Contents
Walnut diseases occur due to an improperly selected planting site or insufficient care. The culture is hardy, with good immunity, it is affected less often than fruit trees.
Fundamentals of proper tree care
Walnut is a tree that grows in almost every garden. He has a long lifespan. There are specimens that bear fruit for 400 years. In order to prevent the appearance of diseases and pests, you need to competently approach planting and fully care for the walnut:
- The soil at the planting site must be fertile. It is dug up with humus or compost.
- The groundwater level should not be high. The landing pit must be drained.
- The place is chosen in the sun. The tree does not tolerate shading, it may die.
- After planting, the root neck of the walnut should be level with the soil.
Planting begins in early spring, in the fall it is possible to plant a nut only in the southern regions. The seedling has time to take root before the first frost.
A complete walnut care consists of several points:
- pruning;
- whitewash;
- watering;
- top dressing;
- winter organization.
Pruning begins in the spring, when the temperature rises to + 4 … + 5 ° С. Cut out all the shoots that thicken the crown and interfere with its good ventilation. After that, dry and poorly overwintered branches are removed. Finish the procedure by whitewashing the trunk and skeletal branches. Previously, the old bark, lichens or growths are removed. The barrel is treated with a solution of copper sulphate, after which it is carefully whitened.
For an experienced gardener, it is no secret that a walnut needs abundant watering, especially if the weather is dry. The soil is moistened to the full depth of the roots. During a period of extreme heat, water the tree 2 or 3 times a month. At the same time, 3-4 buckets of water are consumed per plant.
You can fertilize the seedling 3 years after planting. If the landing pit was filled in accordance with all the rules, then there will be enough top dressing for this entire period. In spring and autumn, ammonium nitrate is introduced, in summer they switch to top dressing with a content of phosphorus and potassium.
Adult nuts winter well without additional shelter, but young seedlings must be insulated before the onset of cold weather. The trunk circle is mulched with humus to a height of 10 cm.
Walnut diseases and their control
There are a lot of diseases in walnuts, there are dangerous and not very dangerous ones. The duration of fruiting depends on the correct treatment. To correctly diagnose the disease, you need to carefully examine the trunk, leaves and buds of the tree.
Bacteriosis
Bacteriosis is an infectious disease of the walnut that affects almost all parts of it. It appears as black spots on the leaves, after which they completely dry out and fall off. Young shoots are also covered with brown dots.
The disease spreads during the flowering period, while part of the flowers and ovaries suffer. After that, the wood and green shoots die off. The pathogen overwinters in the buds, under the bark and in fallen leaves. In the spring, the infection passes to healthy parts of the walnut through frost holes. This is especially true in rainy weather.
For the treatment and prevention of bacteriosis, a 3% solution of Bordeaux mixture and a 1% mixture of urea are used. Treatments are planned 14 days after flowering.
Bacterial burn
Bacterial burn is one of the terrible diseases of the tree. It appears on leaves, young shoots, affects flowers. Walnut leaves are covered with watery black spots, they dry, but do not fall off. Buds and young shoots die off completely, ulcers appear on the trunk and branches. The peel of the fruit is covered with spots, the core completely blackens.
The disease spreads rapidly, especially during the rainy season. Carried by pollen and insects.
To combat bacterial burns, preparations containing copper are used. As a preventive measure, treatments are carried out several times in a row:
- in the spring, before flowering;
- autumn, after harvest.
You can use Zineb or HOM. Spraying is carried out in dry calm weather.
White spot
This disease is quite rare. The causative agent is a fungus that settles on the inside of the leaf. The affected plates are covered with light green spots with a white coating. White spotting develops in cold and damp weather.
To combat the disease, 1% Bordeaux liquid is used. Most often, walnuts are affected in the nursery, where plantings are too dense.
Brown spotting (phyllostictosis)
Fungal disease is manifested by yellow-brown spots on walnut leaves, which lead to tissue necrosis. Dry leaves die off, the growth of shoots slows down, the frost resistance of the plant is significantly reduced. It is difficult to destroy the fungus, the pathogen hibernates in plant debris and under the bark. In a rainy spring, the spores are spread to healthy tissues and the disease progresses again.
To get rid of brown spotting, walnuts are treated with copper chloride or a 1% solution of Bordeaux mixture. Spraying is carried out until complete cure.
Root cancer
The disease affects the root system of young seedlings and adult nuts. It manifests itself as growths on the roots, as a result of which the fruiting of the crop decreases or completely stops, winter hardiness worsens, and growth slows down. In advanced cases, the plant dies.
The walnut disease, which can be seen in the photo, is not easy to detect. It is possible to accurately diagnose root cancer only after digging up a seedling.
The causative agent of the disease enters the roots through frost holes, cracks in the bark or other damage. That is why the trunk and skeletal branches of the tree need careful care. In spring and autumn, all growths, cracks and damaged areas are cleaned to healthy tissue and treated with preparations with copper, a solution of caustic soda, after which they are covered with garden pitch and whitewashed.
