Diseases of Red, White, and Golden Currants

Improper Care and Agrotechnical Errors

Currant is an unpretentious crop, but it reacts acutely to dense plantings. When bushes are located too close together, the crowns are poorly ventilated, humidity inside the bush increases, and this is an ideal environment for fungal infections (Buckingham, 2010). Red and white currants are especially sensitive to density—their branches remain productive longer but are more quickly affected by diseases when ventilation is poor (Potapov et al., 2000).

Excessive watering or stagnation of water at the roots also provokes the development of fungal and bacterial infections. Currants do not like waterlogging: the root system suffers, and the plant becomes vulnerable to pathogens (Hessayon, 1993).

Improper pruning can not only weaken the bush but also become a cause of infection through open wounds. Cuts without treatment are gates for fungal spores and bacteria (Trunov et al., 2012).

Weather Conditions

Cool and wet summers are the main ally of fungal diseases. This is especially true for anthracnose, powdery mildew, and gray mold (Hill & Perry, 2011). In regions with long warm autumns, fungal spores manage to produce several generations, which intensifies infection in the next season (Potapov et al., 2000).

Spring frosts damage tender tissues, weaken the plant, and make it more susceptible to infections (Tretyakov et al., 2000). Red and white currants are more frost-resistant, but sharp temperature fluctuations harm all species (Tarasov et al., 1981).

Weakening of the Plant

Bushes weakened by nutrient deficiencies (especially nitrogen, phosphorus, and potassium) lose immunity. Excess nitrogen, on the contrary, causes rapid growth of green mass, making tissues loose and more vulnerable to fungi (Buckingham, 2010).

Damage by pests is another route for infection. For example, the currant bud mite not only weakens the currant but also transmits viruses (Kurennoi et al., 1985).

Biological Characteristics of Pathogens

Currant diseases are caused by three groups of pathogens:

• Fungi — the most common. Their spores are easily carried by wind, raindrops, or planting material (Hill & Perry, 2011).
• Bacteria — penetrate through tissue damage and often lead to plant death.
• Viruses and phytoplasmas — are transmitted by insects, less often through sap during pruning or grafting. Viral diseases cannot be cured, so the main defense is prevention (Krivko, 2014).

The Importance of Resistant Varieties and Crop Rotation

The immunity of currants is strongly influenced by the variety. Modern varieties of red and white currants (e.g., 'Rovada', 'Jonkheer van Tets', 'Red Lake', 'White Versailles') have good resistance to fungal diseases (Buckingham, 2010). Golden currant, as the most drought-resistant species, also suffers less from fungi in humid regions (Dankov, 2015).

Proper crop rotation is also important: you cannot plant new currants in the place of old ones (especially the same crop). This reduces the risk of soil-borne infections, such as verticillium wilt and root rot (Hessayon, 1993).

Thus, the health of currants begins with the choice of variety, proper planting, and competent care. In the following chapters, we will analyze each group of diseases in detail and tell you how to recognize and treat them.

American Powdery Mildew (Sphaerotheca)

Causal agent: fungus Sphaerotheca mors-uvae (syn. Podosphaera). It primarily affects gooseberries but often spreads to currants, especially in dense plantings (Hessayon, 1993).

Symptoms:

• A white powdery coating appears on young leaves, shoots, and berries.
• Over time, the coating becomes brown and felt-like.
• Leaves curl, shoot growth slows, berries become inedible.

Characteristics: The fungus is active in warm, humid weather. It overwinters on affected shoots and fallen leaves.

Control measures:

• Prevention: Choose varieties resistant to powdery mildew (e.g., red 'Jonkheer van Tets', white 'White Versailles' (Buckingham, 2010)). Avoid overcrowding, carry out timely pruning.
• Treatment: At the first signs, spray bushes with sulfur preparations (colloidal sulfur, 2–4 kg/ha) or fungicides based on penconazole, difenoconazole (Hill & Perry, 2011). In amateur gardens, treatments with a soda ash solution (50 g per 10 L of water) with the addition of laundry soap are effective.
• Sanitary measures: In autumn, collect and burn fallen leaves, cut out diseased shoots.

