Stone FruitsStone Fruits PrunusPrunus is a genus of trees and shrubs, is a genus of trees and shrubs,

including the including the plumsplums, , cherriescherries, , peachespeaches, , apricotsapricots and and almondsalmonds. .

It is traditionally placed within the rose It is traditionally placed within the rose family Rosaceae as a subfamilyfamily Rosaceae as a subfamily

The flowers are usually white to pink, with The flowers are usually white to pink, with five petals and five sepals. The fruit of all five petals and five sepals. The fruit of all PrunusPrunus species is a species is a drupedrupe with a relatively with a relatively large "stone". Leaves are simple and usually large "stone". Leaves are simple and usually lanceolate, unlobed and toothed along the lanceolate, unlobed and toothed along the margin.margin.

Stone fruitsStone fruits

Peach DiseasesPeach Diseases

Black knotBlack knot Brown rotBrown rot Perennial cankerPerennial canker Peach scabPeach scab

Peach DiseasesPeach Diseases

DISEASE: DISEASE: Black knotBlack knot PATHOGEN: PATHOGEN: Apiosporina morbosaApiosporina morbosa

                  (Syn.                   (Syn. Dibotryon Dibotryon morbosummorbosum))

HOSTS: HOSTS: members of the genus, members of the genus, PrunusPrunus,,mainly affecting cultivated plum, mainly affecting cultivated plum, prune and cherry and to a lesser prune and cherry and to a lesser extent wild plum and cherry.extent wild plum and cherry.

SignificanceSignificance

  Black knot is a disease that is most severe on Black knot is a disease that is most severe on cultivated crops in orchard and ornamental cultivated crops in orchard and ornamental planting situations. planting situations.

Black knot disease is mainly a problem in Black knot disease is mainly a problem in North America (Canada, the United States and North America (Canada, the United States and Mexico) where it is indigenous. Mexico) where it is indigenous.

Black knot has been reported on 24 species of Black knot has been reported on 24 species of PrunusPrunus but is most commonly found on wild but is most commonly found on wild and cultivated plums and cherries. The disease and cultivated plums and cherries. The disease can be found throughout North America but is can be found throughout North America but is most commonly found in the northeast. most commonly found in the northeast.

Black knot - SymptomsBlack knot - Symptoms Thick, black, irregular swellings on the twigs. The Thick, black, irregular swellings on the twigs. The

presence of these symptoms is often first noticed presence of these symptoms is often first noticed in the winter season when they are unobscured by in the winter season when they are unobscured by leaves. However, the fungal disease-causing agent leaves. However, the fungal disease-causing agent has been present for quite some time. has been present for quite some time.

The pathogen's presence disrupts the normal The pathogen's presence disrupts the normal growth of the twigs and a tumor-like growth forms growth of the twigs and a tumor-like growth forms at the infection site. at the infection site.

The first symptoms appear as small, light brown The first symptoms appear as small, light brown swellings of the current or previous season's swellings of the current or previous season's growth. The the swellings turn olive-green in color growth. The the swellings turn olive-green in color with a velvety texture in 2with a velvety texture in 2ndnd season. The knots season. The knots darken and appear to have a hard, brittle texture. darken and appear to have a hard, brittle texture.

SymptomsSymptoms

SymptomsSymptoms

Disease CycleDisease Cycle

Disease Cycle cont.Disease Cycle cont. Overwinters in the knots. The first ascospores are Overwinters in the knots. The first ascospores are

forcibly discharged at the time of bud break in early forcibly discharged at the time of bud break in early spring. Temperatures between 16°C and 27°C (60-spring. Temperatures between 16°C and 27°C (60-80°F) are needed for discharge (continues until 2-3 80°F) are needed for discharge (continues until 2-3 wks. after bloom).wks. after bloom).

Ascospores are spread by air currents and rain Ascospores are spread by air currents and rain splashing. Mainly the succulent green shoots and, splashing. Mainly the succulent green shoots and, occasionally, wounded tissues are most susceptible. occasionally, wounded tissues are most susceptible.

The knots develop very slowly, and by the end of the The knots develop very slowly, and by the end of the summer they appear only as small galls that might summer they appear only as small galls that might easily be overlooked. The following spring the knots easily be overlooked. The following spring the knots enlarge very rapidly and are soft in texture with enlarge very rapidly and are soft in texture with become greenish-brown color as conidia develop over become greenish-brown color as conidia develop over their surfaces.their surfaces.

