Why walnut fruits dry out. The main diseases and pests of the walnut tree. American white butterfly

The walnut (Juqlans regia L.) is a walnut-bearing tree species that is currently receiving much attention in terms of its study, selection and breeding, and in large sizes in all areas where it can grow.

As an example, we can cite the Dagestan, North Ossetian and Chechen-Ingush Autonomous Soviet Socialist Republics, in which at present there are about 5000 hectares of walnut crops, created mainly according to the garden type. Walnut cultures are also found in the Kabardino-Balkarian Autonomous Soviet Socialist Republic, as well as in the Stavropol and Krasnodar Territories, especially in Black Sea coast.

walnut for North Caucasus is not a native breed. Previously, he met here mainly on household plots like a fruit tree. In the forest, in forest cultures, it was not at all (not to mention the Black Sea coast). Breeding this valuable nut-bearing breed in significant sizes in forest areas began relatively recently, and, as a rule, according to garden method placement of plants in the forest area. This work is expanding every year. At the same time, it should be noted that the cultivation of walnuts in the North Caucasus (and, apparently, also in other regions of the country) almost everywhere has met with a serious obstacle, which consists in the fact that walnut seedlings grow in the form of a bush with dying shoots, and sometimes the entire trunk dies down to the base. The height of the bush, even at the age of six and seven years, sometimes does not exceed 1-2 m. The death of the apical shoot is very often observed already at the age of one. Along with this, at an older age, the formation of depressed cancerous wounds or cracks occurs on the trunk and branches. different sizes and the death of the bark, which eventually leads to drying out.

bacterial dropsy

Poor growth, bushiness, death of annual and biennial shoots and even trunks, as well as cancerous ulcers on branches and trunks, both in the past and in the present, are explained by freezing.

Our studies of walnut cultures in North Ossetia and the Krasnodar Territory showed that the root cause of poor growth, bushiness, dying off of shoots, and the appearance of cancerous wounds on trunks and branches is not freezing, but the defeat of a bacterial disease, which for this breed has not yet been noted in any our country or abroad. For the walnut, it is the most dangerous of all diseases known to date. The causative agent of it was the same type of bacteria that causes the disease of fir, beech and other species - Erwinia multivora. This bacterium has been isolated from seeds, seedlings, seedlings, bark and wood of young crops in in large numbers. Identification of all isolated strains of bacteria was carried out by inoculation on artificial nutrient media, including a completely colored row (sugar). The complete similarity of biochemical properties, including the formation of gases on sugars and glycerol and the release of hydrogen sulfide on BCH, (indicated that the bacteria should be assigned to the species Erwinia multivora Scz.-Parf.

External signs of walnut bacteriosis may vary depending on the age of the plant, the stage of the disease and the time of year. For example, in autumn and spring, black streaks or black spots of dried liquid are observed on the affected trunks. Under black spots, which can be of various sizes, the bark becomes wet and dies down to the cambium. Cambium and wood also die off. Later, the bark dries out and depressed cancerous wounds are obtained on the trunk. Sometimes longitudinal cracks form in the bark after drying. They can be of different lengths - from 5 to 50 cm, and often much more. On two-year-old and three-year-old branches, one can very often observe depressions of different lengths with some swelling on the sides; in the middle of the depression there is almost always a longitudinal crack in the bark and wood.

In most cases, the development of such wounds does not occur outside, but from within the wood. The wood inside the trunk and branches is dark brown and even black, wet, with a sour smell. Such wet, dark brown wood can be seen even in biennial and annual shoots. Sometimes the core of annual shoots is wet and brown.

Wet wood in the trunk occupies a different position. In most cases, it is not limited to annual rings, has jagged edges, and if it is located at the outer annual ring, then a rupture can occur and then a black liquid comes out through the crack, and a cancerous wound forms in the cortex. Large cancerous wounds are also formed in the trunk if wet wood is in the last outer growth ring. At the same time, the bark and cambium die off and also become wet. The surface of dead sapwood wood is also black.

In young walnut plantings, the dying off of one-year and two-year-old shoots is very often observed. If in autumn or spring the shoot is cut below the dead part, then it is very often found that its core is brown and wet. In spring, one can observe the withering away of the bark of the branches of one-year and two-year shoots up to the cambium over a large area. In such cases, the bark of the shoots of the walnut becomes black and therefore is clearly visible, while in the Manchurian walnut, with such a burn of the branches, the color of the bark does not change and therefore the death of the bark is not outwardly noticeable. This kind of damage to the bark occurs mainly in the spring.

Sometimes the bark turns black and dies off only in the very top layer, without affecting the cambial part at all. This is obviously related to the timing of infection and damage. If the infection occurred in the spring and the lesion has not yet reached the cambial part, then with the onset of summer it stops. In young cultures feature is that the walnut bushes, does not grow in height and does not have a trunk, just as it has already been noted in oak cultures. Shoots growing over the summer in autumn and spring are affected by bacteriosis and often soon die off completely or partially. In many cases, the lesion does not occur from the top of a one-year or two-year-old shoot, but from the middle or base. On the perennial wood of the bole (trunk), longitudinal cracks and cancerous wounds are often noticeable, from which a dark brown liquid flows. On the trunks of older walnut cultures, depressed cancerous wounds and the expiration of a dark brown or black liquid that subsequently dries up are often observed and are the most characteristic external sign of the disease along with wet, dark brown and even almost black trunk wood.

