Tree walnut, like any plant, can disappear due to improper care, poor soil, close ground water, the dominance of harmful insects, lack of sun or severe cold. But to find effective method tree treatment, it is important to correctly identify topical symptoms.
How to identify the problem?
An experienced arborist will not immediately prescribe remedies for all sores, but will conduct a thorough check of the bark, branches and foliage. He will determine whether the plant is a hybrid with increased resistance to pathogens, frost, etc. The specialist will ask the owners about the level of moisture in the garden, the frequency of watering, the nature and regularity of feeding. Before making recommendations, he will pay attention to the manifestations of the disease - blackened branches, spoiled wood, dried fruits or missing buds.
What are the causes of diseases?
Walnut is afraid of late frosts that damage the shoots and pericarp, hail or acid rain. It is worth sounding the alarm if the seedling grows on clay soil with high mineralization, in a place where underground rivers accumulate.
Marsonia (brown spot)
This fungal disease may be the result of prolonged rainy weather. It is especially dangerous at the flowering stage, when 80-90% of the ovary dies, and red-brown, turning into gray spots appear on young leaves, causing contraction and subsequent death of the affected area.
A three-stage spraying with a fresh 1% solution of Bordeaux mixture helps to solve the problem. The first treatment is carried out in the spring before the buds bloom, the second - after the activation of the leaf cover, the third - 2 weeks after the second one. It is noteworthy that without the above measures, the fungus will overwinter in cracks, fallen inflorescences, and become more active next year.
bacteriosis
This is one of the most common diseases, during wet periods it affects the entire woody surface, from cuttings to catkins. Infection is manifested by black or brown marks stretched along the veins, which cause deformation, as well as loss of leaves and fruits.
Bacteriosis can easily overwinter in the foliage, and in the spring season penetrate into the subcortical layer through a slight damage. Therefore, thin-skinned varieties must be kept under constant supervision.
To combat bacterial damage, the remains of organic matter are burned in the fall, and the plantings are also treated 3 times with a mixture of 1% blue vitriol or copper oxide before and after setting nuts, depending on the growing season.
To maintain the health of trees, it is necessary to comply with agrotechnical conditions - fertilize, cultivate and water the soil in time. Regular inspection is also shown, which will help to notice the problem at an early stage.
In this article, I will talk about the main walnut diseases and how to deal with them. There are, strictly speaking, only three of them:
Marsoniosis or walnut brown spot
Marsoniosis affects the leaves, green shoots and fruits of the nut. Symptoms:
- on the leaves - small rounded spots of brown color with a darker brown border. They appear in May. The spots gradually grow and merge. Severely affected leaves fall off;
- on the shoots - the same;
- on fruits - at first small depressed spots of red-brown color. Subsequently, the spots grow and merge. The affected tissue lags behind in growth and begins to crack, sometimes rots and the kernel of the nut turns black. A severely affected ovary often crumbles.
Brown spot is caused by the fungus Marssonina juglandis. The fungus actively develops at high humidity: if the beginning of summer is rainy, walnut crop losses due to disease can be up to 50%.
Control measures
The pathogen overwinters in plant debris and affected shoots - therefore, the most in a simple way the fight is the removal of fallen leaves followed by burning. In addition, effective:
- treatment with a 3% or 3% solution without lime until the buds open;
- for prevention purposes - 2….3 times treatment 1% Bordeaux mixture during the season;
- when signs of damage appear - 3 treatments with Bordeaux mixture or other copper-containing fungicide with an interval of 10 ... 15 days.
It should be noted that the Russian Register of Pesticides does not contain permitted preparations to combat marsoniosis - therefore, it has to be treated by analogy with other similar diseases.
Bacteriosis affects leaves, green shoots, inflorescences and ovary. It manifests itself in the form of small dark spots, which subsequently increase and merge. On the ovary, the spots are quite large and slightly depressed, sometimes they look like a ring, in the center of which there is intact tissue. With a strong lesion, the infection can penetrate to the core, which rots, after which the ovary falls off. Affected shoots turn brown and die.
Ripe nuts themselves are usually not affected, but the pericarp is affected.
