Cork Spot Research Articles

Calcium sprays, time of harvest, and duration in cold storage affects fruit quality of d'Anjou pears in a critical year

Calcium chloride (CaCl2) sprays increased calcium (Ca) concentrations in d'Anjou fruit (Pyrus communis L.), reduced the incidence of cork spot and improved shelf‐life by increasing fruit firmness in a critical year that had lower fruit Ca concentrations due to record high spring and late season temperatures. The third and final harvest in late September resulted in larger fruit size, lower fruit Ca concentrations, higher incidence of cork spot, more extractable juice and yellow fruit skin color, higher soluble solids and sucrose concentrations, but lower acidity than earlier harvested fruits. Fruit held longer in cold storage (145 days) had higher concentrations of fruit Ca, lower concentrations of carbon dioxide (CO2) and ethylene (C2H4), less fruit firmness, soluble solids and acidity, lower concentrations of sucrose, glucose and fructose, and less green color of fruit skin than short term storage (45 days). Shelf‐life of CaCl2‐sprayed fruit was improved because of higher concentrations of fruit Ca that resulted in a lower incidence of cork spot and brown core, fruit firmness was higher, levels of CO2 and C2H4 were lower, and soluble solids, acidity, and extractable juices were affected less for ripened fruit.

COMPARISON OF AMYLASE ACTIVITY AND STARCH CONTENT IN NORMAL AND CORK SPOTTED 'D 'ANJOU'PEARS

Amylase activity and starch content were measured in preharvest calciumtreated and nontreated normal and cork spotted ‘d ‘Anjou’pear fruit prior to and at commercial harvest maturity. Activity of amylase extracted from cork spotted fruit was about 1.8 fold higher as compared to amylase extracted from normal tissue during harvest. Starch contents were less in cork spotted than in normal fruit as evidenced either by a visible iodine stain technique or by quantitative analysis. Amylase activity from calcium-treated pears was greater than that extracted from normal pears. Fruit calcium levels were higher in normal as compared with cork spotted fruit but the calcium content of calcium-treated fruit was no different from their nontreated counterparts. Visible cork spot was not detected until 12 days prior to harvest.

Response of apple and pear trees to nitrogen, phosphorus, and potassium fertilizers

Apple (Malus domestica, Borkh) and pear (Pyrus communis, L.) trees responded to nitrogen (N), phosphorus (P), and potassium (K) fertilizers. In low P soils, leaf, and fruit P concentrations were increased and yield was improved with moderate rates of mono‐ammonium phosphate (MAP) fertilizers. Improved fruit quality including fruit firmness, red fruit color of ‘Delicious’ apples, and a lower incidence of fruit disorders of apples (bitter pit) and pears (alfalfa greening and cork spot) was frequently associated with trees that were fertilized with calcium nitrate [Ca(NO3)2] (CN). Although yield was often improved in experiments containing N‐P‐K or MAP fertilizers, long‐term use of N‐P‐K or MAP could be associated with a higher incidence of fruit disorders and a lower soil pH than with CN fertilizer at equivalent rates of N.

Response of apple and pear trees to phosphate fertilization: A compendium

Earlier reports in the literature indicated that responses to phosphate (P) fertilization of apple and pear trees were rare. Yet more recently in orchard soils low in available P or in leaves with low P concentrations, greenhouse and orchard trials showed a marked response to applications of monoammonium phosphate (MAP) fertilization. Trees receiving MAP fertilizer frequently resulted in improved tree vigor, fruit production, and in some cases fruit quality. Our experimental trials indicated that apple and pear trees responded to soil‐surface applications of MAP fertilizer rates, but excessive usage may result in low soil pH or a high incidence of bitter pit in apples or cork spot in ‘d'Anjou’ pears.

