Source: N Y AGRICULTURAL EXPT STATION submitted to
CULTURAL AND PHYSIOLOGICAL FACTORS AFFECTING APPLE FLOWERING, FRUIT SIZE, TREE GROWTH AND COLD HARDINESS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0185092
Grant No.
(N/A)
Project No.
NYG-632523
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 1999
Project End Date
Sep 30, 2004
Grant Year
(N/A)
Project Director
Schupp, J. R.
Recipient Organization
N Y AGRICULTURAL EXPT STATION
(N/A)
GENEVA,NY 14456
Performing Department
HORTICULTURAL SCIENCE
Non Technical Summary
The world apple market is becoming increasingly competitive. This project is to improve production practices, leading to increased efficiency and fruit quality.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2021110102025%
2041110102040%
2041115102010%
2051110102025%
Goals / Objectives
General: Enhancing the profitability of apple production in New York by evaluating and optimizing horticultural practices that impact fruit set, return bloom, fruit size, tree growth, and cold hardiness of apple. Specific: 1. Evaluate techniques to increase the precision of chemical thinning and optimize fruit size, and to further define the physiological events underlying chemical thinning. 2. Investigate the effects of fall foliar urea, Apogee, and sterol inhibiting fungicides on the growth, cold hardiness, fruit set, and return bloom of apple, and on the efficacy of thinning treatments. 3. Evaluate the response of promising new apple cultivars to chemical thinners and other plant growth regulators. 4.Evaluate plant growth regulators and defoliation treatments that may avoid or ameliorate the effects of cold injury, and evaluate the inherent cold hardiness and growth periodicity of new apple rootstocks and cultivars.
Project Methods
Studies to evaluate the efficacy of several blossom thinner chemicals will be conducted on both apple and pear. The effect of ammonium nitrate on the response of apple trees to NAA will be evaluated by measuring leaf epinasty, ethylene production, and photosynthesis on young trees in the greenhouse and on thinning response of mature field-grown trees. The effects of chemical thinners containing 6 benzyladenine will be evaluated on apples and pears. The role of ethylene in fruit thinning will be investigated by evaluating the response of apple trees treated with AVG to various chemical thinners and environmental stresses. The effects of fall foliar urea and Apogee on growth, nitrogen reserves, and carbohydrate reserves of apple nursery stock will be evaluated. Fall foliar urea will be compared to spring soil applied nitrogen to determine the best timing and method of application, based upon growth, spur quality and fruit yield and fruit quality. Gibberellin inhibitors and gibberellins will be studied for their effects on fruit set, fruit size and russeting of apple and for possible interactions with chemical thinners. The effects of three sterol inhibiting fungicides on fruit set, fruit size, yield and economic returns of Empire apples will be evaluated. A study to evaluate the effect of various chemical thinners on fruit set, yield, fruit size, and post-harvest fruit quality of Honeycrisp apple will be conducted. The effect of copper chelate and Apogee on the cold hardiness of field grown apple trees and the effect of nitrogen fertilization, cultivars, and rootstocks on cold hardiness of apple will be evaluated using a controlled temperature chamber.

Progress 10/01/99 to 09/30/04

Outputs
Honeycrisp was very sensitive to chemical thinners and easily over-thinned. It was especially over-thinned by 6-bezyladenine thinning sprays, so this chemistry should not be used on this cultivar. Alternate bearing of Honeycrisp wiil not be controlled by chemical thinning alone. A tank mix of lime sulfur with fish oil is a very effective thinner when applied at 80 percent bloom, and a double application, is unnecessary under N.Y. growing conditions. Lime sulfur plus fish oil sprays increased fruit size and return bloom of apples. Post-bloom timing was more effective in thinning apples than treatments applied during bloom. Two SI fungicides, Nova and Rubigan, sometimes increased fruit set, thereby reducing fruit size. Trees treated with Procure produced fruit set and size equivalent to that of trees receiving protectant fungicides. The effects of the SI fungicides on set and size were slight and statistically significant in only one of two years. Apogee resulted in about a 40 percent reduction in shoot growth of apples, resulting in a reduction in pruning time, and a 50 percent increase in light penetration in the lower canopy of semi-dwarf apple trees. Apogee had no effect on return bloom of apple. A water conditioner was beneficial for increasing the efficacy of Apogee, even when the spray water is low in dissolved calcium. Post-infection applications of PC are of little value for reducing the severity of fire blight infections. Empire fruit cracking is a serious problem, even at the lowest labeled rate of Apogee. The cracking is unrelated to the water conditioning agents and surfactants commonly used with Apogee, but is caused by the product itself. Early season sprays of a kaolin clay spray product had no effect on fruit color of Honeycrisp and Fuji apples, and while sprays in July and August reduced sunburn, this timing also reduced red color and fruit size. Bitter pit is a severe problem in Honeycrisp. Flint fungicide reduced bitter pit at harvest, but that the incidence of bitter pit was not affected after storage. Sovran, another registered strobilurin fungicide, was ineffective. While boron sprays, Flint, and Messenger were ineffective, foliar calcium sprays reduced the incidence of bitter pit by about half.