Anthracnose

Causal agent: fungus Pseudopeziza ribis (perfect stage). One of the most harmful diseases of currants, especially in regions with wet summers (Kurennoi et al., 1985).

Symptoms:

• Small (about 1 mm) brown spots with a dark border appear on the leaves.
• The spots merge, the leaf turns brown, curls, and falls prematurely.
• Severely affected bushes may lose foliage by mid-summer, weakening them and reducing the next year's yield.

Characteristics: The fungus overwinters on fallen leaves. Spores are spread by raindrops and insects.

Control measures:

• Prevention: In autumn, carefully collect and remove fallen leaves, dig up the root zone.
• Treatment: Before bud break, treat bushes and soil with 3% Bordeaux mixture (300 g copper sulfate + 400 g lime per 10 L water). During the growing season, use 1% Bordeaux mixture or preparations based on copper oxychloride, as well as systemic fungicides (e.g., "Skor", "Rayok"). Repeat treatments every 10–14 days (Potapov et al., 2000).

Cup Rust

Causal agent: fungus Puccinia ribesiicaricis. To complete its cycle, it requires an intermediate host—sedge (Buckingham, 2010; Trunov et al., 2012).

Symptoms:

• In early summer, yellow-orange convex pads (aecia) appear on the upper side of the leaves.
• After some time, small yellowish cup-shaped formations ("goblets") form on the underside of the leaf, in which spores mature.
• Leaves turn yellow and fall.

Characteristics: It manifests especially strongly in rainy years and near water bodies where sedge grows.

Control measures:

• Prevention: Remove sedge within a radius of 100–150 m from the plantings (impossible in most cases—then switch to protective treatments).
• Treatment: Spray bushes with systemic and contact fungicides (Dithane, 1% Bordeaux mixture) before and immediately after flowering (Hill & Perry, 2011). Repeat after 10–14 days.
• Collect and destroy fallen leaves.

Column Rust

Causal agent: fungus Cronartium ribicola (other species—C. comandrae). Intermediate host is five-needle pines (Hill & Perry, 2011). In northern regions, this fungus is closely linked to the white pine problem (Pinus strobus), so some US states still restrict currant cultivation (Buckingham, 2010).

Symptoms:

• Small yellowish spots form on the upper side of the leaves.
• Orange or brown spore columns (pustules) appear on the underside, resembling bristles.
• Leaves dry out prematurely and fall.

Characteristics: It mainly affects black currants, but sometimes also red currants, especially when pines are nearby.

Control measures:

• Prevention: Do not plant currants closer than 200–300 m from pines (Buckingham, 2010). Choose resistant varieties (among reds—'Rovada', 'Red Lake').
• Treatment: Same preparations as for cup rust. The first treatment is carried out immediately after leaf emergence, the second after 2 weeks, the third after flowering (Hessayon, 1993).

Gray Mold (Botrytis)

Causal agent: fungus Botrytis cinerea. Affects berries, especially in rainy summers, as well as shoots and leaves (Buckingham, 2010).

Symptoms:

• A fluffy gray-brown coating appears on the berries; the fruits become watery and rot.
• Shoots and leaves become covered with brown spots, which in wet weather become coated.
• The infection spreads quickly, especially with dense planting.

Characteristics: The fungus overwinters on plant residues. Active at high humidity and temperatures of 15–25°C.

Control measures:

• Prevention: Ensure good air circulation—do not densify plantings, carry out thinning pruning. Mulch the soil to prevent splashing of spores onto the berries.
• Treatment: At the first signs, remove diseased berries and shoots. Use fungicides based on fenhexamid or boscalid (Hill & Perry, 2011). In amateur conditions, treatments with 1% Bordeaux mixture or sulfur preparations are effective (but not in hot weather).

Verticillium Wilt (Tracheomycosis) and Fusarium Wilt

Causal agents: soil fungi Verticillium and Fusarium. They penetrate through the roots and cause blockage of vessels, leading to wilting (Hessayon, 1993; Potapov et al., 2000).