Cold tolerance, yield, and fruit quality of ‘d'Anjou’ pears influenced by nitrogen fertilizer rates and time of application

Low and moderate rates of ammonium nitrate (NH4NO3) fertilizer were applied in late winter or late summer to mature ‘d'Anjou’ pear (Pyrus communis, L.) trees (planted 1963, 1965) from 1976 to 1994. Data on cold tolerance, nutrition, yield and fruit quality in relation to nitrogen (N) fertilization were collected between 1980 and 1988. Early autumn cold tolerance was higher for trees receiving low N rates versus moderate N rates in either late winter or late summer. In late autumn and early winter, cold tolerance increased for all trees, and little difference in winter hardiness existed for any N treatment. By mid‐winter, cold tolerance was higher for trees receiving the moderate rate of N in late winter versus low N in late summer. Cold tolerance was relatively high throughout autumn and winter freeze‐test periods for trees fertilized with low N in late winter. Tree vigor, fruit size, leaf N, and fruit N were highest for trees receiving the late winter, moderate rate of N. Yield was lowest, but fruit firmness, fruit quality and fruit calcium (Ca) concentrations were highest for trees treated with the late winter, low rate of N. The incidence of cork spot was lower from trees with the late winter, low N treatment than for the late summer, moderate N‐treated trees.

Emitter Placement and Calcium Plus Boron Solution Affect Elemental Content of Spur `Delicious' Apples

Physiological disorders of apples, such as cork spot and bitter pit, are a result of low soil calcium, low or excessive soil moisture, large fruit size, and environmental conditions. We report on the effect of microirrigation treatments on apple fruit when irrigation is applied as water alone or water plus a calcium (Ca)/boron (B) solution with applications applied over the tree canopy or under the tree canopy. Apples were harvested from trees in their 4th to 7th leaf and the number of fruit and size of fruit varied from year to year. In most years, there were no significant differences among treatments for fruit Ca. Fruit B was significantly higher in treatments where B was applied through the irrigation. Fruit N/Ca levels were lower when the fruit size was smaller, which was due to a higher number of fruit per tree. Year to year variations in fruit Ca levels also were likely to temperature, humidity, rainfall, fruit size, and shoot growth.

Yield Increased and Fruit Disorders Decreased with Repeated Annual Calcium Sprays on 'Anjou' Pears

Yield of 'Anjou' pears, Pyrus communis L, was increased with repeated annual (9-13 years) calcium chloride (CaCl2) sprays. The incidence of fruit disorders (alfalfa greening and cork spot ) was decreased by CaCl2 sprays with or without Regulaid but some minor calcium spray phytoxicity occurred on fruit and leaves. Fruit calcium concentrations in peel and cortex were increased with calcium chloride sprays; however, these sprays had little or no effect on leaf weight, fruit size, leaf Ca concentrations, tree vigor, shoot growth, fruit firmness, soluble solids, titratable acids, fruit color, fruit rots, or storage scald. This study suggested that long-term calcium chloride sprays of 60.5 g Ca per 100 liters of water or 33 to 44 kg CaCl2 per ha should provide the pear grower with a means of not only controlling fruit disorders but also for increasing 'Anjou' pear yield.

Calcium nutrition affects cold hardiness, yield, and fruit disorders of apple and pear trees1

Abstract Foliar sprays of calcium chloride (CaCl2) and to a lesser extent, soil applications of calcium nitrate [Ca(NO3)2] fertilizer, increased calcium (Ca) concentrations in leaves and fruit of apple, (Malus domestica) and pear (Pyrus communis L.) trees. For most years, CaCl2 sprays or Ca(NO3)2 fertilizer increased cold hardiness of ‘Anjou’ pear trees, and reduced the incidence of fruit disorders (alfalfa greening and cork spot of pears and bitter pit of ‘Delicious’ apples). Yield of ‘Anjou’ pears was usually increased with the higher rates of nitrogen (N) fertilizers [ammonium nitrate (NH4NO3), Ca(NO3)2, or urea]. Calcium chloride sprays increased yield of ‘Anjou’ pears if it was applied over many years.

