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Phytophthora Bleeding Canker: Phytophthora cactorum and P. citricola


Damage Type

Bark killing.

Symptoms & Diagnosis

Scattered drops of a rusty-red, yellow-brown or almost black gummy liquid ooze from small or large patches of bark on stems or limbs. These run a little way down th tree to dry as dark brown or black, often shiny, brittle encrustations. Or, on the underside of branches, as little, pendulous knobbles. (Eventually limbs may die but the weeping is so conspicuous that it is this that is likely to draw attention to the disease.

Additional Indicators

The centre of an oozing patch of bark may be cracked and perhaps bearing fruit bodies of wood-rotting fungi.



The inner bark of oozing patches is dead or a watery orange-brown colour and often clearly mottled or zoned. The underlying wood may be stained blue-black. No fungal mycellium, is evident under or in the dying bark.


As distinct from Phytophthora root disease (where aerial lesions are the result of fungal growth upwards from the roots), Bleeding canker seems rather uncommon, and has been reported only from the south of the country.



As the fungus is only confined to the bark and is slow spreading it can be eradicated, although later invasion of the wood by decay fungi can still be a problem.

Host Trees

Recorded in this country on Aesculus (Horsechestnut), Tilia (Lime), but there is no apparent reason why other species which are attacked elsewhere (Acer, Betula, Liquidamber, Quercus, Salix) should not sometimes succumb here too.

Infection & Development

Not yet fully elucidated. As both of these fungi also cause Phytophthora root disease they are probably present in the soil, in roots of other plants on the site, or asymptomatically in the roots of Bleeding canker infected trees. In suitably wet and warm conditions, spores would be produced and by some means not yet determined, reach the aerial parts of the tree, germinate and infect the bark. He fungus grows through and kills the phlopem (food carrying cells) and cambium and over a number of years may girdle and kill the whole limb or stem. The exuded gum does not contain the fungus.

Control: Therapy

Cut out all dead and dying bark. With a fresh or sterilised blade, remove a strip of healthy bark at least 2” wide from the periphery of the wound. Tyreat the exposed tissues with an approved wound paint based on a fungicide effective against Phytophthora species (e.g. octhilinone or copper). Collect and burn all excised bark.


None available.


P. cactorum was, in 1886, the second Phytophthora to be discovered, the first being P. infestans, the cause of Potato blight. P. citricola was discovered in 1927. Both cause root disease in many crop and ornamental plants. The disease was noted in about 1930 in the USA, but not until the 1970’s in England.