Cultural ManagementCultural Management Cultural management strategies Cultural management strategies

are important in black knot are important in black knot management. Monitoring and management. Monitoring and pruning sources of inoculum. All pruning sources of inoculum. All shoots and branches bearing shoots and branches bearing knots should be pruned out during knots should be pruned out during the winter. This pruning should be the winter. This pruning should be completed before ascospore completed before ascospore discharge begins in the spring.discharge begins in the spring.

Winter is also a good time to look Winter is also a good time to look for and remove sources of for and remove sources of inoculum in nearby wild inoculum in nearby wild PrunusPrunus species in hedgerows and species in hedgerows and woodlots. woodlots.

ManagementManagement Genetic resistanceGenetic resistance

Varieties may vary in their ability to tolerate or resist an Varieties may vary in their ability to tolerate or resist an infection. Resistance is as important as fruit infection. Resistance is as important as fruit characteristics, tree size, and flowering time. characteristics, tree size, and flowering time.

Site selectionSite selectionConsider the site location. Avoid planting new trees near Consider the site location. Avoid planting new trees near areas with known problems such as abandoned orchards.areas with known problems such as abandoned orchards.

Biological controlBiological controlInterest in biocontrol agents is increasing because of the Interest in biocontrol agents is increasing because of the loss of certain fungicides registrations and the fact that loss of certain fungicides registrations and the fact that applicators would prefer to reduce their exposure to applicators would prefer to reduce their exposure to pesticides. pesticides.

Chemical ManagementChemical ManagementFungicides are normally only recommended for sites Fungicides are normally only recommended for sites with valuable trees and/or severe infections levels. with valuable trees and/or severe infections levels. Fungicides work best as a protectant and are ineffective Fungicides work best as a protectant and are ineffective if cultural practices are not also employed. if cultural practices are not also employed.

Brown rot Brown rot

PATHOGEN: PATHOGEN: Monilinia fructicola, M. Monilinia fructicola, M. laxa,laxa,                   and M. fructigena                   and M. fructigena

HOSTS:  HOSTS:  Stone fruits (peach, Stone fruits (peach, nectarine, cherry, plum), almond, nectarine, cherry, plum), almond, and occasionally some pome fruits and occasionally some pome fruits (apple and pear)(apple and pear)

Brown rotBrown rot

The brown rot fungi cause a blight of The brown rot fungi cause a blight of blossoms and twigs and a soft decay of blossoms and twigs and a soft decay of fruits of peaches, cherries, and plums. fruits of peaches, cherries, and plums. Thus, there are two distinct phases of Thus, there are two distinct phases of this disease.this disease. Blossom and twig blightBlossom and twig blight Fruit rot Fruit rot

Blossom and twig blightBlossom and twig blight This phase of the disease occurs in early spring This phase of the disease occurs in early spring

when the trees are blooming, although twig blight when the trees are blooming, although twig blight also can occur during the fruit rot phase. also can occur during the fruit rot phase.

The anthers and pistil of the flower are infected The anthers and pistil of the flower are infected initially. initially.

Infected blossoms wilt, turn brown, and usually Infected blossoms wilt, turn brown, and usually cling to the twig. Extension of the infection into cling to the twig. Extension of the infection into the peduncle and twig results in a necrotic area in the peduncle and twig results in a necrotic area in the woody tissue termed a “canker”.the woody tissue termed a “canker”.

Under moist or humid conditions, ash-gray-brown Under moist or humid conditions, ash-gray-brown colored sporodochia bearing conidia form on the colored sporodochia bearing conidia form on the surface of diseased blossoms and twigs. A gummy surface of diseased blossoms and twigs. A gummy substance usually exudes from the cankers, substance usually exudes from the cankers, causing the blighted flowers to adhere to the causing the blighted flowers to adhere to the twig. twig.

SymptomsSymptoms

SymptomsSymptoms

Blossom and floral tubecolonized by the fungus

Blighted blossom, twig canker, gummy exudate, and tufts of conidia.

Fruit rotFruit rot Fruit susceptibility to brown rot increases Fruit susceptibility to brown rot increases

during the 2 to 3 week period prior to harvest. during the 2 to 3 week period prior to harvest. Increased susceptibility is associated with an Increased susceptibility is associated with an increase in sugar content as the fruits ripen.increase in sugar content as the fruits ripen.

Tan-brown, circular spots are visible on the Tan-brown, circular spots are visible on the fruit. Under humid conditions, ash-gray-brown fruit. Under humid conditions, ash-gray-brown masses of conidia develop on these lesions. masses of conidia develop on these lesions.

If environmental conditions are wet and warm If environmental conditions are wet and warm during fruit ripening, the entire crop can during fruit ripening, the entire crop can literally be destroyed “overnight”.literally be destroyed “overnight”.

