Fire blight Apple trees

Fireblight: Symptoms, Causes, and Treatment

  • Hosts
  • Disease Symptoms
  • Disease Cycle
  • Disease Management
  • Some Resistant or Tolerant Plants

Fireblight is a destructive, highly infectious and widespread disease caused by the bacterium Erwinia amylovora. Fireblight can be a problem in Georgia and is particularly prevalent in some counties. Fire blight attacks blossoms, leaves, shoots, branches, fruits, and roots. In the following paragraphs are some facts and methods to avoid and control the disease.

Hosts

Figure 1. Shephard’s crook, a typical symptom of fireblight.

Disease Symptoms

The bark at the base of blighted twigs becomes water soaked, then dark, sunken and dry; cracks may develop at the edge of the sunken area. Young twigs and branches die from the terminal end and appear burned or deep rust colored. Branches may be bent, resembling what is commonly referred to as a “shepherd’s crook” (Figure 1). Dead leaves and fruit remain on the branches.

Disease Cycle

Initially the disease often enters the tree through natural openings, especially flowers and wounds in the spring. Once established in the tree, fireblight quickly invades through the current season’s growth into older growth.

Fireblight can be spread from diseased to healthy plants by rain, wind, and pruning tools. The bacterium can survive the winter in sunken cankers on infected branches. In spring, the bacteria ooze out of the cankers and attract bees and other insects. Insects also help spread the disease to healthy plants. The bacteria spread rapidly through the plant tissue in warm temperatures (65 degrees F or higher) and humid weather.

Disease Management

During spring and summer, prune out infected branches 8 inches below the damage. Avoid pruning when the plants are wet. Dip pruning tools in 70 percent isopropyl alcohol (rubbing alcohol) or 10 percent bleach solution (1 part bleach to 9 parts water solution) between each cut. Wash and oil shears when you are finished. These practices avoid spreading the pathogen.

Avoid heavy nitrogen fertilization, especially in summer, when succulent growth is most susceptible to fireblight infection. Avoid splashing water. Chemical control is not always effective and needs to be applied preventively. Therefore, in years when warm, humid, wet weather coincides with flowering and leaf emergence, spray plants with a fungicide containing basic copper sulfate (Kocide) or an antibiotic (Agrimycin) to reduce infection. Applications of Agrimycin need to begin at the start of blooming and continue every 3-4 days during the bloom period. Application of Kocide should begin at bloom and continue every 7 days during bloom. Re-application following rain may be needed.

Plant resistant varieties.

Some Resistant or Tolerant Plants

Pyracantha — Laland’s firethorn
Hawthorn — Washington hawthorn
Pear — Kieffer, Moonglow, Orient, Seckel
Apple — Enterprise, Freedom, Liberty, Prima, Priscilla, etc.
Crabapple — Adams, Dolgo, Jewelberry, Liset, etc.

Status and Revision History
Published on Oct 15, 2004
Published on Feb 10, 2009
Published on May 05, 2009
Published with Full Review on May 05, 2012
Published with Full Review on Mar 28, 2017

Taking the fight to fire blight

Pear tree prunings that have fire blight in a Medford, Oregon, orchard in October 2013. The branches are piled up by workers before they are removed from the blocks by hand to reduce spreading the infection. (TJ Mullinax/Good Fruit Grower)

Disease diversity

All fire blight is bad news, but all blight is not created equal.

Erwinia amylovora, the bacterial pathogen that causes fire blight, comes in many different strains and some are much more virulent than others, according to Cornell University pathologist Awais Khan.

For years, both growers and breeders have lacked the tools to see these genetic differences.

But today, with gene mapping technology, Khan can study the genetic variation of the pathogen strains and the genetic variation in apple genes that offer resistance or increase susceptibility.

That information will give breeders better tools to select the most resistant genes and layer multiple genes to improve resistance as they select promising new varieties.

Khan, who recently joined Cornell, is setting up an ambitious research program to study fire blight and apple scab with the latest genetic tools.

He also plans to develop a rapid detection tool for the fire blight pathogen, based on DNA markers, that can be used in the field, he told growers at the Cornell Cooperative Extension Lake Ontario Summer Tour last year.

Locally grown biocontrol

Unfortunately for Northeastern apple growers, Blossom Protect and other biological products that allow for organic fire blight control in the West don’t perform consistently under humid conditions.

But the premise behind the biocontrols — allowing a yeast or bacteria to colonize a flower first so that they are ready to out-compete the fire blight pathogen — should work just as well if researchers can find something that’s suited for the Northeastern climate. So, a team of researchers at the Connecticut Agricultural Experiment Station are trying to find just such a perfect microbe — or three.

“Eventually, I would like to create a cocktail with two or three dominant species found on healthy apple flowers that are compatible and manipulate the flower microbiome to reduce disease,” said pathologist Quan Zeng. Such microbes might make antimicrobial compounds or simply out-compete Erwinia amylovora, the fire blight pathogen

But to create such a new biocontrol, he and his colleagues have started at the beginning, by identifying what the microbiome of an apple flower normally looks like in the region and see if any of those natural inhabitants could act as a biocontrol. It’s a more strategic way to find a biocontrol, said Blair Steven, a soil microbiologist who is using genetic tools to identify what microbes thrive on apple flowers.

“The microbiome of the flower is relatively simple and there are distinct sets of bacteria, so the presence of one predicts another,” Steven said. “We’re hoping to take advantage of that, since Erwinia looks like it’s inhibited by the presence of certain microbes.”

Last year, the U.S. Department of Agriculture awarded the three-year research project $459,978. They already found one biocontrol candidate that’s showing strong disease control efficacy in the lab and the field, Zeng said, although it needs further study.

