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

Plant Disease ◽  
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.

scholarly journals Prevalence of Streptomycin-Resistant Erwinia amylovora in New York Apple Orchards

Plant Disease ◽  
2016 ◽  
Vol 100 (4) ◽  
pp. 802-809 ◽  
Author(s):  
K. A. Tancos ◽  
S. Villani ◽  
S. Kuehne ◽  
E. Borejsza-Wysocka ◽  
D. Breth ◽  
...  
Keyword(s):  
United States ◽  
New York ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
The United States ◽  
Streptomycin Resistance ◽  
Apple Orchards ◽  
Wayne County ◽  
The Past ◽  
Shoot Blight

Resistance to streptomycin in Erwinia amylovora was first observed in the United States in the 1970s but was not found in New York until 2002, when streptomycin-resistant (SmR) E. amylovora was isolated from orchards in Wayne County. From 2011 to 2014, in total, 591 fire blight samples representing shoot blight, blossom blight, and rootstock blight were collected from 80 apple orchards in New York. From these samples, 1,280 isolates of E. amylovora were obtained and assessed for streptomycin resistance. In all, 34 SmR E. amylovora isolates were obtained from 19 individual commercial orchards. The majority of the resistant isolates were collected from orchards in Wayne County, and the remaining were from other counties in western New York. Of the 34 resistant isolates, 32 contained the streptomycin resistance gene pair strA/strB in the transposon Tn5393 on the nonconjugative plasmid pEA29. This determinant of streptomycin resistance has only been found in SmR E. amylovora isolates from Michigan and the SmR E. amylovora isolates discovered in Wayne County, NY in 2002. Currently, our data indicate that SmR E. amylovora is restricted to counties in western New York and is concentrated in the county with the original outbreak. Because the resistance is primarily present on the nonconjugative plasmid, it is possible that SmR has been present in Wayne County since the introduction in 2002, and has spread within and out of Wayne County to additional commercial growers over the past decade. However, research is still needed to provide in-depth understanding of the origin and spread of the newly discovered SmR E. amylovora to reduce the spread of streptomycin resistance into other apple-growing regions, and address the sustainability of streptomycin use for fire blight management in New York.

scholarly journals The Effect of Repeat Annual Applications of Prohexadione–calcium on Fruit Set, Return Bloom, and Fruit Size of Apples

HortScience ◽  
2008 ◽  
Vol 43 (2) ◽  
pp. 376-379 ◽  
Author(s):  
Duane W. Greene
Keyword(s):  
Vegetative Growth ◽  
Fire Blight ◽  
Fruit Set ◽  
Fruit Size ◽  
Application Rate ◽  
Fruit Weight ◽  
Initial Application ◽  
Shoot Blight ◽  
Return Bloom ◽  
Prohexadione Calcium

Prohexadione–calcium (ProCa) is used routinely in orchards to control vegetative growth and to reduce the shoot blight phase of fire blight. This communication reports on multiple-year applications of ProCa with special emphasis on treatment effects on fruit set, fruit size, and return bloom. Increased fruit set was confirmed from high rates of ProCa above 125 mg·L−1. The increase in fruit set was attributed primarily to a reduction of abscission during June drop rather than an increase in initial set. ProCa decreased fruit weight in some instances. Part of this reduction could be attributed to increased fruit set. However, the large reduction in fruit weight at harvest could only be explained by a direct effect of ProCa when used at high rates. When ProCa was applied as a concentrate spray at 250 mg·L−1, terminal growth was reduced comparable to the application made as a tree row volume dilute spray (1×). However, fruit set was increased when the spray volume in which ProCa was delivered was reduced to 4×. A range of ProCa rates was used on ‘Mutsu’. An initial application rate of 42 mg·L−1 followed by similar subsequent rates controlled growth comparably to higher initial and total rates, yet low rates had no effect on fruit weight or return bloom. Low rates of ProCa appear to be effective at controlling vegetative growth yet appear to have minimal side effects. High rates, especially those intended to reduce fire blight, come with the risk of increased fruit set and reduced fruit size and return bloom.