Diseased fruit that do not fall to the ground Diseased fruit that do not fall to the ground dehydrate and become shriveled “mummies” dehydrate and become shriveled “mummies” that cling to the branch. Sometimes the that cling to the branch. Sometimes the fungal infection extends from the fruit into the fungal infection extends from the fruit into the twig and branch. twig and branch.

SymptomsSymptoms

Disease cycleDisease cycle

Management of Brown Management of Brown RotRot

Orchard location is important. Trees planted in orchards Orchard location is important. Trees planted in orchards having poor air movement, and thus slow drying conditions, having poor air movement, and thus slow drying conditions, are more likely to have blossom blight and brown rot. are more likely to have blossom blight and brown rot.

Sanitation practicesSanitation practicesThe removal of diseased fruit mummies and blighted twigs The removal of diseased fruit mummies and blighted twigs from the trees and removal of fruit and mummies from the from the trees and removal of fruit and mummies from the orchard floor can substantially reduce overwintering orchard floor can substantially reduce overwintering inoculum. inoculum.

Post-harvest controlPost-harvest controlPractices used during harvest can significantly impact the Practices used during harvest can significantly impact the amount of fruit decay following harvest. Picking and amount of fruit decay following harvest. Picking and handling fruit carefully to avoid injuries, cooling fruit handling fruit carefully to avoid injuries, cooling fruit promptly after harvest by hydrocooling or forced air cooling, promptly after harvest by hydrocooling or forced air cooling, using clean containers to hold the fruit, and timely using clean containers to hold the fruit, and timely harvesting harvesting

FungicidesFungicidesBlossom blight occurrence is very much dictated by the Blossom blight occurrence is very much dictated by the weather conditions. In areas where blossom infection weather conditions. In areas where blossom infection occurs, 1 to 3 fungicide sprays beginning just as the occurs, 1 to 3 fungicide sprays beginning just as the blossoms open control blossom blight.blossoms open control blossom blight.

Symptoms – SIUC ARC Symptoms – SIUC ARC 20012001

Perennial cankerPerennial canker Also called Valsa canker, Cytospora Also called Valsa canker, Cytospora

canker, Leucostoma canker, and peach canker, Leucostoma canker, and peach canker, is one of the most common and canker, is one of the most common and debilitating diseases of peach trees. debilitating diseases of peach trees. Successful long-term production of Successful long-term production of peaches is seldom possible if the disease peaches is seldom possible if the disease is not controlled. is not controlled.

PATHOGEN: PATHOGEN: Leucostoma cinctaLeucostoma cincta   HOSTS:  HOSTS:  Stone fruits (peach, nectarine, Stone fruits (peach, nectarine,

cherry, plum).cherry, plum).

SymptomsSymptoms SomewhatSomewhat variable depending on which part of the tree variable depending on which part of the tree

is attacked. The most conspicuous and pronounced is attacked. The most conspicuous and pronounced symptoms usually appear on major scaffold limbs and symptoms usually appear on major scaffold limbs and older branches. older branches. Dark, sunken cankers expand along the limbs, Dark, sunken cankers expand along the limbs,

producing large amounts of amber-colored or dark producing large amounts of amber-colored or dark brown gum at their edges. As the cankers enlarge brown gum at their edges. As the cankers enlarge with age, infected tissues crack, dry out, and appear with age, infected tissues crack, dry out, and appear blackened; affected limbs become progressively more blackened; affected limbs become progressively more girdled, lose their vigor, and eventually die.girdled, lose their vigor, and eventually die.

Gumming cankers can also be seen at other common Gumming cankers can also be seen at other common sites of infection, including narrow-angled branch sites of infection, including narrow-angled branch crotches, trunks injured by machinery, rodents, or insect crotches, trunks injured by machinery, rodents, or insect pests, poorly healed pruning wounds, and leaf scars or pests, poorly healed pruning wounds, and leaf scars or winterkilled buds on young shoots.winterkilled buds on young shoots.

SymptomsSymptoms

SignsSigns

In the early spring, conidia are exuded in a In the early spring, conidia are exuded in a sticky mass from pycnidia embedded in the sticky mass from pycnidia embedded in the wood. Perithecia sometimes are also formed wood. Perithecia sometimes are also formed in dead tissue after a couple of years, but the in dead tissue after a couple of years, but the ascospores are considered to be of minor ascospores are considered to be of minor importance in the disease cycle. importance in the disease cycle.

SignsSigns

00

Management Management 1. New plantings.1. New plantings. Do not be establish next to old Do not be establish next to old

cankered blocks of peaches. Nursery stock should cankered blocks of peaches. Nursery stock should be canker free and not excessively large. Trees be canker free and not excessively large. Trees should be protected against peach tree borer should be protected against peach tree borer before planting and promote wide-angle before planting and promote wide-angle branching.branching.