The causative agent of the disease is the bacterium Xanthomonas arboricola pv.juglandis, which can spread with wind, insects, pollen, etc. Bacteriosis is aggressive in warm and humid weather.
Control measures
Measures to combat bacteriosis are poorly developed. Early spring spraying with 3% copper or either 1% urea solution has a certain effectiveness. (before bud break). The second spraying is carried out 2 ... 3 weeks after flowering - 1% Bordeaux liquid or 0.3% urea solution is used. Treatments with metronidazole are likely to be effective.
Root cancer manifests itself on the roots in the form of growths and sagging. With a strong defeat, the plant stops developing - especially if the disease develops against the background of a lack of moisture.
The causative agent of root goiter is the soil-dwelling bacillus Agrobacterium tumefaciens. It penetrates the roots through wounds and provokes active growth root tissues, disrupting its normal structure.
It is impossible to cure root cancer in any way - therefore, one has to limit oneself to prevention. For planting a walnut, use areas where fruit and other crops that can be affected by root cancer have not grown for many years. In addition, you should carefully inspect the root system of seedlings when buying and before planting. If there are growths on the roots, the affected roots are removed. It is advisable to treat the root system with a 1% solution of acoustic soda (exposure time - 5 minutes), and then rinse clean water. Seedlings with severe damage to the main root or root collar are burned.
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Natalia Mironova 01/10/2015 | 23289
Although the walnut is resistant to different kind diseases and pests, the plant cannot fully resist them. Find out what diseases a walnut can get, what pests to be wary of, and how to help a tree in such cases.
So that the walnut does not get sick and is not damaged by pests, it is necessary to keep the main trunk, skeletal and perennial branches in order. Every year, you need to cut the shoots growing inside, affected by diseases, dried branches. Places of cuts should be covered with garden pitch or oil paint, and the fallen nuts to collect and burn.
If autumn leaves collect walnuts in a metal container, pour boiling water and close tightly, then by spring you will have a concentrate that can be used to prepare a remedy against aphids and the Colorado potato beetle.
What can cause walnut disease?
The main diseases of the walnut - Marsoniosis(bacterial spot) and bacteriosis.
Small light spots, turning black over time, on the leaves of young shoots indicate damage to the nut bacterial spotting. The disease begins with the defeat of the tops of young shoots. If you notice affected shoots, remove them immediately. In affected fruits, the kernel liquefies and acquires an unpleasant odor.
bacteriosis affects leaves, young shoots and fruits. The first signs of the disease appear on the leaves - first, black spots form on them, which gradually grow along the veins. Affected leaves are deformed, blacken and fall off. Elongated brown spots appear on young shoots, subsequently the affected shoots dry out and bend. In wet years with insufficient heat and frequent fogs, the disease can kill up to 90% of the flowers. Young fruits affected by bacteriosis fall off.
How to protect a tree from diseases?
The main protection of the walnut against fungal diseases is the treatment of trees with copper-containing preparations. It is best to use ordinary Bordeaux liquid for this purpose. Its substitutes (Tsineb, Hometsin) are less effective and require more frequent spraying.
The first spraying with 3% Bordeaux liquid is carried out even before the buds open. Then switch to a less concentrated 1% solution and spray plants with it in the following development phases:
- in the phase of opening leaf buds;
- before the flowering of female flowers;
- immediately after flowering;
- at the very beginning of fruit formation.
Instead of Bordeaux liquid, before bud break, trees can be treated with a 1% DNOC solution.
Processing a walnut with Bordeaux liquid will be even more effective if you add a 0.3% solution of urea to it, which has a depressing effect on the causative agent of bacteriosis.
walnut pests
The main pests of walnuts are american butterfly(white), which is classified as a quarantine pest, codling moth, nut miner moth, walnut warty mite. Almost all types of pests can be fought with almost the same drugs, since most of them belong to gnawing and sucking species.
In their development, almost all pests go through the caterpillar stage, in which they hibernate on trees. Therefore, to combat them, it is imperative to use trapping belts. Getting on a tree, pests form huge colonies covered with a dense cobweb (American butterfly), fold the leaves into a tube (tick) or settle inside the leaf blade (mining moth), and then spread throughout the tree.
How to deal with pests?