Temperature Declines During Storms and Irrigation May Contribute to Fire Blight Infection of Pear Fruit

2003 ◽  
Vol 4 (1) ◽  
pp. 9
Author(s):  
David A. Rosenberger ◽  
Keri L. VanCamp
Keyword(s):  
New York ◽  
Laboratory Experiments ◽  
Fire Blight ◽  
New York State ◽  
Storm Events ◽  
Pear Fruit ◽  
Rapid Cooling ◽  
Foliar Symptoms ◽  
Air Temperatures ◽  
Overhead Irrigation

During summer of 2002, fire blight caused by Erwinia amylovora appeared in immature pears (Pyrus communis) in five Ulster County pear orchards in southeastern New York State. Foliar symptoms of fire blight were absent or infrequent in many trees that had infected fruit, suggesting that fruit infections occurred after shoots had stopped growing and were no longer susceptible to infection. In one orchard where overhead irrigation was initiated on 23 July when air temperatures were 96°F, incidence of fruit infection in September ranged from 10 to 76% with a mean of 36% of all fruit showing fire blight symptoms. Laboratory experiments showed that non-wounded fruit preheated to 95°F and then submerged in inoculum suspensions at 70°F or 40°F developed fire blight infections whereas similar fruit preheated at 70°F and immersed in 70°F-inoculum did not develop infections. Overhead irrigation initiated during the heat of the day can disperse inoculum at the same time that rapid cooling from irrigation water may cause E. amylovora to be drawn into immature pear fruit. The same combination of water-disseminated inoculum and rapid cooling can occur during summer thunderstorms, and storm events may explain the unusual incidence of fire blight on immature pears that was observed in 2002. Accepted for publication 29 January 2003. Published 10 March 2003.

scholarly journals Evidence that Prohexadione-Calcium Induces Structural Resistance to Fire Blight Infection

2009 ◽  
Vol 99 (5) ◽  
pp. 591-596 ◽  
Author(s):  
Molly J. McGrath ◽  
Jessica M. Koczan ◽  
Megan M. Kennelly ◽  
George W. Sundin
Keyword(s):  
Cell Wall ◽  
Disease Control ◽  
Disease Severity ◽  
Growth Regulator ◽  
Fire Blight ◽  
Shoot Growth ◽  
Disease Incidence ◽  
Wall Width ◽  
Structural Resistance ◽  
Prohexadione Calcium

Mechanisms of fire blight control by the shoot-growth regulator prohexadione-calcium (ProCa) were investigated by comparing disease development in ProCa-treated potted apple trees (cv. Gala) to paclobutrazol (another shoot-growth regulator)-treated and nontreated trees and in ProCa-treated cv. McIntosh trees in the field. Twenty-eight days after inoculation with Erwinia amylovora Ea110, disease incidence on ProCa- and paclobutrazol-treated shoots was significantly reduced compared with that on nontreated shoots. Disease severity (percent shoot length infected) was also significantly lower on both ProCa- and paclobutrazol-treated shoots than on nontreated shoots. However, bacterial populations within inoculated shoots were high and bacterial growth occurred in all treatments. In addition, the mean cell wall width of the cortical parenchyma midvein tissue of the first and second youngest unfolded leaves of ProCa- and paclobutrazol-treated shoots was significantly wider both 0.5 and 2 cm from the leaf tips compared with the cell walls of the nontreated tissue. Taken together, these results suggest that reduction of fire blight symptoms by ProCa and paclobutrazol is not the result of reduced populations of E. amylovora in shoots. Moreover, because paclobutrazol also reduced disease severity and incidence, changes in flavonoid metabolism induced by ProCa but not paclobutrazol does not appear to be responsible for disease control as suggested in recent literature. Finally, although this study did not directly link disease control to the observed cell wall changes, the possibility that an increase in cell wall width impedes the spread of E. amylovora should be investigated in more depth.

scholarly journals Isolation of Streptomycin-Resistant Isolates of Erwinia amylovora in New York