Impacts
The results of my research have used to recommendations to the apple industry to help them increase the profitability of their farms, through increased fruit size and quality and reduced costs of production. Research on prohexadione calcium showed that this product should not be used on Empire, thus alerting growers to prevent losses due to damaged fruit. Research on fish oil plus lime sulfur as a thinner will soon provide apple growers with a new chemical thinning option to replace carbaryl in fruit to be exported to Europe and one that is organically acceptable, for those who wish to address certified organic markets.

Publications

  • Greene, D.W., and Schupp, J.R. 2004. Effect of Aminoethoxyvinylglycine (AVG) on preharvest drop, fruit quality, and maturation of McIntosh apples: II. Effect of timing-concentration relationships and spray volume. HortScience 39:1036-1041.
  • Rosenberger, D.A., Schupp, J.R., Hoying, S.A., Cheng, L., and Watkins, C.B. 2004. Control of bitter pit in Honeycrisp apples. HortTech. 14:342-349.
  • Schupp, J.R., Fallahi, E., and Chun, I.J. 2004. Effect of particle film on fruit sunburn, maturity and quality of Fuji and Honeycrisp apples. Acta. Hort. 636:551-556.
  • Schupp, J.R., and Greene, D.W. 2004. Effect of Aminoethoxyvinylglycine (AVG) on preharvest drop, fruit quality, and maturation of McIntosh apples: I. Concentration and timing of dilute applications. HortScience 39:1030-1035.
  • Moran, R., and Schupp, J.R. 2004. Preplant soil-incorporated compost increases growth and subsequent yield of newly planted Macoun apple trees. HortScience 39:460.
  • Cheng, L. and Schupp, J. 2004. Nitrogen fertilization of apple orchards. N.Y. Fruit Quarterly 12(1):22-25.
  • Schupp, J.R. 2004. Mineral nutrient management for organic fruit production. N.Y. Fruit Quarterly 12(2):31-34.
  • Watkins, C., Schupp, J. and Rosenberger, D. 2004. Calcium nutrition and control of calcium-related disorders. N.Y. Fruit Quarterly 12(2):15-21


Progress 01/01/03 to 12/31/03

Outputs
Empire, a major apple cultivar in the northeastern U.S., is sometimes damaged by applications of PC. The exact cause of the fruit cracking was not understood, and various spray adjuvants and/or pesticides were thought to interact with PC sprays in causing this damage. Our results showed that the formulated product itself causes the injury, and adding water conditioners, which increased product efficacy, exacerbated symptoms. Other spray materials had no effect on the damage. The new plant growth regulator prohexadione-calcium is labeled to reduce vegetative growth of apple, and to reduce the susceptibility to fire blight. PC would not ordinarily be used in situations when growth control is undesirable, such as newly planted trees that have not filled their allotted space in the orchard. However, a grower would try to reduce fire blight damage in such an orchard, if it became infected, and would be tempted to apply PC. Our results show no benefit from this strategy, preventing growers from wasting their money with post-infection PC sprays. Research was conducted to determine if the plant growth regulator activity of certain sterol inhibiting fungicides had an economic impact on fruit set, size, yield, and gross returns for Empire apples. They did nott. A second objective was to determine if, as stated by one manufacturer, trees treated with triflumizol would have larger fruit than trees treated with mycobutanil or fenarimol. This was shown to be true, but only because the mycobutanil or fenarimol increased fruit set. Particle film sprays have been recommended for reducing apple sunburn and improving red fruit color in situations where temperatures are supra optimal. We evaluated the effect of kaolin clay particle film sprays on apple fruit color, size, and sunburn. While effective for reducing sunburn, kaolin particle film reduced fruit weight and red color of both Honeycrisp and Fuji when applied later than June. Conversely, kaolin sprays had no effect on fruit weight or red fruit color of Honeycrisp apples when applied in May and June. This is the first documentation of the possible negative effects from using the kaolin product, Surround, on apple. Based on these findings, growers who choose to use kaolin particle film sprays to reduce sunburn should recognize that applications later than June may reduce red fruit color of apples and result in smaller fruit. FOLS is a tank mix of fish oil and lime sulfur tested to thin apples. Apple may be thinned effectively with FOLS between bloom and PF14. Applications of lime sulfur are ineffective as thinning sprays unless oil is used as a surfactant. Fish oil, ultrafine spray oil and vegetable oil all gave similar results. Other surfactants were not effective. The greater the spray volume of water the greater the thinning efficacy of FOLS sprays.

