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Although many blueberry varieties are characterized by high resistance to disease, this property does not make the crop completely immune to various ailments and pests. Diseases of garden blueberries and their management can confuse inexperienced gardeners, which is especially undesirable in cases where it is necessary to begin treatment immediately. In order not to waste time when faced with the first signs of blueberry disease, you need to understand what ailments this crop has.
Classification of blueberry diseases
At the moment, there is no official classification of blueberry diseases as such.However, for convenience, many gardeners divide all known ailments characteristic of this plant into two conditional groups:
- fungal;
- viral.
Fungal diseases, as the name suggests, are caused by fungal organisms. Most often, they develop as a result of violations of blueberry growing conditions, for example, due to improper watering or a poorly selected planting site.
Viral diseases are spread by various viral vectors. These include both various pests and harmless insects that were near the injured blueberry bush. Through a cut or break, the virus enters the plant cells and, if the crop has weak immunity, begins to actively multiply, which leads to the development of disease in blueberries.
But, regardless of the type of disease, at the first unfavorable symptoms you should immediately begin the treatment process, because due to delay you can lose not only the seasonal blueberry harvest, but also the entire bush. Below we consider in more detail the types of blueberry diseases and methods of their treatment.
Fungal diseases of blueberries and how to treat them
Often the cause of fungal diseases is insufficiently good care. However, even well-groomed plants are not immune from such ailments, and therefore it would be a good idea to familiarize yourself with the symptoms of such diseases.
Stem cancer
The disease, contrary to its name, affects not only the stems, but also the leaves and petioles of blueberries. The first signal of the onset of the disease is small red spots at the base of leaves on young shoots, which increase in size over time and cause them to die. Later, brown cankers with a crimson-red border form on the bark of older branches.If left untreated, their number increases until the plant dries out.
Fortunately, stem cancer is treatable. To prevent the disease from spreading throughout the bush, it is worth regularly cutting off the infected parts of the plant and burning them. In addition to this, it is necessary to treat blueberries with antifungal and copper-containing drugs. Among them, the following have proven themselves well:
- Fundazol;
- Topsin;
- Euparen (0.2% solution).
Treatment with these substances should be carried out 3 times with an interval of 7 days before budding and the same number of times after picking the berries.
Mummification of berries
Blueberry fruits and leaves are often infected by the fungus Monilinia vaccinii-corymbosi. Berries that have been exposed to it develop as usual, but do not reach ripeness and dry out prematurely. The leaves and young shoots of the plant, in turn, turn black and fall off.
Early spring treatment of blueberry bushes with urea will help cope with this disease. It is also useful to mulch the plant by sprinkling the tree trunk circle with a layer of sawdust 5 - 7 cm thick.
Moniliosis
Moniliosis, also known as fruit rot, causes blueberries infected with the fungus to appear as if they have been frozen in extreme cold. Non-interference in the course of the disease leads to the fact that the fungus gradually invades other parts of the plant.
The only way to get rid of moniliosis is to burn dead parts of shrubs and shoots that have become infected.
Phomopsis
Phomopsis is considered one of the most common diseases characteristic of high blueberries.The risk of its occurrence increases if late spring is hot and dry. The symptoms of Phomopsis are in many ways similar to those observed with stem cancer, however, infection begins not from the leaves, but from the upper part of the shoot. Young blueberry branches up to 45 cm in size begin to dry out and curl. Under the influence of the fungus, the bark on the branches becomes brown and appears burnt. Unsightly brown blotches appear on the leaves. The lack of timely measures to protect blueberries from this disease leads to the death of the bush.
Removing and burning damaged shoots will be the first step in treating Phomopsis in blueberries. Good results are obtained by three-time treatment with Tridex, Topsin-M and Skor - before flowering begins. The procedure should be repeated every 7 days.
White spot
Blueberries also have such a well-known disease among gardeners as white spot. It is characterized by the fact that large numbers of round spots appear on the leaves of the bush, the color of which varies from whitish to reddish-brown. The size of the spots ranges from 4 to 6 mm. Affected leaves soon dry out and fall off.
Leaves must be burned immediately so as not to create additional favorable conditions for the fungus to reproduce. Timely mulching of blueberry bushes will help solve the problem of white spotting.
