What to do if the bark on a plum tree trunk has cracked

Plum

There are many reasons why a plum tree's bark cracks. Bark is the outer protective layer of any tree, protecting the interior of the trunk from adverse environmental influences, mechanical damage, pests, and rodents.

Why does the bark on fruit trees crack?

There are many factors that can cause bark damage, but there are four main causes: increased tree growth, various diseases, pests, and sudden temperature changes to which the seedling may not be adapted.

Rapid growth

Normally, the inner and outer parts of a tree—the wood and bark—grow simultaneously. When growth is excessive, the wood grows faster, while the bark doesn't have time to fully form. This disruption in growth rate leads to bark cracking, which can become entry points for various tree diseases, including fungal ones. Insects can also infest these cracks, further damaging the sapling.

Excessive growth of a young tree can be caused by improper care. This is most often due to overuse of nitrogen-based fertilizers designed to increase yield. Fertilizers are applied either too frequently or the amount of nitrogen per application is too high. Another cause can be applying fertilizer during the fruit ripening period, when tree growth is rapid, and fertilizing accelerates this process even further. Overwatering also negatively impacts the bark, which can't withstand the pressure from within and cracks.

Tree diseases

The bark can also crack due to tree diseasesMost often, this is black canker, the main symptom of which is cracked bark on the plum tree. The seedling sheds its leaves, the branches dry up, and the tree stops bearing fruit. The bark begins to darken, hence the name "black canker." Possible causes:

the seedling is located next to the outdoor toilet;
the tree grows in an area with a strong draft;
incorrect application of fertilizers or calculation of components in its composition;
There is a compost pit next to the tree.

Dark spots, invisible to the naked eye but visible under a magnifying glass, appear around the cracks. Black rot then develops, spreading throughout the tree, affecting leaves and fruit. The fruit itself may appear undamaged, but then begin to spoil during storage. As the black rot spreads rapidly along the trunk, the fruit becomes covered with dark spots that increase in diameter, rendering them unfit for consumption.

Pests

Trunks are most often attacked by woodworms and bark beetles. The first insects can live inside the trunks for up to 15 years. Two pests can form a large colony. During a single life cycle, they can tunnel up to 30 meters into the tree. They destroy trees from the inside, including damaging the bark, which causes it to crack. Their presence is indicated by numerous holes in the tree, visible to the naked eye.

The second pest creates holes up to 2 mm wide in the tree, causing gummosis. Their presence is indicated by horizontal grooves on various parts of the trunk. Before laying eggs, the female feeds on the bark, creating tunnels for the eggs. Trees can fight the pest themselves: when tunnels appear, sap secreted from the interior of the trunk clogs the tunnels, and the larvae die from lack of air.

Severe frosts, sunburn

Any tree or plant is adapted to a specific climate. If a heat-loving variety is planted in a harsh climate, it will not survive the winter or will be damaged by frost. Therefore, before purchasing seedlings, it's important to consider their tolerance to low temperatures. In some areas, winter temperatures can drop to -30°C, which is normal, while in others, these temperatures can be abnormal. The mechanism by which bark cracks during severe frosts is based on the laws of physics: after the sap inside the tree thaws, the pressure on the bark increases, causing it to crack, unable to withstand the pressure.

If a seedling isn't adapted to such conditions but has already been purchased and planted, it should be insulated with a special covering material before winter. Protecting a tree that isn't adapted to frost doesn't guarantee its survival. When preparing for winter, consider the temperature—in Siberia, before frost, after insulating the tree, it's not watered to protect the root system. In the Urals, all plum varieties are insulated, but watering continues.

Sunburn is also a common cause; it appears as reddish-brown spots that appear in early spring. If the tree hasn't had time to adapt to warmer temperatures after the winter cold, the bark structure is damaged by the sun's rays, resulting in dryness and cracking. Sunburn can lead not only to cracks but also to the death of large sections of bark.

Important!

Shallow cracks in the bark may heal on their own, but until then, the damaged areas of the tree can become a haven for insects that will destroy the bark and prevent it from healing on its own.

What to do if cracks appear

To remove the damaged area, the trunk is treated with a potassium permanganate solution, and the affected layers of bark are scrubbed off with a stiff brush. The capillary portion is removed with a special pruning knife, capturing up to 2 cm of unaffected area. The cleared area is treated with copper-based products, garden pitch is applied, and the trunk is bandaged with cloth. All the removed bark is burned.

If cracks appeared due to the application of nitrogen fertilizers, severe frosts, or sunburn, the treatment is similar. To combat woodworms, use Confidor and Bi-58, and treat the pest's tunnels with chlorophos. Woodworms are active in the spring, so they can be caught by hand. To get rid of bark beetles, use insecticidal bark treatments such as Confidor Maxi, Aktara, and Mospilan. Treatments are carried out twice: 1-2 weeks after the tree blooms, and a second time 2 weeks after the first spray. Decis or Sherpa can also be injected under the bark with a disposable syringe.

Crack sealants

After removing the damaged areas, they should be treated with copper-containing products and sealed with garden pitch, which can be purchased ready-made or made at home. There are many recipes for making it, the most popular being Zhukovsky's pitch and Pashkevich's pitch. The first pitch consists of three components in equal parts:

yellow wax;
melted mutton fat;
rosin.

Melt all the ingredients separately in a double boiler and mix them together while hot until smooth. Once the mixture has cooled slightly (to avoid burning your hands), pour it into a container of cold water. Skim the mixture from the surface of the water and knead it in your hands like play dough, forming a ball. The tar can be used directly to seal the plums, or wrapped in plain paper lightly coated with oil and stored in a cool, dark place. After sealing the affected area, wrap it in natural fabric or burlap to allow air to circulate. Pashkevich's tar contains:

rosin – 200 g;
yellow wax – 400 g;
turpentine – 400 g;
rendered fat – 100 g.

Add rosin and turpentine to the melted wax and mix until smooth. Add melted fat and stir. Pour the mixture into a container of cold water and form a ball. Apply the wax to a bandage and wrap it around the damaged area where the bark has cracked on the seedling.

Important!

To determine the extent of the damage to the trunk, lightly prick it with a knife. If the trunk and its upper layer are firm, the tree can be treated and cured. If the plum tree trunk is cracked and loose, easily punctured, and the bark is peeling, the tree is cut down and burned to prevent insects and diseases from spreading to other seedlings.

Prevention of cracks

To reduce the risk of damage, the trunk is painted with whitewash or a special ready-made paint, which is also used to treat the pruned branches. Instructions for use are provided on the packaging. To protect against frost and sunburn in early spring, the trunk is wrapped with special materials for the winter. Every three to four years, the bark is grooved to prevent cracking due to high pressure from the inside. To do this, use a garden knife to make shallow cuts in the form of dotted lines. The distance between the lines is 10 cm.