Plant canker : symptoms treatment and prevention

A real scourge for many plants, canker (Cancer), whether bacterial or fungal, causes severe damage and can even, in the absence of sanitary measures, lead to the death of affected subjects. Frequent in trees, it also affects tomatoes, roses… in short, plant canker is to be taken seriously from the first symptoms. Let’s see how to treat it and what are the best solutions to prevent plant canker.

The two types of cankers and their manifestations

A chancre is a necrotic ulceration which can affect all plants with woody tissue. There are two types: bacterial canker and fungal canker.

Bacterial canker or gummosis

Well known to gardeners, it is the canker that affects, among other things, fruit trees. It is also called gummy. Its culprits are bacteria such as Xanthomona implicated in the occurrence of citrus canker (Xanthomonas campestris) or Pseudomonas syringae which causes canker in the Chestnut tree, the Cherry tree, the Actinidia (kiwi fruit tree), the Apricot tree, the Plum tree, the Apple tree and others, namely that stone fruit trees are particularly concerned.

The phytopathogenic bacteria penetrate the plant tissue through pruning wounds or caused by insects. Bacterial canker symptoms begin to appear when the affected tree enters its dormant period.

fungal canker

Its leaders are pathogenic fungisuch as Nectria et Coryneum whose spores are carried by the wind when the weather is humid and mild. The slightest wound of size or other small cracking represents an opportunity for these seeds which then penetrate easily under the bark, in the heart of the cells which constitute the cambium. It is a canker that can affect many trees (oak, plane, birch, cypress, maple, rose, vine and many more).

It is quite quickly that the tissues are attacked by a canker (bacterial or fungal), but you should know that the most devastating is bacterial canker because it contaminates its entire host if no measures are taken, causing significant necrosis and then the death of the subject.

Plant canker: symptoms

They appear in the following chronological order.

  • Weakening of the branch,
  • yellowing of leaves,
  • Death of the buds,
  • Fruit yellowing,
  • Premature fruit drop,
  • Detachment of the bark,
  • Death of the contaminated branch,
  • Formation of a dark brown spot (on other branches and/or the trunk) which quickly grows in size, creating deformations such as blisters, cracks, cracks but also necroses,
  • Appearance of a flow of sap or resin (depending on the species), of a vegetable exudate or amber gum (it is a means of defense for the tree).

These symptoms are common to bacterial and fungal cankers.

On the other hand, only gummosis leads to multiple perforations on the leaves as well as brownish-red spots.

It is important for the gardener to know that a canker is already present long before the appearance of symptoms, that is to say as early as summer, but only in stade latent. Autumn or winter weather, mild or cold and humid, favors its development. It is essential to react at the first symptoms to save a tree contaminated by a canker.

Plant canker: treatment

We start with cut the branches very diseased 25 or 30 cm below the cankers. Of course you have to burn them to avoid any risk of contamination of the rest of the plant or other plants. Then it is appropriate to clean the trunk well if he too is affected by a canker. The entire infected area must be dug out with a sickle (the tool must be thoroughly disinfected beforehand). You have to dig until you reach the healthy part of the trunk. It then remains to apply a healing putty to completely cover the wound.

As far as canker treatments are concerned, the following solutions can be used:

  • Bordeaux mixture in the presence of a fungal canker. It should be used in moderation as it can make fungi resistant. In addition, its too frequent use represents a risk of toxicity for the environment.
  • Horsetail decoction boosts plant defenses. It is diluted to 5% before use.
  • Comfrey juice, which disinfects wounds and promotes the formation of a protective crust, must be diluted to 5%.
  • A preparation based on Bacillus subtilisa bacterium active against bacterial canker (kiwi, tomato, etc.).
  • A bactericide is needed to eradicate the plant pathogens responsible for bacterial canker.
  • A fungicide eliminates pathogenic fungi in plants affected by fungal canker.

In order not to harm the environment, it is essential to use only treatment products bearing the mention EAJ (Authorized use in gardens).

Plant canker: prevention

different cultivation methods significantly reduce the risk of transmission of cankers, namely:

  • Limit as much as possible the severe pruning of trees because they cause their weakening,
  • Systematically check the health of a plant at the time of purchase and only opt for plants that are perfectly healthy and free from wounds, even seemingly insignificant,
  • Opt for crop rotation,
  • Remove any diseased part of a plant and burn it (above all, do not compost it or grind it with the aim of using it as mulch),
  • Always thoroughly disinfect with alcohol or a flame the tools that are used in particular to prune trees, shrubs, roses, vegetable garden plants, ornamental plants, etc.
  • Take precautions so that rain or watering water does not stagnate at the foot of the plants,
  • Orient the pruning axis so that the water does not stagnate at the base of the buds,
  • Throughout the year, eliminate dead branches because they represent, for pathogenic organisms, entry points into the heart of the plant,
  • When passing the brushcutter, do not approach too close to tree trunks in order to limit the risk of injury,
  • Immediately repair damaged bark by brushing it with a homemade bactericide/fungicide made up of 70% water, 30% kaolin clay, 10% fresh cow dung, then bound with 3 tablespoons of black soap.

If you have no knowledge in the field of plants, it is better call a professional to cure his plants affected by a canker. At the first suspicious signs, do not wait to act because the sooner you intervene, the more likely you are to obtain good results. However, let’s not hide the fact that plants infested with cankers are difficult to treat.

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