Symptoms:

• Leaves turn yellow and wilt, starting from the lower tiers.
• Vessels on the cut branch have a brownish tint.
• Over time, entire shoots or the whole bush die.

Characteristics: Fungi persist in the soil for a long time (up to 10 years). The disease intensifies with lack of moisture or damage to the roots.

Control measures:

• Prevention: Do not plant currants after crops susceptible to verticillium wilt (tomatoes, potatoes, peppers). Apply organic matter and observe crop rotation (Hessayon, 1993).
• Treatment: There are no effective drugs for treatment. Affected plants are removed and burned. The soil is disinfected (e.g., drenched with 2% copper sulfate solution) and left fallow for at least a year (Hill & Perry, 2011).

Alternaria and Cercospora (Leaf Spots)

Causal agents: fungi of the genus Alternaria and Cercospora. More common on currants in southern regions with hot summers (Trunov et al., 2012).

Symptoms:

• Dry brown or grayish spots, often with concentric rings, form on the leaves.
• Affected tissues eventually die, the leaf becomes "torn."
• With severe infection, leaves fall, weakening the bush.

Characteristics: Fungi overwinter on fallen leaves. Develop at high humidity and temperatures above 20°C.

Control measures:

• Prevention: Autumn leaf collection, thinning of bushes.
• Treatment: Spray with 1% Bordeaux mixture or systemic fungicides (e.g., "Quadris", "Skor") at the first signs. Repeat after 14 days (Potapov et al., 2000).

Brief Summary of Fungal Diseases

Fungal infections are easier to prevent than to treat. The main principles of protection:

• Choose resistant varieties (for red and white—'Rovada', 'Red Lake', 'White Versailles', 'Jonkheer van Tets'; golden currant is generally more disease-resistant) (Buckingham, 2010; Hill & Perry, 2011).
• Maintain spacing when planting (at least 1.5 m between bushes) and regularly thin the crown.
• Avoid waterlogging and stagnation of water.
• Annually remove fallen leaves and affected shoots.
• Use fungicides only if there are clear signs of disease, strictly according to instructions.

Bacterial Crown Gall (Agrobacterium tumefaciens)

Causal agent: bacterium Agrobacterium tumefaciens (formerly Rhizobium radiobacter). Widely distributed in soil and affects many fruit and berry crops (Hill & Perry, 2011).

Symptoms:

• Growths (galls) form on the roots and root collar—initially soft, light green, then woody, dark, with an uneven bumpy surface.
• The size of the growths varies from a pea to a fist.
• Affected bushes lag in growth, shoots become short, leaves become smaller and turn yellow.
• In dry years, bushes may die quickly.

Characteristics: The bacterium persists in soil and plant debris for up to 3–5 years. It penetrates through fresh wounds on the roots (during planting, digging, damage by soil-dwelling pests). It is especially active in neutral and slightly alkaline soils (Trunov et al., 2012).

Control measures:

• Prevention: Thorough inspection of the root system when purchasing seedlings—healthy roots without growths. Treatment of roots before planting with a clay-manure mash or bacterial preparations (e.g., "Fitosporin-M"). Avoid mechanical damage to roots during care.
• Treatment: There are no effective treatment methods. If galls are found on the roots of an adult bush, the plant is removed and burned. The soil in this place is disinfected (drenched with 2% copper sulfate or formalin) and currants are not planted there for 3–5 years (Potapov et al., 2000).
• Important: Do not establish a nursery or plant young plants on plots where there have been cases of bacterial cancer.

Bacterial Wilt (Erwinia amylovora)

Bacterial wilt of currants caused by Erwinia spp. is rare, and there is little information about systematic damage to red/white currants. However, wilting with signs of bacterial infection can occur in hot years, especially on weakened plants (Hessayon, 1993). A close relative, Erwinia amylovora (the causative agent of fire blight of pome fruits), is sometimes mentioned as a pathogen for some Ribes (Hill & Perry, 2011), but this diagnosis is often made erroneously due to external similarity to verticillium or fusarium wilt.

