How to deal with white bloom on currants?

The most common fungal disease in Russia is powdery mildew, which affects most fruit and berry shrubs. Mealy dew often appears on currants. Many gardeners are interested in why it arises, how to deal with it, what means to treat the disease in order to save the harvest.

The first symptom of this disease is the appearance of white bloom on the plant. The inner side of the leaf plates and young shoots that are close to the ground surface are attacked first, and the infection later passes to mature stems and fruits. After all, disputes are easily transferred by the wind. A diseased plant cannot normally cope with photosynthesis, which leads to a loss of yield. Powdery mildew appears mainly on blackcurrant, since red and white varieties are most resistant to this disease. If you do not take any action, you can lose a large amount of harvest (80%), as well as infected currant bushes often do not tolerate wintering.

The signs of plant disease include the following points:

• white bloom appears on the leaf plates and shoots;
• leaves curl, decrease in parameters, lose their natural color, and then disappear;
• ripe fruits are covered with a touch of brownish tinge, and those ovaries that did not have time to form, disappear.

To avoid the occurrence of this disease, it is necessary to familiarize yourself with such basic causes of the disease as:

• the cause of the fungal disease can be the prevailing high temperature from +5 to +28 degrees and an increased level of humidity from 60 to 80%; such climatic conditions are ideal for the life of the fungus;
• not enough light;
• planting too thick;
• the soil contains a large amount of nitrogenous substances;
• crops with powdery mildew are planted near the currant;
• improper care for currant bushes; pruning of excess shoots was not performed according to the rules, therefore harmful microorganisms penetrated the sections.

Many experts argue that mostly fungal disease affects the old varieties of currants. Therefore, they should be immediately removed, and in their place plant new varieties that are most resistant to powdery mildew attack. To cure a diseased shrub, it is necessary to organize measures for treating the plant with special means.

It is impossible to completely get rid of the powdery mildew, it will occur annually on the currant bushes, therefore the bushes should be processed every year. To get rid of the powdery mildew, they use various specialized products with a high content of sulfur, copper, and also use systemic fungicides. But in the early stages of the disease can be applied mechanical methods to eliminate the disease or folk remedies, but when the shrub is infected completely, you should use chemical means.

At the initial stage of infection of the currant, when white spots only appeared on the leaves, it is necessary to perform certain actions. Mechanical methods of struggle are the most economical, because you will not need to spend money to buy drugs. There are the following solutions to combat white bloom:

• if the bushes are planted too close to each other, that is, the distance between them is less than 1.5 meters, then you need to plant them for a longer distance; too thick planting causes darkening of the lower parts of the shrub and poor air circulation, which leads to the appearance of various fungal diseases;
• before planting new varieties of currants, should be treated with fungicides;
• damaged branches and leaf plates at the initial stage of disease development must be cut and burned.

The most effective methods of controlling fungal diseases are preparations containing toxic chemicals. The only drawback of the use of chemicals is a high level of toxicity, so the use of such products requires proper preparation of the solution, namely the ratio of water and special means. Spraying with special means is best done not only at the time of infection of the plant, but also as a preventive measure. To effectively irrigate currant bushes you will need a spray gun with a special nozzle or a wide brush. Thus, when spraying a shrub from above or below, a solution in the same amount will fall on the plant.

The spray pattern is as follows:

• processing is carried out in the period of thawing of snow;
• spraying is performed until the buds are dismissed;
• the procedure is carried out before flowering shrubs;
• the treatment is applied after the flowering of currants;
• The last processing is carried out in the autumn, when there will be no leaves on the bush.

It is worth considering the most popular means to combat powdery mildew

• Sulfur. Sulfur-based products are the safest, they can be used at any time, even when the plant is bearing fruit. After processing by such means, the fruits are eaten, but not earlier than in 2–6 days. The main condition for the use of sulfur is the temperature regime, which should not be lower than +20 degrees, but not higher than +35 degrees. Indeed, lower degrees significantly reduce the effectiveness of the drug, and at higher temperatures, sulfur becomes toxic, which leads to burns on the plant. For the treatment of fungal diseases use special means such as colloidal sulfur, "Thiovit Jet".

• Copper. Copper-containing agents are less effective than sulfur-based drugs. To cure shrubs, it is necessary to spray them 3 times for the entire season. It is worth paying attention to the fact that with each subsequent treatment the preparations will need to be changed, because the fungus quickly adapts and acquires resistance to such special means, therefore the use of one and the same means will not give the best results. To prepare the solution will require 100 grams of copper sulphate and 10 liters of liquid. All ingredients are thoroughly mixed to avoid grains. After you need to filter the solution, and then proceed to the wetting of the shoots and the ground around the shrub. This procedure is performed until the buds are dismissed.

• Systemic fungicides. Such products are used not only in the treatment of powdery mildew, but also as a preventive measure. Systemic fungicides include drugs such as Topaz, Tilt, Topsin-M, Scor, Raek. After spraying, such products penetrate the plant tissue for 1 hour. In the affected areas, the fungus is destroyed, and also become an obstacle to the further development of the fungal disease. At the same time, the infection is eliminated not only outside, but also inside the plant. Fungicides are able to accumulate in the fruit, so it is possible to process currant bushes with such special preparations 2–3 weeks before harvesting.