The Connecticut team partnered with colleagues in Massachusetts, Michigan and Wisconsin to study flowers and test promising candidates. Hopefully, it will lead to a better organic disease control options for the growers in rainy, humid regions.

“We have a lot of pick-your-own farms and people who come to the orchard and pick, and for those growers, there’s an additional selling point to have an organically managed orchard so people feel safe,” Zeng said.

—by Kate Prengaman

Fire blight

Fire blight, plant disease, caused by the bacterium Erwinia amylovora, that can give infected plants a scorched appearance. Fire blight largely affects members of the rose family (Rosaceae). It has destroyed pear and apple orchards in much of North America, in parts of Europe, and in New Zealand and Japan. Many other economically important agricultural and ornamental plants can also be affected, including almond, apricot, cherry, cotoneaster, crabapple, flowering quince, hawthorn, loquat, medlar, mountain ash, plum, quince, raspberry, rose, serviceberry, and spirea.

fire blightFire blight on the branch of an apple tree.Peggy Greb, Agriculture Research Service/U. S. Department of Agriculture (Image Number: K10805-2)

Symptoms of fire blight include a sudden brown to black withering and dying of blossoms, fruit spurs, leaves, twigs, and branches. Very susceptible plants appear as if scorched by fire and may die. Cankers—slightly sunken, encircling, dark brown to purplish black lesions with a sharp, often cracked margin—form on twigs, branches, and trunk, causing terminal dieback. Fruits are water-soaked, later turning brown or black and shrivelled. In warm moist spring weather, droplets of bacterial ooze appear on the surface of “holdover” cankers. The oozing bacteria are carried by insects, wind, and rain to infect new plants and tissues. The bacteria spread intercellularly and up to 1.2 metres (4 feet) through vascular tissue in the wood, during late spring and early summer, darkening and killing the tissue. A small percentage of the bacteria overwinter at the margins of branch and trunk cankers, ready to repeat the disease cycle starting the following spring about blossoming time.

Fire blight is difficult to control, especially in warm moist weather conditions. Infected wood should be removed in late summer, fall, or winter, when the bacteria are not actively spreading. Copper blossom sprays can be applied when plants first begin to flower but are of limited effectiveness and can damage fruits. Streptomycin sprays have been used to prevent new infections but have also contributed to antibiotic-resistant outbreaks in some areas. Resistant varieties of several susceptible plants have been developed.

Fire Blight Remedies And Symptoms

While there are numerous diseases affecting plants, the plant disease fire blight, which is caused by bacteria (Erwinia amylovora), affects trees and shrubs in orchards, nurseries, and landscape plantings; therefore, no one is safe from its path.

Plant Disease: Fire Blight

The plant disease fire blight is oftentimes influenced by seasonal weather and generally attacks the plant’s blossoms, gradually moving to the twigs, and then the branches. Fire blight gets its name from the burnt appearance of affected blossoms and twigs.

Fire Blight Symptoms

The symptoms of fire blight can appear as soon as trees and shrubs begin their active growth. The first sign of fire blight is a light tan to reddish, watery ooze coming from the infected branch, twig, or trunk cankers. This ooze begins to turn darker after exposure to air, leaving dark streaks on the branches or trunks.

Fire blight infections often move into twigs and branches from infected blossoms. The flowers turn brown and wilt and twigs shrivel and blacken, often curling at the ends. In more advanced cases of fire blight infection,

cankers begin to form on branches. These discolored oozing patches contain masses of fire blight bacteria and heavy infections can be fatal.

Fire Blight Remedies

Fire blight bacteria is spread through various easily means such as rain or water splashing, insects and birds, other infected plants, and unclean gardening tools. The maximum risk of exposure to this bacterium is late spring or early summer as it emerges from dormancy. Unfortunately, there is no cure for fire blight; therefore, the best fire blight remedies are regular pruning and removal of any infected stems or branches. It may also help to avoid overhead irrigation, as water splashing is one of the most common ways to spread the infection.

Special attention should also be given to garden tools, especially those that have been exposed to the bacteria. Tools should be sterilized in an alcohol solution containing three parts denatured alcohol to one part water. Ethanol and denatured alcohol are very different. While ethanol alcohol is not poisonous and quite safe to use, denatured alcohol is a toxic solvent oftentimes used as Shellac thinner. Diluted household bleach (one part bleach to nine parts water) can also be used. Always make sure to thoroughly dry tools to prevent corrosion. It sometimes helps to oil them down as well.

Fire Blight Treatment

Since there are no curing fire blight remedies, fire blight is very difficult to control; however, one fire blight treatment to reduce it is by spraying. A variety of bactericides has been developed to combat fire blight, although chemicals to treat fire blight may not always be effective. For instance, fixed copper products are often used as a fire blight treatment but this only reduces the bacteria’s ability to survive and reproduce.

Always read and follow instructions carefully before using any chemicals to treat fire blight. Since chemicals aren’t always effective in fire blight control, organic control, such as extensive pruning may be the only option for fire blight treatment.

Colorado State University

Print this fact sheet

by R.D. Koski and W.R. Jacobi* (12/14)

Quick Facts…

  • Fire blight is a bacterial disease that can kill branches and whole plants of many members of the rose family, including apple, pear, quince and crabapple. .
  • Symptoms include dead branches, water-soaked blossoms, light brown to blackened leaves, discolored bark, black “shepherd’s crook” twigs, and dried fruits. .
  • Fire blight bacteria can be spread by insects, splashing rain or contaminated pruning tools..
  • Management includes resistant varieties, cultural practices, pruning and preventive chemical sprays.

