Why do plums rot on trees and what should be done?

Main signs of fruit rot

In terms of external signs, fruit rot is similar to monoliosis (gray rot), but occurs only on those fruits that have received mechanical damage.
Fruit rot is caused by fungi that attack the foliage and fruits of trees. Warm and humid weather promotes the spread of the disease.

The carriers of infection are:

• wind;
• rain;
• insect pests.

Symptoms

The first symptoms of the disease can be seen on damaged fruits.

• Brown spots appear at the site of damage, quickly growing and covering most of the surface of the fruit.
• Approximately in mid-July, plums begin to pour, at which point brown spots appear on fruits with mechanical damage, quickly increasing in size. Upon closer inspection of the fruits, you can notice spores of putrefactive fungus on them, located in a circular or chaotic manner. These spores are separated from the damaged fruit by the action of wind and rain and are transferred to other trees in the garden. Warm, rainy weather accelerates the transfer of fungal spores.
• Rotten plums that continue to hang on the branches become mummified and can spread fungal spores for about two more years. From the fruit, the fungus moves along the stalk to the branch, where it overwinters. With the arrival of spring warmth, the fungus becomes more active and attacks new fruit ovaries.

Infected fruits should not be left on the branches!

• The shoots and branches of trees are covered with brown spots and cracks, and gum oozes through the broken bark, forming sagging. The branches dry out and die. Fungal spores in the form of grayish growths can also be seen on the bark. The inflorescences turn pale and dry out, but do not fall off and remain hanging on the tree.

Unpleasant situation

Under favorable conditions, the fungus spreads along the branches and leaves of the tree.

This contributes to the loss of most of the crop and the drying out of shoots damaged by the disease. Not only ripened fruits are affected, but also green ones. The pulp of ripe plums damaged by fungus loses its taste.

If during harvest the fungus gets on good fruits, they will not be stored for long. The disease provokes blackening of plums and a change in their taste. Infected fruits should not be eaten.

Errors in care

If plums rot directly on the tree, the reason for this may be improper care, especially when it comes to adding nutrients under the tree’s crown. Often this process is accompanied by an excess of fertilizers in the soil. To prevent possible rotting, nutrients must be added according to certain rules.

The first time this is done is from the 3rd to 5th year of the seedling’s life; in the initial phase of development, it has enough fertilizer added to the hole during planting. Fertilizer is made from minerals. The first of them is applied 12-15 days before the plum blossoms, using special solutions for this. Add 20 grams of urea to 10 liters of water.

Complex mineral fertilizers alternate with organic fertilizers. A nutrient solution is applied under the tree crown. To prepare it, you need to dilute 2 kilograms of mullein in 10 liters of water.

Proper plum care is not only about fertilizing. Formative pruning of the tree will help prevent crown thickening. Such operations are carried out in the spring. The gardener trims frost-damaged and dry branches, as well as shoots that point downward or grow deep into the crown. In autumn, leaves and fruit residues are collected. Organic remains must be placed in a compost bin or burned.

Causes of rot

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For the disease plum fruit rot, control measures can be different. But first of all, it is necessary to understand the causes.

Remember! It is easier to fight the disease at the initial stage.

The main reasons why plum fruits rot on a tree, experienced gardeners include:

• Thickened plantings. If the trees are too close to each other, then there is an obstacle to the free circulation of air.
• Incorrect crown trimming. For example, dense foliage creates high humidity, which is an excellent environment for the spread of rot on plums.
• Poorly chosen place to plant a tree. The lack of light or the location of the plum in low-lying parts of the site also contributes to the development of infection. This occurs due to stagnation of moist air.
• Damage to fruits. There may be several reasons for mechanical impact on plums. For example, precipitation or harmful insects.
• Failure to comply with preventive measures. If the wood is not treated in a timely manner with special disinfectants, then the spores living in the soil will “wake up” and become activated with the arrival of heat.
• The presence of fallen leaves and fruits under the tree. Untimely harvesting of fallen crops, which were also infected, will lead to infection of the future crop. This is due to the fact that the spores tolerate even low temperatures well.
• Failure to comply with the rules for applying fertilizers. Improper feeding leads to decreased immunity.

Remember! After working with an infected tree, it is necessary to thoroughly treat all garden tools.

Why do plums rot on the tree?

Every summer, garden fruits are at risk of becoming infected with moniliosis. Fruits with damaged shells are more susceptible to this than others. There are many reasons why cracks and wounds appear on plums, pears, and quince: past hail, attacks by birds or wasps, deformation after strong winds, disease.

Improper care

Fruit rot can appear when the timing of fertilizing is violated, or when there is an excess of fertilizers. The following rules must be observed:

1. The plum tree is fed for the first time no earlier than 5 years after planting. Fertilize with urea 14 days before flowering.
2. During the next season, the trees are fed with organic matter (liquid manure: 2 kg per bucket of water).
3. Alternating types of fertilizers are used every year: organic - mineral.
4. Weather factors are taken into account: the day of fertilizing should be warm and windless.
5. Sanitary pruning, preventative spraying of trees, and digging up the soil around them are carried out in a timely manner.

