`Honeycrisp' apples (Malus × domestica) were harvested over 3-week periods in 2001 and 2002. Maturity and quality indices were determined at harvest. Fruit quality was evaluated after air storage [0.0 to 2.2 °C (32 to 36 °F), 95% relative humidity] for 10-13 weeks and 15-18 weeks for the 2001 and 2002 harvests, respectively. Internal ethylene concentrations (IEC), starch indices (1-8 scale), firmness and soluble solids content (SSC) did not show consistent patterns of change over time. Starch hydrolysis was advanced on all harvest dates, but it is suggested that a starch index of 7 is a useful guide for timing harvest of fruit in western New York. After storage, firmness closely followed that observed immediately after harvest, and softening during storage was slow. No change in SSC was observed during storage in either year. Incidence of bitter pit and soft scald was generally low and was not affected consistently by harvest date. The incidence of stem punctures averaged 18.5% over both years, but was not affected by harvest date. Development of stem end cracking in both years, and rot development in one year, increased with later harvest dates. A panel of storage operators, packers, growers, and fruit extension specialists evaluated the samples for appearance and eating quality after storage, and results suggested that a 2-week harvest window is optimal for `Honeycrisp' apples that are spot picked to select the most mature fruit at each harvest.
James M. Wargo and Chris B. Watkins
James M. Wargo, Ian Merwin and Christopher Watkins
`Jonagold' apple often has problems of inadequate red blush development at harvest, and loss of firmness and skin “greasiness” after refrigerated storage. During two growing seasons we tested factorial combinations of three preharvest treatments for managing these problems: 1) N fertilization (no applied N, 34 kg N/ha in May, or 1% (w/w) foliar urea sprays in May and June); 2) mid-summer trunk scoring (girdling); and 3) aminoethoxyvinylglycine (AVG) applications 3 weeks prior to harvest. Fruit were harvested at four weekly intervals each year, and evaluated for size, blush, firmness, soluble solids, ethylene, and starch hydrolysis. Nitrogen delayed blush development in 1998, but not 1999, and there was no difference in fruit surface blush coverage between foliar urea and soil applied N. Nitrogen applications increased fruit size, decreased fruit firmness, and increased post-storage flesh breakdown in 1999. Trunk scoring increased blush coverage and intensity both years, and improved market-grade packouts. Blush increase after trunk scoring was not caused by advanced fruit maturity (based on ethylene and starch indices) in either year, although it did increase skin greasiness slightly. AVG treatments delayed maturity and blush development of `Jonagold' by 7 to 10 days both years, relative to untreated fruit. Flesh firmness increased and greasiness decreased in AVG treated fruit harvested on the same dates as controls. However, in AVG fruit harvested at comparable stages of maturity 7 to 10 days later, firmness and greasiness were equivalent to untreated fruit on the previous harvest date. Trunk scoring and no N fertilizer were effective for improving fruit blush coloration, and AVG for delaying harvest maturity.
James M. Wargo, Ian A. Merwin and Christopher B. Watkins
`GoldRush' is a new scab (Venturia inaequalis) resistant apple (Malus ×domestica) with excellent flavor and storage qualities that tends to produce small and russeted fruit. We investigated the effects of rate, timing, and method of nitrogen (N) fertilizers on `GoldRush' fruit size and quality during 1998-99. Fertilizer treatments were 1) no N fertilizer (control); 2) a low N rate of 45 kg·ha-1 (40.1 lb/acre) applied in April (LN-Apr); 3) a low N rate of 45 kg·ha-1 applied half in April and half in June (LN-Apr+Jun); 4) a high N rate of 90 kg·ha-1 (80.3 lb/acre) split in April and June (HN-Apr+Jun); 5) a high N rate of 90 kg·ha-1 applied in April, May, June, and July at 22.5 kg·ha-1 (20 lb/acre) each month (HN-Apr+May+Jun+Jul); and 6) canopy sprays of 1% (wt/wt) urea-N, equivalent to 7 kg·ha-1 (6.2 lb/acre) applied monthly in May, June, July, and August (foliar urea). In 1998, an additional foliar urea spray at 5% (wt/wt) concentration was applied to trees after harvest. The first year's Ntreatments did not affect relative average fruit weights or total yields, but unfertilized trees produced more fruit in smaller size categories. Nitrogen fertilization resulted in greener and softer fruit both years. In the second year, all N additions increased yields compared with controls, but average fruit weight was inversely correlated with crop load. Foliar urea sprays and HN-Apr+May+Jun+Jul treatments increased yields the most. Fruit from LN-fertilized trees were normally distributed across a range of eight box-count size categories, peaking at size 100 both years. In the unfertilized control, fruit size was skewed into smaller size categories and yield was reduced. Total yields were greatest in foliar urea and HN-Apr+May+Jun+Jul treatments, but fruit-size distribution was skewed into smaller categories, peaking at size 138 in the second year. Foliar urea and HN-Apr+May+Jun+Jul treatments produced the highest crop value, but when estimated labor and fertilizer costs were considered, foliar urea and LN-Apr+Jun were the most efficient treatments. Nitrogen fertilizer improved fruit size and market value, but average fruit size in all treatments remained relatively small in both years, indicating that N fertilization alone may not increase fruit size in `GoldRush.'