Disease incidence varies from year to year and severity is influenced by cultivar susceptibility, tree age, succulence of tissues and spring meteorological conditions. The disease is most serious when spring temperatures during pre-bloom and bloom are warmer than average. Warm rainy springs are particularly conducive to rapid spread of the pathogen, resulting in blossom blight. Blight of twig terminals can occur in late May through June during wind driven rain events. Hail and wind damage provide wounds that allow the pathogen to enter at other times. Hot summer weather generally slows or stops the disease.

Disease Cycle

Fire blight is caused by the bacterium Erwinia amylovora. The bacteria overwinter in blighted branches and at the edge of cankers (areas of bark killed by bacteria) (Figure 1). In spring, when temperatures frequently reach 65 F, the bacteria multiply rapidly.

Figure 1: Fire blight life cycle.

Masses of bacteria are forced through cracks and bark pores to the bark surface, where they form a sweet, gummy exudate called bacterial ooze. Insects such as aphids, ants, bees, beetles, and flies, are attracted to this ooze, pick up the bacteria on their bodies, and inadvertently carry the bacteria to opening blossoms. Bacterial ooze splashed by rain can also spread the pathogen.

Once in the blossom, bacteria multiply rapidly in the nectar and eventually enter the flower tissue. From the flower, the bacteria move into the branch. When the bacteria invade and kill the cambial tissue of the branch, all flowers, leaves and fruit above the girdled area die.

Infection also can take place through natural openings in leaves (stomata), branches (lenticels), pruning wounds, insect feeding and ovipositing, and hail. Droplets of bacterial ooze can form on twigs within three days after infection.

Diagnosis

Symptoms of fire blight are first seen about the time of petal fall. Infected blossoms appear water-soaked and wilt rapidly before turning dark brown; this phase of the disease is referred to as blossom blight. As the bacterial invasion progresses, leaves wilt, darken and remain attached to the tree (Figure 2); this gives the tree a fire-scorched appearance, thus the name “fire blight.”

Figure 2: Blighted leaves on ornamental apple.

Infected twigs darken and branch tips may bend over forming a “shepherd’s crook.” During wet conditions infected tissue may exude creamy bacterial ooze in droplets or fine, hair-like strands. Infected fruits also exude bacterial ooze. Rather than dropping from the tree, infected fruits gradually dry and remain attached to the branch.

Fire blight cankers on branches or stems appear as dark discolored areas that are slightly sunken, with a narrow callus ridge along the outer edge (Figure 3). The narrow callus ridge is diagnostic for differentiating fire blight cankers from fungal cankers. Under the bark associated with a canker, the inner bark turns from green to brown, but the appearance varies depending on plant variety. Droplets of bacterial ooze may appear on the canker.

Figure 3: Sunken black canker on apple branch.

Disease Management

There is no cure for this disease, so prevention is the best solution for the management of fire blight. Fire blight management methods include: planting resistant varieties, implementing cultural practices that favor growth of the plant rather than the pathogen, pruning to remove infected plant parts, and chemical sprays. Using resistant varieties is the most effective prevention method. Spraying chemicals is not recommended for homeowners because of chemical availability, potential phytoxicity and the critical timing of sprays.

Resistant varieties: Cultivars of apple, crabapple, and pear differ in their degree of susceptibility to the bacterium (Table 1) although some cultivars are less susceptible than others, no cultivar is immune to infection when the pathogen is abundant and conditions are favorable for infection. Avoid blight susceptible apple rootstocks especially when grafted to susceptible scions (Table 2). To minimize stress that may predispose the tree to other disease-causing agents, select varieties adapted to the growing area. Local weather conditions from year to year also affect the amount of fire blight found in a variety.

Cultural practices: Minimizing rapid growth and succulent tissue will reduce the risk of fire blight developing on the susceptible young, succulent tissue. Annual pruning with avoidance of major cuts will help minimize tree vigor. Similarly, limiting the amount of nitrogen fertilizer will reduce twig terminal growth. Fertilization should be based on the results of foliar and/or soil nutrient analysis and should not be applied in excess.

Pruning: Remove all blighted twigs and cankered branches. Prune twigs and branches 8 to 12 inches below the edge of visible infection. CAUTION! After each cut, surface sterilize all tools used in pruning. Dip tools in household bleach or ethyl alcohol, or use household spray disinfectants. Spreading the blight bacteria risk is lowered if pruning is delayed until mid winter. Winter pruning can also be accomplished more efficiently because pruning tools need not be disinfected between cuts if pruning is done when trees are fully dormant. To decrease the chance of new infections, promptly remove from the site and destroy all infected branches.

To remove a canker that does not extent more than 50 percent around a large stem, first make a cut through the bark down to the wood 1 to 2 inches outside the canker margin. The cut should not have any sharp angles. Next, cut and scrape away all infected bark down to the wood. Treat exposed wounds with a 70 percent alcohol solution. The whole stem should be removed if a canker extends around more than 50 percent of the stem.

During pruning, take care to avoid unnecessary wounds to the tree. When climbing trees, wear soft-soled shoes to prevent bark injuries.

Remove fire blight infected branches during summer only if the following conditions exist:

  • Infections are in young, vigorous trees and the bacteria may girdle the main stem or main branches.
  • Infections are in dwarfing trees on highly sensitive rootstocks, such as M.9 or M.26.
  • The number of infections in older trees is limited and can easily be removed.
  • It is a dry, sunny day when there is no chance of rain for 48 hours.

