Tree walnut, like any plant, can disappear due to improper care, bad soil, close groundwater, dominance of harmful insects, lack of sun or severe cold. But to find effective method tree treatment, it is important to correctly identify the current 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 a consequence 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. Infestation manifests itself as 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 it can penetrate into the subcrustal layer through minor damage. Therefore, thin-barked varieties must be kept under constant supervision.
To combat bacterial infection in the fall, burn the remains of organic matter, and also treat the plantings 3 times with a mixture of 1% copper sulfate 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 on time. Regular inspection is also recommended, which will help to notice the problem at an early stage.
In this article I will talk about the main diseases of walnuts and ways to combat 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. 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 is stunted in growth and begins to crack, sometimes the nut kernel rots and turns black. A severely affected ovary often crumbles.
Brown spot is caused by the fungus Marssonina juglandis. The fungus actively develops in high humidity: if the beginning of summer is rainy, the loss of walnut yield 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 in the Russian Register of Pesticides there are no approved drugs to combat marsoniosis - therefore it must be treated by analogy with other similar diseases.
Bacteriosis affects leaves, green shoots, inflorescences and ovaries. It appears in the form of small dark spots, which subsequently increase and merge. On the ovary, the spots are quite large and slightly depressed, sometimes looking like a ring, in the center of which there is intact tissue. With severe damage, 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 be spread by 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 1% urea solution has a certain effectiveness. (before buds open). The second spraying is carried out 2...3 weeks after flowering - 1% Bordeaux mixture or 0.3% urea solution is used. Metronidazole treatments are likely to be effective.
Root cancer appears on the roots in the form of growths and swellings. With severe damage, 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 into the roots through wounds and provokes active growth root tissue, disrupting its normal structure.
There is no way to cure root cancer - so you have to limit yourself to prevention. To plant nuts, you should use areas where fruit and other crops that may be affected by root canker have not grown for many years. In addition, you should carefully inspect the root system of seedlings when purchasing 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.
To print
Natalya Mironova 01/10/2015 | 23289
Despite the fact that walnut is resistant to different types diseases and pests, the plant cannot fully resist them. Find out what diseases a walnut can get, what pests you should be wary of, and how to help the 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 trim off shoots growing inward, affected by diseases, and dried branches. The cut areas should be covered with garden pitch or oil paint, and collect and burn fallen nuts.
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 a walnut get sick with?
The main diseases of nuts are: marsoniosis(bacterial spot) and bacteriosis.
Small light spots, turning into black over time, on the leaves of young shoots indicate damage to the nut bacterial spot. The disease begins with damage to 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 become deformed, turn black and fall off. Elongated brown spots appear on young shoots; subsequently, the affected shoots dry out and become bent. In humid years with insufficient heat and frequent fogs, the disease can destroy up to 90% of the flowers. Young fruits affected by bacteriosis fall off.
How to protect a tree from diseases?
The main protection of walnuts from fungal diseases is the treatment of trees with copper-containing preparations. It is best to use ordinary Bordeaux mixture for this purpose. Its substitutes (Tsineb, Khomecin) are less effective and require more frequent spraying.
Carry out the first spraying with 3% Bordeaux mixture even before the buds open. Then switch to a less concentrated 1% solution and spray the plants with it during the following development phases:
- in the phase of leaf bud opening;
- before female flowers bloom;
- immediately after flowering;
- at the very beginning of fruit formation.
Instead of Bordeaux mixture, you can treat the trees with a 1% DNOC solution before the buds open.
Treating walnuts with Bordeaux mixture will be even more effective if you add to it a 0.3% solution of urea, 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, walnut 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 catching 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 timely pruning and burning of damaged branches. The main thing is to prevent the caterpillars from spreading across 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.
Despite the fact that walnut is resistant to various kinds diseases and pests, the tree still needs some care. And if you follow the measures described above, then healthy and beautiful tree will certainly please you with a good harvest.
Walnut pests. This crop is damaged much less frequently than other fruit trees. However, according to various reasons Sometimes walnuts can be affected by various insects - pests. The most common ones are described below.
The American white butterfly is recognized as one of the harmful insects, which produces 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 inflicted by the third generation. Butterfly caterpillars settle on leaves and young shoots, and over time they gradually spread to all parts of the tree. To destroy this pest, places where caterpillars accumulate are destroyed with insecticides, or sprayed with modern microbiological preparations: bitoxybacillin, lepidocide, dendrobacillin.
