Bacterial Canker Control – Treating Apricots With Bacterial Canker Disease

By: Teo Spengler

Apricot bacterial canker disease is a disease that attacks apricot trees, as well as other stone fruit. The bacteria often enter the tree through pruning wounds. Anyone growing fruit in a home orchard should learn something about apricots with bacterial canker. If you’d like information on treating apricot bacterial canker, read on.

Apricot Bacterial Canker Disease

Apricots with bacterial canker are hardly rare, and the apricot bacterial canker disease is widespread in most places. This is a disease that often enters apricot trees and other stone fruit trees through wounds, often gardener-inflicted pruning wounds.

You’ll know that your tree has apricot bacterial canker disease if you see necrosis girdling a branch or trunk. Keep your eye out for branch dieback and cankers in spring. You’ll sometimes also notice leaf spot and blast of young growth and orange or red flecks under the bark just outside canker margins.

The bacterium causing the disease is a fairly weak pathogen (Pseudomonas syringae). It is so weak that trees are only susceptible to serious damage when they in a weakened condition or else dormant. They can be damaged from leaf drop through leaf budding.

Bacterial Canker Control

The key to bacterial canker control is prevention. And preventing bacterial canker on apricots isn’t as difficult as you might think. Prevention is the best way of treating apricot bacterial canker.

Apricots with bacterial canker are usually trees in one of two situations: trees in orchards where ring nematodes flourish and trees planted in areas that get spring frosts.

Your best bet at preventing bacterial canker on apricots is to keep your trees in vigorous health and to control ring nematodes. Use any cultural practice that is likely to keep your tree healthy, like offering sufficient irrigation and feeding with nitrogen. Nematodes stress apricot trees, making them weaker. Control nematodes by using preplant fumigation for ring nematodes.

When you think about treating apricot bacterial canker, think prevention. It’s not that hard to take an important step toward preventing bacterial canker on apricots. One proven method of bacterial canker control is to avoid winter pruning.

The entire disease begins in winter, when the trees are susceptible to the bacteria. If you prune the apricot trees in spring, instead, you can largely avoid the issue. Evidence suggests that pruning during the dormant season makes apricot trees vulnerable to this disease. Instead, prune after the trees start active growth in spring.

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Integrated Pest Management

Bacterial canker (blossom blast)

Pseudomonas syringae pv. syringae van Hall Pseudomonas syringae pv. morsprunorum (Wormland) Yound et al.

Distribution: Common to all fruit-growing regions in eastern North America. The disease is most common on sweet cherry and apricot.


Cankers on a limb. William Turechek, USDA-ARS

Leaf scars, stomata, and areas of injury are the principal sites of infection. The most conspicuous symptoms are limb and trunk cankers (A, B), blossom blast (C), "dead bud", and leaf spotting these symptoms may or may not occur together. Cankers can girdle and kill entire limbs, reducing the tree's fruiting capacity. Infection of the trunk, particularly on young trees, often results in tree death. Crotches are particularly susceptible to infection, which often leads to extensive gumming (D). Infections of the blossoms cause blossom blast and loss of fruiting spurs (E). Infections of dormant flowering and vegetative buds result in a condition called "dead bud" in which buds fail to break dormancy in spring. On leaves, lesions are tan to brown and initially surrounded by a yellow halo. Lesions may be small or they may coalesce to form large areas of infection. They are eventually walled off and the center of the lesion drops out to give the leaf a shot-holed appearance (F). On fruit, lesions tend to be circular, brown, and sunken (G).

Crops Affected: Cherries, Peaches, Plums


Although most serious on sweet cherry and apricot, the disease also affects tart cherry, peach, and plum. Orchards should not be established on poor sites such as those on acidic or sandy soils, in areas prone to flooding or drying, or in the vicinity of wild Prunus spp., which can harbor the disease. Stone fruit are most susceptible to infection in late autumn and early spring. Copper bactericides can be used to manage disease, although they are generally considered ineffective. Cankers should be pruned from trees when feasible. Infection of pruning cuts can be minimized by pruning trees during the summer rather than in spring, when the bacteria are active. Tree training methods that cause bark injury should be avoided (e.g., limb spreaders), especially on sweet cherries and apricots.

Similar Species

Blossom blast can be confused with blossom blight, caused by Monilinia fructicola (G. Wint) Honey fungal sporulation (although not always present or evident) helps to differentiate brown rot from bacterial canker. X-disease can cause a dieback in older cherry trees that might be confused with bacterial canker. Branch or trunk cankers may be confused with perennial canker however, perennial cankers form alternating callus rings, whereas cankers caused by Pseudomonas do not.

Treatments Of Apricot Diseases


The Apricot (Prunus armeniaca) tree is quite small in statue, but with a large expansive canopy. The leaves are oval with a pointed tip, and the flowers are white to pink in colour. The fruit is smooth, smallish in size and yellow to orange, often tinged red in colour. The Apricot tree and its produce can be inflected with a range of different diseases. These Apricot diseases each have different causes, symptoms and treatment plans, and in this article we will explore some of these.


Apricot Bacterial canker and blast is caused by the bacteria Pseudomonas syringae. This bacterial infection thrives in high moisture and low temperatures conditions thus making for a common occurrence in the season of spring. Young trees (2-8 years) are more susceptible to this variant of apricot diseases, and places in an orchard that are low, gravelly, or sandy will likewise be more a risk. Symptoms that accompany this apricot diseases manifestation include limb dieback, rough cankers, amber colored gum, leaf spot and blast of immature flowers and shoots, and the inner bark will be brown, fermented, and sour smelling. An important practice that growers should carry out is to maintain the trees vigor though lighter irrigation with drip or micro-sprinklers and improved tree nutrition. By doing this you will help reduce the incidence of this disease. Spraying your trees with a copper compound in the fall months also seems to help reduce the manifestation of bacterial canker.

Crown gall is another type of bacterial Apricot diseases. This variant is caused by the pathogen Agrobacterium tumefaciens and enters the tree via wounds for example grafting and budding scars.This Apricot diseases symptoms are as follows rough, abnormal galls on roots or trunk that are soft and spongy in texture, stunted growth in younger trees, secondary wood rots in older trees and small, red or yellow leaves. Galls are typically a few inches across in size, new galls will be light, tan-colored whilst older ones will be darker and almost black in its color. The best method of control for this type of apricot diseases is to remove the infected from the orchard to prohibit spreading of Crown Gall. To prevent the disease form manifesting in the first place make sure that you Sterilize the grafting and budding tools before using them on your tree and paint the wounds of tree fruits and nuts with Gallex has helped reduce the incidence of crown gall.


Brown rot (Monilinia fructicola) is a fungal disease that affects stone fruits, including apricots. This type of apricot diseases will first manifest symptoms in spring when the blossoms open, with the flowers wilting and turning brown and are overrun with multitudes of brownish-gray spores. The infection will then spread to the twigs with cankers manifesting, these cankers will be small in size with tan centres with dark margins. The next zone that will be infected is the fruit of the tree. These will be in the form of soft brown spots that develops into the whole fruit rotting, drying and shrinking. It will have a shrivelled appearance. This type of Apricot diseases can spread with ease either via spores, rainfall or by insects. If your tree has contracted this disease then you must take measures to prevent the spread of it. A chief feature of this is to ensure that the environment is clean this can be done by removing the diseased fruit from the region and deposed of in a appropriate manner. Additional measures are to prune out all cankers, and to remove overripe fruit promptly. Also fungicide should be applied to trees that are affected with these apricot diseases.

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