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Bacterial Canker can be a serious bacterial disease of sweet cherry in New Jersey.
Bacterial canker or bacterial gummosis of sweet cherry is caused by a Pseudomonas
bacterium. This disease infects flower buds and spurs. it can completely kill new spurs
and leaves and then move into the trunk. In our humid climate in New Jersey the
cankers can continue to develop in lateral branches and the central leader. In some
cases the cankers have grown to girdle and kill two year wood. I have observed
central leader die back as a result. In older wood the canker looks very much like a fire
blight canker in apple. In most cases the canker begins to ooze a brown to amber
exudate.
We have several trials of sweet cherry at the Rutgers Snyder Farm composed of
numerous rootstocks and cultivars. Bacterial canker has infected numerous
combinations. We will be compiling data this fall to see if there are particular cultivars,
rootstocks or cultivar/rootstock combinations that are particularly sensitive.
The best information I could obtain on this disease is from a fact sheet from Ontario
Canada written by W.R. Allen "Bacterial Canker of Sweet Cherry" NO. 88-0886.
It has good color plates and control measures. We were surprised to see this disease
develop as we had been on a preventative copper program with applications in the fall
after leaf drop and in the spring before bud break. However it appears that under our
humid conditions this disease is very hard to control and can be devastating.
This bacterial disease is most troublesome in young plantings where it can cause
loses of up to ten percent of the trees. On mature trees it can reduce yields from
10-50%.
Control
Cankers get started mainly in the fall after most of the l[eaves have fallen and the trees
are beginning to go dormant. The only effective way to control this disease is to reduce
the number of bacteria before the trees enter their susceptible period. The bacteria that
start these cankers are found on the surfaces of mature leaves and other green
tissues, and do notcome from existing cankers.
The only successful control we have found is repeated applications of the old
Bordeaux Mixture in September, October, November and repeated again in the spring.
Bordeaux Mix consists of Hydrated lime and Copper Sulfate. The rates and methods of
mixing are important. We began our sprays the first week in September. Note however
that sprays of Bordeaux applied to green leaves must be Safened with vegetable oil to
avoid burning the foliage. Four additional sprays 14 days apart will be applied.
Bordeaux mix will also be applied in the spring with several applications before bud
break.
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