Symptoms (assuming bacterial nature):

• Sudden wilting of individual shoots or the whole bush during the period of active growth.
• Leaves become dark green, then brown and dry up, not falling off.
• On the cut of the affected stem, darkening of the vascular bundles is noticeable, sometimes with the release of sticky bacterial slime.
• In wet weather, amber-colored exudate may appear on withered branches.

Characteristics: Bacteria are spread by rain, wind, and insects. They overwinter in affected shoots and plant residues.

Control measures:

• Prevention: Avoid mechanical damage during pruning, treat tools with a disinfectant solution. Remove weeds—they can be reservoirs of infection.
• Treatment: At the first signs, remove and burn all wilted shoots, capturing 10–15 cm of healthy tissue. Treatment with copper-containing preparations (1% Bordeaux mixture, copper oxychloride) before bud break and after flowering may limit spread (Hill & Perry, 2011). No systemic bactericides are registered for currants.
• Severely affected bushes are removed.

Bacterial Blight (Pseudomonas syringae pv. syringae)

Causal agent: bacterium Pseudomonas syringae. Affects many fruit crops, including currants, especially in regions with wet and cool springs (Trunov et al., 2012).

Symptoms:

• In early spring, watery dark green or black spots appear on young shoots and leaves.
• The spots grow rapidly, shoots turn black and dry up, often bending into a hook ("bacterial blight").
• On leaves, spots are more often on the edges—they become dry, brown, and the leaf blade deforms.
• Gum may form on affected areas, and the bark cracks.

Characteristics: The bacterium overwinters in affected shoots and buds. In spring, it activates at temperatures of 5–15°C and high humidity. Infection often occurs through damage from spring frosts (Potapov et al., 2000).

Control measures:

• Prevention: Early spring pruning with mandatory disinfection of tools. Removal and burning of diseased branches. Choose resistant varieties (red varieties with dense bark, e.g., 'Rovada' or 'Jonkheer van Tets', show less susceptibility).
• Treatment: Before bud break—spraying with 3% Bordeaux mixture. During the growing season—1% Bordeaux mixture or copper-containing preparations ("Hom", "Oksihom", "Abiga-Pik") (Hessayon, 1993). Treatments are repeated every 10–14 days in wet weather.
• If severely affected, the bush is removed completely.

Specifics of Protection Against Bacterial Diseases

1. High-quality planting material—the main defense. Buy seedlings from reputable nurseries, inspect roots for galls and spots on shoots.

2. Crop rotation—do not plant currants after strawberries, raspberries, as well as other crops affected by bacterial cancer (potatoes, tomatoes) (Hill & Perry, 2011).

3. Sterility of tools—when pruning, treat the pruner and saw with 70% alcohol or 1% potassium permanganate solution after each bush.

4. Pest control—aphids, leafrollers, gall midges carry bacteria from diseased plants to healthy ones (Kurennoi et al., 1985).

5. Avoiding mechanical damage—be careful when loosening and weeding, so as not to injure the bark and roots.

6. Maintaining immunity—balanced nutrition (potassium and phosphorus strengthen tissues, increasing resistance to bacteria) and regular watering during dry periods.

Brief Summary of Bacterial Diseases

Bacterial infections are a serious threat as they rarely respond to chemical treatment. Your main strategy:

• Buy healthy planting material.
• Follow agrotechnical practices.
• Timely remove and burn all suspicious plant parts.
• Use copper-containing preparations for prevention, but do not rely on a complete cure.

Reversion (Doubleness)

Causal agent: phytoplasma (previously thought to be a virus). One of the most dangerous diseases of black currant, but sometimes also affects red currants, especially if infected black varieties grow nearby (Kurennoi et al., 1985; Tarasov et al., 1981).

Symptoms:

• Leaves become small, elongated, with altered shape—three-lobed instead of five-lobed, with sparse large teeth.
• The leaf blade loses its characteristic currant smell (in black currant).
• Flowers are deformed: petals become narrow, thread-like, acquire a purple hue (hence the name "doubleness"—flowers look "double," but do not set fruit).
• Berries almost do not set, yield drops sharply, the bush eventually stops fruiting.
• Shoots become thin, internodes short.

