Effect of Prohexadione-Calcium Dose Level on Shoot Growth and Fire Blight in Young Apple Trees

Prohexadione-calcium suppresses both shoot growth and fire blight in apple. In young apple orchards, there are conflicting requirements to control fire blight and allow sufficient tree growth for tree establishment. Application of prohexadione-calcium to various cultivars of orchard-grown apple trees ranging in age from newly planted to fifth-leaf trees indicated that fewer high-dose (125 or 250 mg ·liter-1) applications of prohexadione-calcium provided a better balance between fire blight control and growth in young orchards than multiple low-dose (30 or 63 mg·liter-1) applications. The response of early-season shoot growth to prohexadione-calcium treatment dose was linear. However, trees that received high doses of prohexadione-calcium tended to grow more in the latter part of the season, resulting in little or no difference in total seasonal growth between trees that received a few high or multiple low doses of prohexadione-calcium. Enhancement of fire blight resistance by prohexadione-calcium was correlated with shoot growth suppression at the time of inoculation, and the resistance response to prohexadione-calcium treatment dose was linear. Fire blight management strategies that use prohexadione-calcium in young apple orchards are discussed.

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USING PROHEXADIONE-CALCIUM TO CONTROL FIRE BLIGHT IN YOUNG APPLE TREES

Acta Horticulturae ◽

10.17660/actahortic.2006.704.29 ◽

2006 ◽

pp. 217-224 ◽

Cited By ~ 4

Author(s):

J.R. Norelli ◽

S.S. Miller

Keyword(s):

Fire Blight ◽

Apple Trees ◽

Prohexadione Calcium ◽

Young Apple

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The effect of Regalis® (prohexadione calcium) on the reduction of fire blight (Erwinia amylovora) severity in apple trees

International Journal of Horticultural Science ◽

10.31421/ijhs/10/2/462 ◽

2004 ◽

Vol 10 (2) ◽

Cited By ~ 2

Author(s):

P. Sobiczewski ◽

T. Bubán

Keyword(s):

Active Ingredient ◽

Fire Blight ◽

Shoot Growth ◽

Control Strategies ◽

Fruit Trees ◽

Pome Fruit ◽

Apple Trees ◽

Obvious Effect ◽

One Year ◽

Prohexadione Calcium

Due to the lack of effective and non-phytotoxic materials for control of the blossom and shoot blight phase of fire blight in pome fruit trees, two novel control strategies have emerged: shoot growth retardation by bioregulators and applying resistance inducer compounds. Prohexadione calcium (ProCa) is the active ingredient of the bioregulator Regalis® registered in several European countries. The reduction of shoot growth elongation is the most obvious effect of ProCa. Furthermore, it causes significant changes in the spectrum of flavonoids and their phenolic precursors, leading to the considerable reduction of susceptibility to fire blight. In Poland, potted one-year-old apple trees of cvs. Gala Must grafted on M.26 and Sampion on M.9 (in 2001) as well as Gala Must on P.60 (in 2002) were treated with Regalis® at a range of concentration of 250, 150 or 150 + 100 ppm, respectively. The inoculation of shoots was made with the strain No.691 of E. amylovora (107 cfu/ml), on the 7th and 21st'day after treatments with Regalis. In Hungary, during the years of 2002 and 2003 one-year-old container grown apple trees of the cvs. Idared/M.9 and Freedom/M.9 were treated with the prohexadione-Ca, the active ingredient of Regalis® 100, 150 or 200 ppm, two weeks before inoculation with the Ea 1 strain of E. amylovora (107 cfu/m1). In Poland, the suppression of fire blight in shoots reached up to 80%, depending on concentration and application time of Regalis®. In Hungary, the effect of prohexadione-Ca treatments, determined by the length of necrotic lesion developed, proved to be better than that of streptomycin used for comparison.

