Scab is the scourge of apple culture. Many varieties of apple trees resistant to this disease have been obtained. However, they do not always meet the requirements of the consumer. It is often necessary to grow old apple varieties loved by many generations. And they, as a rule, are highly susceptible to scab. We will help the gardener cope with this problem.
Scab is a well-known disease of apple trees. Even before the 19th century, they knew about it, but it did not bring many problems. In the scientific literature, the first mention of it dates back to 1819, when the causative agent of scab, the fungus Venturia inaequalis, was first described. Somewhere from the middle of the last century, the disease began to spread and cause significant damage in industrial gardens with a high density of tree plantations with the same genotype.
The causative agent hibernates on fallen leaves and fruits in the stage of pseudothecia (immature fruiting bodies). With the beginning of the growth of young shoots, the spores of the fungus are scattered. The most dangerous periods for infection are swelling of the buds, staining of buds, flowering and massive fall of petals. Due to the presence of a mucous membrane, spores attach to the underside of the apple tree leaves and, if there is sufficient moisture, germinate in the outer layer of the skin of leaves and young shoots. The next stage - conidial - occurs in two to three weeks, when the fungus, which has passed into conidia - immobile spores of asexual reproduction - infects the crown leaves for the second time. Temperatures from +18 ° C to +20 ° C are most favorable for this process. It is well noticeable at this time the appearance on the leaves, ovaries, tips of young shoots of spots of light olive color, which turn brown and crack when growing.
The first symptom of scab is the appearance of light olive-colored spots on the leaves, which turn brown when overgrown, cracking
As a result of the defeat, the leaves and ovaries fall off, and the fungus continues its development on them, laying the pseudothecia already known to us, which will hibernate there until next spring. The cycle is closed. In summer, scab forms skin cracks, seals and hard, necrotic, brown-brown spots on fruits. Apples become deformed, small - their growth stops.
In summer, scab on fruits forms skin cracks, seals and hard, necrotic, brown-brown spots.
Scab is common in regions that are characterized by rainy summers - the northwestern regions and the North Caucasus region. In hot and arid regions, scab is much less common.
Dealing with scab requires a systematic approach. There are several general recommendations, following which you can protect the apple orchard from this problem:
And besides this, in areas with a high risk of scab occurrence, mentioned above, the necessary preventive measures are regularly carried out.
It is the spring preventive and sanitary measures that are most important in the fight against this harmful fungus. They are started even before the onset of sap flow and swelling of the kidneys.
Before the onset of sap flow, it is necessary to carry out treatment with potent pesticides
In the summer, they mainly monitor the development of the plant and, if necessary, take emergency measures. They may be needed if leaves and (or) fruits affected by scab are seen. In this case, the gardener's actions are as follows:
Fitosporin is not addictive
Whey is also used to fight scab
Autumn preventive measures are the most important in the fight against scab and other diseases, as well as pests.
After the end of the leaf fall, you need to collect all the fallen leaves
The trunk and thick branches are whitewashed with lime mortar
To combat scab, as with other fungal diseases, fungicides are used. When working with them, you need to know some features:
It is believed that treatment with ammonium or potassium nitrate copes with scab no worse than treatment with fungicides. In this case, the tree is fertilized with nitrogen at the same time. For prophylaxis, spraying with a 0.5-3% solution of nitrate is used in early spring and (or) late autumn. For the treatment of the disease, the concentration is increased to 10%.
Ammonium nitrate can be used to combat scab
Summing up, I want to express my opinion based on personal experience. I will clarify that my orchard is located in the east of Ukraine. We got it two years ago in a rather neglected state. Including some apple and pear trees were sick with scab. The first thing we started with was cleaning the garden, intensive thinning of thickened crowns. I had to do it in stages, as there were too many unnecessary branches. I am a proponent of prevention, and I try not to lead to treatment. Therefore, collecting and burning fallen leaves, digging near-trunk circles, whitewashing trees, installing trapping belts - I never miss these events. I try not to overuse treatments. Be sure to spray the crowns of apple trees and pears with a 5% solution of ferrous sulfate in late autumn. I believe that this not only helps to prevent fungal diseases (including scab), but also eliminates iron deficiency in plants. And my father taught me from childhood that iron is the main element for apple trees. In early spring, I definitely use copper sulfate and Nitrafen. It's mid-April now - Horus is scheduled for tomorrow - this is my favorite anti-fungal drug this time of year. Another drug that I regularly use throughout the season and for all plants is Fitosporin-M. This is an effective biological preparation and I do not use any other drug without urgent need. In emergency cases, when an infection occurs, I use Strobi. I can say that in two years I got rid of scab and other ailments in the garden.
