Genotypes BN1 and V had higher mean fruit weight, yield per plant and per hectare, and fruit quality (fruit sugar concentration) than did BN2. Spacing affected all traits, except primary branch number and fruit sugar concentration. Fruit number and yield per plant and average fruit weight were higher with wider spacing, but yield (t·ha-1) and fruit number per hectare were lower.
Timothy E. Elkner* and David H. Johnson
Medium-sized triploid watermelons were evaluated in southeast Pennsylvania in 2002 and 2003 to determine the best adapted cultivars for this region. The 2002 season was unusually hot and dry, while 2003 was unusually cool and wet. Yields and fruit quality were compared for the eight cultivars that were grown both seasons to determine the effect of weather on seedless watermelon. Cooler temperatures reduced total fruit number and total yield but not average fruit weight or soluble solids. Researchers evaluating triploid watermelons over several seasons can compare size and °Brix among cultivars, but will need to be cautious when predicting total yields.