Anthracnose
Like many leaf diseases, anthracnose in blueberries develops when the bush is waterlogged. Other reasons include poor breathability due to the crown being too dense. The foliage of a diseased plant becomes covered with spots of varying sizes, and the berries begin to rot and become overgrown with an orange coating.
The fungus that causes anthracnose can be eliminated using various fungicides:
- Speed;
- Switch;
- Signum;
- Rovral;
- Topsin-M;
- Euparen;
- Polyverse.
Using these products 2-3 times during the flowering period will help preserve the harvest and prolong the health of the bush.
Witch's broom
Witch's broom is an unusual disease of blueberry shoots. A fungus of the genus Taphrina causes shoots to grow vigorously on the affected area of the stem, causing it to look like a broom. Fruits and leaf blades on such stems develop very poorly.
The most reliable way to combat witches' brooms is to trim and burn the affected parts of the bush. However, this is only true if the disease is fungal in nature.
Powdery mildew
If blueberry leaves dry out and turn gray, it is quite possible that this is the result of powdery mildew. This disease, caused by the activity of the fungus Sphaerotheca mors, manifests itself in the form of a white coating on the leaf blades of the bush, which later darkens and spreads to the fruits and cuttings. A long course of the disease reduces the level of winter hardiness and negatively affects the yield of the plant.
Timely treatment with chemical compounds such as Sulfaride, Topaz, Bayleton can save blueberries from this disease.
Double leaf spot
Dry leaves on blueberries during the height of the season may be a sign that they are affected by double spot. At the end of spring, small smoky spots 2-3 mm in size appear on the leaf blades of the bush.With high humidity in July-August, they increase in size up to 15 mm and take over the entire plant. The infected parts of the plant dry out and, falling off the blueberries, pose a danger to other crops, since the fungus remains active for a long time. Such shoots and leaves should be burned regularly.
Gray rot
Gray mold, also called botrytis, can cause the foliage and branches of a bush to gradually turn brown, then turn gray and die. The causative fungus botrytis enters plant tissue through cuts and injuries. The disease can also affect already harvested blueberries that are not stored correctly.
It is possible to stop the spread of fungus with the use of fungicides. To do this, blueberries are sprayed with Fundazol up to 3 times with an interval of 1 week.
Viral diseases of blueberries
As already mentioned, in addition to fungal diseases of blueberries, there are also viral diseases that threaten the health of the bush.
Mosaic
This disease gets its name from the patterns that appear on the leaves when exposed to the virus. The leaf blades turn yellow unevenly, causing the surface or edges of the leaf to appear to be covered with a mosaic pattern. Over time, the foliage may turn completely yellow. Such a virus not only spoils the appearance of blueberries and their taste, but also poses a danger to other crops, as a result of which it is necessary to get rid of the diseased bush.
Bush dwarfism
Another viral disease transmitted by mycoplasma is bush dwarfism.The virus inhibits the growth of blueberries, which is why the branches develop defectively, and the berries become smaller and have an unpleasant taste. In addition, the crown of the bush changes the color of the foliage even before the onset of autumn. Therefore, if blueberry leaves turn yellow ahead of schedule, and other symptoms of dwarfism are observed, it is necessary to destroy the bush, and this must be done as soon as possible. Viruses spread no less quickly than fungi and can spread to healthy plants if measures are not taken in time.
Red ring spot
The disease under this name is characterized by the appearance of round-shaped spots with a bright red border on blueberry leaf blades. As the disease progresses, the leaves turn completely red and die. However, in the early stages of the disease, you can try to save the bush by destroying all the affected leaves.
Threadiness of branches
Threading of branches can be asymptomatic for a long time and only enter the active phase after years. The following symptoms are noted with this disease:
- slower growth of blueberries;
- redness of leaves during the initial period of the disease;
- at later stages - twisting and wrinkling of leaf plates;
- the appearance of characteristic thin stripes on young branches.
To date, no treatment has been found for the virus that causes stringiness in blueberries, and therefore all plants with this disease must be disposed of.
Lack of nutrients in the soil
Impaired development of blueberry bushes and a decrease in yield can occur not only due to disease, but also due to a lack of certain nutrients in the soil.