James M. Wargo, Ian A. Merwin and Christopher B. Watkins
`Jonagold' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] often fail to develop adequate red coloration at maturity and become soft and greasy in storage. During two growing seasons, we tested factorial combinations of three preharvest treatments affecting `Jonagold' quality at harvest and after storage: 1) three nitrogen (N) treatments [36 kg·ha-1 soil applied N, 6.9 kg·ha-1 of urea-N (1% w/v) in foliar sprays mid-May and June, or no N fertilizers]; 2) trunk girdling in early August each year; and 3) foliar applications of aminoethoxyvinylglycine (AVG, formulated as ReTain) 3 weeks before the first scheduled harvest. Fruit were sampled at four weekly intervals each year and evaluated for maturity and quality at harvest and after storage. Foliar urea and soil-applied N delayed red color development in 1998 but not 1999, increased fruit size in girdled and nonAVG treated trees in both years, and increased greasiness in 1999 only. AVG reduced fruit greasiness after storage both years. Nitrogen uptake was reduced in the dry Summer 1999, but N treatments still increased poststorage flesh breakdown. Mid-summer trunk girdling increased red coloration and intensity both years and improved market-grade packout. This effect was not caused by advanced maturity, although trunk girdling slightly increased skin greasiness. Girdling reduced fruit size only on trees of low N status. The AVG applications delayed maturity and red color development by 7 to 10 days in both years compared with untreated fruit. In 1998, the combination of AVG and N fertilization delayed red color development more than either treatment alone. Fruit softening and greasiness were reduced in AVG-treated fruit harvested at the same time as untreated fruit, but this effect was not observed when AVG treated fruit were harvested at comparable maturity 7 to 10 days later. Trunk girdling and withholding N fertilizer were the best treatments for enhancing red coloration, and foliar N concentrations of ≈2.0% (W/W) resulted in better packouts compared with higher leaf N levels. AVG was an effective tool for delaying fruit maturity and maintaining fruit quality awaiting harvest, but not for improving red coloration of `Jonagold' apples.
Steven McArtney, Duane Greene, Terence Robinson and James Wargo
Freeze events during bloom can be a relatively frequent occurrence in many apple (Malus ×domestica) production areas in the United States that significantly reduce orchard productivity and profitability. This study investigated the potential for a proprietary mixture of gibberellin A4 + A7 and 6-benzyladenine (GA4+7 plus 6-BA) to increase fruit set and cropping of apple following freeze events at three locations across the United States during bloom in 2012. GA4+7 plus 6-BA increased fruit set in two of five experiments, and increased fruit number and yield per tree in three of five experiments. GA4+7 plus 6-BA increased fruit set and yield of ‘Taylor Spur Rome’ following freezes on two consecutive days during bloom when the minimum temperature reached 23.9 and 28.4 °F. Fruit set was increased due to a stimulation of parthenocarpic fruit growth. Using locally obtained market prices, GA4+7 plus 6-BA treatments increased the crop value of ‘Taylor Spur Rome’, ‘Ginger Gold’, and ‘Jonagold’ by $3842, $977, and $6218 per acre, respectively. Although GA4+7 plus 6-BA application(s) after a freeze increased fruit set and cropping in some instances, tree yields were well below the average yields previously obtained in the test orchards.