Plant Disease ◽  
2008 ◽  
Vol 92 (5) ◽  
pp. 714-718 ◽  
Author(s):  
Nicole L. Russo ◽  
Thomas J. Burr ◽  
Deborah I. Breth ◽  
Herb S. Aldwinckle
Keyword(s):  
New York ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
New York State ◽  
The United States ◽  
Streptomycin Resistance ◽  
Antibiotic Resistant ◽  
Wayne County ◽  
Unintentional Movement ◽  
Growing Region

Streptomycin is currently the only antibiotic registered for the control of fire blight, a devastating disease of apple (Malus), pear (Pyrus), and other rosaceous plants caused by the bacterium Erwinia amylovora. Resistance of E. amylovora to streptomycin was first identified in California pear orchards in 1971 and is currently endemic in many parts of the United States. The Northeast remains the only major U.S. apple-growing region without streptomycin-resistant isolates of E. amylovora. In 2002, during a routine survey for streptomycin resistance, isolates from two neighboring orchards in Wayne County, NY were found to be highly resistant to streptomycin at a concentration of 100 μg/ml. This constitutes the first authenticated report of streptomycin resistance in New York State. Infected trees were shipped at the same time from a single nursery in Michigan. Resistance was caused by the acquisition of the strA-strB gene pair, inserted into the ubiquitous nontransmissible E. amylovora plasmid pEA29. Previously, streptomycin-resistant E. amylovora populations from Michigan were described with a similar mechanism of resistance, although the strA-strB genes are not unique to Michigan. These findings illustrate how unintentional movement of nursery material could undermine efforts to prevent the spread of antibiotic-resistant E. amylovora.

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

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1099-1106 ◽  
Author(s):  
J. L. Norelli ◽  
S. S. Miller
Keyword(s):  
Fire Blight ◽  
Shoot Growth ◽  
High Dose ◽  
Apple Orchards ◽  
Calcium Treatment ◽  
Apple Trees ◽  
Resistance Response ◽  
Treatment Dose ◽  
Prohexadione Calcium ◽  
Young Apple

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.

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

2004 ◽  
Vol 10 (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.

scholarly journals (315) Geneva® 935: A New Fire Blight Resistant, Semidwarfing Apple rootstock

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1027B-1027
Author(s):  
Gennaro Fazio ◽  
Herb S. Aldwinckle ◽  
Terence L. Robinson ◽  
James Cummins
Keyword(s):  
United States ◽  
New York ◽  
Fire Blight ◽  
Agricultural Research ◽  
New York State ◽  
Fruit Size ◽  
The United States ◽  
Breeding Program ◽  
Apple Rootstock ◽  
Individual Tree

The Geneva® Apple Rootstock Breeding program, which was initiated in 1968 by Dr. James Cummins and Dr. Herb Aldwinckle of Cornell University and which has been continued as a joint breeding program with the U.S. Dept. of Agriculture Agricultural Research Service (USDA-ARS) since 1998, has released a new semi-dwarfing apple rootstock which is named Geneva® 935 or G.935. G.935 (a progeny from a 1976 cross of `Ottawa 3' × `Robusta 5') is a selection that has been widely tested at the New York State Agricultural Experiment Station in Geneva, N.Y., in commercial orchards in the United States and at research stations across the United States and Canada. G.935 is a semi-dwarfing rootstock that produces a tree slightly larger than M.26. G.935 is the most precocious and productive semi-dwarf rootstock we have released. It has had similar yield efficiency to M.9 along with excellent fruit size and wide crotch angles. It showed no symptoms of winter damage during the 1994 test winter in N.Y. G.935 is resistant to fire blight and Phytophthora; however. it is susceptible to infestations by woolly apple aphids. G.935 has shown tolerance to replant disease complex in several trials. It has good propagation characteristics in the stool bed and produces a large tree in the nursery. G.935 has better graft union strength than M.9, but will require a trellis or individual tree stake in the orchard to support the large crops when the tree is young. G.935 will be a possible replacement for M.26. Suggested orchards planting densities with this rootstock are 1,500-2,500 trees/ha. It has been released for propagation and sale by licensed nurseries. Liners will be available in the near future.