Of course, scab is an unpleasant disease of the apple tree. But, using modern drugs, as well as regularly taking the necessary preventive measures and treatment, the gardener is able to cope with the problem.
Hello! My name is Pyotr Vladimirovich. I am 63 years old. By education - a mechanical engineer.
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The fight against scab always begins with the detection of an ailment on a tree. However, in order to correctly identify the disease, you need to know what scab is.
This is a disease that provokes the marsupial fungus Venturia unequal. The causative agent is distributed throughout the territory of the Russian Federation. The disease is typical for the Moscow region. The fungus infects fruits and leaves. Most often, scab can be found in areas where there is a temperate climate with cold and wet springs. If it rains heavily in summer (especially in July), the apple scab variety can infect almost 90% of the trees.
The spread of the disease is carried out in early spring. It is during spring rain that the fungus actively infects young shoots of apple trees, clinging to the bark with its mucous membrane. The following factors are necessary for the development of the fungus:
The presence of the disease provokes a decrease in the yield of the apple tree, as well as the quality indicators of the fruits. Affected apples are poorly stored, quickly lose their value, and also have an unattractive appearance. The disease rarely provokes the death of a tree, but it can provoke its freezing. Scab control on various apple trees is difficult, as the pathogen can be transmitted from tree to tree. Therefore, it is extremely difficult to cure an apple tree from scab. But wrestling is effective with the right approach.
Literally everyone can determine the presence of scab on trees: spots (on leaves, fruits) immediately catch the eye, which at the very beginning of their development have a yellow-green color, and later turn black and often crack.
The causative agent of scab on an apple tree is a marsupial mushroom, namely Venturia unequal (Venturia inaequalis)... This fungus usually infects leaf blades, as well as ovaries and, of course, fruits. The fungus manifests itself most actively in wet years and periods of the season when there are prolonged rains, fogs, or damp weather for a long period.
Usually, the scab fungus gets on the bark and shoots of trees even in early spring, it literally clings to the shoots with the help of the mucous membrane and immediately begins to develop, sometimes very actively.
The first noticeable signs of the appearance of the fungus can usually be observed during the flowering period of the apple tree, which often occurs in the month of May. Often this period is characterized by abundant precipitation combined with heat, which is just "on hand" to the fungus.
Spores of the scab fungus with water, wind, animals and humans spread quite actively and if they fall on the leaf blades, they begin to develop very rapidly, literally penetrating into the leaf tissue quite deeply. The vital activity of the fungus leads to the appearance of spots on the leaf blades at first, and then - just through, round holes.
In the summer, scab develops even more actively, which is facilitated by abundant dew and rain in combination with a high positive temperature. The scab develops most actively at temperatures from +22 to +25 degrees. Developing during the season, scab forms spores of the fungus closer to autumn, they just ideally winter in the soil and shoots, "hiding" in leaf litter. The vital activity of the fungus disrupts the processes of photosynthesis, but, as a rule, it is not critical, therefore the tree does not die, and the fungus is actively spreading.
Often, scabbed leaf blades crumble only a few days earlier than the due date, the fruits may not crumble at all, however, their shape often changes to an irregular one, wrinkles, cracks appear on them (in place of spots), the mass of fruits decreases.
With the onset of spring, the overwintered fungus reactivates and the entire cycle of its development is repeated anew. Thus, it will not work to prevent the appearance of scab on the site and get rid of it with the help of only treatments, the whole complex of necessary measures is important here.
An apple tree that prematurely threw off yellowed and dried leaves after being hit by a scab apple tree. © S.K. Porter
Measures aimed at suppressing the scab fungus should begin with adherence to agrotechnical rules when planting and growing apple trees. There should be an acceptable distance between the trees, the crown should be thinned out in time, one should not forget about sanitary pruning of branches and timely feeding.
Now you know what scab on an apple tree is, how to deal with this scourge, how and when to carry out preventive treatments. Pay attention to the first symptoms, because the disease is easiest to overcome early.