Fruit Russet Research Articles

Strong synergistic effects of gibberellins with the synthetic cytokinin N-(2-chloro-4-pyridyl)-N-phenylurea on parthenocarpic fruit set and some other fruit characteristics of apple

The induction of parthenocarpic fruit set was investigated using the apple cvs. Golden Delicious and Jonagold. The gibberellins GA3, GA4, GA5 and GA7 and the synthetic phenylurea-type cytokinin CPPU (N-(2-chloro-4-pyridyl)-N-phenylurea), were applied alone and in combination to unpollinated flowers at the end of petal fall. Gibberellins induced only a marginal final set of parthenocarpic fruits. CPPU sprays were more effective, particularly in the first year. When applied in combination, CPPU and gibberellins had a positive synergistic effect on parthenocarpic fruit set and fruit size, but a negative effect on flower induction the next year. After CPPU + GA sprays, percent fruit set was similar, or greater, compared to natural pollinated trees. The parthenocarpic fruits induced by CPPU + GA had an increased length to diameter ratio. CPPU stimulated, and GA4 and GA7 reduced, the russeting of the parthenocarpic fruits. The internal quality of the fruits was hardly affected, but Ca-deficiency symptoms occurred more frequently in parthenocarpic fruits.

186 INFLUENCE OF HYDROGEN CYANAMIDE AND WILTH IN ON BLOSSOM THINNING OF APPLE AND PLUM

Effects of hydrogen cyanamide and Wilthin on blossom thinning and the consequences of thinning on fruit set, yield and fruit quality of `Rome Beauty' was studied. A full bloom application of hydrogen cyanamide at the rate of 0.25% (Dormex formulation) or 0.25% of Wilthin both followed by a fruit thinning by Sevin + NAA effectively thinned mature trees of `Rome Beauty' and had a similar effect on fruit set, yield and fruit quality. The effects of these two chemicals at these rates on several aspects of fruit set, yield and quality were similar to the effects of Elgetol. Hydrogen cyanamide, Elgetol and 0.25% Wilthin at full bloom resulted in a higher percentage of single fruit set, thus, less labor for hand thinning. Application of 0.37% Wilthin at 20% bloom or at full bloom resulted in larger fruit size, but induced fruit russetting. Soluble solids of fruit from trees with Elgetol, 0.37% Wilthin at 20% bloom or at full bloom were higher than fruit from other treatments. Hydrogen cyanamide at 0.50% resulted in a satisfactory level of blossom thinning in `Friar' plums.

CHEMICAL THINNER RESULTS ON `GALA' AND `FUJI' APPLES

`Gala' and `Fuji' apples are being extensively planted and are rapidly becoming important cultivars in California. `Gala' requires early and precise fruit thinning to produce good size and quality fruit. Preliminary studies indicated that this cultivar might be relatively easy to chemically thin with a program similar to that used for the `Granny Smith' cultivar in California. `Fuji' is subject to severe biennial bearing and must be thinned early. However, previous research has shown it to be a difficult cultivar to chemically thin. High rates and/or combinations of materials showed promise of effective fruit thinning of `Fuji' in limited trials in 1992, but not without phytotoxic effects of “pygmy” fruit, reduced fruit size and fruit russetting and marking. More extensive trials with both `Gala' and `Fuji' are planned for 1993 and preliminary results from these trials will be reported at this workshop.

STUDYING THE CAUSE AND CURE OF `ROME BEAUTY' APPLE RUSSETTING

Effects of several growth regulators and mineral nutrient sprays on `Rome Beauty' apple (Malus domestica Borkh.) russetting under climatic conditions of southwest Idaho were studied in the 1990 and 1991 growing seasons. Zinc (Zn-50), Calcium as a 12% liquid nutrient (Stopit-6), and fungicide (Polyram) sprays slightly increased, while GA (Provide) decreased fruit russetting. In 1991, GA and repeated Semperfresh (sucrose ester, carboxymethyl cellulose and mono and diglycerides) applications reduced russetting while Bayleton application increased russetting. Russetting varied from year to year. In 1991, a season of severe fruit russetting, trees which received a fungicide treatment for powdery mildew had generally higher incidence of fruit russetting regardless of treatments. It is believed that interaction between relative humidity, temperature, and systemic sprays used for powdery mildew control contribute to `Rome Beauty' russetting.