The black walnut disease, which causes the expiration of black fluid, was described by the Americans under the name "melaxuma". As P. Miller (1956) pointed out, this disease is caused by a fungus. Dothiorella gregaria, which infects the twigs, branches, and trunk of a tree and usually causes an ink-black liquid to ooze onto the surface of the affected areas. The bark underneath becomes discolored and gradually dies off, leaving slightly depressed ulcers. As you can see, there are some similarities in the external signs of the disease, but the pathogens are completely different.

A disease similar to the melaxuma described above was found by us on walnut and Manchurian walnut with fruiting on the bark of the fungus Physalospora gregaria Saccardo, which is the marsupial stage for the conidial fungus Dothiorella gregaria. In passing, we note that the marsupial stage was long ago described in Transcaucasia on willow by Voronikhin. Therefore, this species is known in the Caucasus. But, in addition, we also isolated the bacterium Erwinia multivora from freshly infected tissues of the bark, wood of the trunk and branches. Therefore, it can be assumed that the fungus Dothiorella gregaria is not an independent cause of the disease, but only a companion of the primary bacterial infection. In other words, the fungus develops in tissues only after they are damaged by bacteria. The expiration of liquid is the result of the vital activity of bacteria outside the fungus. In this way, external signs melaxums testify in favor of a bacterial rather than a fungal origin of the disease, and one that occurs in many tree species.

Development, ways of infection and spread of walnut disease not yet fully elucidated at present. Obviously, they are the same as those of other tree species. It has already been noted above that the active development of walnut disease occurs in autumn, spring and in warm weather. winter periods. In summer, the activity of bacteria does not manifest itself at all in the entire phloem. Apparently, their activity in the xylem is also weak at this time. But the bacteria are stored right here, in the wood. The wood of the walnut trunk, like other species, after the defeat is extremely saturated with moisture. Such wood is already dead. The more it takes up space in the trunk, the more negatively it affects the movement of water-mineral solutions. In addition to a large amount of liquid, wood, which is toxic, also produces many gases, including hydrogen sulfide, which is poisonous to plants and dissolves easily in water. Under the pressure of gases, the outer annual ring breaks and the liquid flows out through the resulting crack. In this case, a cancerous wound usually forms in the cortex. If wet wood captures the outer annual ring, then the bark and cambium die off and a wound forms. This is one of the ways of external manifestation of the infection contained in the wood. But the defeat (burn) of the bark and cambium of shoots and branches is possible not only from the inside, from the side of the wood, but also after infection from the outside, if it occurs in the fall, warm winter or in early spring. Observations have shown that infection often occurs through a leaf scar before leaf fall. This indicates that walnut leaves are also infected. It is not excluded that infection through the leaves is the most important way of spreading the infection. The role of insects in this respect, apparently, is not as great as for other breeds, but it is not excluded.

As with other breeds, seedlings become infected from seeds that are internally infected. As an example, the following cases can be cited: 10 kg of nuts collected from one mother tree, stratified in calcined sand after preliminary pickling in a solution of potassium permanganate, completely died long before the onset of spring. The shell of the nuts turned black, and the cotyledons rotted. They did not sprout, and the emerging sprouts turned black and died off. Analysis of these nuts showed that they were infected with the bacterium Erwinia multivora, which was the cause of rotting of the cotyledons. The rot of the cotyledons is white, cheesy, with a sharp sour smell. Mushrooms were not found in it. The tree from which these nuts were collected turned out to be infected with bacteriosis. When stratifying nuts from other mother trees in the same way, it turned out that from some trees they were completely preserved, while from others, under the same conditions, they completely died - they rotted. Thus, during stratification, those nuts that were infected with bacteria were identified and died.

Examining the annual walnut seedlings grown in one of the fruit nurseries, we found that most of them had a rotten (up to 5 or even 10 cm) root tip. Some specimens had black necrotic spots on the root surface. There is no doubt that planting such seedlings does not promise anything good for the future. Analysis of the seedlings showed that they were infected with Erwinia multivora, which caused root rot. Infection could occur both in the soil and from seeds.

The defeat of one-year-old walnut seedlings with characteristic external signs of bacteriosis was also found in another forest nursery. So, in one of the most developed seedlings, along the entire length of a long and thick tap root, almost all the wood was dark brown and wet. There were no other outwardly noticeable signs of disease on the root, except for a small longitudinal crack on the side of the root, starting from the neck. The crack was the result of a rupture from a high gas pressure in the wood of the root, and not any mechanical damage. Such affected seedlings were rare. When examining all other seedlings, no outwardly noticeable signs of damage were found.