Chemical sprays: Chemical sprays are preventive treatments that must be applied prior to the onset of fire blight symptoms; sprays have little effect after the onset of symptoms. Expect blossom infections and plan to apply chemical sprays if: temperatures remain between 65 F and 86 F for a day or more during flower bloom, there is at least a trace of rainfall, the relative humidity remains above 60 percent for 24 hours, there is abundant succulent shoot growth, or there are fruit injuries from hail or other agents. For specific instruction on sprays and timing please use the Midwest Tree Fruit Spray Guide. The chemicals may be sold on various trade names.

Streptomycin is an antibiotic that is acceptable for use to protect trees but may be difficult to obtain. Do not use streptomycin after symptom development since it may lead to antibiotic resistance in the bacterial population.

Aluminum tris is a bactericide used prior to and during bloom.

Copper sprays are toxic to many species of bacteria. Copper sprays are best used during dormancy and prior to bud break because they may damage leaves and young fruit. Do not apply sprays within 50 days of apple harvest or within 30 days of pear harvest. Do not mix with oils or phytotoxicity issues can occur. Copper is available in several forms and sold under various trade names, including Bordeaux mixture.

Prohexadione-calcium is a plant growth regulator that reduces longitudinal shoot growth by inhibiting gibberellin biosynthesis. Prohexadione-calcium does not possess antibacterial activity but alters host biochemistry and tissues in ways that are not favorable for infection by E. amylovora. The length of time that shoot growth is inhibited depends on the application rate and tree vigor. Prohexadione-calcium is ineffective for control of the blossom blight phase of fire blight.

Table 1: Varietal susceptability to fire blight.