Impacts
The results of my research have used to recommendations to the apple industry to help them increase the profitability of their farms, through increased fruit size and quality and reduced costs of production. Research on prohexadione calcium showed that this product should not be used on Empire, thus alerting growers to prevent losses due to damaged fruit. Research on fish oil plus lime sulfur as a thinner will soon provide apple growers with a new chemical thinning option to replace carbaryl in fruit to be exported to Europe and one that is organically acceptable, for those who wish to address certified organic markets.

Publications

  • Schupp, J.R., T.L. Robinson, W.P. Cowgill, and J.M. Compton. 2003. Water conditioners and surfactants increase vegetative growth control and fruit cracking of Empire apple caused by Prohexadione-calcium. HortScience 38:1205-1209.
  • Moran, R. E., and J. R. Schupp. 2003. The effect of preplant monoammonium phosphate fertilizer and apple compost on the growth of newly planted Macoun apple trees. HortScience 38:32-35.
  • Rosenberger, D. A., T. L. Robinson, J. R. Schupp, C. A. Engle-Ahlers and F. W. Meyer. 2003. Effect of sterol-demethylation inhibiting fungicides on apple fruit set, fruit size, total yield, and gross returns. HortScience 38: 601-604.
  • Noordijk, H., and J. Schupp. 2003. Organic post bloom apple thinning with fish oil and lime sulfur. HortScience 38:690-691.
  • Schupp, J.R., D.A. Rosenberger, T.L. Robinson, H. Aldwinkle, J. Norelli, and P.J. Porpiglia. 2003. Postsymptom sprays of prohexadione-calcium affect fire blight infection of Gala apple on susceptible or resistant rootstocks. HortTechnology 13:216.
  • Cheng, L. and J. Schupp. 2003. Nitrogen fertilization of apple orchards. Cornell In-depth Fruit School on Mineral Nutrition, p. 46-52.
  • Ferree, D. C. and J. R. Schupp. 2003. Pruning and training physiology, p. 319-344. In: D. C. Ferree and I. J. Warrington (eds). Apples: Botany, production and uses. CABI Publishing, Wallingford, Oxon, United Kingdom.
  • Osborne, J.L., A.J. Landers and J.R. Schupp. 2003. Efficacy of Apogee (prohexadione calcium) on McIntosh apple comparing two pesticide application technologies, a disc-core type hollow cone nozzle and air induction nozzle. p. 213-220. Pesticide Formul. and Applic. Syst.: 23 Intl. Symp., ASTM STP 1449, G. Volgas, R. Downer and H. Lopez (eds.). ASTM Intl. W. Conshocken, Pa.
  • Rosenberger, D., J. Schupp, S. Hoying, L. Cheng, and C. Watkins. 2003. Managing bitter pit in Honeycrisp. N.Y. Fruit Quarterly 11(3):17-21.
  • Schupp, J.R. 2003. Research on Organic Apple Thinners. Proc. New England Veg. and Berry Conf. 2003:143-147.
  • Schupp, J.R., and R. Moran. 2003. Mineral nutrient management for organic fruit production. Proc. New England Veg. and Berry Conf. 2003: 133-140.
  • Schupp, J. R. and R. E. Moran. 2003. Testing pre-plant MAP and apple compost for improving the growth of newly planted apple trees. Compact Fruit Tree 36: 52-54.
  • Schupp, J.R. 2003. Mineral nutrient management for organic fruit production. Proc. Cornell In-depth Fruit School on Mineral Nutrition, p. 76-82.
  • Watkins, C., J. Schupp and D. Rosenberger. 2003. Calcium nutrition and control of calcium-related disorders. Proc. Cornell In-depth Fruit School on Mineral Nutrition, p. 4-17.
  • Agnello, A. M., A.J. Landers, W. W. Turechek, D. A. Rosenberger, T. L. Robinson, J. R. Schupp, J.E. Carroll, L. Cheng, P. D. Curtis, D. I. Breth, and S. A. Hoying. 2003. Pest management guidelines for commercial tree-fruit production 2003. A Cornell Coop. Ext. Publ.
  • Schupp, J.R. 2003. Timing ReTain applications for best results. Scaffolds 12(22).
  • Schupp, J.R. 2003. Getting the most from the old stop-drop: NAA. Scaffolds 12(23).


