Agriculture Reference
In-Depth Information
Bacterial Canker
This fungal disease is found across North America. The pathogen attacks
sweet cherries in the Pacific Northwest and sweet and tart cherries in
Michigan and Ontario and is a problem on peaches in the southeastern Un-
ited States. Sweet cherries are most susceptible, but bacterial canker also
attacks apricots, tart cherries, nectarines, peaches, and plums. The disease
is caused by two closely related strains of the bacterium
Pseudomonas syr-
ingae
. Consult with fruit specialists in your region to determine if this disease
is likely to be a serious problem for you.
Damage occurs not only directly to the plant tissues, but the bacterium
also increases the risk of frost damage. It does this by producing a protein
that causes ice crystals to form on plant tissues at higher subfreezing tem-
peratures than normal. In a vicious cycle, the wounds formed by frost dam-
age are susceptible to invasion by the bacterium. Anything that weakens the
trees, such as incorrect pruning, poor mineral nutrition, improper soil pH, and
damage from other diseases, increases the incidence and severity of bacteri-
al canker. Trees on sites susceptible to damaging spring frosts are most at
risk. Sites infected with the soil-borne ring nematode are also at greater risk
of bacterial canker.
Sweet cherry varieties 'Bing', 'Lambert', 'Royal Ann', 'Napoleon', 'Sweet-
heart', and 'Van' are very susceptible to bacterial canker, while 'Corum', 'Sam',
and 'Sue' appear to be fairly resistant. In areas with a history of bacterial
canker problems, clonal Mazzard F12-1 or Mazzard seedling rootstocks are
recommended.
Symptoms.
Signs of the disease include cankers on the trunks, limbs, and
twigs; dead limbs; dead buds; and brownish, gummy sap being discharged
from the bark and wounds. Girdled limbs may appear to grow normally dur-
ing spring, then die suddenly at the onset of warm weather.
Management.
Control involves using good management practices to main-
tain healthy trees with moderate growth. As with many other diseases, avoid