Walnut seedlings from the same nursery were dug up in the autumn and planted on the silvicultural area with the usual and inevitable pruning and wounding of the roots. When digging and examining seedlings in the middle of winter, all seedlings, without exception, were found to have wet rotten wounds with a sour smell in places of root damage. For example, in the place where the root was injured with a shovel during digging, the root rotted to 3/4 of its thickness. Roots macerated during rough pruning rotted for 5-6 cm. Thus, infection occurred in the soil through root cuts during autumn planting.

At the present time, it is still impossible to fully say what the further development of these wounds will be with the onset of spring and summer. It is quite possible that the active development of rot will stop for the summer period and resume again in the fall already in new form. During the summer, callus does not form around rotten wet wounds, and further development of bacteria will occur only in wood. In the future, breaks in the wood at the root, on the trunk and branches and the release of bacteria to the outside are possible. Observations and experiments on artificial infection show that bacteria cannot actively develop in the cambial part of the bast in summer. At the same time, there is no reason to expect that bacteria will disappear by themselves from infected tissues. An analysis of two-year and three-year-old walnut plantings showed that their root rotting did not stop and the wounds did not heal.

Thus, the quality of nuts is seed material and the condition of the seedlings, the timing and methods of their planting, as well as the contamination of the soil with pathogenic bacteria are of decisive importance for the future growth and development of walnut and other walnut species. The mistakes made here cannot be corrected in any way later. It is quite clear, for example, that the sowing of infected walnuts, autumn plantings, in which the roots are inevitably injured during pruning, and even the digging of seedlings in general, are completely unacceptable, if we mean the cultivation of healthy long-term trees, and not infected bushy forms of walnuts, which in such form can exist for decades without any benefit.

The course of the disease in walnuts often takes a chronic form and can last a very long time. In fruit-bearing trees, the death of branches and twigs is often observed, which leads to thinning of the crown.

The bacterial disease of walnut described by us in equally it also affects the Manchurian walnut and the black walnut, and the symptoms of the disease and the nature of the lesion are basically the same.

Bacterial bark cancer

A walnut disease similar in appearance in California was described by E. E. Wilson, M. R. Starr and J. A. Berger (1957). This disease they called " bark cancer”, characterized by the formation of asymmetrical dark brown dead areas in the bark of the trunk, as well as the drying of the branches. The necrotic areas appear first as round specks in the bark tissue below the corky outer covering, but later they coalesce into larger patches. The contours of such spots on the bark are invisible, but they are recognizable by the dark watery substance that stands out through cracks in the bark. As a rule, ulcers in the cortex are shallow and do not reach the cambium. Their development occurs in the summer and stops in the winter. The disease affects walnuts at least 10-15 years old and is caused by a new type of bacterium called Erwinia nigrifluens.

Despite some similarities, this disease differs from the one we have described above. The types of bacteria that cause the disease are also different. For example, the bacterium Erwinia multivora forms gas on sugars and hydrogen sulfide on meat-peptone broth, while the bacterium Erwinia nigrifluens does not form gases and hydrogen sulfide. Thus, there is no basis for identifying the walnut disease either by external signs or by the types of its pathogens. In our country, shock cortex cancer has not yet been discovered.

Bacterial root cancer

In addition to the bacterial diseases of the walnut described above, the so-called root cancer, or otherwise, root goiter, the causative agent of which is Bacferium tumefaciens Smith et Iown. The bacterium that causes this disease develops on many plants, including walnut and fruit breeds where it occurs more frequently.

As V. P. Izrailsky points out (1952), the root cancer of fruit trees begins in the tissues of the meristem and causes its rapid growth. Bacteria penetrate tissues only through plant wounds, but they do not kill cells, but, on the contrary, begin to stimulate their further growth and random division. On the surface of the root, and sometimes on the surface of the stem, small bulges form, which then turn into tumors and are the main external sign of the disease. The tumor grows and its surface in most cases becomes bumpy, as if annular structure. Tumors of root cancer subsequently shrink and fall off, and new ones sometimes grow in their place. In most cases, tumors, especially in fruit trees, persist until the next year and give new growths. Tumors can be different in shape and size depending on the condition of the plant, on the site of the lesion, as well as on the season, lighting, temperature, humidity and other conditions. external environment. The tumor can be the size of a millet grain or reach the size of a fist. In trees, tumors in most cases become lignified, in herbaceous plants they sometimes shrink and fall off, and sometimes grow.

Root cancer is more common in fruit nurseries. As for forest nurseries, it is relatively rare here and has no particularly important practical significance.

Bacterial burn

On walnut, in addition to bacterial dropsy, bark cancer and root cancer, it is very common and almost everywhere bacterial burn caused by the bacterium Xanthomonas juglandis Pierce. The disease affects leaves, nuts, catkins, buds and shoots. current year. P. Miller (1950) considers this disease in the USA the most important in economic terms compared to all other walnuts known. During outbreak years, more than 50% of the nut crop is lost in orchards if it is not sprayed against.