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Fire Blight Symptomatic Shoots and the Presence of Erwinia amylovora in Asymptomatic Apple Budwood

Plant Disease ◽

10.1094/pdis-06-16-0892-re ◽

2017 ◽

Vol 101 (1) ◽

pp. 186-191 ◽

Cited By ~ 3

Author(s):

K. A. Tancos ◽

E. Borejsza-Wysocka ◽

S. Kuehne ◽

D. Breth ◽

Kerik D. Cox

Keyword(s):

New York ◽

Fire Blight ◽

Erwinia Amylovora ◽

Causal Agent ◽

Economic Losses ◽

Apple Trees ◽

The Mean ◽

Collection Practices ◽

Time Of Collection ◽

Young Apple

Erwinia amylovora, the causal agent of fire blight, causes considerable economic losses in young apple plantings in New York on a yearly basis. Nurseries make efforts to only use clean budwood for propagation, which is essential, but E. amylovora may be present in trees that appear to have no apparent fire blight symptoms at the time of collection. We hypothesized that the use of infected budwood, especially by commercial nursery operations, could be the cause, in part, of fire blight outbreaks that often occur in young apple plantings in New York. Our goal was to investigate the presence of E. amylovora in asymptomatic budwood from nursery source plantings as it relates to trees with fire blight symptoms. From 2012 to 2015, apple budwood was collected from two commercial budwood source plantings of ‘Gala’ and ‘Topaz’ at increasing distances from visually symptomatic trees. From these collections, internal contents of apple buds were analyzed for the presence of E. amylovora. E. amylovora was detected in asymptomatic budwood in trees more than 20 m from trees with fire blight symptoms. In some seasons, there were significant (P ≤ 0.05) differences in the incidence of E. amylovora in asymptomatic budwood collected from symptomatic trees and those up to 20 m from them. In 2014 and 2015, the mean E. amylovora CFU per gram recovered from budwood in both the Gala and Topaz plantings were significantly lower in budwood collected 20 m from symptomatic trees. Further investigation of individual bud dissections revealed that E. amylovora was within the tissue beneath the bud scales containing the meristem. Results from the study highlight the shortcomings of current budwood collection practices and the need to better understand the factors that lead to the presence of E. amylovora in bud tissues to ensure the production of pathogen-free apple trees.

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The Effect of Prohexadione-calcium on Fruit Set and Chemical Thinning of Apple Trees

HortScience ◽

10.21273/hortsci.42.6.1361 ◽

2007 ◽

Vol 42 (6) ◽

pp. 1361-1365 ◽

Cited By ~ 8

Author(s):

Duane W. Greene

Keyword(s):

Vegetative Growth ◽

Fire Blight ◽

Fruit Set ◽

Fruit Size ◽

Load Level ◽

Apple Trees ◽

Management Tools ◽

Crop Load ◽

Prohexadione Calcium ◽

Treated Apple

Prohexadione-calcium (ProCa) has emerged as one of the most important management tools that an orchardist has available to control vegetative growth and to reduce the incidence and severity of fire blight. It has also been implicated in increased fruit set on treated apple trees. This investigation was initiated to confirm the effects of ProCa on fruit set and to evaluate different thinning strategies that might be used to appropriately thin treated trees. ProCa increased fruit set when applied at petal fall at initial rates of 125 or 250 mg·L−1 in three of the four experiments described in this article. Thinners were applied before, at the time of, and after application of ProCa. In all experiments, chemical thinners did not reduce fruit set to the same crop load level on ProCa-treated trees as they did on untreated trees. It was concluded that a different and more aggressive chemical thinning strategy must be used on trees that were treated with ProCa. Fruit size was reduced on ProCa-treated trees. This reduction was usually, but not always, related to increased fruit set. ProCa increased the number of pygmy fruit on ‘Delicious’ apple trees.

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Draft Genome Sequences of Four Streptomycin-Sensitive Erwinia amylovora Strains Isolated from Commercial Apple Orchards in Ohio

Microbiology Resource Announcements ◽

10.1128/mra.00893-21 ◽

2021 ◽

Vol 10 (50) ◽

Author(s):

A. M. Jimenez Madrid ◽

T. Klass ◽

V. Roman-Reyna ◽

J. Jacobs ◽

M. L. Lewis Ivey

Keyword(s):

Causative Agent ◽

Fire Blight ◽

Erwinia Amylovora ◽

Draft Genome ◽

Apple Orchards ◽

Genome Sequences ◽

Apple Trees ◽

Content Type

Erwinia amylovora is the causative agent of fire blight, a devastating disease of apples and pears worldwide. Here, we report draft genome sequences of four streptomycin-sensitive strains of E. amylovora that were isolated from diseased apple trees in Ohio.

