Diseases of Saskatoons

• infected leaves and berries develop yellowish-orange spots often raised
• later in season, spots may be covered with numerous spiny projections (like whiskers) which contain large numbers of spores
• leaf can tolerate large quantities of spots, but one spot ruins the berry
• on juniper there is a gall on branch

• most of the rust diseases in Alberta are 2 host, meaning they move from one host to second, then return to first
• when the weather is wet in spring jelly-like yellow-brown horns erupt from galls on juniper
• spores are produced that blow to the saskatoon
• heavy dew on the saskatoon enables the spores to infect the saskatoon
• temps 10-24^oC, with wet plant surfaces favor disease development

• remove all junipers within a 2 km distance of orchard
• junipers within a 1.5 km distance can cause a significant loss of fruit once every 5 years

• leaves,small angular brown spots, often with a yellow halo or margin around spots
• spots can grow in size and cause blight phase
• leaf stem, petiole, berry stalks and fruit cluster can become infected causing defoliation and fruit loss
• infected fruits have dark brown spots which are often paler or silvery in centre
• berry spots tend to be darker brown than leaf spots, are round, may or may not have yellowish halo

• high humidity and leaf succulence
• grows rapidly at 20^oC
• disease explodes in wet and warm weather
• disease can move up the plant, bouncing from leaf to leaf then attack the fruit
• primary infection begins when spores are splashed onto the leaves
• fungus overwinters on fallen leaves

• water the ground, not foliage, allow for the foliage to dry
• in young plantings, keep the bottom one third of plant clean of foliage

• common on lower leaves or root sucker leaves
• rare on the berries
• found on one or both leaf surfaces, eventually the leaf discolors and dies
• can cause stunting of stem and distortion of immature leaves if infection happens at that time
• diseased parts may become chlorotic before premature death

• warm, dry weather 15-27^oC favors production and spread of spores
• poor air circulation and shade
• disease overwinters in leaf buds and on fallen infected leaves

• collect and destroy infected leaves in the fall

• flowers turn prematurely brown
• brown spots on fruit surfaces, and gray to light brown tufts on the rotted surface
• fruit shrink and mummify

• humid weather during flowering, with temps around 24^oC
• insect damage to flowers and fruit can increase the disease incidence
• disease is spread by wind or splashing water
• overwinters on the fallen mummified fruit

• removal of fallen mummified berries, and leaves
• cultivation to bury the fallen fruit and leaves

• non-lethal to saskatoon plant
• fungus penetrates the shoot tips and stimulates many new shoots to develop
• resulting in a broom with numerous short twigs that arise close together, often at a swelling or knot on the branch
• only new wood is affected
• suckers are very susceptible
• shrub growth and berry production reduced
• leaf edges roll downwards and underside becomes covered with grey felt
• eventually leaves become coated with heavy covering of olive brown to black fungal mat
• easily seen as dead leaves remain on the brooms during the winter
• overwinters on dead leaves
• infection is systemic and perennial

• prune and destroy the infected shoots

• drying and shrivelling of buds and leaves in spring
• leaves developing fall coloration earlier than normal
• bark wrinkled or has vertical splits and folds, bark peeling off the branches
• abrupt transition between dead and live bark
• cut surfaces of infected shoots may be stained black
• fungi can cause the eventual death of plant, as moves down into the root crown
• cankers,sunken areas of cracked, broken bark
• Cytospora canker has little, black pimple-like protrusions from the canker surface
• Nectria canker has orange protrusions from the canker surface
• Cytospora and Nectria are secondary colonizers, they move into damaged wood
• silverleaf causes the leaves to become pale and silvery looking, may have a purple staining in the heartwood

• drought, cold, frost, wind, mechanical injury from harvesting equipment, pruning wounds (especially heading back on larger diameter stems), rodent damage, poor soil drainage, late summer pruning and late fall injuries
• canker fungi infect shoots through cracks caused by injury

• remove all dead and dying stems and branches when observed, cutting back 30 cm (12 in) back from infection
• sterilize pruning equipment between cuts if disease is present
• harden plants properly for winter
• good site selection, wind shelter

• individual flowers or entire flower clusters
• appear water-soaked, droop, shrivel and turn brown, some fall off but most remain on the
• plant
• disease moves back into the stems of flowers and spurs
• often the first noticeable symptom is where young shoots die forming a shepards crook, and discolor
• if this discoloration occurs on many of the shoots, the plant can look like it has been
• scorched by fire,hence the name
• if the bark of the infected area is cut away
• with a knife, a brown discoloration is noticed
• can girdle branches with cankers
• lesions look water-soaked
• cream to carmel colored bacterial ooz comes out in beads from the lenticels and wounds on recently infected parts in humid weather
• diseased portions become sunken and wrinkled
• often the only way to tell the difference between fireblight and bacterial blast is to get a lab to culture the diseased material

• bacteria is present from overwintering cankers on diseased plant material
• fireblight favored by warm temperatures (18-25oC) and light rains
• prolonged host flowering due to wet cool springs
• flowers, fruit, and succulent growth become infected
• blight appears within 1-3 weeks of inoculation depending on the temperatures and moisture
• hail storms that open up the bark, followed by warm and humid temperatures also favor inoculation
• pruning wounds

• pruning is the best method of control, sterilize the pruning equipment between cuts
• disease can be delayed or halted by careful pruning
• when pruning, go back into healthy wood 30-45 cm (12-18 inches)

• blackening or browning of tissue
• unlike fireblight disease is slow spreading
• can also be confused with several other disorders like winter injury, cane borer, or some herbicides
• very similar to fireblight symptoms

• cool and moist weather
• overwinters on the canes and buds
• bacteria needs a place to enter, whether frost damage or mechanical damage
• bacteria is systemic in the plant, and infection spreads as long as weather is cool and wet, once weather begins to warm up disease subsides until fall

• pruning is the best method of control
• harden plants for winter properly

• pre-emergent,seedlings and germinating seeds destroyed
• post-emergent,rotting stems (near surface of media)

• pre-emergent, cold, wet germinating media
• post emergent, warm, humid conditions with overcrowding

• pasturized media

• related to prolonged periods of extreme cold temperatures in winter
• also sudden temperature drops following a warm spell in winter
• desiccation occurs when dry winds blow over the plant and dry it out, the roots when frozen can not replace the moisture that is being lost

• death of entire plant
• death of susceptible parts like new wood, leaf and flower buds
• canker diseases often follow

• killing frosts -2.2^oC or lower
• can kill any actively growing plant tissue
• light browning of flowers and leaves
• damaged parts fall off
• flowers are susceptible to frost damage, could be restricted to internal parts of flower and and may not be noticeable except under magnification

• strong winds can abuse plants
• abrasion, tearing and desiccation
• hard brown edges of leaves, torn leaf margins
• new leaves and shoots are susceptible to wind damage

• on cold sunny days during the winter, bark exposed to sun can warm up, sun goes down and the bark splits, due to expansion and contraction of the cells
• in hot summer bark can discolor and bubble
• this damage then gives the canker diseases an entry point

• proper site selection
• low levels of soil moisture and fertility in late summer and fall
• windbreaks reduce the effects of strong, persistent winds
• slight NE slope will help prevent sunscald and also can delay flowering