P. Miller (1956) indicates the appearance of small reddish-brown spots on young leaves in the spring (along the edges of the leaves or on the tissue between the veins) as a symptom of the disease. Black, slightly depressed spots appear on the shoots, which often ring the shoots and destroy them. Young leaves and buds of male inflorescences turn dark brown or black and die off. On nuts, more precisely on the pericarp, bacteria cause the formation of black spots of various sizes.

The causative agent of the disease - the bacterium Xanthomonas juglandis Pierce - lives from year to year mainly in infected buds and less often in ulcers left on the growth branches of the previous year. The bacterium spreads mainly by rain, penetrates into the growth tissues of the current hearth through pores (stomata). Prolonged rains can cause severe disease outbreaks. annuals and biennial plants in nurseries, mature fruit-bearing trees are more easily affected than young non-bearing trees.

The bacterium Xanthomonas juglandis has the form of a rod with rounded ends measuring 0.3-0.5 × 1.5-3.01 μ; sticks - single or connected in pairs, rarely in chains, no spores or capsules; monotrich, dyes well, gram-positive, aerobic. On agar, colonies are round, shiny, light yellow, with regular edges; Gelatin dilutes funnel-shaped, milk coagulates, peptonizes; causes acid formation on galactose; there is no gas formation; does not grow on Kohn's medium, does not restore nitrates, restores methylene blue, decomposes starch.

In nurseries and cultures in the North Caucasus, walnut blight caused by the bacterium Xanthomonas juglandis is a common occurrence, but, to the best of our knowledge, it has not been and is not being controlled, since damage to the leaves is not paid attention to, and the defeat of annual shoots is always explained only freezing. On annual shoots, this bacterium is sometimes found and isolated together with Erwinia multivora. Judging by the growth on a nutrient medium, both of these species, apparently, are not antagonists.

The one-year shoot of a seedling very often turns out to be infected and dies off completely or partially already in the fall, which is why the nut begins to bush already in the second year. New shoots, sometimes appearing at the neck in large numbers, also become infected the next year and partially die off. Thus, in case of infection, the nut begins to bush from the second year of its life.

Measures to combat bacteriosis of walnut

The features of walnut bacterial diseases described above indicate that the fight against them, despite the fact that walnuts in the North Caucasus are only found in cultures, will be a complex and difficult matter, in any case more complex and difficult than all work on walnut cultures. walnut, taken together, including selection.

The bacterioses of the walnut that we have identified have so far been completely unknown. Therefore, in relation to bacterial diseases, at present, much remains still insufficiently clear, requiring further study. There is no experience of dealing with them. At the same time, they are of exceptional importance for walnut and other species, they are very widespread, and the scope of work on culture is increasing more and more. In this situation, the implementation of possible measures to combat walnut bacterioses is an urgent and urgent need. The following are practical recommendations for the control of walnut bacterioses, which, in our opinion, give positive results.

It is advisable to consider measures to combat bacterioses of walnut in three directions:

1) the fight against bacteriosis of fruit-bearing trees;

2) fight against bacteriosis of young crops;

3) measures for the creation of new walnut crops.

The need for such a consideration is based on the fact that at present in the North Caucasus, as well as on the Black Sea coast, there are many fruit-bearing trees and crops of different ages infected with bacteriosis, which require various practical measures.

Fight against bacterioses of fruit-bearing trees. In old fruit-bearing walnut trees, individual branches and twigs become infected and gradually die off, fresh cancerous wounds appear on the trunks, old last year's wounds take the form of dry holes of various sizes on the trunk and branches. Nuts on diseased branches are also infected with both bacterioses and often die while still on the trees. Such trees, if they do not yet have root damage, dry out slowly. They can live and bear fruit for a long time, although some of the nuts will be infected. At the same time, such trees and individual branches and twigs infected on them are sources of infection for healthy trees and branches. But since they still bear fruit, cutting them down could hardly be considered justified only because they themselves are infected and infect healthy trees. Obviously, it is more advisable to leave them for further fruiting, but it is necessary to take some preventive measures in relation to such trees.

First of all, pruning of infected branches and branches is necessary, which are determined by the blackened bark, some ribbing, and cancerous depressions with longitudinal cracks. Pruning should be done in the spring, before bud break. Sections should be disinfected and covered with any kind of garden putty or only lubricated with garden carbolineum.

On trunks and thick branches, all fresh oozing wounds, regardless of their size, must be protected to sapwood. Inspection of trees should be done twice a year - in late autumn and in spring, after the leaves bloom. Bark cut from wounds and infected branches must be collected and burned. The cleaning tool must be disinfected every time. Opened wounds should be lubricated with garden carbolineum or first moistened with a 1% solution of copper sulfate and then covered with commercially available garden pitch. It can also be prepared from fresh unsalted pork fat or nigrol, wax and rosin, taken in equal parts. In the absence of wax or rosin, you can take nigrol with furnace ash at the rate of 300 g of ash per 1 kg of nigrol. The composition for covering wounds can also be prepared from 60-70% nigrol, 15-20% rosin and 15-20% paraffin or wax.