The main control measure is the timely pruning and burning of damaged branches. The main thing is not to let the caterpillars crawl along the tree.
Do not use pesticides, it is better to use one of the biological products against pests: Lepidocide, Bitoxibacillin, Dendrobacillin. Before use, be sure to read the instructions and follow the specified concentrations. The consumption of the working solution per 1 tree is at least 3-5 liters.
During flowering, walnuts cannot be processed. chemicals, because they can kill bees and other pollinating insects.
In case of severe damage by caterpillars, moths and mites during the period of fruit growth, you can spray the trees once with Decis Profi. The drug has a short decomposition period, so it does not accumulate in plants.
Although the walnut is resistant to different kind diseases and pests, the tree still needs some care. And if you follow the measures described above, then a healthy and beautiful tree will certainly please you with a good harvest.
Walnut pests. This crop, compared with other fruit trees, is damaged much less frequently. However, according to different reasons sometimes walnuts can be affected by various insect pests. The most common of these are described below.
One of the harmful insects is the American white butterfly, which gives two generations: the first - from July to August, the second - from August to September. In rare cases, the 3rd generation is hatched - in September-October. Most great harm the plant is applied by the third generation. Butterfly caterpillars settle on leaves and young shoots, gradually spreading over all parts of the tree over time. To destroy this pest, caterpillar accumulation sites are destroyed with insecticides, or they are sprayed with modern microbiological preparations: bitoxibacillin, lepidocide, dendrobacillin.
Apple or walnut codling moth also gives 2 generations: the first - in June, the second - in August. Caterpillars of the first generation eat out the kernels of young nuts, subsequently the fruits die. Caterpillars of the second generation settle inside the nuts, eat out the cotyledons. Damaged nuts fall off. The second generation causes great harm to the plant, negatively affects its yield, since one caterpillar can damage several nuts. To combat the codling moth, pheromone traps containing an attractant are used that attract males of this insect. Such traps reduce the number of male butterflies, for this reason, the possibility of fertilization of females is reduced. They should be installed from May to September. Affected trees are sprayed with a special viral preparation that causes granulosis in caterpillars of the pest, which destroys them within 7 days. In addition, in June-July, it is recommended to regularly inspect the walnut, and if found, collect its caterpillars and remove damaged fruits.
It affects leaves and buds, feeding on their juice and thereby weakening the tree. At in large numbers aphids curl and fall off. The fight against insects is carried out using a solution of "Decis" or "Karate".
- the destroyer penetrates into the thickness of the bark, so the insect is not visible on its inner or outer surface. Gradually, the beetles gnaw out the bark on the shoots. The pest can be seen through curved canals in the tree near the buds and petiole bases. Sapwood settles mainly on weakened plants and leads to their abundant sap flow. The first generation of beetles flies in June, the second in August. To prevent the appearance of the sapwood - the destroyer, a sanitary cutting of a tree is carried out, which includes the removal of diseased, dried and damaged branches. At the initial stage of the appearance of the beetle, the plant is sprayed with insecticides.
Walnut diseases and their photos
Walnut tree diseases can occur for several reasons: due to lack of light, soil poverty, improper care, close groundwater, excess moisture, alkaline rainfall, late spring frosts.
The most common walnut diseases are brown leaf spot, bacterial burn, bacteriosis, root cancer and others.
Brown spotting appears during prolonged rains, when the soil is waterlogged. If the disease develops during flowering, it usually destroys up to 90% of the flowers, for this reason the tree is left without a crop. It affects brown spotting and young leaves, appearing on them with reddish-brown and gray-brown spots. The fungus that spreads the disease overwinters in fallen infected leaves, fruits, and cracked branches. When brown spotting occurs, 1% Bordeaux liquid is used, which is sprayed on the plant at least 3 times. The first spraying before bud break, the second - during the appearance of leaves, the third - 2 weeks after the second. The solution is prepared before use.