Experienced gardeners advise cutting healthy branches (in spring) by about 12-16 cm to thin out tree crowns.

Landing location

Plum trees are best grown in a dry area; this crop does not like excess moisture. Compliance with the following conditions will help to avoid the appearance of gray rot on fruits:

• good lighting of the tree, at least for several hours (daily);
• depth of groundwater - at least 1.5 m;
• absence of strong winds.

Types of rot

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Regardless of the type of rot, all parts of the tree are affected. Dark brown spots form on the fruits, the flesh becomes soft and brown. The leaf blades quickly wither and, as a result, dry out. The main difference is the time of infection. Fruit rot appears around mid-July, and gray rot appears at the time of sudden temperature changes, that is, in autumn and spring.

Fruit

This type of infectious disease is characterized by the following symptoms:

• The occurrence of rot is promoted by air temperatures from +25 to +30 degrees. Humidity level – at least 70%.
• The time of mass destruction occurs at the end of the first month of summer, when the warmest weather sets in.
• As infected fruits rot, they release toxins into the environment.
• At the initial stage, small brown spots appear on the plum, which gradually increase in size.
• When the fruits are completely rotten, they become wrinkled, and the colonies of spores living inside contribute to the very rapid spread of infection.

Gray rot

This disease has another name – monilial burn. It damages fruits grown in regions with high humidity.

The disease can be described by the following symptoms:

• The optimal temperature for fungal development is no higher than +15 degrees, air humidity is more than 90%.
• The first signs of infection appear at the time of flowering, and the spread of the fungus occurs throughout the summer.
• The pores grow deep through the flowers and are located on the pistils.
• Despite the fact that the inflorescences fade, they do not fall off and are a source of infection.
• The ovary begins to rot at a late stage of infection. Externally, this manifests itself in the form of burns.

Important! Gray rot can very quickly affect all stone fruit trees on the site and turn the garden into a source of infection for other cultivated plants.

Stone fruit scab

The causative agent of scab is the fungus Cladosporium. It harms stone fruits in the same way as most other fungi: it appears as an olive-colored spot that gradually grows and turns black.

Stone fruit scab is widespread in the southern regions. Winter thaws and late spring frosts, frequent rains in May at a temperature of +25 degrees are favorable for it. It spreads quickly on plants planted in lowlands, on heavy, clay soils, and unventilated areas.

Heat, drought and good ventilation stop the development of the fungus.

Andrey Vasiliev Consultant of the “Orchard” section

Sometimes the weather just helps - dry heat comes and the mushrooms are finished.

To prevent scab, spraying with preparations containing copper is used, plus specialized spraying against scab (twice with systemic fungicides, with an interval of two weeks).

Treatment

Since moniliosis is a fungal disease, it can only be effectively combated by using fungicides. However, some of these drugs are highly toxic to bees, and the tree will have to be sprayed during the flowering period, so the product should be selected taking into account its hazard class.

If treatment of moniliosis is started in the early stages of development, then the infection can be completely eliminated by 2-3 treatments of the tree with fungicides. An advanced infection is more difficult to treat: first of all, the infected plum is radically pruned, methodically removing all damaged branches, and then the “patient” is prescribed a course of chemical treatments. At first, it is recommended to carefully care for a sick plum, scrupulously observing the requirements of agricultural technology and in every possible way increasing the immunity of the tree. When the ward fully recovers from the stress she suffered, she will only need preventive support.

Prevention measures

In order not to waste time and effort on treating the disease, you need to take timely preventive measures that will help prevent the occurrence of infection in the area.

These include:

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• regular inspection of trees to detect rot at an early stage;
• pruning plum branches - helps eliminate thickening of leaves and improves air circulation in the crown;
• treating mechanical damage to bark and branches with garden varnish prevents fungal spores from entering them;
• cleaning up fallen leaves in the fall and digging up the tree trunk circle helps get rid of fungal spores located on the soil surface;
• spring treatment of trees with an aqueous solution of 10 liters of water, 500 g of salt, a small piece of laundry soap and 0.5 buckets of wood ash;
• feeding plums with potassium-phosphorus fertilizers in the spring before flowering, in the summer during the period of fruit formation and in the fall after harvesting - provides the trees with the necessary nutrients for better resistance to diseases and pests;
• Regular pest control helps to avoid mechanical damage to fruits;
• autumn whitewashing of the lower part of the plum trunk with a solution of lime and iron sulfate;
• spraying with Bordeaux mixture - carried out in the spring during the swelling of the buds and in the fall after harvesting.