Such an operation as cleaning and dressing fresh wounds and cutting off infected branches, of course, will not cure the trees, since the infection is contained in the wood, including the central part of the trunk, but it will to a certain extent prevent the spread of infection and infection of still healthy trees. Timely cleansing of small or newly formed fresh wounds will stop their further increase in size. Therefore, it is important to clean and putty wounds at the very beginning of their appearance. With the onset of summer, the development and increase of wounds in the cortex ceases on its own. New wounds begin to appear only in autumn, when the fruits ripen.

In order to better preserve the nut crop, it is useful to spray the trees Bordeaux liquid. Such spraying, as P. Miller (1956) points out, is carried out in many areas of the USA with a more humid climate. For spraying, Bordeaux liquid is used with a ratio of constituent ingredients (copper sulfate, quicklime and water) - 4-2-100, as well as other preparations that we do not list here due to the fact that they are not on sale. The number of sprays required for effective fight disease, fluctuates over the years. In years with low rainfall during the period of infection, one timely spraying is sufficient to combat it. But with heavy and frequent rains, three timely sprayings are required for greater efficiency. Since it is impossible to foresee the weather during the period of infection, it is recommended to spray the maximum number of times in the following periods:

1) in the early phase before flowering;

2) in the late phase before flowering;

3) in the early phase after flowering, when female flowers open.

There is no doubt that this method, proven and widely used in the United States, will give positive results in our country under similar climatic conditions.

The fight against bacterioses in young cultures. On the trunks of young (10-15-year-old) trees, wound cleaning will be advisable only at the very beginning of their appearance in the bark. If there are one or more wounds on the trunk that have already reached the sapwood, then such trees will subsequently dry out, grow poorly and produce. In the future, new fresh wounds inevitably appear on them due to the vital activity of bacteria in the wood. This will weaken the trees more and more. In this case, it is better to plant them on a stump and grow healthy trees from the shoots, provided that the stump is not infected. If wet dark brown or almost black wood is noticeable on the cut of the stump, then it is better to uproot such a stump than to grow shoots on it, since it will subsequently inevitably become infected from the stump. Uprooting of stumps is also necessary if the neck and roots are affected. If rotting of the roots is found, then new plantings on the site of uprooted trees are permissible only after disinfection of the soil. For soil disinfection, the same methods can be used that were already adopted in 1951 and are used in the fight against root canker caused by Bacterium tumefaciens in fruit nurseries. According to the instructions of V. P. Izrailsky (1952), soil disinfection in nurseries is carried out by adding bleach to the soil at the rate of 150 g per 1 m 2. Nice results gives disinfection with chloropicrin or polychlorides at a dosage of 500 g per 1 ha. 25 g of poison is poured into pits made with an iron stake or an injector every 0.5 m with a depth of 10-15 cm. The pits are dug in with earth, which, after cleaning the pits, is compacted from above. These works are carried out in spring - from half of April to half of May, or in autumn - from half of September to half of October. Planting is carried out a month after disinfection.

For soil disinfection, you can also use the methods described in the "Technical Guidelines for Forest Protection", used to combat the lodging of seedlings of coniferous species.

The issue with young (up to 10-15 years of age) walnut cultures, of which there are a lot, is very difficult and difficult. In many cases, they are infected with bacteriosis, grow poorly in height, bush, and do not have a normal stem (trunk). Very often, their shoots appear and die off, and the trunk often dies off. This state of walnut planting can last for many years. We know such landings even 20 years ago.

Planting or sowing walnuts should produce large, healthy, long-lasting, fruit-bearing trees. In practice, we see that they often turn into stunted, bushy trees without a trunk, with shoots growing from the neck of the root. Their total height is small and often even at the age of seven is not more than 1 m. Is there any reason to expect that the bushes will themselves turn into what is the goal of all work - large, durable fruit-bearing trees? In our opinion, confirmed by already existing experience, there are no grounds. Depressed, poor growth, bushiness, damage and death of branches and trunk in walnut cultures are often the result of bacteriosis damage, and not freezing, which in certain cases is also, of course, not excluded.

In connection with the foregoing, in a practical aspect, two questions arise: what explains high degree bacteriosis infection of existing young walnut crops and what can and should be applied to such crops at the present time and whether it is possible to correct them and bring them to a normal state. As for the first question, there is no doubt that the infection of plantings or crops proceeded in two ways, internally - from infected seeds, seedlings and soil, and externally - through infection of the healthy from the sick. Consequently, when creating new cultures of walnut, it is necessary to exclude the possibility of both. This path, i.e. the path of prevention, is the main measure to combat the disease. The old rule of medicine - diseases are easier to prevent than to cure - is very appropriate in this case. Practical measures in this direction will be discussed below.

As regards the second question, at the present time it is still impossible to give a completely definite answer. The answer must be sought in the pilot production order. In our opinion, young walnut crops affected by bacterial dropsy are also hopeless in relation to their future: it is impossible to grow large, healthy fruit-bearing trees from them. Experience speaks in favor of this. At the present time, it cannot yet be said that all such plantings must be uprooted and new, healthy ones created anew. This is quite clear only in one case, when three studies turn out to be infected roots (rotting and browning or blackening of the wood of the roots) or neck (blackening of the bark).