The effectiveness of the above drugs will depend entirely on the implementation of the following actions:

• Before proceeding to the treatment of shrubs such means, you should prepare the plant - the affected parts of the plant (shoots, leaf plates, flowers, berries) should be removed;
• cut bush should be washed under the pressure of cold water;
• next to each affected shrub, the top layer of soil must be removed, because pests spend the winter in the plant waste (fallen leaves and fruits) that are in the upper layers of the soil;
• after these manipulations, you can start spraying the plants.

Traditional methods of treatment of powdery mildew are preventive measures, because it is very difficult to get rid of this ailment. There are several folk remedies that experienced gardeners use to combat fungal disease.

• Kefir. In this case, 1 liter of kefir is diluted in 10 l of water, but for better adhesion of the solution to the shrub, you must add soap, which is rubbed on a grate. This solution is necessary to spray the upper and lower leaf plates of currants. After irrigation with whey, a thin oil film is formed on the shrub, which has a detrimental effect on fungal spores. This method is the most effective in use, because the bacteria that are in kefir, prevent the active development of the fungus. Before you carry out such a procedure, you need to know the weather forecast for the near future, because the solution is valid only in dry, calm weather.

• Iodine. This method requires 10 ml of 5% iodine, which is diluted in 10 liters of liquid, and then currants are sprayed with the prepared solution. This special solution creates an acidic environment that is not suitable for normal pest life. Alcohol contained in iodine disinfects leaf plates and destroys spores, and also prevents the fungus from penetrating into berries and other parts of the plant.

• Infusion of wood ash. 2–3 kilograms of ash are poured into 10 l of liquid, the resulting solution is brought to a boil over low heat. After add 40 g of household soap shavings. When the mixture is cool, you can proceed to the treatment of the affected leaves.
• Rapeseed oil. After the first use of such an ingredient on a bush, a large number of spores is significantly reduced (approximately 200 times). 10 ml of liquid used 10 ml of oil. 14 days after spraying, the plant is cured, but this is if the shrub is treated in the early stages of the disease.
• Garlic infusion. It is necessary to fill ½ a bucket with a volume of 10 l with garlic arrows and fill them with 10 l of warm liquid, let it stand for 24 hours. The filtered solution must be applied to all affected shrubs. Garlic arrows can be replaced with regular peeled garlic (250 grams).

• Reformed hay. It should be 1 kg of the ingredient pour 3 liters of warm liquid, leave to insist means for 3-4 days. Before spraying it is necessary to dilute the prepared infusion with water in the ratio 1: 3.

As already mentioned, to get rid of powdery mildew is quite difficult, and in some cases even impossible. Therefore, in order to prevent the occurrence of this disease, you should regularly carry out such preventive measures as:

• experts recommend for planting to choose new varieties of currants, which are most resistant to the attack of fungal diseases; in conditions with high humidity values, it is better to plant shrubs of such varieties as “Bagheera”, “Agat”, “Black Pearl”;

• seedlings are best purchased in proven specialized stores or nurseries, where a qualified specialist will consult on the rules for caring for a particular currant variety;
• before planting, seedlings should be treated with a special solution, which contains copper, some gardeners replace specialized preparations with ordinary boiled water; good results are also given by immersion of seedlings in boiling water for a few seconds, but you should not increase the immersion interval, because in this way the plant will disappear;
• the proper technology of planting shrubs should be observed;
• before the onset of the winter period, currant bushes should be carefully inspected; dry and weakened branches should be cut with a pruner;
• it is necessary to remove weeds from the beds in a timely manner, because in such plants pests can hide;
• if a large number of insects have got on the bushes, then you should not postpone the implementation of measures to combat them, because they are the sources and carriers of the disease;

• at the first signs of infection, it is necessary to immediately cut off the infected parts of the shrub, thereby stopping further development of the disease;
• need to reduce the amount of fertilizer with a high nitrogen content;
• every 7–10 years it is worth changing the planting of currant bushes, because over time the soil is depleted, and regular feeding will not give the desired result, which will lead to a weakening of the plant immunity.

As a preventive measure, it is necessary to process currant bushes with humus in early spring. Capacity of any size should be filled with 1/3 of humus and fill with warm water. This solution should be placed in a warm place for 5–6 days so that it is infused. At the same time every day you need to mix it. The finished solution is filtered through cheesecloth. The first irrigation is carried out at the moment when the leaves are just starting to grow. The second spraying is carried out after 7 days, and the third - during the flowering period of the shrub.

Every currant grower should know what to do if the currant is covered with white spots. And only in extreme cases it is necessary to turn to chemical agents, because a large amount of pesticides adversely affects not only the shrub, but also the ripe fruits that will be eaten later.

On how to deal with powdery mildew on currants, see the following video.