Characteristics: Phytoplasma is transmitted with planting material (cuttings, layers) and carried by the currant bud mite (Cecidophyopsis ribis)—the main vector (Kurennoi et al., 1985). Symptoms become noticeable 2–4 years after infection. The disease progresses each season.

Control measures:

• Prevention: Use only healthy, certified planting material. Control the bud mite (acaricide treatments before bud break and after flowering).
• Treatment: Does not exist. The only way out is uprooting and burning the entire diseased bush. Currants cannot be planted in this place for at least 3–5 years (Hessayon, 1993; Potapov et al., 2000).

Mosaic (Currant Mosaic Virus)

Causal agent: a group of viruses (including radish mosaic virus, cucumber mosaic virus). More often affects black currants, but can spread to red and white currants when grown together (Hill & Perry, 2011).

Symptoms:

• Light green or yellow irregularly shaped spots appear on the leaves, scattered throughout the plate.
• The spots may merge, creating a "mosaic" pattern.
• Leaves become wrinkled, edges curl downward.
• Bush growth weakens, shoot increment decreases, berries become small, sometimes deformed.

Characteristics: The virus is transmitted with the sap of diseased plants through tools during pruning, by sucking insects (aphids, leafhoppers), and with infected cuttings (Buckingham, 2010).

Control measures:

• Prevention: Purchase healthy seedlings. Regularly treat plantings against aphids (with insecticides or soap solution). Disinfect tools during pruning.
• Treatment: Diseased plants cannot be cured. If mosaic is detected, the bush is dug up and burned (Hessayon, 1993).

Ring Spot

Causal agent: Raspberry ringspot virus, tobacco necrosis virus, as well as a number of other viruses causing similar symptoms (Hill & Perry, 2011; Trunov et al., 2012).

Symptoms:

• Ring-shaped spots appear on the leaves—yellow or pale green rings with a darker center.
• Sometimes the rings merge, creating a complex pattern.
• Leaves may become deformed and asymmetrical.
• The bush weakens, growth decreases, berries become smaller.

Characteristics: Ring spot viruses are often transmitted by soil nematodes and with sap during pruning (Potapov et al., 2000). They can remain asymptomatic for a long time, especially in resistant varieties.

Control measures:

• Prevention: Use healthy planting material. Prevent nematode infestation—follow crop rotation, do not plant currants after crops affected by these pests (potatoes, tomatoes, strawberries). Soil treatment with nematicides is not recommended for amateur gardens—prevention is more effective.
• Treatment: Diseased bushes are removed. In case of partial damage (1–2 branches), you can try cutting them out with a margin of healthy tissue, but often the virus has already spread throughout the vascular system (Hessayon, 1993).

Witches' Brooms (Phytoplasma)

Causal agent: phytoplasma (related to the causative agent of reversion, but causes different symptoms). Relatively rare on currants, but can affect all species, including golden currant (Krivko, 2014).

Symptoms:

• From dormant buds on the branches, many thin, shortened shoots grow in dense bundles, resembling a "witch's broom."
• Leaves on these shoots are small, yellowish, sometimes twisted.
• Affected branches often do not flower or flower poorly, berries do not set or are very small.
• Over time, such "brooms" grow, weakening the entire bush.

Characteristics: Phytoplasma is transmitted by sucking insects (leafhoppers, psyllids) and with sap during grafting (Trunov et al., 2012). Symptoms appear 1–2 years after infection.

Control measures:

• Prevention: Control of vectors—treatment with insecticides and acaricides during the mass flight of leafhoppers. Culling of suspicious seedlings.
• Treatment: Does not exist. The only way is cutting out affected branches "to the ring" at the first signs (if the "broom" is single). If witches' brooms appear on several branches, the bush is removed entirely (Hill & Perry, 2011).

Common Signs and Diagnosis of Viral/Phytoplasma Diseases

Viral and phytoplasma infections are often difficult to recognize in the early stages. The main alarming signs:

• Changes in the shape and color of leaves (mosaic, rings, deformation).
• Flower deformity (thread-like petals, change in color).
• Dwarfism, small shoots, "witches' brooms."
• Sharp decline in yield for no apparent reason (even with good care).
• Gradual deterioration of the bush's condition year after year.