Taking into account the nature of the disease and the nature of the lesion, our proposals for young walnut crops affected by bacteriosis will be reduced to the following practical measures to be carried out in a pilot production order: wounds with fresh or old black streaks and longitudinal cracks should be planted on a stump in the spring before the buds open, in order to get two or three healthy shoots on the stump, of which only one healthy shoot is left next year to form a bole. The affected shoots are determined by the bark, blackened completely or at least partially, some ribbing, large swellings and depressed wounds. The cut of the stump must be disinfected and covered with putty. If dark brown, almost black wet wood appears on a fresh cut of a stump, then growth cannot be grown on such a stump and it should be uprooted. New landing in this place is permissible only with healthy seedlings after mandatory disinfection of the soil.

Young (two-year-old and three-year-old) plantings should be immediately examined and, if rotting or browning and blackening of the wood of the roots is found, immediate uprooting should be carried out, given that long-term healthy trees cannot be obtained on the affected roots.

Young shoots on cut stumps and young crops starting from one year of age should be sprayed with 0.5% and 1% Bordeaux liquid as a preventive measure against both types of bacteriosis. The number of sprays and the best timing are established empirically, depending on local climatic conditions. In dry climates one spray is enough, in wetter climates, for example on the Black Sea coast of the Caucasus, three sprays may be required. Approximately the first spraying can be done in the second half of May, shortly after flowering, the second - in June, the third - in July. Of great importance, in our opinion, will be the so-called "blue" spraying with 4% Bordeaux liquid during leaf fall and in the spring before bud break.

Often, already at the age of one year, a walnut is more or less damaged and the apex shoot dies off, which is why it begins to bush in the second year, that is, to give side shoots and shoots from below, near the neck. As usual, this is due to freezing of the shoot, although in fact it can and does be caused by both types of bacteria and is usually the result of a preliminary infection of the leaves. In such cases, the affected and dead main shoot must be cut off with a margin in the spring before the leaves bloom and instead create a bole (trunk) due to one of the side shoots, preventing further growth in the form of a bush. The cut must be immediately disinfected and covered with putty, and each new cut must be made with a newly sterilized instrument. In a nut, when counting on fruits, and not on wood, it is necessary to form a stem and crown, preventing their infection, just as is done in gardening. Given the above feature associated with bacterial infection, this work should be carried out starting from the age of one.

Fight against bacterioses when creating new walnut cultures. At present, when breeding walnuts, all attention is paid only to agricultural technology. They also conduct research in the direction of selection in nature. the best forms according to the size of fruits (nuts) and frost resistance. There can be no doubt that all this is important and necessary, but such an approach by no means ensures that the desired result is obtained from the walnut culture, that is, good healthy trees, since only they can provide long life and good fruiting.

Growing good healthy fruit-bearing walnut trees and keeping them healthy for many decades is a task many times more complex and difficult than sowing, planting and selecting the best forms taken together.

The first measure to combat nut bacterioses should be selection not only for fruit quality and resistance to frost, but also necessarily for resistance to bacteriosis. Such work is important for all places where walnut crops (plantations) are created.

Infected nuts may show external signs of black spots on the shell and asymptomatic internal infection. They can be infected with both types of bacteria, i.e. Xanthomonas juglandis and Erwinia multivora. Phytopathological analysis of nuts for internal contamination with fungi and bacteria is, of course, necessary. Infected nuts should not be sown. Stratification of nuts is mandatory. It is better to produce it in appropriate rooms in coarse washed sand. Infected nuts rot during stratification and must be sorted out. Rotten nuts are identified by their sour smell. Healthy nuts are best sown on permanent place and not in a seedling nursery. When digging up seedlings, in no case should short pruning of the roots be allowed, as is always done in forestry by analogy with other hardwoods. The root system of walnut seedlings must be dug out completely. It is permissible to trim only the thinnest tip of the root.

Experience has shown that in a dig or autumn plantings almost always infection occurs through cuts on the roots and rotting of the roots, which is the stronger, the shorter the root is cut. On rotten roots, one cannot get healthy, durable trees in the future.

Walnut seedlings are subject to strict control before planting. Those that have longitudinal cracks on the root, black, slightly depressed spots or rotting of the end of the root are to be rejected. Pruning a rotten root is permissible only if the very end of the root is affected by rotting. The root system of seedlings before planting in a school or a permanent place must be disinfected by immersion in a 1% solution of copper sulphate for 5-10 minutes or in a 5% solution of copper sulphate in liquid clay.

Did you know? Walnut is also called Voloshsky, Greek, royal, sometimes mahogany.

Walnut Disease Control Methods

The main reasons why a Volosh nut can get sick:

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  Mistakes in agricultural technology;

• unsuitable soil composition;
• lack of light;
• excessive soil moisture;
• close occurrence of groundwater;
• pest infestation.

To detect diseases early walnut and begin their treatment, it is necessary to inspect the tree more often for changes in appearance. As a rule, the first signs of the presence of the disease appear in the form different kind spots on leaves and shoots.

