What to do if the bark on the apple tree trunk cracks and the trunk becomes exposed

Bark cracks reduce the yield of fruit trees by disrupting the flow of sap to the skeletal branches. Any wounds on the trunk are an entry point for fungi and bacteria. Bark cracks can take several forms: breaks (exposing the core), girdling rings, transverse cracks, or longitudinal cracks. Treatment for apple trees can only be determined after the cause is determined.

Reasons

Bark cracking on both old and young apple trees can be caused by various factors, most commonly disease, pests, rapid tree growth, and temperature fluctuations. Another possible cause is the apple trees' lack of zoning. In this case, the trees are unable to adapt to the weather conditions, causing the bark to crack and peel.

Rapid growth, improper watering

Wood and bark must grow simultaneously. If wood growth accelerates, the bark cannot form quickly and cracks. When growth rate fluctuates, cracks appear in the trunk, allowing bacteria and fungi to enter, further deteriorating the bark. Pests can also infest these cracks, which can also damage apple trees.

Rapid growth can be triggered by frequent nitrogen-containing fertilizers or improperly prepared fertilizers that exceed a certain concentration. Fertilizing apple trees during the fruiting period can be a cause. Saplings grow rapidly during this period, and if they are over-fertilized, the wood growth rate will increase two- to threefold, leading to cracks in the bark. If trees are constantly overwatered, the pressure inside the trunk will increase. At a certain point, the bark will not withstand the pressure and will begin to crack.

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Pests

In autumn and winter, mice may appear on the property. They love to gnaw on the bark of apple trees, as unlike other fruit trees, apple bark doesn't have a bitter taste. Rodents most often damage young trees due to their soft bark. A massive pest infestation can completely destroy an apple tree, damaging the trunk down to the cambium layer. If a tree has been damaged by hares, the only way to save it is usually through grafting, as they always gnaw down to the cambium layer.

Bark beetles are another pest. These insects have a dark-brown, cylindrical body, approximately 4 mm long. They live in wood, making them difficult to detect. After the trees bloom, the insects emerge, mate, and infest other trees. The beetles lay eggs under the bark of seedlings, creating numerous tunnels in the trunk. The larvae feed on the apple tree's sap, creating additional tunnels until the following spring. During bloom, they pupate and emerge as adult beetles. The insects can be identified by small holes in the bark (burrows) from which wood flour spills out.

Trunk diseases

The most common disease is black cancer. The bark on the apple tree is cracking and becomes covered with a brown-black coating, hence the name "black canker." The apple tree sheds its leaves, branches gradually dry out, and yield declines. The most common causes of canker are:

• the seedling grows next to the outdoor toilet;
• there is a compost pit near the seedling;
• strong drafts on the site;
• the apple trees are old and weakened;
• moss, lichen on branches;
• frequent rains;
• Incorrect calculation and application of fertilizers.

The disease is caused by a fungus, and its spores are quickly spread through the air, so infection from one tree can quickly spread to other fruit trees in the garden. Signs of the disease are most often detected in the spring on the trunk and branches. Small brown dents initially appear. As the fungus spreads, the bark darkens, peels, and falls off. Fruit in the initial stages of the disease remain intact and rot during storage. If the fungus spreads rapidly along the trunk and skeletal branches, the fruit is also affected.

Fire blight is another common bacterial disease. It most often affects apple, pear, quince, and hawthorn trees. Typically, the disease develops in the spring, and the bacteria are spread by birds, insects, and wind. If the fruit has already set, it darkens and dries out, but does not fall from the tree. The bark becomes soft and covered with white spots, which eventually turn yellow. The bark then swells and cracks.

Cold winter, sunburn

If heat-loving apple trees are planted in an area with cold winters and severe frosts, they will either not survive the winter or will suffer severely: the bark will crack, yield will decline, and they will become susceptible to diseases. Therefore, before choosing a seedling variety, it's important to consider the climate. During severe frosts, the sap inside the trees freezes; after thawing, the pressure increases, causing the bark to crack.

Sunburn is more common on young apple trees and appears as reddish or brown spots. It appears in early spring if the tree hasn't had time to recover from frost and adapt to warmer weather. Sunburn causes the bark to dry out, causing it to crack. Severe sunburn can damage a large section of the trunk and even kill the tree.

What to do if the bark of an apple tree is cracked and peeling off

If the bark of an apple tree is cracked, remove all damaged areas with a wire brush, after spreading plastic on the ground to prevent soil contamination. The exposed surface is treated with antiseptic solutions and garden pitch, which are available at specialty stores. If multiple beetle tunnels are found in the trunk and skeletal branches, they are destroyed using Antizhuk, Calypso, and other pesticides. The solution is drawn into a syringe, injected into the tunnels, and sealed with garden pitch. If there are numerous tunnels, branches, and fruit have dried out, the tree is cut down, the stump is uprooted, and the entire tree is burned.

If the inner layer is damaged by mice or hares, a bridge graft is used to restore the tree's nutrition. Cuttings are harvested in early spring for grafting. The damaged bark is removed and treated with disinfectant solutions. T-shaped cuts are made above and below the damaged area, and the bark is slightly bent back. The cuttings are inserted into the cuts, sealed with garden pitch, and wrapped with electrical tape. Once the cuttings take root, nutrients will flow through the cuttings to the upper part of the trunk, bypassing the damaged area.

If a tree is infected with black canker, it can only be cured in the early stages of the disease. Damaged branches are pruned, and the infected bark is scraped off, removing about 2 cm of healthy bark. The infected parts of the apple tree are burned. Wounds are treated with copper or iron sulfate; a solution of manganese or brilliant green can also be used. Fungicidal putties (Funaben and others) are available at specialty stores. If the apple tree is completely infected, the leaves have dried out, and the fruit has rotted, the tree is cut down and burned.

Preventive measures

Frost-sensitive apple trees should be protected with covering material before winter, but this does not guarantee complete tree protection. If the area is frequently attacked by mice, it is recommended to use special baits, ultrasonic repellents, fences around trees, etc. Regularly inspect apple trees for cracks and tunnels, and carry out preventative treatments against pests and diseases in the spring and fall.

All damaged parts of the tree must be burned, otherwise infection or pests can spread throughout the area and to neighboring trees. The trunk and skeletal branches should be whitewashed in the fall; this protects against frost, early sunlight, some pests, and diseases. If any wound is discovered, treat the defects with antiseptic solutions or garden pitch.

To prevent bark cracking due to overfertilization, follow the recommendations on the product packaging. In the spring, nitrogen-rich fertilizers are recommended, while in the fall, fertilizers containing potassium and phosphorus are recommended. When choosing a seedling, consider the variety's growing zone to avoid bark cracking due to frost.

Some gardeners recommend regularly removing the bark from older trees (over 7 years old), which begins to peel naturally. The bark is removed with a metal scraper to remove any potential pests or bacteria that may live in the bark. However, some gardeners discourage such regular bark removal, as it has been observed that "peeled" apple trees have a poor winter performance and are prone to freezing. Furthermore, the risk of disease increases if the surface is not properly cleaned.

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Timely treatment and removal of affected tree parts can prevent bark cracking due to diseases and pests. When planting apple trees, choose a sunny location free from drafts, groundwater, compost bins, and outdoor toilets to reduce the risk of infection.