Preparations for moniliosis (fungicides)

We offer you a list and brief description of drugs used in the fight against moniliosis:

• Abiga-Pik is a copper-containing preparation, a broad-spectrum contact fungicide to combat fungal and bacterial diseases;
• Alirin-B is a fungicide of biological origin used to suppress fungal diseases on plants and in soil. Used as a therapeutic and prophylactic agent;
• Bordeaux mixture is a broad-spectrum contact fungicide;
• Gamair is a biological fungicide for suppressing certain fungal and bacterial diseases on plants and in soil;
• Captan is a broad-spectrum contact fungicide designed to protect fruit trees from scab, moniliosis and black spot;
• Kuproxat is a contact fungicide with preventive and eradicating action, designed to combat a complex of fungal diseases;
• Copper sulfate is a copper-containing contact fungicide with a broad spectrum of action to combat fungal diseases on stone fruit and pome crops;
• Mikosan-B is a biological fungicidal preparation that stimulates the immune system of plants;
• Nitrophen is an enteric contact fungicide, insecticide and herbicide used as a means for the prevention of fungal diseases;
• Planriz is a highly effective and environmentally friendly fungicide based on soil bacteria;
• Strobi is a highly effective broad-spectrum fungicide for the control of fruit, ornamental and vegetable plants;
• Topsin-M is a systemic fungicide with therapeutic and prophylactic action, most effective during preventive treatment;
• Phytoflavin is a systemic biological bactericide used for the prevention of many fungal and bacterial diseases;
• Fitosporin-M is a biological fungicide of contact action, a microbiological preparation for protecting plants from a complex of bacterial and fungal diseases;
• Horus is a systemic fungicide used to protect plants from scab, moniliosis and other diseases;
• Zineb is a fungicide with preventive and therapeutic action to combat fungal diseases.

Areas of distribution

This disease is widespread in almost all Russian regions, affecting all stone fruit crops in gardens, including plum trees.
Areas with high air humidity are especially affected by moniliosis:

• Northwest;
• Central regions;
• Ural;
• Siberia;
• Altai;
• North Caucasus.

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Folk remedies to combat moniliosis

Among the folk remedies for combating moniliosis, we can offer you autumn treatment of fruit trees with a solution of 1 kg of urea in a bucket of water. Approximately half a bucket of the product is used to spray each adult plant. For better “adhesion”, you can add 40 grams of dishwashing detergent to the solution. It is necessary to wet all the leaves on both sides and all the branches of the tree, and after leaf fall, you need to cover all the litter in the tree trunk circle with a thick layer of straw: the urea solution will clean the fungus from the branches and leaves of the tree, and the straw mulch will preserve the pathogens of the disease in the soil that were not killed during treatment. In addition, mulch will serve as good protection for the tree’s root system from winter frosts. In the spring, before the sap begins to flow, you can once again treat the fruit trees with a urea solution.

Adviсe

Not all plum varieties are equally susceptible to the disease. Breeders obtain rot-resistant varieties with good fruit taste. These are the common Hungarian, the Azhan Hungarian, and the green Renklod. In the middle zone, the plum varieties Voloshka, Kirke, President, Sopernitsa, Vengerka Yubileinyaya are severely affected.

Usually, simultaneously with plums, apple trees, pears, cherries and other stone fruit and seed fruit trees are affected. If signs of damage appear in any corner of the garden or among neighbors, it’s time to start preventive treatment of the plum.

If you follow the rules for crown formation, timely fertilize trees, and carry out preventive measures, it will be possible to avoid mass damage by moniliosis.

Bacterial diseases of plum trees

These diseases occur under the influence not of viruses, but of pathogenic bacteria and microbes. Pathogens can enter plants in different ways - through seedlings, dirty tools, birds or insects.

Root cancer

This disease can affect any garden trees. The cause of the disease is bacteria living in the soil. They can only enter the tree body through damaged roots. That is why when planting seedlings you need to be extremely careful not to damage them.

Root canker pathogens become more active in dry weather. A slightly alkaline environment is most comfortable for them.

The disease is manifested by the appearance of growths on the roots. After this, slow rotting of the roots begins. The tree receives less and less life-giving moisture from the soil and dies

Root cancer is incurable. The tree has to be removed by the roots, and the soil where it grew needs to be watered with an aqueous solution of copper sulfate. A last resort, but there is no cure. All tools that the gardener worked with must be disinfected with a bleach solution.

Bacterial burn

This disease can affect even the strongest trees in the garden. Mature plum trees are also unable to withstand fire blight. As a rule, the disease occurs in spring or autumn. Damp air promotes bacterial burns. Bacteria come to plums exclusively from other diseased plants.

Fire blight affects the entire above-ground part of trees. This is immediately visible: there are cracks in the bark, and the buds and leaves have turned black. If bacteria attack a plum tree while it is blooming, the entire color turns brown and falls off.

The fight for the tree will be ineffective. Why? It is impossible to save such a plum. It is removed from the garden along with the roots, and the soil is disinfected with an aqueous solution of copper sulfate.

To prevent the disease, plums are treated with antibiotics.