The apple or walnut moth also produces 2 generations: the first in June, the second in August. The first generation caterpillars eat up the kernels of young nuts, and subsequently the fruits die. The second generation caterpillars settle inside the nuts and eat away the cotyledons. Damaged nuts fall off. The second generation causes great harm to the plant and negatively affects its yield, since one caterpillar can damage several nuts. To combat the codling moth, pheromone traps are used that contain an attractant that attracts males of this insect. Such traps reduce the number of male butterflies, and for this reason the possibility of fertilizing females is reduced. They should be installed from May to September. Affected trees are sprayed with a special viral preparation that causes granulosis in the 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 attacks leaves and buds, feeding on their sap and thereby weakening the tree. At large quantities aphids, leaves curl and fall off. Insect control is carried out using Decis or Karate solution.
– 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 in curved channels on the tree near the buds and bases of the petioles. 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 sapwood, a destroyer, sanitary cutting of the 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, poor soil, improper care, close groundwater, excess moisture, alkaline rain, late spring frosts.
The most common diseases of walnut are brown leaf spot, bacterial burn, bacteriosis, root cancer and others.
Brown spotting appears during periods of prolonged rains, when the soil is waterlogged. If the disease develops during flowering, it usually destroys up to 90% of the flowers, leaving the tree without a harvest. Brown spot also affects young leaves, appearing on them as reddish-brown and gray-brown spots. The fungus that spreads the disease overwinters in fallen infected leaves, fruits and cracks in branches. If brown spot occurs, use 1% Bordeaux mixture, which is sprayed on the plant at least 3 times. The first spraying is before the buds open, the second is when the leaves appear, the third is 2 weeks after the second. The solution is prepared before use.
Bacteriosis usually develops in the 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.
Almost the most frequently asked question from gardeners - why does a nut turn black? But before answering it, it is important to understand what type of spots arose, when and how they appeared. Walnut diseases are very common, because due to the height and spreading nature of the crown, old trees are not treated for years - so they become breeding grounds for diseases for younger trees. God forbid you cut down nuts because of such trifles as illness! Below in the article I will tell you how to cope with nut diseases.
You can read more about growing walnuts.
The most common walnut diseases
Before moving on to describing diseases, it is important to ensure that the soil has sufficient nutrition. Walnut diseases occur more often on poor or rocky soils. Also, the appearance of spotting on walnuts is facilitated by freezing of the tree in winter or weakening from drought. To save diseased trees, the affected branches are cut out in the spring, including 5–7 cm of healthy wood, and the sections are disinfected with copper-containing preparations.
Marsoniosis (brown spot)– common fungal disease, which becomes active on walnut trees in May rainy weather. First, the leaves and green nuts become covered with brown spots, then they turn black, the leaves curl and fall off. The fruits lose moisture, causing the kernels to grow a third less than their normal weight. 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, causing disease, can enter the plant with pollen during the flowering period. Inflorescences affected by bacteriosis do not form an ovary, which is why you can lose most of the harvest in the spring. If bacteria
become more active later, young shoots dry out, the wood inside darkens, 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 nut shell, bacteria damage only the green shell. On young seedlings, bacteriosis is manifested by the formation of a constriction on the root collar, as a result of which the tree stops growing and breaks.
From bacteriosis before 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 spot- a fungal disease that becomes active 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 raised, as if the leaves were infected with mites. Severe infestations can result in leaf drop, which greatly weakens the tree. I recommend the same treatments as for the previous two diseases.
Root cancer- a disease that manifests itself as growths on the roots. Any mechanical damage roots of seedlings when planting: cracks or wounds. Large swellings and growths form on the roots, due to which the growth of the tree stops, the yield drops, or fruiting stops altogether. If the nut is heavily infected, 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 growths when transplanting a seedling is to cut them off. Then soak the roots for 5 minutes in a 1% solution caustic soda, then rinse the roots running water and plant.
What to process
In addition to the one accepted for everyone fruit trees early spring treatment with 3% Bordeaux mixture, and later with a 1% solution, I advise the use of special preparations. They can be combined in tank mixtures with pest control products. For short-term, quick protection, I recommend the drug Garth(30 g per 8–10 liters of water). For long-term protection, spray trees with systemic preparations, for example, 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 grow for 300–400 years. Proper care and timely processing - and useful and nutritious fruits will only arrive every year.