Marsonia
The disease manifests itself on walnut leaves with brown dots, which gradually grow and occupy the entire surface of the leaf plate. As a result, leaf fall begins earlier than usual. In addition, unripe fruits that were affected by marsoniosis also fall off. The yield drops sharply.
At the first signs of the disease, the leaves are removed from the affected tree, the crown is treated with copper-containing preparations. Marsonia spreads in rainy weather. If there is little precipitation, then waterlogging of the soil as a result of improper watering may be the cause. The regime should be reviewed, otherwise the whole tree will suffer.
As a preventive measure of the disease in the spring, the nut is sprayed with the Strobi preparation, which is diluted according to the instructions. Processing is done before bud break. In the summer, Vectra will save you from illness.
Walnut pests and their control
A tree weakened by diseases is more often affected by pests, which are not always easy to get rid of quickly. Several treatments are required to achieve a lasting result.
American white butterfly
The most common and dangerous walnut pest. The butterfly is white, sometimes it has black or brown spots on its wings. One individual lays up to 1500 eggs per season, the third brood is especially dangerous. Caterpillars pupate and overwinter on the surface of the soil, under the leaves, in the bark of a tree, in the cracks of the trunk. With the advent of spring, they begin to harm again.
In one season, the insect gives several generations, so that a single spraying does not give anything. The butterfly lays its caterpillars on the leaves and young shoots of the walnut. Voracious young growth quickly eats them and spreads throughout the tree.
In the fight against insects, it is important to destroy the first generation, as the rest do even more harm. The walnut is examined, the caterpillars’ nests are removed and destroyed. The procedure is repeated every week. The most effective remedy against a butterfly is the microbiological preparation Lepidocid. Processing is carried out before and after the flowering of the walnut.
king nut moth
The pest lays eggs in walnut leaves. You can determine the lesion by the presence of dark tubercles on the surface of the leaf plate. Walnut moth caterpillars feed on the cell sap of the leaves, eating away the flesh from the inside. With severe damage, the tree is treated with pesticides:
- “Decamethrin”;
- “Decis”.
The preparations are diluted according to the instructions, the treatments are repeated every 15-25 days.
Walnut warty (gall) mite
Fungal diseases of the walnut lead to damage to the tree by a gall mite, which attacks it during a period of high humidity. The pest feeds on young foliage and does not harm the fruits. You can determine its presence by characteristic features:
- dark brown tubercles appear on the leaves;
- the growth of young shoots slows down;
- leaf plate spontaneously dries and curls;
- a thin cobweb is visible on the reverse side of the sheet.
Against the tick, acaricides such as “Aktara”, “Akarin” are used. Spray the nut several times with an interval of 15 days.
A woodcutter
The pest settles on a weakened plant. It is simply impossible to notice its presence at the initial stage, as it climbs under the bark. Gradually, the beetle gnaws out passages near the kidneys, eats them. The tree begins gumming.
You can protect the walnut from the sapwood. In spring and autumn, be sure to trim the crown, cutting out dry and affected shoots. In order to prevent the tree is sprayed with insecticides.
Plodojorka
The pest is dangerous for the fruit, as the nut kernels will leave, significantly reducing the yield. Damaged fruits fall prematurely. One caterpillar eats 2-3 nuts. Peak pest activity occurs between May and September.
You can catch the codling moth mechanically. For this, traps with pheromones are used, into which males fall. They are removed and destroyed, which significantly reduces the number of offspring. With severe damage to the tree, preparations with viruses are used that cause inflammation of the granulomas in the pest.
aphid
The pest settles on the underside of the leaf plate, sucks the juice from the tissues. As a result, the leaves curl, die and fall off. The nut quickly weakens and slows down growth. The fruits do not have time to ripen at the right time and also fall off.
Aphid invasion can be observed after rain. First of all, young leaves suffer, which leads to their diseases. At this time, the walnut is sprayed with Karate or Decis preparations. Processing should not be carried out during flowering, so as not to destroy the bees. The interval between sprayings is 15-25 days. After rain, the treatments are repeated.
Prevention of walnut diseases
As a preventive measure for diseases and pests of walnuts, it is important to properly care for the plant. Particular attention is paid to the tree in spring and autumn.
In early spring, the soil under the nut is loosened, granular mineral fertilizers are laid out to increase the plant’s immunity to diseases. Pruning is mandatory. Before bud break, preventive treatments are carried out with complex preparations from various diseases and pests.
In summer, the near-stem circle area is kept clean, weeds are removed in a timely manner to prevent pests from breeding in them. After all, it is they who transfer various fungi and viruses to the plant.
In autumn, the nut is re-cut, after which the crown is sprayed with approved preparations for prevention. Before frost, all fallen leaves, fruits and plant debris are removed to reduce the number of wintering pests. When a stable sub-zero temperature is established outside, the soil under the nut is dug up. Part of the pupated pests will die. To increase the immunity of the tree and its winter hardiness, experienced gardeners advise late watering. It is planned for the end of autumn, before the frosts have yet begun.
Conclusion
Walnut diseases lead to a significant loss of yield, so their occurrence should be prevented. To do this, the tree is not left unattended for a long time and is grown in accordance with the recommendations of experienced gardeners.