Packout Audits of Apples from Five Orchard Management Systems

Apple packout audits were conducted during 1991 to 1993 to assess effects of five orchard systems (three cultivars, two age groups) on fruit packout and determine if relationships exist between light quality and productivity. Cultivar/rootstock combinations on 1979 T-trellis and central-leader systems had the lowest light levels and relative yields. Trees on either 1979 3-wire trellis, 1986 MIA, or 1985 West Virginia spindle had the highest light transmission, and trees on 1979 or 1985 West Virginia spindle systems had the highest yields. Extra fancy/fancy packouts across systems ranged from 40% to 85%. `Empire', regardless of system, had the highest packouts, and `Golden Delicious' on 1979 or 1986 central leader had the lowest packouts. A regression analysis comparing percentage packout in grades below fancy to percentage full sun indicated that reduced packouts were related to low light conditions. Orchard system influenced the number of fruit downgraded due to color, russet, bruises, bitter pit, cork spot, apple scab, rots, sooty blotch/fly speck, and tufted apple budmoth. Regression analyses comparing defects to field data indicated that bitter pit decreased as yield efficiency increased, and rot and sooty blotch/fly speck incidence were related to low canopy light penetration. Revenue losses were disproportionate to percentage of downgraded fruit because some defects had a greater impact on grade than others. The greatest revenue losses were for russet in `Golden Delicious' on 1986 central leader ($1656.60/acre) and for bitter pit in `Golden Delicious' on 1979 T-trellis ($1067.30/acre). Total losses in returns for individual systems ranged from $453.71/acre for `Empire' on 3-wire trellis to $3145.49/acre for `Golden Delicious' on 1986 central leader. The comparisons of young versus mature system yields and packouts indicate that medium- to high-density vertical or inclined canopy systems are superior to horizontal or low-density vertical freestanding systems. The cost-benefit analyses prescribe areas where management can be changed in existing systems to increase profitability.

Calcium Sprays and Timing Affect Fruit Calcium Concentrations, Yield, Fruit Weight, and Cork Spot of `Anjou' Pears

Calcium sprays (CaCl2, Mora-Leaf-Ca + Link Ca, or Stopit) increased fruit Ca concentrations and reduced the incidence of cork spot of `Anjou' pears (Pyrus communis L.) during four seasons. All Ca sprays increased yield relative to the control. All sprays resulted in some injury to leaves and fruit, but fruit was acceptable for marketing. At the low rate, Stopit sprays were the least injurious. Early season sprays, in June to July, produced less leaf and fruit injury than late-season sprays, in July to August, or early + late-season sprays. Early or late-season Ca sprays resulted in slightly larger fruit than early + late sprays. Either late or early + late-season sprays led to higher Ca concentrations in fruit cortex than early sprays.

Influence of different calcium materials and spray timing on mineral composition, yield, fruit quality, and control of fruit disorders of ‘anjou’ pears

Abstract During a six‐year period (1980, 1985–1989), 20 different calcium (Ca) materials were sprayed at an early (3X; June to July), late (3X; July to August), and an early plus late (5X; June to August) timing on 25‐year‐old ‘Anjou’ pear (Pyrus communis L.) trees. Calcium chloride (CaCl2) sprays increased fruit Ca in the cortex by an average of 10.5% greater than in unsprayed controls and cork spot was reduced by an average of six‐fold. Yield from trees sprayed with Ca materials averaged greater than 13% more crop load than the unsprayed control trees. Leaf and fruit injury from CaCl2 sprays in 1980 were near borderline acceptability, but injury was reduced slightly by halving the spray concentration rate to 681 g CaCl2 per 379 liters of water in 1985 to 1989. Due to temperatures above 26°C, leaf and fruit injury from Ca sprays, particularly calcium nitrate [Ca(NO3)2], were more severe for the late or early plus late sprays than for the early sprays. Fruit size was slightly larger on trees sprayed only ...