If you notice at least one of these symptoms, do not wait—remove the diseased bush. In most cases, radical removal is the only effective solution (Kurennoi et al., 1985).

Main Measures for Prevention of Viral and Phytoplasma Diseases

1. Buy planting material only from certified nurseries. Varieties free from viruses are labeled as "virus-tested" or "elite" (Potapov et al., 2000).

2. Control vectors—aphids and mites. Their mass reproduction is a direct path to the spread of infection. Use acaricides and insecticides according to instructions.

3. Disinfect tools. When pruning currants, treat the pruner with 70% alcohol or 1% potassium permanganate solution between bushes.

4. Cull diseased plants immediately. Do not try to "cure" a bush with symptoms of reversion or mosaic—this will only increase the spread of infection (Hessayon, 1993).

5. Do not use cuttings from diseased or suspicious bushes. When propagating currants, select cuttings only from healthy, verified plants.

6. Observe crop rotation. Do not plant new currants in the place of old ones for 3–5 years (especially if there were viral diseases) (Hill & Perry, 2011).

Brief Summary of Viral and Phytoplasma Diseases

Viruses and phytoplasmas are a death sentence for currants. The disease inevitably progresses, and chemicals are powerless. Therefore, the main rule for the gardener is:

The best defense is prevention; the best treatment method is removal.

Do not take risks, do not spare diseased bushes. Only this way can you preserve the health of the remaining plants and the harvest for many years.

5.1. Choice of Location and Soil Preparation

Proper placement of currants lays the foundation for its health:

• Lighting: Currant is a light-loving crop. In the shade, it not only bears fruit worse but is also more affected by fungal diseases (Buckingham, 2010). Choose open, well-lit areas.
• Drainage: Currants cannot tolerate stagnant water at the roots. This provokes the development of root rot, verticillium wilt, and bacterial cancer (Trunov et al., 2012). The site should be flat or with a slight slope, groundwater no closer than 1 m to the surface.
• Ventilation: Avoid enclosed lowlands and places with poor air circulation. This reduces the risk of powdery mildew and gray mold (Hessayon, 1993).
• Crop rotation: Do not plant currants after currants, gooseberries, raspberries, and other crops affected by common diseases. The optimal break is 4–5 years (Hill & Perry, 2011).

Soil preparation:

• In autumn (2–3 weeks before planting), dig the area to a spade's depth, remove perennial weeds.
• Add organic matter (humus or compost—1–2 buckets per sq. m) and phosphorus-potassium fertilizers (superphosphate 30–40 g/sq. m, potassium magnesium 20–30 g/sq. m). Nitrogen fertilizers in spring—during active growth (Potapov et al., 2000).

5.2. Selection of Healthy Planting Material

High-quality seedlings—the main barrier to infections. More than half of viral and bacterial diseases are introduced into the garden with diseased plants (Hessayon, 1993; Krivko, 2014).

Rules for choosing a seedling:

• Buy seedlings only from specialized nurseries with a good reputation.
• Prefer varieties resistant to diseases (for red and white—'Rovada', 'Red Lake', 'Jonkheer van Tets', 'White Versailles'; for golden—'Laysan', 'Venus', 'Shafak') (Buckingham, 2010; Dankov, 2015).
• Inspect the root system: roots should be moist, light on cut, without growths and dark spots (bacterial cancer).
• Above-ground part: shoots healthy, without cracks, necrosis, swellings (bud mite). Bark smooth, typical color for the variety.
• Ask for documents (certificate of varietal purity and absence of viruses)—a good nursery is always ready to provide them.