Progress 01/01/02 to 12/31/02

Outputs
Alternate bearing of Honeycrisp was not controlled by chemical thinning alone. Preliminary studies have shown that mid-summer applications of ethephon, naphthalene acetic acid, and their combination on return bloom of Honeycrisp were not effective for increasing return bloom. Research on this objective is continuing. Post bloom thinning sprays of fish oil plus lime sulfur caused more thinning when applied fourteen or twenty one days after petal fall, however thinning at petal fall or seven days after petal fall resulted in the largest fruit size. Post bloom thinning sprays of fish oil plus lime sulfur caused petal browning and a marginal leaf burn. Double applications applied with high water volume and slow drying conditions caused more severe foliar injury than single applications, and caused fruit russeting. Both 6 benzyladenine and fish oil plus lime sulfur were effective post bloom thinners for Liberty apples, while seaweed extract was without effect. Both 6 benzyadenine and the fish oil plus lime sulfur tank mix increased the proportion of fruit greater than 7.0 cm in diameter, however 6 benzyladenine resulted in more fruit in the most profitable size classes of 7.6 cm and up. Adding a water conditioner to prohexadione calcium sprays reduced shoot growth more than an application of prohexadione calcium in hard or soft water. Ammonium sulfate and Choice were equally effective water conditioners. Prohexadione calcium provided no growth control of water sprouts and had no effect on fruit set or yield. Prohexadione calcium applied at 250 mg per liter reduced fruit size. 'Empire' fruit cracking and corking was severe, despite the use of only 63 mg per liter prohexadione calcium in two of the three experiments. This damage was exacerbated by the addition of a water conditioner, however ammonium sulfate applied with a surfactant but without prohexadione calcium had little or no effect on either the severity or extent of fruit injury. The addition of surfactants, calcium chloride, or captan fungicide to 250 mg per liter prohexadione calcium plus a water conditioner had no effect on the severity of fruit damage. Fruit cracking caused by prohexadione calcium increased preharvest drop in two of three experiments, and increased post-harvest rot in one experiment where fruit were stored. Application of prohexadione calcium plus a water conditioner reduced estimated gross return per hectare for Empire apples. We conclude that the formulated prohexadione calcium product itself under certain environmental conditions causes the fruit injury, and that this product should not be used on Empire. Neither Messenger, a systemic acquired resistance inducer, nor prohexadione calcium, a gibberellin synthesis inhibitor, increased cold hardiness of young apple trees in winter, when applied in autumn. Fall foliar applications of urea had no adverse effect on cold hardiness of bearing apple trees.

Impacts
The results of my research have used to recommendations to the apple industry to help them increase the profitability of their farms, through increased fruit size and quality and reduced costs of production. Research on fish oil plus lime sulfur as a thinner may soon provide apple growers with a new chemical thinning option to replace carbaryl in fruit to be exported to Europe and one that is organically acceptable, for those who wish to address certified organic markets.

Publications

  • Schupp, J. R., D. A. Rosenberger, T. L. Robinson, H. Aldwinkle, J. Norelli and P. J. Porpiglia. 2002. Effect of post-symptom sprays of Apogee on fire blight infection of 'Gala' apple on susceptible or resistant rootstocks. HortScience 37:903-905.
  • Schupp, J. R., E. Fallahi and I. J. Chun. 2002. Effect of particle film on fruit sunburn, quality and maturity of 'Fuji' and 'Honeycrisp' apples. HortTech. 12:87-90.
  • Moran, R. E. and J, R. Schupp. 2002. Apple pomace compost and pre-plant monoammonium phosphate for improving the growth of newly planted apple trees. Fruit Notes 67(1):1-4.
  • Schupp, J. R. and R. E. Moran. 2002. Testing pre-plant monoammonium phosphate and apple compost for improving the growth of newly planted apple trees. N. Y. Fruit Quarterly 10(1):5-7.
  • Schupp, J. R., E. Fallahi, and I. J. Chun. 2002. Effect of Surround particle film on fruit sunburn, maturity and quality of 'Fuji' and 'Honeycrisp' apples N. Y. Fruit Quarterly 10(1):17-19.
  • Schupp, J., and D. Greene. 2002. Thinning McIntosh apple trees with blossom thinners, with and without post-bloom NAA. Fruit Notes 67(2):9-12.