Effects of preharvest calcium sprays on apple and pear quality

Abstract Fruit from apple (Malus domestica Borkh.) and pear (Pyrus communis L.) trees sprayed with calcium chloride (CaCl2) had higher fruit calcium (Ca) concentrations by 10% or more than the unsprayed control trees. In ‘Delicious’ and ‘Golden Delicious’ apples, the incidences of bitter pit, scald, and internal breakdown were substantially reduced with CaCl2 sprays. In most instances, firmness, total acidity, and juiciness ratings of apples were improved with CaCl2 sprays. In ‘Anjou’ pears, the incidence of cork spot was reduced with CaCl2 sprays. Only sprays of NutriCal and CaCl2 + Regulaid showed substantial increases in fruit firmness of ‘Anjou’ pear. In 1991, yield of ‘Anjou’ pear trees was increased by 36% with CaCl2 sprays compared with the control trees.

CPPU Influences Fruit Quality, Fruit Set, Return Bloom, and Preharvest Drop of Apples

CPPU was applied to whole spur `Delicious' apple (Malus domestica Borkh.) trees in central Washington at 0,6.25,12.5,25, or 50 mg·liter-1 at full bloom (FB) or FB plus 2 weeks. At both application times, the flesh firmness of treated fruit linearly increased with increasing concentration. CPPU applied at 0,5,10,15, or 20 mg·liter-1 to spur `Delicious' trees in Massachusetts at king bloom resulted in a linear increase in flesh firmness at harvest and following 28 weeks in air storage at 0C. CPPU did not affect the incidence of senescent breakdown, decay, or cork spot. Fruit length: diameter (L/D) ratios generally increased at all doses. Fruit weight was not influenced at either location. All CPPU concentrations reduced return bloom on `Delicious' apples in Massachusetts in 1989. Of the 10, 20, or 40 mg·liter-1 treatments for `Empire' apples, only CPPU at 40 mg·liter-1 reduced return bloom. CPPU applied to `Empire' apples in Massachusetts did not effect fruit set, soluble solids concentration, L/D, or firmness; however, fruit weight increased linearly with concentration. CPPU applied at 100 mg·liter-1 retarded preharvest fruit drop of `Early McIntosh' in Massachusetts for ≈7 days but was not as effective as NAA at 20 mg·liter-1. In a larger semicommercial trial, `Delicious' fruit treated with CPPU at 5,10, or 15 mg·liter-1 at FB, petal fall (PF), or PF plus 1 week, respectively, were harvested and graded over a commercial packing line. Malformities caused by CPPU at the highest doses reduced packout, although all CPPU application rates reduced the percent fruit culled due to poor color. CPPU increased packed fruit size, since the size of fruit (64 mm in diameter) in the >150-fruit/box size decreased, while the size of fruit (72 mm in diameter) in the 100- and 130-fruit/box sizes increased. Treated fruit stored for 7 months at 1C were firmer than nontreated controls. Chemical names used: N-(2-chloro-4-pyridyl)- N' -phenylurea (CPPU); 1 naphthalene-acetic acid (NAA).

EFFECTS OF SEVERAL GROWTH CONTROLLING TECHNIQUES ON APPLE TREES

In 1991, experiments were conducted to assess the effects of several growth controlling techniques on tree growth and fruit set, abscision, ripening, and other qualities. The first two experiments assessed the effects of root pruning (4-8 days after petal fall, 1 m from the trunk, 30 cm deep) in commercial orchards. Compared to controls, root pruning reduced fruit abscision from mature `Cortland'/M.7A trees by 70% on 17 Sept. In another orchard, root pruning reduced fruit abscision from mature `McIntosh'/MM.106 trees by 47% on 24 Sept. The third experiment utilized vigorous `Gardiner Delicious'/MM.106 trees. Treatments included root pruning (as described above), trunk scoring (single, complete circle, approximately 40 cm from the soil), trunk ringing (single, complete circle, 1 mm wide, approximately 40 cm from the soil), ethrel spray treatment (500 ppm), and dormant-pruned and unpruned controls. Treatments were applied on 15 May, when terminal growth was 12-15 cm. No treatment affected fruit set. Trunk growth was less for ringed and scored trees than other treatments. Ringing and scoring advanced ripening compared to controls, and ethrel resulted in intermediate ripening. Treatments had no effect on fruit size, flesh firmness, or the development of bitter pit and cork spot. Fruit abscision was least from controls and root-pruned trees. Trees that were treated with ethrel in May had the most rapid abscision rate.