2. Pruning and training. 2. Pruning and training. It is critical to train in a It is critical to train in a manner that maintains wide branch angles and manner that maintains wide branch angles and an open center to the tree. Two of the most an open center to the tree. Two of the most common sites of canker initiation are narrow-common sites of canker initiation are narrow-angled branch crotches and the weak twigs that angled branch crotches and the weak twigs that develop within tree centers. develop within tree centers.

Management Management 3. Winter hardiness. 3. Winter hardiness. Horticultural practices Horticultural practices

should be designed to promote hardening off should be designed to promote hardening off in the fall and prevent winter injury.in the fall and prevent winter injury.

4. Pest control. 4. Pest control. Brown rot, oriental fruit moth, Brown rot, oriental fruit moth, peach tree borers, and rodents all cause peach tree borers, and rodents all cause cankers or injuries that can subsequently be cankers or injuries that can subsequently be invaded by the perennial canker fungi.invaded by the perennial canker fungi.

5. Canker eradication. 5. Canker eradication. During the pruning During the pruning operation, remove all cankers on small operation, remove all cankers on small branches or limbs, making a thinning cut at branches or limbs, making a thinning cut at least 4 inches (10 cm) beneath the edge of least 4 inches (10 cm) beneath the edge of the cankered zone. the cankered zone.

Peach scabPeach scab

PATHOGEN: PATHOGEN: Cladosporium carpophilumCladosporium carpophilum    HOSTS:  HOSTS:  Stone fruits (peach, nectarine, Stone fruits (peach, nectarine,

cherry, plum).cherry, plum).

This disease can affect twigs and leaf This disease can affect twigs and leaf petioles, but the most serious damage results petioles, but the most serious damage results from fruit infection.from fruit infection.

SymptomsSymptoms First appear on fruit when they are half formed to First appear on fruit when they are half formed to

nearly full grown, about six to seven weeks after petal nearly full grown, about six to seven weeks after petal fall. fall.

Small, round, olive-green spots about l/l6-l/8 inch in Small, round, olive-green spots about l/l6-l/8 inch in diameter develop on the fruit. diameter develop on the fruit.

Spots are superficial and slowly enlarge. They may Spots are superficial and slowly enlarge. They may merge to form large, irregular blotches that turn merge to form large, irregular blotches that turn velvety, dark olive-green or black. velvety, dark olive-green or black.

Severely infected fruit may be stunted, become Severely infected fruit may be stunted, become misshapen, or crack open. When fruits crack open, misshapen, or crack open. When fruits crack open, they are often invaded by other fungi that rot the fruit. they are often invaded by other fungi that rot the fruit.

Leaves may also be infected by scab. Small (l/4 inch), Leaves may also be infected by scab. Small (l/4 inch), round, and yellowish-green to yellowish-brown spots round, and yellowish-green to yellowish-brown spots develop on the underside of the leaf. develop on the underside of the leaf.

SymptomsSymptoms

SymptomsSymptoms

Disease CycleDisease Cycle The fungus overwinters in lesions on twigs. The fungus overwinters in lesions on twigs. Conidia are produced in the spring after petal-Conidia are produced in the spring after petal-

fall and are windblown or splashed about by fall and are windblown or splashed about by rain. rain.

The conditions which favor disease development The conditions which favor disease development are temperatures above 60°F for spore are temperatures above 60°F for spore production, over 50°F (optimal 72°F to 86°F) for production, over 50°F (optimal 72°F to 86°F) for spore germination, and between 36°F and 95°F spore germination, and between 36°F and 95°F for disease development. Most infection occurs for disease development. Most infection occurs at the shuck-split stage of growth, although the at the shuck-split stage of growth, although the fruit remains susceptible through harvest. fruit remains susceptible through harvest.

Spores from the fruit reinfect the twigs and Spores from the fruit reinfect the twigs and leaves, completing the disease cycle. leaves, completing the disease cycle.

ManagementManagement Fungicides - Most scab infection occurs Fungicides - Most scab infection occurs

between shuck-split and 6 weeks after shuck between shuck-split and 6 weeks after shuck split. This period coincides with the peak spore split. This period coincides with the peak spore production by the fungus. production by the fungus.

Fungicide sprays during bloom and petal fall Fungicide sprays during bloom and petal fall are not necessary for scab control.are not necessary for scab control.

Proper pruning increases air movement within Proper pruning increases air movement within the tree crown and decreases the likelihood of the tree crown and decreases the likelihood of twig infection. twig infection.