Influences of gibberellins A4, A4+7, and A4+iso—A7on apple fruit quality and tree productivity. I. Effects on fruit russet and tree yield components

Mature ‘Golden Delicious’ apple trees in British Columbia (B.C.) and Quebec, Canada and Cox’s Orange Pippin apple in Canterbury, New Zealand were sprayed weekly for four weeks, commencing at petal fall, with formulations of GA4, GA4+7 mixture (1:1) or GA4+iso—GA7 (a less active isomer). This study was predicated on previous work suggesting that GA4 is more effective than GA7 for fruit russet control and is less likely than GA7 to inhibit return flowering. It was hypothesized that conversion of GA7 in the GA4+7 mixture to iso—GA7 might ameliorate the expected negative effect of the GA treatment on return flowering. Surface russet was prevalent on Quebec ‘Golden Delicious’ and all GA treatments reduced its severity. Stem-end russet was reduced by GA4+iso—GA7 in the B.C. ‘Golden Delicious’ trial but none of the treatments influenced stem-end russet of New Zealand ‘Cox’s Orange Pippin’. All G As and GA mixtures reduced fruit set and seed number per fruit and increased average fruit weight in one or more exper...

Effects of simulated acid rain on the foliage and fruit yield ofMalm domesticaBorkh.

The effects of rain acidity on field-grown apple trees (Malus domestica Borkh. cv. Sum- merred) under natural conditions were investigated. One group of four trees was exposed to ambient rainfall. Four other groups were covered with rain-shields and for two growing seasons received simulated rain consisting of deionized water or an acid solution at pH 5.6,4.0 or 3.0 respectively. Simulated acid rain, particularly at pH 3.0, injured leaves and petals, reduced fruit production and impaired marketability. SEM examination showed that damage to the leaves (necrosis and lesions) was most extensive at the moment of full leaf expansion, whereas damage to the fruit (russeting and lesions into the mesocarp) was most severe when the fruit was almost fully ripe. The reduction in production was 19% with the pH 4.0 spray and 37% with the pH 3.0 spray (compared with rainfall-fruit). The acidity of the ambient rainfall encountered in this study caused spotting and necrosis of the leaves but did not significantly affect f...

Apple, Evaluation of Experimental Miticides, 1991

Abstract Treatments were applied to 7 tree plots replicated 4 times in a randomized complete block design. The orchard block consisted of 'Empire', 'Red Delicious', and 'Rome' on M7a, planted in 1982 on a 15 by 18 ft spacing. Replicates 1 and 2 were on 'Red Delicious', while replicates 3 and 4 were on 'Empire'. Sprays were applied with an FMC handgun sprayer using a 5 HP diaphragm pump at 280 psi until run off, with approx. 4 gal of spray applied to each tree. One application of Pydrin 2.4 EC 178 ml/100 gal was made on 6 Jun in order to build mite populations, since few mites were present early in the season. Miticides were applied on 1 Jul and again on 10 Jul. Conditions during applications were 75°F on both dates, with 2 mph winds and cloudy skies on 1 Jul, and 2-4 mph winds and clear skies on 10 Jul. Treatments were as follows: 1) BAS 300 00 I 20 WP .05 lb AI/100 gal, 2) BAS 300 00 I 20 WP . 12 lb AI/100 gal, 3) BAS 300 11 I 75 WP .05 lb AI/100 gal, 4) BAS 300 11 I 75 WP . 12 lb AI/100 gal, 5) Omite (propargite) 30 WP .60 lb AI/100 gal, and 6) Omite 30 WP .30 lb AI/100 gal, 7) Untreated. ERM counts were taken in samples of 15 leaves per tree on 7 Jun (pre-treatment), and again on 3, 8, 15, 22, 29 Jul, and 5, 12 Aug. SP populations were evaluated on 12 Aug. Predacious mites and beetles were not present early in the season, since they had been eliminated by the Pydrin application. Fruit finish was evaluated by taking 30 fruit from each tree and evaluating for fruit russet on a 0 to 5 basis. Values were used as follows: 0 = no russet, 1 = raised lenticels, 2 = 1-10% russeted, 3 = 11-15% russeted, 4 = 16-50% russeted, and 5 = >51% russeted. Each fruit was evaluated, and an average per replicate was used in the calculations.

Effect of Chemical Thinning Sprays on Apple Fruit Set

Apple growers of different regions need different chemical fruit-thinning responses for thinning trees of different tree ages, cultural conditions, rootstocks, climates, and amounts of fruit removal desired. In this research, a range of chemical thinning responses was achieved by combinations of thinning materials or addition of potentiating agents. Superior oil, certain organic phosphates, and a light-absorbing agent (ferbam, a fungicide) increased the thinning of carbaryl. In addition, combinations of 50 or 200 ml 6-BA/liter + carbaryl + oil defruited `Campbell Redchief Delicious'/M.111 trees, and 50 ml 6-BA/liter alone over-thinned in one year (however, oil or 6-BA has been shown previously to cause russet in `Golden Delicious'). Carbaryl 50 WP and the 4L carbaryl formulations were equally effective for thinning `Golden Delicious', `Stayman', and `Redspur Delicious', and did not affect fruit russet. Three days of cloudy weather is typical at least once in most seasons in the eastern United States during the fruit set period. Two days of artificial polypropylene shading (92%) (which was nearly equivalent to 3 days of cloudy weather) caused more thinning of `Golden Delicious' and `Stayman' than carbaryl or 10 mg NAA/liter + Tween. Shading reduced viable seed numbers about 50% for `Golden Delicious' in fruit remaining at harvest, but chemical thinning agents (NAA or carbaryl) did not affect viable seed number.