DESORDENS FISIOLÓGICAS EM MACIEIRA INDUZIDAS POR DEFICIÊNCIA DE CÁLCIO E SEU CONTROLE

Muitas das desordens fisiológicas que afetam os frutos estão relacionadas com baixo conteúdo de cálcio nos tecidos, sendo sua ocorrência diminuída quando há incremento deste nutriente. A deficiência de cálcio em madeira afeta os frutos que apresentam manchas de cortiça próximos a colheita e durante a frigoconservação. Em vista disto, é importante o estudo sobre a absorção, distribuição e funções bioquímicas, bem como a apresentação de alternativas para prevenir ou reduzir desordens fisiológicas causadas por deficiência de cálcio em macieira.

CORK SPOT IN PEAR FRUIT

Cork spot is a serious physiological disorder in pear (Pyrus communis L. cv. d'Anjou) in the United States, but a reliable technique for diagnosing it has not been developed. A review of the scientific literature indicated the disorder was generally linked with low calcium concentration in the fruit. In the present study, mineral analyses were conducted in 1987 and 1988 on soil, leaves, and fruit peel from normal trees and trees prone to cork spot. Soil tests and leaf analysis did not provide measureable differences between the two groups of trees. Fruit analysis provided variable differences between normal and cork spotted fruit, but no single nutrient or ration of nutrients could be consistently associated with the disorder. An assay for pyruvate kinase was evaluated as a diagnostic tool for cork spot. The assay did not provide measureable differences between normal and cork spotted fruit. An important finding of this study was to learn cork spotted fruit had higher soluble protein concentration than normal fruit.

Reduced Rates and Multiple Sprays of Paclobutrazol Control Growth and Improve Fruit Quality of `Delicious' Apples

`Gardiner Delicious'/MM.lO6 apple (Malus domestics Borkh.) trees were initially sprayed in 1985 with paclobutrazol (PB) at 250 mg.liter-1 at tight cluster and again on 10 and 25 June and 29 July. From 1986 through 1988, PB sprays of 85 or 100 mg·liter-1 were applied at either petal fall (PF) + 2 or PF + 4 weeks and one to two additional sprays were applied per year when growth resumed. Promalin was applied to one group of trees that received PB starting at PF + 2 weeks. PB reduced terminal, lateral, and total shoot growth the year of application and in subsequent years. Although average shoot length of lateral and terminal shoots was reduced, the greatest reduction in growth occurred because PB prevented spurs from growing into lateral and terminal shoots. Compared to unsprayed trees, PB reduced pruning time in all 4 years by 23% to 70%. PB increased bloom only the first year after application, but increased fruit set for 2 years due to a carryover effect. Application of PB in 1985 caused a reduction in fruit size, sometimes in soluble solids concentration, length: diameter (L : D) ratio, and pedicel length. Promalin either overcame the reduction in the ratio or increased it in 1986. Reduced rates of PB in subsequent years caused few adverse effects on the fruit. PB increased flesh firmness when applied at PF + 2 weeks but not at PF + 4 weeks. Trees treated with PB produced fruit with higher flesh Ca and less bitter pit, cork spot, and senescent breakdown following regular air storage. Chemical names used: ß -(4 -chlorophenyl)methyl α -(1,1-dimethylethyl) -1H-l,2,4-triazole-1-ethanol (paclobutrazol, PB); gibberellins A4+7 plus N-(phenylmethyl) -1H-purine-6-amine (Promalin).

