DISEASE

NAME
Canker (General)
Various Canker Species

Description
This is a fungal problem that enters the plant through wounds causing dieback of twigs and stems.

Symptoms
The stems become discoloured (pale brown) usually from a pruned point, working its way down the stem and normally intersecting or surrounded with live cambium. The bark splits or cracks, foliage dies and infected areas can develop tiny black fruiting bodies. Heavy infected plants eventually die, though certain varieties are resistant halting the spread of the infection.

     

Black Canker(Phyaslospora miyabeana) forms dark brown spots with concentric rings on the upper leaf surface and grey spots on the stems. The tiny black fruiting bodies develop in the stem lesions. It is found on Salixspecies and persistent attacks will kill the tree.

The Canker(Cytospora valsa) causes the browning and death of branches in Picea abiesand Picea pungens. This infection occurs normally from the base of the tree with infected needles falling, and white resinous patches appearing on the bark accompanied by cankers with tiny black fruiting bodies.

The Canker(Corynneum cardinale) is a casual fungus that invades wounds and infects living bark and associated cambium turning the foliage yellowish. As it spreads it girdles the branch killing it and ultimately the top of the tree dies out. Cankers eventually form in the trunk and ooze resin. It is found on Cypress.

Platanus x hybrida

Cankerstain(Ceratocystis fimbriataf. platani) forms sunken cankers on the trunk and large limbs forming longitudinal cracks and roughened bark. Infected areas form callus around the margins which dies off and when cut open, dark coloured streaks are revealed extending to the central pith. These streaks then radiate out into uninfected wood resulting in the thinning of the crown and producing unusual small leaves. It is normally transmitted through poor tree surgery techniques and infected tools.

Cytospora Canker

Cytospora Canker(Cytospora chrysosperma) is a casual fungus that infects the young twigs, then moving to the stems, branches and trunk causing brown sunken areas to appear that is covered in red pustules. The fungus tends to attack trees that are in poor health. Control requires the removal of infected branches and improved culture to regain the plants vigour. Sorbus aucuparia, Salixand Popularspecies are susceptible.

Cypress Canker

Cypress Canker(Seiridiumspecies) enters the plant through wounds or through insect damage causes the bark to spread revealing brown powdery spores that are accompanied by oozing resin. The canker eventually girdles the branch or trunk causing ringbarking and the death of the plant.

Nectria Canker(Nectria Cinnabarina) forms cankers on the twigs and small branches producing red fruiting bodies and eventually killing the tree. It is found in many parts of the world infecting a range of trees including hardwoods.

     Populus nigra

Poplar Canker(Cryptodiaporthe populea) infects the cambium layer damaging the bark and sapwood where the elongated sunken canker forms. Branches are girdled causing the upper portion to die off. This is a serious problem for Populus nigra var.Italica entering the plant through wounds or the leaves then spreading to twigs and branches. Control is difficult as removal of infected parts will not eradicate the problem, but encourage it. Young plants may be sprayed with a copper based fungicide to reduce leaf infection and heavily infected plants should be removed the burnt.

Stem Canker of Red Flowering Gum(Sporotrichum destructor) enters through wounds in the bark forming cankers in the trunk and branches, splitting the bark apart, revealing the wood and infesting the surface with powdery spores. This infection causes the leaves to wither and then the branches die, eventually killing the tree.

Stem Canker(Strumella coryneoidea) is a casual fungus that forms on the trunks of trees as a smooth, dispersed or sunken infection. On mature trees the infection sheds the bark with the canker forming callus tissue around the margins and the centre being exposed. These cankers then tend to extend up and down the trunk, only girdling over a long period of time. It is found on Quercus, Fagus, Aesculusspecies, andAcer rubrum, Nyssa sylvatica, Carya ovataandMorinda citrifolia.



Source and Dispersal
The spores are found on infected dead plant material and can be dispersed by wind and with splashing water.

Favoured Conditions
It prefers a warm humid conditions and plants that have a wounds derived from poor pruning techniques and insect or other damage, especially if water is allowed to settle on the wound.
     
Affected Plants
Cankers may infect a wide range of trees and shrubs with some species being specific to its host. Examples are listed below.