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Management of Fire Blight Using Pre-bloom Application of Prohexadione-Calcium

Plant Disease ◽

10.1094/pdis-09-19-1948-re ◽

2020 ◽

Vol 104 (4) ◽

pp. 1048-1054

Author(s):

Anna E. Wallis ◽

Kerik D. Cox

Keyword(s):

New York ◽

Tree Growth ◽

Cell Walls ◽

Fire Blight ◽

Shoot Growth ◽

New York State ◽

Bacterial Disease ◽

Cortical Parenchyma ◽

Shoot Blight ◽

Prohexadione Calcium

Fire blight, a bacterial disease of rosaceous plants caused by Erwinia amylovora, is one of the most important diseases affecting commercial apple production worldwide. Antibiotics, applied at bloom to protect against blossom infection, are the most effective means of management but raise concern due to the potential for antibiotic resistance in both the pathogen population and nontarget organisms. In addition, most fire blight outbreaks in New York State often emerge in late June to July as shoot blight, calling into question the role of blossom infections and the antibiotic applications made to manage them. Prohexadione-calcium (PhCa) is a gibberellic acid inhibitor used post-bloom to control shoot vigor and to manage shoot blight. However, the magnitude of shoot blight management is directly related to the suppression of shoot growth, which is undesirable, especially in young orchards during establishment years. PhCa is believed to control shoot blight by thickening cell walls in cortical parenchyma, preventing invasion of host tissues by E. amylovora. We hypothesize that PhCa applied pre-bloom could similarly prevent invasion of blossom pedicels following infection, leading to reduced disease incidence. We evaluated novel pre-bloom PhCa programs for their effects on disease management (blossom and shoot blight) as well as their impact on shoot growth for three years in a mature ‘Gala’ orchard in New York. In all three years of the study, all PhCa programs resulted in less than 27% incidence (71% control) of blossom blight and less than 13% incidence (77% control) of shoot blight with minimal effect on tree growth. Inclusion of a biopesticide during bloom further reduced the incidence of blossom blight in one year of three. Using light microscopy, we found that cell walls in the cortical parenchyma of fruitlet pedicels on trees receiving pre-bloom PhCa applications were significantly thicker than those of untreated trees 40 days after full bloom and inoculation. Overall, we found that pre-bloom applications of PhCa had utility in reducing blossom blight and shoot blight with minimal impacts on tree growth. These pre-bloom programs would fit with standard production practices and may contribute toward the development of fire blight management programs without the use of antibiotics.

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Managing Vegetative Growth of Apples with Prohexadione Calcium can Influence Mid-season Spray Coverage

HortScience ◽

10.21273/hortsci.33.3.451f ◽

1998 ◽

Vol 33 (3) ◽

pp. 451f-452

Author(s):

J.R. Evans ◽

J.A. Balles ◽

L.H. Bennett ◽

B.A. Brinkman ◽

A.H. Harrell ◽

...

Keyword(s):

Vegetative Growth ◽

Plant Growth Regulator ◽

Shoot Growth ◽

Crop Protection ◽

Shoot Length ◽

Tree Canopy ◽

Apple Trees ◽

Air Blast ◽

Previously Treated ◽

Prohexadione Calcium

Prohexadione calcium (BAS 125W or Apogee™) is a plant growth regulator being developed to control vegetative growth in apples. Prohexadione calcium acts within a plant by blocking the biosynthesis of growth-active gibberellin. The result is decreased cell elongation; thus, reduced shoot length. Applications of prohexadione calcium beginning when the apple trees have 2 to 15 cm of new shoot growth significantly reduce seasonal vegetative growth. Mid-season measurements of air blast spray coverage using water-sensitive cards show that trees previously treated with prohexadione calcium have greater spray coverage within the tree canopy than untreated trees. Hence, more efficient crop protection can be expected in apple trees treated with prohexadione calcium.

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