Progress 01/01/01 to 12/31/01

Outputs
Honeycrisp apple trees on M.26 rootstock were chemically thinned with naphthalene acetic acid at 2.5 ppm plus carbaryl at 125 ml per 100 L; or with Accel at 53 or 74 g a. i. per ha, with or without carbaryl. The sprays of Accel alone, and Accel plus carbaryl all over-thinned Honeycrisp. All thinning treatments increased fruit size relative to unthinned trees, with average fruit diameter exceeding 76 mm. Blossom thinning trials comparing organically acceptable and conventional compounds were conducted. A tank mix of 2.5 percent lime sulfur with 2% fish oil was a highly effective thinner when applied at 80% bloom, and a double application, starting at 20% bloom provided no additional thinning. Lime sulfur plus fish oil sprays increased fruit size and return bloom of Gala and Golden Delicious apple. A proprietary magnesium brine product, NC 99, was also effective as a blossom thinner. Both these mixtures caused leaf spotting and chlorosis of spur leaves. Both compounds were effective thinners, while monocarbamide dihydrogensulfate, the only blossom thinner compound currently registered for use on apple, was ineffective. Post-bloom timing was more effective in thinning ?Gala? and ?Golden Delicious? apples than treatments applied during bloom. A study was conducted to determine how prohexadione calcium and gibberellin applications interact to affect fruit set, fruit finish, or the response of Golden Delicious trees to chemical thinners. Prohexadione calcium and gibberellin did not interact, nor did either material affect the response to two different concentrations of NAA. Prohexadione calcium resulted in a 40% reduction in shoot growth of apples, with a comparable reduction in pruning time, and a 50% increase in light penetration and red fruit color of apples in the lower canopy of semi-dwarf apple trees. Prohexadione calcium has no effect on return bloom. A water conditioner increased the efficacy of prohexadione calcium, even when the spray water is low in dissolved calcium. Fruit spotting, corking, and cracking associated with prohexadione calcium use on the Empire cultivar, was a serious problem, even at the lowest labeled rate of 62 mg.L-1. The cracking problem is unrelated to the water conditioning agents and surfactants commonly used with prohexadione calcium, rather the formulated product itself causes it.

Impacts
Honeycrisp is responsive to all currently registered post-bloom chemical thinners and easily over-thinned. It is especially responsive to 6-bezyladenine thinning sprays, and this chemistry should not be used on this cultivar. Alternate bearing of Honeycrisp is not controlled by chemical thinning alone. Carbaryl is under review by EPA under the Food Quality Protection Act. Apple growers will need alternatives to carbaryl, should it no longer be an option. This line of research will provide apple growers with new chemical thinning options for those who wish to sell fruit in either the export and/or organic markets. Apple growers will not have to take the use of prohexadione calcium or gibberellin into consideration when thinning Golden Delicious, nor will the main effects of prohexadione calcium or gibberellin be negated by use of the other. This information will greatly simplify the decision-making process when using these valuable plant growth regulators. Use of a water conditioner will enable growers to get the optimal response from prohexadione calcium with minimal chemical usage. These studies demonstrate that growers save up to 50% on pruning labor, and loss of crop value will be avoided by recommending that prohexadione calcium not be used on Empire.

Publications

  • Landers, A., and J. R. Schupp. 2001. Improving deposition and reducing drift in orchards. N. Y. Fruit Quarterly 9(1): 3-6.
  • Schupp, J. R., T. L. Robinson, J. Norrelli, and H. Aldwinkle. 2001. Apogee: A New Plant Growth Regulator for Apple. N. Y. Fruit Quarterly 9(2): 19-21.
  • Schupp, J. R. and D. Rosenberger. 2001. Post-infection Apogee for fire blight control? Compact Fruit Tree 34(3): 92-93.
  • Schupp, J., R. Straub, D. Rosenberger and C. Watkins. 2001. Managing Honeycrisp for production and quality. Compact Fruit Tree 34:107-109.
  • Rosenberger, D., J. Schupp, C. Watkins, K. Iungerman, S. Hoying, D. Straub, and L. Cheng. 2001. Honeycrisp: A darling new apple variety or just another problem child? N. Y. Fruit Quarterly 9(3): 9-13.
  • Schupp, J. R., L. Cheng, W. C. Stiles, E. Stover, and K. Iungerman. 2001. Mineral nutrition as a factor in cold tolerance of apple trees. N. Y. Fruit Quarterly 9(3): 17-20.
  • Schupp, J. R. 2001. Regulating fruit set and maturity of Macoun apples. Fruit Notes 66: 43-44.
  • Schupp, J. R. 2001. Improving the growth of newly planted apple trees. Fruit Notes 66: 45-46.
  • Marini, R. P., J. A. Barden and J. R. Schupp. 2001. Wind effects on apples. HortScience 36: 247-249.