And in order to avoid illnesses, it is important to carry out preventive spring spraying, sanitary pruning, and cleaning of fallen leaves and fruits. You need to know how to spray a nut in the spring to prevent various diseases.

bacteriosis

Favorable conditions for the development of bacteriosis on walnuts appear in warm and damp spring weather. The disease manifests itself as dark spots on leaves, shoots, fruits, flowers. It can cause the greatest harm during flowering, destroying most of the flowers. If bacteriosis develops after flowering, then in such trees the wood becomes brown, and young shoots die off. The fruits are covered with dark spots.

Control measures. To prevent bacteriosis, the walnut should be treated in the spring before flowering with a 3% Bordeaux mixture. Re-spraying must be done two weeks after flowering.

Important!In order for the treatment with Bordeaux liquid to have a greater effect, a 0.3% solution of urea can be added to it.


One of the most serious walnut diseases is bacterial blight. It affects leaves, flowers, shoots and fruits. It is this disease that is the reason why the leaves of the walnut turn black. At first they are covered with watery spots, then they turn black, however, even when they die, they do not fall off the tree, but remain on the branches for a long time. Walnut stalks are covered with ulcers. Shoots wither, buds die. Affected parts of the plant cover drops of liquid.

A bacterial burn also becomes the reason why nuts turn black on a tree. First, black spots appear on the fruits, and then the entire kernel turns black and becomes unfit for food.

Factors that are favorable for the development bacterial burn on the walnut, are long heavy rainfall. The causative agent of the disease is spread by insects and wind.

Control measures. If symptoms of a bacterial burn are detected, treatment with preparations with copper in the composition (Bordeaux liquid, Zineb, HOM, etc.) will be required. Affected parts of the tree must be destroyed.

Important! The processing of walnuts from diseases should be carried out in dry calm weather with the obligatory observance of personal safety measures. Eyes should be protected with goggles, hands with gloves, nose and mouth with a mask.

Brown spotting (Marsoniosis)


Brown spot spreads to fruits, young shoots and leaves of the tree. The first symptoms are oval spots irregular shape brown on leaves. Such leaves dry quickly and fall prematurely. The disease is especially dangerous during the flowering period, since it can harm up to 90% of the flowers. Accordingly, the yield loss will be very significant.

Wet weather and prolonged precipitation contribute to the development of the disease.

Control measures. In order to prevent brown spotting, the walnut must be treated with a 1% Bordeaux mixture until the moment of budding. Re-treatment is carried out in the phase of leaf appearance, the third - two weeks after the previous one. Affected leaves and shoots must be destroyed by burning.

Root cancer affects the roots of the plant, and penetrates into them through cracks and damage.
As a result of the disease, growths form on the root system. In the case of severe damage, the tree may stop growing and stop producing fruit.

Control measures. Upon detection this disease growths from the roots should be removed, then the rhizome should be treated with a 1% solution of caustic soda. After treatment, the roots should be washed well with water.

Did you know? Depending on the growing conditions, a walnut tree can bear from 10 to 300 kg of fruit per season.

Walnut Pest Control

The main control measures for walnut pests will be regular inspections for the detection of caterpillars - the sooner you notice their settlement, the faster and easier you can get rid of them. You also need to cut and burn damaged branches in a timely manner to avoid the spread of pests to the entire tree.

Caterpillars of the American white butterfly pose a serious threat to the walnut as they produce two to three generations per season. For the same reason, it is very difficult to deal with them.


The first generation enters the harmful trade in July-August, the second - in August-September. And the third eats leaves in September - October. Thus, the invasion of these insects can destroy almost all the foliage on the tree.

Control measures. Caterpillars of the American white butterfly can be combated mechanically by finding and burning their nests. You can also use trapping belts to prevent the caterpillars from getting to the leaves, but to catch them on the trunk, then destroy them by burning. At advanced cases microbiological preparations are used: Bitoxibacillin, Lepidocid, Dendrobacillin or insecticides.

Such a walnut pest as sapwood, on initial stage lesions cannot be detected, as it settles under the bark. The first generation of beetles appears in May, the second - in August. Gradually, the beetles gnaw through the bark, and their presence can be seen through curved canals that are located next to the buds and the bases of the petioles. The tree starts sap flow.


As a rule, sapwood settles on weak plants.

Control measures. For the purpose of prevention, it is necessary to carry out timely sanitary pruning of the walnut, which involves the removal of diseased, weak, damaged branches. When a beetle is damaged, the tree must be sprayed with insecticides.

Did you know?The content of vitamin C in walnuts is almost 50 times higher than in citrus fruits and 8 times higher than in currants.

Nut warty mite

Sucking insects are usually miniature in size, and the damage to the plant is enormous. So, the walnut warty mite reaches sizes up to 1 mm, and can significantly spoil the leaves already at the stage of their formation. Signs that a tick has settled on a nut are small dark brown “warts” on the leaves.

Control measures. If symptoms of damage by the walnut wart mite are found, the tree should be treated with any acaricide approved for use on the walnut.


