Category : Bacterial
Bacterial canker Pseudomonas syringae
Symptoms
Cankers on twigs at bases of flower and leaf buds, in pruning wounds or at the base of spurs which exude amber colored gum; cankers spread upwards and form sunken areas in winter; if pathogen enters dormant buds they may be killed or open normally in Spring before collapsing in early Summer; infected buds may be symptomless
Cause
Bacterium
Comments
Disease emergence favors high moisture and low temperatures in the spring; young trees particularly susceptible; trees grown in sandy soils that drain poorly are also susceptible
Management
Ensure that a suitable cherry variety and rootstock is chosen based on geographic location and environmental conditions to prevent stress to tree which predisposes tree to canker disease; apply protective copper spray to trees before flowering; prune trees in early summer to decrease likelihood of infection
Category : Fungal
Black knot Apiosporina morbosa
Symptoms
Elongated swellings (knots) on woody parts of tree which can reach up to 30 cm (12 in) long; knots are initially olive green in color with a corky texture but turn black in color and become hard and brittle; knots grow in length each year
Cause
Fungus
Comments
Infections occur on new shoots after rainfall and knots develop rapidly in second year
Management
Prune knots on twigs and branches 8-10 cm (3-4 in) below the swelling and remove the pruned branches from the orchard; remove knots on older branches by removing the knot plus 2 cm (0.8 in) of surrounding tissue; removal of knots is most effective when done in midsummer; disease can be controlled by application of appropriate fungicides, if available, during shoot elongation
Brown rot Monilinia fructicola
Cherry fruits infected with brown rot fungus
Symptoms
Brown discoloration of fruit skin and inner tissue; fruit skin wrinkled; collapsed flowers exuding sap from their bases; tan cankers with dark edges on twigs; gray-brown spore masses may be present on cankers
Cause
Fungus
Comments
Fungus survives in mummified fruit on the tree, blighted blossoms, cankers and infected twigs; blossom and twig blights are promoted by periods of wet weather
Management
The currently most effective method of controlling brown rot is through the application of appropriate protective fungicides timed so that they are applied when the susceptible flower parts are exposed or after a wet period; avoiding sprinkler irrigation protects the leaves and flowers from wetness that promotes the disease. Cultural control methods include: removing mummified fruit from tree, pruning infected twigs and reducing plant stress by providing adequate levels of water and fertilizer
Cherry leaf spot Coccomyces hiemalis
Symptoms
Small, red-purple spots on upper surfaces of leaves which turn brown and may coalesce; leaves may become chlorotic if there are a few lesions present; if tree becomes severely defoliated fruit may fail to develop properly and remain light in color and watery in texture
Cause
Fungus
Comments
Fungus overwinters on infected leaves on the ground; disease development is promoted by warm temperatures and high humidity
Management
Disease can be controlled through applications of appropriate fungicides, Bordeaux mixture is also effective; no cherry varieties are resistant to leaf spot, plant less susceptible varieties if available
Powdery mildew Podosphaera spp.