Host Degree of Susceptability
High Moderately Susceptable Moderately Resistant
Apple
Malus pumilla
Baldwin* Baldwin* Arkansas Black
Barry Beacon* Ace Delicious
Beacon* Belle de Boskoop Akane
Ben Davis Blushing Golden Britemac
Binet Rouge Cortland* Carroll
Black Twig Discovery Cascade Spur Delicious
Braeburn Delbarestival Classic Delicious
Brown Snout Dutchess Cox’s Orange Pippin
Burgundy Earligold* Dana Red Delicious
Chisel Jersey Early McIntosh Dixi Red Delicious
Cortland* Elstar Red Early McIntosh
Dabinette Elstar* Early Red One McIntosh
Durello di Forli Empire* Empire*
Earli Jon Enterprise Enterprise*
Earligold* Florinia Empire*
Early Spur Rome Freedom* Freedom*
Ellis Bitter Fulford Gala Goldrush
Elstar* Gloster Gold Spur
Fuji Gala* Haralson*
Gala* Golden Delicious Jamba
Geneva Early Granny Smith James Grieve
Ginger Gold Gravenstein Holly Jonafree*
Gloster 69 Grimes Golden Jonamac*
Golden Delicious* Haralson* Honeygold
Golden More Super Imperial Gala Keepsake*
Golden Russet Jersymac Kidd’s Orange Red
Granny Smith* Jonafree* Liberty*
Hereford Redstreak Jonagold* Lurared
Idared Jonamac* Lustre Elstar
Jonafree* Julyred* Lysgolden
Jonagold* Liberty* Macfree
Jonathan Macoun Macspur
Jonnee Maiden Blush Marshall McIntosh
Kingston Black McIntosh Melba
Late Harrison Minyon Melrose
Lodi Missouri Pippon Mor Spur Mac
Magog’s Redstreak Milton Northern Spy
Margil Mollies Delicious Northwestern Greening
Medaille d’Or Monroe* Nova Easygro
Milwa Mutsu* Nured Delicious
Monroe* Northern Spy Nured Winesap
Mutsu* (Crispin) Novamac Ozark Gold
Niagra Northern Spy Perfect Spur Criterion
Nicobel Jonagold Pinova Pioneer Mac
Nittany Prima* Prima*
Northwest Greening* Puritan Priscilla
Nured Jon Quinte* Quinte*
Otava Red Cort Reanda
Paulred Redfree *
Raritan Royal Gala* Red Max
Red Fuji Nagano Rubinette Red Winesap
Red Yorking Scotia Regent
Reglindis Sharon Remo
Reine de Hatives Sir Prize* Rubinola
Reine des Reinettes Smoothee* Scarlet Gala
Rhode Island Greening Spartan Scarlet Spur Delicious
Roberts crab Spijon Sir Prize*
Rome Stark Gala Smoothee*
Rome Beauty Starkspur Earlibase Stamared
Royal Gala* Starr Stark Bounty
Sampion Staybrite Stark Splendor
Santana Summerred Starking Delicious
Sir Prize* Summer Treat Starkrimson
Somerset Redstreak Super Chief Red Delicious Starkspur Ultra Stripe Delicious
Sops of Wine Topaz Starkspur Supreme Red Delicious
Spigold Tydeman’s Red Starkspur Compact Red Delicious
Spur Gala Go Red Wayne* Stayman
Starkspur Law Rome Wealthy* Sturdeespur Delicious
Starr Winesap* Swiss Gormet (Arlet)
Stembridge Jersey Virginiagold Top Spur Delicious
Stokes Red Turley
Super Jon Wellington
Summer Rambo Williams Pride
Tremletts Bitter Williams Red
Twenty Ounce Winesap*
Ultra Red
Wayne*
White Jersey
Yellow Transparent
York Imperial
Crabapple
(Malus species)
Bechtel Brandywine Centurion
Hyslop Dolgo Coralburst
Mary Potter Hopa David
Old Hope Indian Magic Evereste
Ormiston Roy Kelsey Indian Summer
Red Barron Red Splendor Prairie Fire
Red Jade Snow Cloud Profusion
Royalty Spring Snow Radiant
Snowdrift Hilleri Red Vein Russian
Strathmore Golden Hornet Thundercloud
Transcendent Manchurian Vanguard
Rosedale White Cascade
Thunderchild
Common Pear Abbe Fete Anjou Ayers
Pyrus communis Aurora Barlett* Beurre Bosc
Bartlett* Comice* Bradford
Bosc Coscia Carrick
Clapp’s Favorite Dawn Harrow Delight
Conference Douglas Harrow Sweet
Comice* Duchess Harvest Queen*
Flemish Beauty Ewart Honey Sweet
Flordahome Garber Kieffer*
Gorham Harvest Queen* Le Contet
Hardenpont Kieffer* Lincoln*
Hardy Lincoln* Luscious*
Hood Luscious* Magness
Oliver de Serres Tyson
Passe Crassane Waite
Red Bartlett Warren
Reimer Red US 309
Sheldon
Spaulding
Starkrimson
Williams
Winter Nallis
Asian Pear
(Pyrus pyrifolia)
Hosui* Chojuro* Chojuro*
Nijisseki (20th Century)* Hosui* Hosui*
Nijisseki (20th Century)* Kosui
Nijisseki (20th Century)* Kosui
Shinseiki (New Century)*
*Degree of susceptability may vary in different locations.
Host Degree of Susceptability
High Moderately Susceptable Moderately Resistant
AppleMalus pumilla Baldwin* Baldwin* Arkansas Black
Barry Beacon* Ace Delicious
Beacon* Belle de Boskoop Akane
Ben Davis Blushing Golden Britemac
Binet Rouge Cortland* Carroll
Black Twig Discovery Cascade Spur Delicious
Braeburn Delbarestival Classic Delicious
Brown Snout Dutchess Cox’s Orange Pippin
Burgundy Earligold* Dana Red Delicious
Chisel Jersey Early McIntosh Dixi Red Delicious
Cortland* Elstar Red Early McIntosh
Dabinette Elstar* Early Red One McIntosh
Durello di Forli Empire* Empire*
Earli Jon Enterprise Enterprise*
Earligold* Florinia Empire*
Early Spur Rome Freedom* Freedom*
Ellis Bitter Fulford Gala Goldrush
Elstar* Gloster Gold Spur
Fuji Gala* Haralson*
Gala* Golden Delicious Jamba
Geneva Early Granny Smith James Grieve
Ginger Gold Gravenstein Holly Jonafree*
Gloster 69 Grimes Golden Jonamac*
Golden Delicious* Haralson* Honeygold
Golden More Super Imperial Gala Keepsake*
Golden Russet Jersymac Kidd’s Orange Red
Granny Smith* Jonafree* Liberty*
Hereford Redstreak Jonagold* Lurared
Idared Jonamac* Lustre Elstar
Jonafree* Julyred* Lysgolden
Jonagold* Liberty* Macfree
Jonathan Macoun Macspur
Jonnee Maiden Blush Marshall McIntosh
Kingston Black McIntosh Melba
Late Harrison Minyon Melrose
Lodi Missouri Pippon Mor Spur Mac
Magog’s Redstreak Milton Northern Spy
Margil Mollies Delicious Northwestern Greening
Medaille d’Or Monroe* Nova Easygro
Milwa Mutsu* Nured Delicious
Monroe* Northern Spy Nured Winesap
Mutsu* (Crispin) Novamac Ozark Gold
Niagra Northern Spy Perfect Spur Criterion
Nicobel Jonagold Pinova Pioneer Mac
Nittany Prima* Prima*
Northwest Greening* Puritan Priscilla
Nured Jon Quinte* Quinte*
Otava Red Cort Reanda
Paulred Redfree *
Raritan Royal Gala* Red Max
Red Fuji Nagano Rubinette Red Winesap
Red Yorking Scotia Regent
Reglindis Sharon Remo
Reine de Hatives Sir Prize* Rubinola
Reine des Reinettes Smoothee* Scarlet Gala
Rhode Island Greening Spartan Scarlet Spur Delicious
Roberts crab Spijon Sir Prize*
Rome Stark Gala Smoothee*
Rome Beauty Starkspur Earlibase Stamared
Royal Gala* Starr Stark Bounty
Sampion Staybrite Stark Splendor
Santana Summerred Starking Delicious
Sir Prize* Summer Treat Starkrimson
Somerset Redstreak Super Chief Red Delicious Starkspur Ultra Stripe Delicious
Sops of Wine Topaz Starkspur Supreme Red Delicious
Spigold Tydeman’s Red Starkspur Compact Red Delicious
Spur Gala Go Red Wayne* Stayman
Starkspur Law Rome Wealthy* Sturdeespur Delicious
Starr Winesap* Swiss Gormet (Arlet)
Stembridge Jersey Virginiagold Top Spur Delicious
Stokes Red Turley
Super Jon Wellington
Summer Rambo Williams Pride
Tremletts Bitter Williams Red
Twenty Ounce Winesap*
Ultra Red
Wayne*
White Jersey
Yellow Transparent
York Imperial
Crabapple (Malus species) Bechtel Brandywine Centurion
Hyslop Dolgo Coralburst
Mary Potter Hopa David
Old Hope Indian Magic Evereste
Ormiston Roy Kelsey Indian Summer
Red Barron Red Splendor Prairie Fire
Red Jade Snow Cloud Profusion
Royalty Spring Snow Radiant
Snowdrift Hilleri Red Vein Russian
Strathmore Golden Hornet Thundercloud
Transcendent Manchurian Vanguard
Rosedale White Cascade
Thunderchild
Common Pear Abbe Fete Anjou Ayers
Pyrus communis Aurora Barlett* Beurre Bosc
Bartlett* Comice* Bradford
Bosc Coscia Carrick
Clapp’s Favorite Dawn Harrow Delight
Conference Douglas Harrow Sweet
Comice* Duchess Harvest Queen*
Flemish Beauty Ewart Honey Sweet
Flordahome Garber Kieffer*
Gorham Harvest Queen* Le Contet
Hardenpont Kieffer* Lincoln*
Hardy Lincoln* Luscious*
Hood Luscious* Magness
Oliver de Serres Tyson
Passe Crassane Waite
Red Bartlett Warren
Reimer Red US 309
Sheldon
Spaulding
Starkrimson
Williams
Winter Nallis
Asian Pear(Pyrus pyrifolia) Hosui* Chojuro* Chojuro*
Nijisseki (20th Century)* Hosui* Hosui*
Nijisseki (20th Century)* Kosui
Nijisseki (20th Century)* Kosui
Shinseiki (New Century)*
*Degree of susceptability may vary in different locations.

