Gummosis

Cherry gummosis on an ornamental species

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Klejotok 13023

Klejotok 13028

Gummosis is a pathological condition in plants where sap or gum exudes from the bark of a tree. This phenomenon can be due to various causes, including physical damage, insect infestations, fungal infections, and bacterial diseases. Gummosis can affect a wide range of tree species, both fruit trees and ornamentals, and is particularly common in members of the Prunus genus, such as peach, cherry, apricot, and plum trees.

Causes

Gummosis can be caused by several factors, which can be broadly classified into biotic (living organisms) and abiotic (environmental factors) causes.

Biotic Causes

Biotic causes of gummosis include:

• Fungal infections, such as those caused by the pathogens Botryosphaeria dothidea and Cytospora spp., which invade the tree through wounds.
• Bacterial diseases, like bacterial canker caused by Pseudomonas syringae.
• Insect damage, particularly from boring insects that penetrate the bark, allowing pathogens to enter.

Abiotic Causes

Abiotic causes of gummosis involve:

• Mechanical injuries, such as those from improper pruning, lawn mowers, or environmental damage.
• Environmental stress, including drought, excessive watering, or temperature extremes, which can weaken the tree and make it more susceptible to diseases.

Symptoms

The most obvious symptom of gummosis is the oozing of gum from the bark. This gum can be clear, amber, or reddish-brown, depending on the tree species and the cause of the gummosis. Other symptoms may include:

• Cracking or splitting of the bark.
• Discoloration of the bark and underlying wood.
• Wilting, yellowing, or dropping of leaves.
• Reduced growth and fruit production.

Management

Management of gummosis focuses on prevention and control of the underlying causes. Strategies include:

• Proper tree care practices, such as appropriate watering, fertilization, and pruning to avoid wounds.
• Monitoring for and controlling insect pests and diseases.
• Applying wound dressings to large cuts or injuries, although this practice is sometimes debated among arborists.
• Removing and destroying infected plant material to prevent the spread of pathogens.

Prevention

Preventive measures are crucial to avoid gummosis. These include:

• Selecting disease-resistant tree varieties when available.
• Maintaining tree health through proper cultural practices.
• Avoiding mechanical injuries to the tree.
• Implementing integrated pest management (IPM) strategies to reduce insect and disease problems.

Gummosis can be a sign of serious problems in a tree, and addressing the underlying cause is essential for the tree's health. In some cases, particularly with severe infections or when the structural integrity of the tree is compromised, it may be necessary to remove the affected tree to prevent the problem from spreading to nearby plants.