5.3. Proper Planting

Proper planting is the key to quick establishment and resistance to infections:

• Spacing: For bush forms—at least 1.5 m between plants and 2–2.5 m between rows. For tall golden currant—2.5 × 1.2 m (Dankov, 2015). Overcrowding is one of the main causes of fungal disease outbreaks.
• Depth: Plant currants 5–7 cm deeper than they grew in the nursery (for red and white). Golden—6–8 cm. This stimulates the formation of additional adventitious roots and strengthens the bush (Potapov et al., 2000).
• Root protection: Before planting, dip the roots in a clay-manure mash (clay + manure + water)—this protects against soil infections and promotes rooting (Trunov et al., 2012).
• After planting, water abundantly (3–5 buckets of water per bush) and mulch the root zone with peat, humus, or mowed grass with a layer of 5–8 cm (Hessayon, 1993).

5.4. Balanced Nutrition

A healthy plant has strong immunity. Overfeeding or underfeeding are equally harmful:

• Nitrogen (N): needed in spring for shoot growth. Excess nitrogen causes rapid growth of loose tissues, which are easily affected by powdery mildew and aphids (Buckingham, 2010). The norm is 15–20 g of urea or 20–30 g of ammonium nitrate per sq. m, once, at the beginning of the growing season.
• Phosphorus (P): strengthens roots and increases resistance to diseases. Superphosphate (30–40 g/sq. m) is applied in autumn under digging.
• Potassium (K): increases frost resistance and resistance to fungi and bacteria. Potassium magnesium or potassium sulfate (20–30 g/sq. m)—in autumn and during fruiting (Potapov et al., 2000).
• Microelements: zinc, boron, copper, manganese participate in the synthesis of protective substances. They can be applied as foliar feeding (2 times per season—before flowering and after harvesting) with ready-made complex fertilizers with microelements.

Signals of nutritional deficiency:

• Yellow leaves with green veins—lack of iron or manganese (chlorosis). Treat with iron chelate or manganese sulfate (Tretyakov et al., 2000).
• Brown leaf edges—potassium starvation (Kurennoi et al., 1985).

5.5. Proper Pruning

Pruning is not only a formative technique but also a powerful sanitary measure that removes sources of infection (Hessayon, 1993; Hill & Perry, 2011).

Sanitary pruning (annually, in autumn or early spring):

• Remove all dry, broken, damaged, and diseased branches.
• Cut out shoots affected by bud mites (swollen, rounded buds).
• Remove shoots growing inside the bush, crossing and rubbing against each other—they thicken the crown and worsen ventilation.
• Remove branches older than 5–6 years (for red and white—older than 7–8 years)—they are weaker and more susceptible to diseases (Tarasov et al., 1981).
• For golden currant (more long-lived), remove branches older than 7 years (Dankov, 2015).

Rules for safe pruning:

• Prune in dry weather so that wounds heal faster.
• Use sharp, clean tools.
• After each bush, wipe the pruner with alcohol or a 1% potassium permanganate solution (this is mandatory if viral or bacterial diseases are suspected).
• Cover all cuts with a diameter greater than 1 cm with garden pitch or "Rannet" paste.
• Do not put cut material (especially diseased branches) into compost—burn it (Hessayon, 1993).

5.6. Watering and Mulching

Currant is a moisture-loving plant, but improper watering is one of the causes of fungal diseases.

Watering rules:

• During drought (especially in June–July, during berry filling), water 1–2 times a week, 2–3 buckets per adult bush.
• Water at the root, trying not to wet the leaves—water drops on leaves in hot weather increase the risk of powdery mildew and anthracnose (Buckingham, 2010).
• Avoid drying out and waterlogging. Optimal soil moisture is 70–80% of full field moisture capacity (Potapov et al., 2000).
• Drip irrigation is an ideal option for currants.
• In late October—early November, carry out water-charging irrigation (5–6 buckets per bush) if autumn is dry—this increases winter hardiness and reduces the risk of damage from frost (Trunov et al., 2012).

Mulching:

• Mulch the root zones with peat, humus, compost, or mowed grass with a layer of 5–8 cm.
• Mulch retains moisture, suppresses weeds, provides plants with nutrition, and, most importantly, prevents fungal spores overwintering in the soil from getting onto the leaves (Hill & Perry, 2011).
• Do not use fresh sawdust for mulching—they acidify the soil and deplete it of nitrogen.