Rootstocks of fruit trees also differ in susceptibility to fire blight (Table 2). Cultivars are usually grafted onto a different rootstock in order to control tree height, apple cultivars on dwarfing rootstocks usually begin bearing fruit at an earlier age compared to cultivars growing on their own rootstock.

Table 2: Susceptability of Apple and Pear Rootstocks to infection by Erwinia amylovora.

Host Rootstock Highly Susceptible Moderately Susceptible Moderately Resistant
Apple (Malus species) Alnarp Malling 7 EMLA Bemali
Malling 26 Budagovsky 9* Budagovsky 118
Malling 9 Vineland 3 Budagovsky 490*
Malling 26 Geneva 16 Geneva series
Malling 27 Malling Merton 106 Malling 7
Malling Merton 111 Malling Merton 111 Malling Merton 106
Malling Merton 106 Malling Merton 111
Mark Series Robusta
Ottawa Vineyard 1
Poland 2 Vineyard 2
Poland 16 Vineyard 5
Poland 22 Vineyard 6
Vineyard 4 Vineyard 7
Pear (Pyrus species) Provence quince (Cydonia obonga) Pyrus betulaefolia ‘Old Home x Farmingdale’
Pyrus communis ‘Bartlett’ Pyrus calleryana
Pyrus communis ‘Winter Nelis’ Pyrus communis ‘Old Home’
Pyrus communis ‘Old Home X Farmingdale’

Additional Information:

Swift, C.E., Hammon, R., and Larsen, H.J. 2007. Backyard Orchard: Apples and Pears. Colorado State University Fact Sheet 2.800.

Jones, A.L. and Sutton, T. B. 1996. Diseases of Tree Fruits in the East. North Central Regional Publication No. 45 (NCR 045). Available for $10 from Michigan State University, Bulletin Office, 10-B Agriculture Hall, East Lansing, MI, 48824-1039. This publication has excellent color photos.

Bessin, R.T., McManus, P.S., Brown, G.R. and Strang, J.G. (editors). Midwest Tree Fruit Pest Management Handbook.University of Kentucky.

Lewis, D., Domoto, P.A. and Gleason, M. (editors). 2009. Midwest Tree Fruit Spray Guide.

Beckerman, Janna. 2006. Disease Susceptibility of Common Apple Cultivars. Purdue University, Purdue Extension Publication BP-132-W. This publication contains an extensive list of apple and edible crabapple cultivars and cultivar susceptibility to common diseases, including fire blight.

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Fire Blight Of Loquats – Learn How To Treat Fire Blight In Loquat Trees

Loquat is an evergreen tree grown for its small, yellow/orange edible fruit. Loquat trees are susceptible to minor pests and diseases as well as more serious issues like fire blight. In order to control loquat fire blight, it is crucial to learn how to identify fire blight of loquats. The following information will help to identify the disease and provide tips on how to treat fire blight in loquat plants.

What is Fire Blight of Loquats?

Fire blight of loquats is a serious bacterial disease caused by the bacterium Erwinia amylovaora. The first signs of the disease occur in the early spring when temps are above 60 F. (16 C.) and the weather is a typical spring mix of rain and humidity.

This disease attacks some plants in the rose family, Rosaceae, to which loquat belongs. It may also infect:

  • Crabapple
  • Pear
  • Hawthorn
  • Mountain ash
  • Pyracantha
  • Quince
  • Spirea

Symptoms of a Loquat with Fire Blight

First, infected flowers turn black and die off. As the disease progresses, it moves down the branches causing young twigs curl and blacken. Foliage on infected branches also blacken and wilt but remain attached to the plant, making it look as if it has been burned. Cankers appear on branches and on the main stem of the tree. During rainy periods, a wet substance may drip from infected plant parts.

Fire blight may afflict blossoms, stems, leaves and fruit and can be spread by both insects and rain. Affected fruit shrivels and blackens and the overall health of the plant can be compromised.

How to Treat Fire Blight in Loquat Trees

Loquat fire blight control relies on good sanitation and the removal of all infected plant parts. When the tree is dormant in the winter, prune out any infected areas at least 12 inches (30 cm.) below the infected tissue. Disinfect pruning shears between cuts with one-part bleach to 9 parts water. If possible, burn any infected material.

Minimize damage to tender young shoots that can become open to infection as much as possible. Do not fertilize with too much nitrogen since this stimulates new growth that is most at risk for infection.