It is difficult to notice the moth in walnuts, since it has a protective color and, with closed wings, is practically indistinguishable from the bark. Its caterpillars damage the leaves by gnawing out the flesh.

Control measures. To get rid of the nut moth, systemic poisons recommended for fruit plants are used in the same dosage.

codling moth

Nut codling moth causes serious damage to the kernels of nuts. The first generation of its caterpillars damage the kernels, causing them to fall off the tree. The second brood settles inside the fruit and eats out the cotyledons. One caterpillar can damage several nuts.

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)- a common fungal disease that is activated 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. 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 mixture 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 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 to the roots of seedlings during planting: cracks or wounds. Large swellings-growths form 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 of caustic soda, then rinse the roots running water and plant.

What to process

In addition to the early spring treatment with 3% Bordeaux liquid, and later with 1% solution, accepted for all fruit trees, 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 every year.

To print

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 the autumn leaves of the walnut are collected in a metal container, poured with boiling water and tightly closed, 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 they talk about the defeat of 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 leaves into a tube (tick) or settle inside leaf blade(mining moth), and then spread throughout the tree.

How to deal with pests?

The main control measure timely pruning and burning 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. At the drug short period decomposition, so it does not accumulate in plants.

Despite the fact that the walnut is resistant to various 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, like any other living organism, can get sick. The main causes of walnut disease can be: improper care, bad soil, deficiency sun rays, excess moisture, nearby groundwater, harmful insects.

Walnut: pests

American white butterfly

The most dangerous insect for walnuts is the American white butterfly. American white butterfly damages almost all fruit tree species. An insect can develop in two or three generations:

first generation - July-August

second - August-September

the third - September - October.

Caterpillars of the American white butterfly settle on the shoots and on the leaves of the walnut, and later spread throughout the tree, destroying all the leaves on the tree.

Fighting methods

Methods for controlling the American white butterfly include burning nests (along with caterpillars), using trapping belts to collect and further destroy caterpillars, or using microbiological preparations.

Nut codling moth

Nut (apple) codling moth also damages all fruit tree species. The codling moth develops in two generations:

first - May-June

second - August - September

The first generation of codling moth caterpillars damage the walnut kernel, subsequently the nuts fall off. The second generation of caterpillars settles inside the walnut and eats the cotyledons. One caterpillar can damage several nut fruits, the nuts fall prematurely, which negatively affects the yield.

Fighting methods

To combat the codling moth, pheromone traps are used. These traps contain a certain agent that attracts male codling moths, thereby reducing their numbers and the number of fertilized females.

Also, do not forget to regularly collect wormy carrion and inspect the walnut for the presence of caterpillars.

Nut warty mite

The walnut warty mite is a kind of "minor dirty trick". Its size does not reach even 1 mm. The nut mite damages the leaves before they develop, because. it lives in dormant buds. Recognizing the "work" of the tick is quite simple: it leaves small but numerous dark brown "warts" on the leaves. Acaricides are used to control ticks.

No less harm to the walnut is caused by aphids, sapwood and moth-moth. To combat these pests, special solutions, microbiological preparations and sanitary tree felling are used.

walnut diseases

If we talk about walnut diseases, then brown spotting comes to mind first of all.

Walnut and brown spot

Brown spotting (Marsoniosis) affects walnut fruits, green shoots and leaves. Signs of brown spotting can be considered the appearance of rounded brown spots on the leaves. Affected leaves fall off faster. Brown spotting most often occurs during prolonged rains, when too much moisture accumulates in the soil.

This walnut disease is especially dangerous during the flowering period of the tree. During this period, it is able to destroy up to 90% of the flowers, which will undoubtedly have a negative impact on the crop. As for the affected fruits, they either shrink, crack, rot, or crumble.

Fighting methods

To combat brown spot Walnut(even before the appearance of the kidneys) is treated with 3% Bordeaux mixture. Fallen leaves are burned.

root cancer

Root cancer is a disease that affects root system tree. Cancer enters the roots of the tree through wounds and cracks. A sign of this disease are convex growths. Due to severe damage by root cancer, the walnut may stop its growth and fruitfulness.

Fighting methods

Methods for dealing with root cancer include removing growths on the roots, treating the roots with a 1% solution of caustic soda, followed by washing the tree roots with running water.

Bacterial burn

Bacterial burn is especially dangerous disease walnut. This disease affects the leaves, shoots, flowers and fruits of the tree. Watery spots can be seen on the leaves and petioles, which later turn black, but the leaves do not fall off for a long time. Ulcers appear on the stems. Shoots wither, buds die. Black spots also appear on the fruits, the walnut kernel turns black and dries up. Liquid droplets appear on the affected areas.

The disease will spread faster in the rainy season. Carriers of fire blight are insects and pollen.

Fighting methods

To combat this disease, copper-containing drugs are used. Severely affected walnut trees are culled, the fruits are destroyed.

So, we looked at the most common walnut diseases, learned what walnut pests exist and how to deal with them. Regular inspection of a tree is the best prevention of any disease.