Thus, the lack of nitrogen compounds affects the growth rate and color of young blueberry shoots, which first turn pink and then become pale green. A lack of phosphorus is indicated by the inability of the plant to bloom, as well as the base of the leaves, which acquires a purple color. Sulfur deficiency leads to blackening of the tops of shoots and their subsequent death.
Blueberry pests and how to deal with them
Some insect pests can cause blueberry connoisseurs no less problems than fungal and viral diseases. The most common pests include:
- heather lancet;
- blueberry moth
- aphids;
- leaf roller;
- kidney mite.
These insects, even in small clusters, can significantly worsen the yield of blueberries and even provoke the death of the plant if their activity is ignored for a long time. Therefore, it is worth studying the characteristics of these pests in more detail.
Sagittarius heather
Adults of this butterfly do not harm blueberries, but its caterpillars are known as serious pests. They are easily distinguished from other insects by their black-brown color with white patches and an elongated body covered with short hairs. These pests appear throughout the summer and actively eat the leaves and young shoots of the plant. A fairly large number of insecticides are effective against lancets, including Fufanon, Actellik and Kemifos. The spraying procedure is carried out in the spring, before the beginning of the growing season, and in the summer, if the number of pests is too large. If there are no adult insects on the site, and there are few caterpillars themselves, then they can be collected manually.
Blueberry moth
The blueberry moth is another butterfly whose caterpillars are not averse to feasting on blueberry leaves. These pests are distinguished by the fact that, in addition to the usual legs, they have four abdominal legs, which are clearly visible in the photo. They have a noticeable yellow color with black lines along the body. The appearance of these pests occurs in May.
Measures to combat moths are identical to those used against lancets. In addition to the above remedies, we can mention the benefits of drugs such as Kinmiks, Inta-Vir or Iskra against these pests.
Triangular flat leaf roller
Unlike adult specimens, which attract attention with their snow-white color, leaf roller caterpillars are light green and hardly noticeable against the background of foliage. These pests have darker stripes on the sides of the body and on the back, and black spots can be seen on their brown heads. Like all caterpillars, leaf rollers are pests of leaves, but they not only eat foliage, but also wrap themselves in it for protection from birds. For this reason, cobwebs are often noticed on the tops of shoots affected by pests.
This property allows you to get rid of individual caterpillars by simply tearing off and destroying curled leaves. In case of a large-scale pest invasion, the bushes are treated with insecticidal compounds.
Aphid
Aphids also bring a lot of trouble to blueberry owners. These pests often accumulate on young growth, starting in May. In addition to the fact that aphids drink juice from the plant, they also serve as carriers of various viral diseases, so treatment of blueberries against these pests should be carried out in early spring without delay. The following agents have shown their effectiveness in the fight against aphids:
- Aktellik;
- Calypso;
- Karate.
Kidney mite
This pest is very small in size - up to 0.2 mm. Together with the larvae, it overwinters in the axils of blueberry leaves, and with the arrival of spring it moves to the buds, which it eats away from the inside, slowing down the growth of the bush.
You can cope with the mite by treating blueberries with Nitrafen, KZM or iron sulfate in early spring.
Prevention measures
To ensure that diseases and pests bother blueberries as little as possible, you should listen to a few simple tips:
- When choosing a blueberry variety to plant, you should give preference to disease-resistant varieties grown in the same region or country.
- The soil at the planting site should be acidic and fertile, with a sufficient amount of mineral supplements. In addition, the soil must be moist, since blueberries are a moisture-loving plant.
- Blueberry bushes should not be more than 2 meters apart from each other.
- It is advisable to regularly inspect and trim blueberries so that the crown does not thicken too much.
- Damaged, frozen or injured parts of the bush must be removed immediately.
- After leaf fall, all fallen leaves must be destroyed, since pests and pathogens can easily overwinter in them.
- If possible, it is worth treating blueberries with Bordeaux mixture in the spring, and in the fall after harvesting, spray the plant with fungicides, this way the bush can be protected from pests and diseases.
Conclusion
Although blueberry diseases and their control can require a lot of effort from the gardener, a competent approach to treatment will help maintain the health of the plant.However, it is much easier to prevent a disease than to treat it, and therefore it is especially important not to ignore timely preventive treatments against diseases and pests.
Red ring spot: how to treat it with medications correctly?