Citrus Rust Mite Control on ‘Hamlin’ Orange, 1989

Abstract The experiment was conducted with a completely randomized block design with single tree plots and 5 replications. Treatments were applied with a truck-mounted handgun sprayer at 400 psi on 30 May. Numbers of CRM on fruit were counted within 2-1 cm2 using 10X handlens on opposite sides of 20 fruit/replicate. Cumulative mite days after treatment and percent fruit russet was determined after 12 wk.

Perspectives on Wound Healing in Resistance to Pathogens

Precise information about wound responses in plants is essential for un­ derstanding the processes that facilitate or interfere with the development of many diseases. Since many serious diseases are induced by pathogens that gain entrance through wounds, such information will likely reveal opportuni­ ties for innovative control measures based on modification of the host re­ sponse. Recent advances in biochemistry and molecular biology are shedding light on the nature and importance of signal molecules exchanged between host and pathogen in wounded tissues, and on the regulation of wound metabolism (72). Indeed, plant responses to wounding and to infection by pathogens are often similar in many ways, which suggests the participation of common signals. The corky lesions and barriers observed in diseases such as fruit russeting and the shotholc diseases affecting Prunus spp. share the anatomical features of wound periderms, and many of the chemical and structural barriers associated with expression of resistance to pathogens are also induced by mechanical injury (3, 104). A wound, in the context of this article, is any external or internal injury that breaches the outer protective layers of the plant and leads to the destruction of cells in a specific area of tissue. Implicit in this definition is the physical rupturing of cells with concomitant loss of compartmentation (50, 81).

Citrus Rust Mite Control on Grapefruit, 1988

Abstract A completely randomized block design with single tree plots replicated 4 times was used with buffer trees sprayed to prevent possible mite reinfestation. Treatments of 235 gal/acre were applied on 15 Jun with a high pressure handgun sprayer at 400 psi. CRM were counted in 2-1 cm2 using a 10 X hand lens on opposite sites of 25 fruit selected at random from each tree. There were 100 fruit/treatment. Cumulative mite days after treatment and percent fruit russet was determined after 10 wk.

Effect of Early Sprays on Control of Powdery Mildew Fruit Russet on Apples

Effect of Early Sprays on Control of Powdery Mildew Fruit Russet on Apples

Effect of Early Sprays on Control of Powdery Mildew Fruit Russet on Apples

Effect of Early Sprays on Control of Powdery Mildew Fruit Russet on Apples

Effectiveness of a Soft-Pesticide Program on Pear Pests1

During 1980 and 1981, spray programs using soft pesticides were compared with programs using pesticides normally applied to commercial pear orchards in central Washington for the control of the insect-mite pest complex. In 1980, all pest species present except pear psylla, Psylla pyricola Foerster, were held below damaging densities by both soft and standard programs or by predators and parasites that survived. In the soft-pesticide plot, two prebloom sprays of petroleum oil and four postbloom tree washes failed to prevent serious fruit russetting by honeydew from pear psylla. In the standard program, fenvalerate and oxythioquinox sprays before bloom and three postbloom sprays of amitraz provided better control of this pest than did the oil sprays and tree washes. In 1981, both soft and standard programs controlled all pest species present. In the soft plot, pear psylla density was kept below damaging level by two prebloom petroleum oil sprays and four postbloom sprays of mancozeb. Codling moth, Cydia pomonella (L.), was controlled in the soft plot by four cover sprays each year of diflubenzuron in 1980 or Bay Sir 8514, 2-chloro-N-([L(4-trifluoromethoxy)phenyl]amino)carbonyl benzamide) in 1981. Azinphosmethyl applied on a similar schedule in the standard plot also provided good codling moth control. Densities of major predators of pear psylla were higher in the soft than in the standard plot, but not as high as those in the untreated check.