Nectarine Pox: A Disorder of Nectarine Fruit

“Nectarine pox” is a disorder that reduces packout of commercially grown nectarines [Prunus persica (L.) Batsch Nucipersica (Schneid)]. Although accounts of the occurrence of nectarine pox are widespread across fruit growing regions and cultivars, we found no studies describing it in the literature. The disorder is characterized by superficial warty outgrowths (Fig. 1) and, in some years, may occur on 20% to 80% of the fruit in an orchard block. Suggested causal agents include low levels of B or a virus (S. Johnson, personal communication). The expression of the disorder follows a trend similar to that of cork spot on apple. Nectarine pox is not observed every year in an orchard; it tends to be most severe when the crop load is light, shoot growth is excessive, N, K, and/or Mg levels are excessive and Ca and/or B levels are low. We have studied nectarine pox in West Virginia in a block of ‘Firebrite’ nectarines since 1984. Symptoms initially are observed 40 days after anthesis, sometimes as a pale white or light-colored circular spot 0.5 to 1.0 mm in diameter but more often as a slightly raised area similar in color and surface texture to the surrounding epidermal tissue. At this stage the

Pyruvate Kinase Activity and Protein Concentration in `d'Anjou' Pear Fruit with Cork Spot

An assay for pyruvate kinase (PK) was tested as a diagnostic tool for cork spot, a major physiological disorder in pear Pyrus communis L. cv. d'Anjou) fruit. PK activity and Ca and protein concentrations were measured in peel of normal and affected fruit during selected months in 2 years. Protein concentration was more closely associated with cork spot than PK activity or Ca concentration. These preliminary results suggested the PK assay was a poor diagnostic tool for cork spot.

リンゴ果実のコルク•スポット及びビター•ピットの形態的差異

Cork spot and bitter pit are the main spotting disorders of apple fruit in Japan, but it is difficult to separate these two disorders macroscopically, as intermediate symptoms are sometimes found. In this paper, the morphology of both disorders was compared microscopically and macroscopically.Under climatic conditions of the Morioka district, cork spot appeared at the immature stage of fruit development, from mid-August to early September, while bitter pit appeared at the mature stage and during storage.When analysed microscopically, it was found that cell collapse in the discolored cortical tissue of bitter pit was more severe than in that of cork spot.When examined during the harvest season, intact cells in the discolored tissue of cork spot affected fruit were significantly smaller than those of the neighboring sound tissue. This may be due to a retardation of cell enlargement in the discolored tissue after the occurrence of the disorder. In contrast, no difference in cell sizee were found between the discolored and sound tissues in fruit affected by bitter p t which appeared after the mature stage.Starch grains in the discolored cortical tissue of cork spot disappeared just after the occurrence of the disorder.Small, specialized cells, approx. 50μm in diameter, appeared in the intercellular space of the discolored cortical tissue of cork spot. In rare cases, a layer of these small cells surrounded the discolored tissue. Formation of these small cells may have been stimulated by tissue injury caused by the disorder. A similar type of small cells was also found arround mechanically crushed cortical tissue.No small cells were found in the discolored cortical tissue of bitter pit. The ability to induce the formation of small cells may have already ceased before the mature stage of fruit development during which this disorder appeared.These microscopic differences between cork spot and bitter pit may be related mainly to the stage of fruit development at which each disorder occurred. The ‘intermediate’type was seldom found when using these differences as the basis of classification.The occurrence of each disorder differed among cultivars and strains. Almost all spots found on ‘Tohko’, ‘Redgold’, ‘York Imperial’and ‘Aori No. 3’were cork spot, and those found on ‘Ohrin’ and ‘Tsugaru’ were due to bitter pit. Both disorders were found on ‘Starking Delicious’, ‘Megumi’, ‘Jonathan’ and ‘Fuji’.Spots caused by cork spot were usually more than 5mm in diameter, while those caused by bitter pit were generally less than 5mm. However, spots of about 3mm in diameter caused by cork spot, and of about 10mm in diameter caused by bitter pit were sometimes found.