Symptoms
Light colored circular lesions on leaves inside tree canopy which develop a powdery appearance; lesions may coalesce to cover leaf; if infection is severe, leaves may blister and infected shoots may be distorted and stunted; infected fruits may have slightly depressed areas on the surface containing fungal hyphae (filamentous fungal structures)
Cause
Fungus
Comments
Infection of fruit is more likely if there are rainfalls close to harvest
Management
Management of powdery mildew in cherry is reliant on the application of appropriate fungicides and cultural practices which promote good air circulation around tree canopies to lower humidity
Rust Tranzschelia discolor
Symptoms
Pale yellow-green spots on both upper and lower leaf surfaces which are angular in shape and turn bright yellow in color; spots on lower leaf surface develop orange-red spores
Cause
Fungus
Comments
Fungus overwinters in twigs or in leaves which remain attached to the tree
Management
Rust can be prevented by spraying trees with protective fungicides; application is usually carried out one, two and three months before harvest in areas prone to early season outbreaks of the disease and after harvest in areas where disease is less problematic or emerges later in the season
Silver leaf Chondrosterum pupureum
Symptoms
Leaves have a silvery appearance; if infection is severe the leaves may curl upwards and become necrotic; death of individual limbs or entire tree may occur; fungal fruiting bodies appear on the surface of the dead bark
Cause
Fungus
Comments
Pathogen is spread via spores released after rainfall during periods of high humidity and can enter trees through pruning wounds; risk of infection is increased if tree is pruned during late winter or early spring; trees also susceptible when they are heavily pruned
Management
Control of silver leaf disease is difficult and infection can be widespread after rainfall in areas where the disease is present; strategies to reduce the incidence of the disease include: removing all plant debris e.g. pruning waste, stumps, and logs; pruning tree during dry periods and treating large pruning wounds with fungicidal dressing
Verticillium wilt Verticillium dahliae
Symptoms
Withering of leaves on one or more spurs on 1 year old wood; leaves are dull and stunted; fruit small; older cherry trees do not recover from disease
Cause
Fungus
Comments
Disease is more severe in wet soils
Management
Plant cherry in soil with no history of disease; keep trees adequately fertilized and watered
Category : Viral
Cherry rasp leaf Cherry rasp leaf virus (CRLV)
Symptoms
Leaf like growths (enations) on underside of leaves near center; symptoms spread from lower parts of tree upwards; defoliation of limbs; decline of tree
Cause
Virus
Comments
Distinguished from PNRSV by the leaves remaining green; virus is transmitted by nematodes and through grafting
Management
Fumigants to control nematodes may control cherry rasp leaf
Sour cherry yellows Prune dwarf virus (PDV)
Symptoms
Chlorotic rings or mottled pattern on newly expanded leaves of sour cherry which become necrotic and may drop out of leaves, giving them a shot hole appearance; leaves that expand after the initial symptoms have become visible display lesser and lesser symptoms; one or more years later leaves on infected trees become yellow with green mottle and drop from tree; fruit yield may be reduced by up to 50%; sweet cherry trees develop chlorotic spots or rings with some shot holes; fruiting spurs decrease in later years as the disease progresses; fruit on infected trees are generally firmer and larger than on uninfected
Cause
Virus
Comments
Virus can infect a wide range of Prunus species
Management
No control strategies are currently known; always purchase certified, disease-free material
Category : Oomycete
Crown and root rot Phytophthora spp.
Symptoms
Poor new growth; leaves chlorotic, small in size and sparse; fruit may be small, brightly colored and susceptible to sunburn; shoots may suffer from dieback and tree will often die within weeks or months of first signs of infection or decline gradually over several seasons; root crown may show signs of decay which develops into a canker; bark of infected crown tissue turns dark brown; cankers may occur on aerial parts of plant
Cause
Oomycete
Comments
Symptoms can be similar to those of bacterial infections or mechanical damage; severity of disease is linked to soil moisture content; water-saturated soils promote development of disease
Management
Management of phytophthora is reliant on good management of water: cherry trees should be planted in well-draining soil to minimize the frequency and duration of water saturated soil; trees should be propagated from resistant rootstock and application of appropriate systemic fungicides may provide some protection from the disease
Category : Bacterial, Fungal
Crown gall Agrobacterium spp
Symptoms
Galls on root and/or crown of tree which can range in size from so small they are not visible to the naked eye up to 10 cm (4 in) in diameter; galls first become visible as white, fleshy swellings that grow rapidly and become tan to brown in color; galls typically develop at the site of a wound and new galls form adjacent to old ones the next year
Cause
Bacterium
Comments
Infection with crown gall begins at the site of plant wounds; disease emergence is favored by poorly-drained, alkaline soils and previous feeding damage by nematodes
Management
Chemical control of the disease is generally ineffective; an effective bacterial biological control is available for commercial production; cultural control methods include: planting only certified, disease-free material, planting cherry in well-draining soil, rotating infected fields with a non-host before peach is planted and also using good sanitation practices