Effect of Nitrogen and Daminozide on Shoot Growth for Pear Psylla Suppression and on ‘Bartlett’ Pear Performance1

Abstract Three consecutive annual nitrogen applications on trees of ‘Bartlett’ pear (Pyrus communis L.) at 120 kg/ha increased leaf N, shoot growth, number of expanded shoot leaves, crop density, fruit size, and yield compared to no N. N application without butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) increased late bloom and fruit russet associated with pear psylla honeydew. Daminozide at 2 g/liter sprayed twice annually for 3 years, 30 and 50 days after bloom with or without N application, reduced minal growth, number of expanded shoot leaves, late bloom, fruit size, density of psylla nymphs, (Psylla pyricola Foerster) and fruit russet from psylla honey dew. The effects of N and daminozide on tree growth, fruit size, and yield, as well as on psylla density, varied from year to year. Daminozide can reduce shoot growth of pear and subsequently reduce psylla densities and resultant damage but with some reduction in fruit size.

Fruit Russeting in Apple as Affected by Various Gibberellins

SummaryThe effects of GA3, GA4, GA7, and GA4+7 on apple fruit russeting were studied on the cvs Karmijn de Sonnaville and Golden Delicious. Four sprays of 10 ppm a.i. applied at 10-day intervals from the end of flowering were compared. Fruit russeting was reduced by all gibberellins in Karmijn and by all but one (GA3) in Golden Delicious. GA4 appeared slightly more effective than GA7, and in Karmijn GA7 was better than GA3. Differences between GA4 and GA4+7 were small. Fruit number per tree was generally not affected by the treatments, and only in one trial was a slight thinning effect observed. Fruit growth was slightly stimulated by some treatments, and flower-bud formation was affected negatively by the gibberellin treatments in two of the four trials. Results pertaining to fruit russeting, fruit bearing, fruit growth and flower-bud formation are briefly discussed.

Citrus Rust Mite Control with Avermectin B1, 1981

Abstract Avermectin, citrus oil spray (Sunspray 6N), and avermectin with citrus oil were compared to Vendex for efficacy against the citrus rust mite (CRM). Treatments were completely randomized and replicated on 4 single-tree plots of Ruby Red grapefruit on 30 ft x 25 ft spacing. All treatments were applied initially on May 29 with a John Bean Model 1010-MTBYT sprayer hand-gun at 225 psi, ca 10 gal/tree. Treatments were not reapplied until residual control of CRM was lost. At each count date, 25 fruit/replicate were randomly selected and CRM counted in a 1 cm2 lens field at 10X on the top, medium and bottom of each fruit. CRM counts were terminated after Sep 2 due to extensive fruit russet and low CRM populations in the untreated control. Fifty fruit/replicate were randomly selected and evaluated for CRM damage. Damage was expressed as percent russet, i.e. fruit with moderate to severe damage (US#2 fresh or process fruit).

Pear Psylla: Relationship of Early-Season Nymph Densities to Honeydew-Induced Fruit Damage on Two Pear Cultivars13

The relationship of early-season densities of nymphs of Psylla pyricola Foerster to honeydew-induced fruit russet was measured on D’Anjou and Bosc pear cultivars in southern Oregon. Overall, fruit injury ratings based on percent downgrading caused by psylla honeydew indicated D’Anjou to be ca. fivefold more susceptible to damage induced by equivalent nymph densities than Bosc. An average nymph density of 1.0 per leaf resulted in ca. 2.5 and 17% downgrading on the Bosc and D’Anjou varieties, respectively. This difference was attributed to the nature of the pear cultivars, with damage being more apparent on the clear skinned D’Anjou compared with that on the normally russeted Bosc.

Potential of Tree Washes as a Management Tactic Against the Pear Psylla12

The effects of tree washes on populations of Psylla pyricola Foerster and fruit quality were examined. Handgun applications of tree washes removed pear psylla honeydew and reduced fruit russet. In addition, tree washes which contamed a wetting agent increased mortality of pear psylla nymphs. Tree washes applied by a speed sprayer were as effecttve as handgun washes in removing pear psylla honeydew. Tree washing holds promise as a tactic to be integrated with biological and chemical control to manage arthropod pests of pear in north central Washington.

Effects of Gibberellin Sprays on Fruit Russet and Tree Performance of Golden Delicious Apple

SummaryFoliar sprays of GA4+7 applied at petal fall (PF) were more effective than GA3 sprays at equivalent concentrations for reducing fruit russeting on mature Golden Delicious trees. Early GA4+7 sprays (close to PF) were more beneficial than late GA4+7 sprays (3 to 4 weeks after PF) for controlling fruit russeting on young Golden Delicious trees. Though higher concentrations of GA4+7 reduced fruit set, increased shoot extension growth and reduced return bloom (young trees only), dilute sprays (e.g. 10 ppm) applied close to PF improved skin finish largely without harmful side effects.