scholarly journals Effect of Preplant Fertilization, Annual Fertilization, Irrigation, and Fertigation on `Empire' Apple Fruit Size and Yield

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 582c-582
Author(s):  
Terence L. Robinson ◽  
Warren C Stiles
Keyword(s):  
New York ◽  
Tree Growth ◽  
Shoot Growth ◽  
Fruit Size ◽  
Growth Yield ◽  
Fertilizer Treatment ◽  
Eastern United States ◽  
Trickle Irrigation ◽  
Cross Sectional ◽  
Yield Efficiency

A field experiment was established in 1992 with `Empire' apple trees on either M.7 or M.9 rootstock. Preplant fertilization with NPKB plus lime compared to the lime only control did not increase tree growth during the first 4 years, but did increase cumulative yield (10%) and average fruit size (7%). The addition of annual applications of ground-applied NKB after planting increased total shoot growth 17%, as well as yield (26%) and fruit size (14%) compared to the lime only control. Trickle irrigation significantly increased trunk cross-sectional area (17%), shoot growth (16%), yield (18%), fruit size (5%), and yield efficiency (7%). The interaction of ground fertilization and trickle irrigation showed that trickle irrigation increased the benefits of ground applied fertilizers. Without trickle irrigation, ground-applied fertilizers increased shoot growth only 6% and yield 14% compared to the unfertilized controls, but, with the addition of trickle irrigation, the ground-applied fertilizers increased shoot growth 21% and yield 21% over the irrigated but unfertilized control. Ground fertilization increased yield efficiency and fruit size by the percentage by whether or not trickle irrigation was present. Fertigation gave similar results as the trickle plus ground fertilizer treatment on tree growth, yield, fruit size, and yield efficiency. Our results indicate that trickle irrigation in the eastern United States can improve tree growth, yield, and fruit size in the first few years after planting. The addition of ground-applied fertilizer or fertigation can improve tree performance even more. However, in the humid New York climate, there does not appear to be a significant benefit from injecting the fertilizer into the trickle water compared to applying the fertilizer on the ground.

scholarly journals A New Approach to Fire Blight Control: Mycorrhiza

HortScience ◽  
2006 ◽  
Vol 41 (5) ◽  
pp. 1309-1312 ◽  
Author(s):  
Kubilay Kurtulus Bastas ◽  
Aysen Akay ◽  
Salih Maden
Keyword(s):  
Fire Blight ◽  
Shoot Growth ◽  
Glomus Intraradices ◽  
Erwinia Amylovora ◽  
New Approach ◽  
Vesicular Arbuscular ◽  
Pome Fruits ◽  
Shoot Blight ◽  
Apple Cultivars ◽  
And Control

The first outbreak of fire blight incited by Erwinia amylovora (Burr.) Winslow et al. occurred on pome fruits in Turkey in 1985, and it is now one of the most serious diseases of pear, apple, quince, and loquat (Oktem and Benlioglu, 1988). In this study, experiments were conducted in Konya Province to evaluate the efficacy of Glomus intraradices Schenck & Smith vesicular–arbuscular mycorrhiza (VAM) and bactericides for control of the shoot blight phase of fire blight and control of shoot growth on the different apple cultivars (Gala, Red Elstar, Pinova, Jonagored) on M9 rootstock in 2002 to 2003. Streptomycin provided 84.38% to 95.24% and 85.28% to 89.97% disease control in 2002 and 2003, respectively. Copper complex was not so effective against shoot blight phase of the disease, and it reduced disease by 16.18% to 27.75% and 14.48% to 19.06% in 2002 and 2003, respectively. Results of VAM application were encouraging, indicating a reduction of fire blight by Glomus intraradices of between 9.7% and 50.5% in 2002 and between 23.9% and 48.4% in 2003, respectively.

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