Chemical sprays can prevent bloom infection but may require several applications. When the tree is just beginning to bloom, or just prior to bloom, apply spray every 3-5 days until the tree is finished blooming. Re-spray immediately after raining.

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Insects and Diseases that occurs in Loquat Plants and Measures to Control It!

A. Insect Pest:

1. Bark Eating Caterpillar (Inderbela Quadrinota):

Bark eating caterpillars cause huge damage to loquat trees.

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Caterpillars feed on the bark and make tunnels in the trunk. Due to tunnelling, girdling is caused, which may kill the plant.

Management:

Clear the holes/tunnels with wire, inject kerosene oil or chloropyriphos solution 50: 50 water.

2. Fruit Fly (Dacus dorsalis)

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At fruit maturity fruits are attacked by fruit fly. On hatching maggots bore into the fruits and feed on the pulp. The infested fruits become unfit for human consumption.

Management:

It is difficult to control the fruit flies, once they enter the fruits. One can reduce the attack.

(i) Hoeing of the tree basins should be done to expose the pupae to their natural enemies.

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(ii) Collect the infected fruits and dump in deep pits.

(iii) To repel the fruit fly spray Thiodan 35E (endosulphan) @ 2 ml/L. of water in first week of February and repeat the spray in the last week of February or spray Sevin 50 WP (carbaryl) @ 2 g/L. of water twice.

B Diseases:

1. Shoot/Fruit Blight and Bark Canker (Phoma glumerata sp.)

The canker appear on bud scars, twigs or in crotches. Small circular brown spots appear around a leaf scar or superficial wound. As the canker enlarges the centres become sunken with the surrounding healthy bark. The fungus perpetuates itself on the trees in bark cankers.

Control:

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Remove the cankers and decorticate along with 2 cm of healthy bark. Apply Bordeaux paste on the cut ends and wounds. Spray Bordeaux mixture 2:2: 250 twice at an interval of one month.

2. Collar Rot:

It is caused by Phytophthora species. Some are of the view that it is caused by Diplodia natalensis. The fungus produces canker from ground level to point from where scaffolds emerge. The rot girdless the trunk during 2-3 years. Affected trees flower profusely. The foliage become yellowish green. The tree show wilting and ultimately dry up completely.

Control:

(i) Avoid flooding the orchard.

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(ii) Uproot the infected trees and destroy.

(iii) Scrap the infected portion and cut some healthy bark also. Apply Bordeaux paint. Spray the trees with Bordeaux mixture 2:2: 250.

3. Root Rot/White Rot:

It is caused by a fungus Polyporus palustrisis. The affected trees show symptoms of wilt during early leaf fall and increased fruit set. The fruiting bodies appear, when the rot is fairly well advanced.

Control:

(i) Locate the infected trees at the early stage, by examining the roots and root collar region of trees. Dig out decayed roots and cut them completely right from the collar region.

(ii) Treat the cut ends with disinfectant solution. Then apply Bordeaux paste. Drech the soil from where roots have been dug out, with Bordeaux mixture 2: 2: 250.

First Report of Epicoccum nigrum Causing Brown Leaf Spot of Loquat in Southwestern China

Eriobotrya japonica (Thunb.) Lindl., commercially known as loquat, is a subtropical evergreen fruit tree in the Rosaceae that is native to southern China. It is highly valued on the fresh market for its tasty and nutritional fruits, and its leaves have been used in natural medicine for the treatment of coughs and chronic bronchitis (Badenes et al. 2013). Tree growth and fruit production in China are under pressure from increased levels of leaf spot diseases. In November 2015, gray-brown necrotic spots ranging from 5 to 10 mm in diameter were observed on the adaxial surface of leaves of loquat trees growing in three orchards in Beibei District of Chongqing in southwestern China. Within these orchards, spotting affected 30 to 80% of leaves on individual trees over the course of the season. To isolate the causal agent, nine symptomatic leaves were surface disinfested and three small sections of each leaf were cut from the diseased area and placed onto PDA. After 7 days of incubation at 25°C, felty colonies of mycelia giving off a strong reddish-orange diffusible pigment appeared across the plate. Microscopy revealed globose to pyriform, dark, solitary, verrucose, and multicellular conidia measuring 14.3 to 28.6 μm diameter (n = 30) were produced on the myclia. The morphological characteristics of the mycelium and reproductive structures of the isolates fully fit the description of Epicoccum sp. (Sheikhloo et al. 2011). To further substantiate our identification, DNA was extracted from 10-day-old mycelia cultures and used to carry molecular phylogenetic analysis. The internal transcribed spacer (ITS) region of the sampled isolate was amplified using ITS1 and ITS4 universal primers and the resulting amplicon subjected to DNA sequencing. The resulting sequence (GenBank accession no. KY303832) shared 99% maximum identity with other reported isolates of E. nigrum (KT276979.1) found in public databases. To test the pathogenicity under Koch’s postulates, nine disease-free leaves were removed from a 2-year-old ‘Longquan No. 1’ tree and inoculated in vitro by injecting a suspension of ∼106 spores/ml using a sterile syringe into the lamina. In parallel, similar inoculations were made on disease-free leaves of trees growing under greenhouse conditions. Sterile water was used as a control and the entire experiment was replicated in triplicate. Symptoms were scored beginning at 5 days postinoculation. By 10 days postinoculation, spore-infected leaves showed the appearance of gray-brown necrotic spots identical to those observed in the field, whereas control leaves remained symptomless. The reisolated fungus was found to be identical morphologically and by DNA sequence analysis to the original isolate. Epicoccum nigrum has been reported on many hosts. For instance, it has been found to cause leaf spot on Lablab purpureus (Mahadevakumar et al. 2014) and as an endophyte on the grapevine (Martini et al. 2009). To our knowledge, this is the first report of E. nigrum causing brown leaf spot of loquat in southwestern China.