Abies species are infected by several cankers including (Cytospora pinastri), (Cryptosporium macrospermum) and (Scoleconectria balsamea). These fungi form dead sunken areas on the trunk and branches.

Alnus species are infected by a few cankers including (Nectria coccinea) and (Physalospora obtusa) these attack the branches causing die back.

Betulaspecies may be infected by the Canker (Nectria galligena) that occurs in the forks of trees causing splitting and cracking of the bark by swelling, to reveal the canker. Callus rings may form around the affected areas as a defence mechanism triggered by the tree.

Buxusspecies are infected by the Canker (Pseudonectria rousseliana) which shows signs of poor new growth during spring with the leaves turning from light green to a tan colour. These leaves tend to lay flat along the stems and reddish pustules appear both on the stems and leaves. The bark becomes loose and on inspection reveals a darkish colour underneath. It is difficult to control and the canker can kill the plant.

Castaneaspecies are infected by the Twig Canker(Cryptodiaporthe castanea), a fungal problem that causes significant damage to the twigs and small branches, but tends to attack stressed trees.

Cercisand Ribes species are infected by the Canker (Botryosphaeria ribis) which forms small sunken areas on the stems causing wilting and eventually killing the branch by girdling. The cankers turn the bark black then split it open and the adjoining wood becomes discoloured. This is a serious problem for this and many other plant species.

Cotoneaster, Betula, Catalpaand Aesculusspecies are infected by the canker (Physalospora obtusa).

      Cypress Canker

Cupressusspecies and Chamaecyparis lawsonianaare susceptible to Cypress Canker(Seiridiumspecies) which causes leaf browning and then girdles the trunks resulting in ringbark. There is also another Canker (Coryneum cardinale) that has simular characteristics and is found in the northern hemisphere.

Cupressus sempervirensis infected byCytospora Canker(Cytospora cenisiavar.littoralis).

Larix speciesare susceptible to several fungal cankers including (Trichoscyphella wilkommii), (Trichoscyphella ellisiana), (Aleurodiscus amorphus), (Leucostoma Kunzei) and (Phomopsis spp.)

Nyssa sylvaticais attacked by three cankers including (Strumella coryneoidea).

Pinusspecies are infected by many types of cankers.

Platanusspecies are infected by Cankerstain.

Cytospora Canker on Salix babylonica

Pseudotsuga menziesii Douglas Fir is attacked by several cankers including (Cytosporaspecies), (Dasyscypha ellisiana), (Dasyscypha pseudotsugae), (Phacidiopycnis pseudotsugae) and (Phomopsis lokoyae). These infections normally do not require control and are more prevalent on the coastal form.

Salixand Populusspecies are infected by several cankers includingCytospora Canker(Cytospora chrysosperma), Hypoxylon Canker (Hypoxylon pruinatum), Septoria Canker(Mycosphaerella populorum)and Branch Gall (Macrophoma tumefaciens). Many of these fungi can cause the death of the plant.

Thuja orientalis, Cupressusand Juniperus species are infected by the canker (Corynneum cardinale).

Tiliaand Acerspecies are infected by (Nectria cinnabarina) attacking twigs or branches.

Tsugaspecies are infected by several cankers including (Dermatea balsamea) and ( Cytospora species).

Ulmusspecies are infected with up to eight fungal cankers including (Apioporthe apiospora) and (Nectria coccinea).

Vaccinium ovatumis infected by the canker (Coryneum microstictum) which attacks the stems.

Vinca species are infected by canker-dieback (Phomopsis livella) causing the shoots to wilt, turn brown and die. This can reduce the plant to ground level, and normally occurs during rainy periods.

Non-chemical Control
It is very difficult to control and correct pruning techniques with sharp tools for repairing wounds or prune well below the infected areas. Ensure that there are no ragged edges on the cuts and the angle should cut allows water to run off or dress the wound. Plant resistant varieties when available. Heavily infected trees should be removed to avoid spreading the disease.
Improve the culture of the affected plant to increase vigour for greater resistance.

Chemical Control
There is no satisfactory chemical control and prevention is imperative.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.