Bacteriosis usually develops in spring, during warm, damp weather. Dark spots form on leaves, inflorescences, fruits and branches. During the flowering period of a tree, the disease can destroy most flowers and young ovaries. The bacteriosis that developed after flowering leads to browning of the wood and the death of green shoots. Dark spots form on the fruits, which gradually grow. The pathogen overwinters in infected shoots, buds and leaves. To prevent bacteriosis, before flowering, the nut is treated with a solution of 3% Bordeaux liquid and 1% urea. The next spraying is carried out 2 weeks after flowering.
Hardly the most frequently asked question from gardeners - why does the walnut blacken? But before answering it, it is important to understand what kind of spots arose, when and how they appeared. Walnut diseases are very common, because due to the height and spreading of the crown, old trees have not been processed for years - so they become breeding grounds for diseases for younger trees. God forbid you cut down nuts because of such trifles as diseases! Below in the article I will tell you how to deal with walnut diseases.
You can read more about growing walnuts.
The most common walnut diseases
Before proceeding to the description of diseases, it is important to take care of the sufficient nutritional value of the soil. On poor or stony soils, walnut diseases occur more frequently. Also, the appearance of spotting on a walnut contributes to the freezing of a tree in winter or weakening from drought. To save diseased trees, the affected branches are cut out in the spring with the capture of 5–7 cm of healthy wood and the cuts are disinfected with copper-containing preparations.
Marsoniosis (brown spot)- common fungal disease, which is activated on walnut trees in May in rainy weather. First, the leaves and green nuts become covered with brown spots, then they turn black, the leaves curl and fall off. Fruits lose moisture, which is why the kernels grow a third less than their usual mass. Severely affected fruits crack and fall off prematurely. A nut with marsoniosis often freezes slightly. For the prevention and treatment of the tree, an annual spraying of 1% Bordeaux liquid is used. It is necessary to process during the period of bud break and twice more with an interval of 2-3 weeks, depending on the drug. In autumn, it is also important to collect fallen leaves and burn them away from the site.
bacteriosis- a common problem of nuts, which can be noticed even in the spring. Brown spots appear on leaves, young shoots, inflorescences, and then on fruits. bacteria, disease-causing, can get on the plant with pollen during the flowering period. Inflorescences affected by bacteriosis do not form ovaries, which is why in the spring you can lose most of the crop. If bacteria
activated later, the young shoots dry up, the wood darkens inside, and depressed ulcers appear on the fruits. If the disease appears in the middle of summer, the kernels of many fruits will rot. During the period of ossification of the nutshell, bacteria damage only the green shell. On young seedlings, bacteriosis is manifested by the formation of a constriction on the root neck, as a result of which the tree stops growing and breaks.
From bacteriosis to flowering, the tree must be sprayed with 3% Bordeaux mixture, and 2-3 weeks after flowering with 1% Bordeaux mixture or 0.5% urea solution.
white spotting- a fungal disease that is activated in wet weather and manifests itself as light spots on the leaves. At first they are pale green, faded, and soon turn white. Then the spots become convex, it seems as if the leaves are affected by a mite. Severe infestation can lead to leaf shedding, which greatly weakens the tree. I recommend that the treatments be carried out the same as for the previous two diseases.
root cancer- a disease that manifests itself as growths on the roots. This is facilitated by any mechanical damage roots of seedlings when planting: cracks or wounds. Large swellings-growths are formed on the roots, due to which the growth of the tree stops, the yield decreases, or fruiting stops altogether. If the nut is heavily infested, the disease can lead to the death of the tree. Unfortunately, there is no cure for root cancer. The maximum that can be done if you find outgrowths when transplanting a seedling is to cut them off. Then soak the roots for 5 minutes in a 1% solution caustic soda, after rinse the roots running water and plant.
What to process
In addition to the accepted for all fruit trees early spring treatment with 3% Bordeaux liquid, and later with 1% solution, I advise you to use special preparations. They can be combined in tank mixes with pesticides. For short-term fast protection, I recommend the drug Garth(30 g per 8-10 liters of water). For long-term protection, spray trees with systemic products, such as Guardian(3-4.5 ml per 5 liters of water) and Defender (Zakhisnik)(30 ml per 5-8 liters of water).
Walnut diseases are not a reason to retreat and not grow this crop, especially since in favorable conditions these trees take 300–400 years to grow. Proper Care and timely processing - and useful and nutritious fruits will only arrive annually.