Fire Blight look alike in Carmen Cherry

I sent your pictures to several people and most were also stumped.
No I do not believe it is a stress response for cold then hot. Browning at the base of the stems and wilt of stems are a disease. One colleague suggested European Brown Rot (Monilinia laxa), This is an uncommon disease of cherries which infects the blossoms and kills them and the spurs that they are on. It does not usually kill new shoots.
Bacterial canker (Pseudomonas syringae) but again the symptoms are not right. But several people have suggested this as the most likely disease.
When I first looked at the pictures I thought it looked a lot like fire blight (but fire blight does not go to cherries). It showed several classic symptoms. The shepard’s crook wilting of new shoots and the death of the base of the leaves as the infection moves into the leaf from the stem. I did a internet search on fire blight in cherries and found references to fire blight (Erwinia amylovora) on cherries.
Both Bacterial canker and fire blight are bacterial diseases. The infection took place during bloom and was probably accompanied with rain which washed the bacteria down into the base of the flowers where it entered the plant and began to kill plant tissues. The bacteria is now spreading in the plant. There are no treatments after infection. I recommend cutting out all the infected shoots 8 inches below where you see any sign of the the disease. Here are some links to more information. Most of the literature is on apples where it is a common and devastating disease but all the recommendations would be the same for cherries.

See the links at the bottom of the article.
You may want to contact the University of Minnesota’s Diagnostic Plant Clinic to have them confirm the presence of a bacteria in the infected tissues or in the apparently healthy tissue adjacent to it..
Pruning out the infected tissues is probably worthwhile.
I attach a picture of fire blight in apples showing the same symptoms as in your photos.

Brown Rot on Ornamental Cherries – Trees


Brown rot infected leaves of a cherry tree

Spring weather often brings with it the chances of diseases in our landscapes and unfortunately the past few springs have brought a serious disease to our flowering cherries, especially the cultivar ‘Kwansan”. This new disease is really an old orchard disease of stone fruit called brown rot. In Maryland landscapes, this new problem is caused by the fungus Monilinia laxa.

The first symptoms often seen are browning and the collapse of the blossoms followed closely by the death of the small twigs. The symptoms look like fire blight, but cherries are not susceptible to that disease. If infected blossoms do not drop off, the fungus may grow through the flower stem (pedicel) and into the twig below. Twigs develop elliptical cankers with profuse gumming at the margin between diseased and healthy tissue. Leaves on these infected shoots turn brown and wither, but remain attached. In some instances, twigs are girdled and killed. During wet weather in May and June, the fungus sporulates on the surface of infected twig cankers. Cankers enlarge from season to season, and sporulation may continue on large cankers for 4 years or more.

Visible presence of the pathogen is easy under wet conditions and appears as powdery tufts of brown-gray spores that are visible on the outside of infected flowers and on infected fruit or twig surfaces.

Management

This is a common disease found in fruit orchards and management relies on good sanitation and proper timing of protectant fungicides. However, in ornamentals, this disease is a new problem and the control has not been studied extensively.

By: Sheila McBride and David Appel

Fire blight causes vascular wilt in many varieties of pome trees (apples, pears, and ornamental pears) and members of the Rosaceae family (a wide range of trees, shrubs, herbs, and ornamental plants such as roses, strawberries, figs, and mulberries). With vascular wilt diseases, pathogens block the water-carrying (vascular) system of the plant, causing the leaves, stems, and branches to wither, weaken, and die.

One of the most destructive diseases of commercial apples and pears, fire blight is also a serious disease of the popular ornamental Bradford pears used in many Texas landscapes (Fig. 1). Other common Texas woody ornamentals affected by fire blight are loquat, cotoneaster, and pyracantha.

Symptoms

  • Infected flowers become water-soaked (translucent and wilted), shrivel, and turn brown.
  • Leaves progressively turn brown, develop black blotches, curl, and eventually shrivel.
  • Twigs wilt from the tip downward, turning black and curling in a “shepherd’s crook,” giving them a burnt appearance (Fig. 2).
  • Branches develop dark, sunken cankers that enlarge and girdle the branches. Eventually, the branch dies (Fig. 3).

Cause and Environmental Factors

The bacterium, Erwinia amylovora, causes fire blight. The pathogen

  • over-winters in cankers, budscars, and branches;
  • forms an ooze that attracts insects, including bees, that then spread the bacteria via the nectarthodes (openings at the base of flowers);
  • also spreads by rain, which splashes onto the bacterial ooze and causes new infections; and
  • infects new, tender, succulent twigs and leaves.

Control

  • During winter dormancy, use sanitation pruning to remove infected wood:

– Cut an infected branch 4 to 6 inches below the visible injury or canker.

– To avoid spreading bacteria during pruning, sanitize the pruning tool before each cut, using a 10-percent bleach solution (one part bleach to nine parts water).

– To prevent rust, dry and oil tools after using them.

  • Reduce excessive succulence by avoiding extreme fertilization and watering.
  • Plant moderately resistant varieties.
  • Reduce new infections by spraying an antibiotic such as streptomycin sulfate (Ferti-lome® Fire Blight Spray) on flowers or shoots before the bacteria infect them. A copper sulfate fungicide (Bonide® Copper Fungicide) is also an option when applied several times while the blossoms are open. (Neither option will eliminate all new infections or those already existing in the wood.) Refer to product labels for proper rates and use.

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