Progress 01/01/00 to 12/31/00

Outputs
Honeycrisp apple trees on M.26 rootstock were chemically thinned with carbaryl at 125 ml per 100 l; naphthalene acetic acid at 2.5 ppm, 5 ppm, or 7.5 ppm; NAA at 2.5 or 5 ppm plus carbaryl; or Accel at 74 g a. i. per ha plus carbaryl. Thinning activity increased with increasing NAA concentration. The combination sprays of 5 ppm NAA plus carbaryl, and Accel plus carbaryl over-thinned Honeycrisp. Carbaryl alone was inconsistent. All thinning treatments increased fruit size relative to unthinned trees, with average fruit diameter exceeding 76 mm Six year old McIntosh /M. 9 apple trees were treated as follows: 1) unthinned control; 2) 5 PPM Fruitone N; 3) 75 PPM Accel; 4) 75 PPM VBS 30001; 5) 150 PPM VBS 30001; 6) 2.5 PPM SNAAP 8; and 7) 5 PPM SNAAP 8. None of the chemical thinners in this study had any effect on fruit set. Fruit set was unusually high. None of the treatments had any effect on yield, fruit diameter, individual fruit weight, fruit firmness, or percent soluble solids. The lack of response to chemical thinners is probably attributable to weather conditions. Final crop loads were excessive for all trees in this study, despite supplemental hand thinning. Fruit size was sub optimal. Mature Delicious/ M.7 trees in the Hudson Valley were thinned with either NC 99, calcium and magnesium brine solution, or Crocker's fish oil tank mixed with liquid lime sulfur. Timings were at 80% bloom, or a double application, with one spray at 20% bloom plus a second spray at 80% bloom. Fish oil plus lime sulfur reduced fruit set compared to controls, and, when applied at 80% bloom, reduced yield. Both organic thinners increased fruit size; however double applications were no better than a single spray at 80% bloom Post-infection treatment with Apogee did not reduce the incidence of fire blight cankers on Gala apple tree scion or rootstock, had no effect on the number of diseased scaffolds removed, or the amount of diseased leader removed. Post-infection treatment with Apogee did not reduce the incidence of rootstock blight, or reduce mortality of young `Gala' trees on M.9 or M. 26. Late season sprays of Apogee and Copper chelate accelerated defoliation of late growing young McIntosh apple trees. Copper treated trees were defoliated by 7 November, while untreated trees weren't defoliated until 20 November. Apogee treated trees had 17% and 25% less electrolyte leakage at negative 24C and negative 30C than untreated controls. Trees treated with Copper chelate had the same amount of electrolyte leakage as the untreated controls throughout the range of test temperatures, while trees that received both Apogee and Copper chelate had about 20% greater electrolyte leakage when exposed to temperatures of negative 24C and lower. In January 2001, Apogee alone and Copper chelate alone had 18% less electrolyte leakage than controls at negative 30C, while the combination of Apogee and Copper chelate increased electrolyte leakage by 12%.

Impacts
Honeycrisp is a large fruited cultivar that is easy to thin chemically at the traditional 10 to 12 mm growth stage. NAA at 2.5 or 5 ppm provided adequate thinning to produce fruit of good quality and size. If initial set is heavy and a stronger thinning response is desired, the combination of 2.5 ppm NAA plus carbaryl could be used. Honeycrisp appears to be very sensitive to Accel, when used in combination with carbaryl. Further research needed before Accel is used to thin Honeycrisp. The organic thinners tested were effective and the preliminary conclusion is that both NC 99 and Fish oil plus lime sulfur show promise as organic thinners for apple. Reducing susceptibility of young apple trees to cold injury will lessen the risk of losses in orchard profitability that occur when trees are damaged or killed outright. Treating actively growing apple trees in the autumn with Apogee increased early winter cold hardiness. Applying both Apogee and Copper chelate to the same trees reduced early winter cold hardiness. The suppression of shoot blight conferred by Apogee is a result of growth control, and therefore Apogee is not effective against post infection fire blight.

Publications

  • No publications reported this period