5.7. Maintaining Cleanliness of Plantings

Removal of plant residues is a simple but extremely effective preventive measure that is often underestimated (Potapov et al., 2000).

Mandatory measures:

• Annually, in late autumn, collect and burn all fallen leaves (spores of anthracnose, rust, powdery mildew, and gray mold overwinter in them).
• Dig up the root zones and row spacings in autumn and spring—this destroys the overwintering stages of fungi and pests.
• Do not leave weeds in the row spacings—they create additional humidity and can be carriers of diseases (Hessayon, 1993).

5.8. Protective Treatments (Calendar)

The system of preventive treatments is built according to seasons:

Early spring (before bud break, March–April) — "blue spraying":

• Treat bushes and soil with 3% Bordeaux mixture (300 g copper sulfate + 400 g lime per 10 L water) or preparations based on copper oxychloride. This destroys overwintering fungal spores on the bark and in the soil (Hessayon, 1993).
• If there were strong disease outbreaks in the previous season, add urea to the treatment (500–700 g per 10 L water)—it burns spores and simultaneously feeds with nitrogen (Potapov et al., 2000).

Green cone phase (beginning of bud break):

• Treatment against bud mites (acaricides—"Fitoverm", "Aktara", "Inta-Vir") and prevention of powdery mildew (sulfur preparations) (Hill & Perry, 2011).

Before flowering (budding):

• 1% Bordeaux mixture or systemic fungicide ("Skor", "Rayok")—against anthracnose and rust (Buckingham, 2010).

After flowering (10–14 days later):

• Repeat fungicide treatment if the weather is wet.
• If necessary—treatment against aphids and other pests.

During berry growth:

• Use only biopreparations ("Fitosporin-M", "Alirin-B", "Gamair") or folk remedies (garlic infusion, tobacco, soap solution)—chemicals are not recommended during this period (Trunov et al., 2012).

Autumn, after leaf fall:

• 3% Bordeaux mixture or urea (500 g/10 L) on bare branches and soil.
• Removal and burning of fallen leaves and cut branches.

5.9. Control of Vectors (Insects)

Diseases do not come by themselves—they are often brought by insects:

• Bud mite—the main carrier of reversion (phytoplasma) (Kurennoi et al., 1985).
• Aphids—transmit mosaic viruses.
• Leafhoppers and psyllids—spread phytoplasmas and viruses.

Control measures:

• Inspect bushes regularly, especially in May–June.
• If mites are detected (swollen buds), remove them manually or use acaricides before bud break (Hill & Perry, 2011).
• Against aphids, use insecticides ("Fitoverm", "Aktara", "Iskra") or folk remedies (soap solution, ash).
• Carry out treatments in tank mixtures with fungicides (if allowed by instructions).

5.10. Choosing Resistant Varieties

Resistance to diseases is the most important varietal trait:

• Red currant: 'Rovada'—resistant to powdery mildew and anthracnose, 'Jonkheer van Tets'—reliable, high-yielding, 'Red Lake'—known for its resistance (Buckingham, 2010; Westwood, 1993).
• White currant: 'White Versailles'—an old proven variety with good resistance, 'Blanka'—a modern productive variety (Buckingham, 2010).
• Golden currant: 'Venus', 'Laysan', 'Shafak'—resistant to fungal diseases and pests, drought-resistant (Dankov, 2015; Krivko, 2014).

5.11. Preventive Table by Seasons

5.12. Summary: 10 Golden Rules of Prevention

1. Plant currants in the sun, in well-ventilated, drained areas.

2. Choose healthy planting material and resistant varieties.

3. Maintain distances between bushes—do not overcrowd.

4. Regularly carry out sanitary pruning, remove diseased and old branches.

5. Monitor nutrition—fertilize in a balanced way, do not overfeed with nitrogen.

6. Water at the root, avoiding waterlogging and drying out.

7. Annually remove and burn fallen leaves and plant residues.

8. Carry out preventive spraying according to the seasonal calendar.

9. Timely control vector pests (aphids, mites, leafhoppers).

10. Inspect bushes regularly—the earlier the disease is detected, the higher the chance of containing it.

6.1. General Principles of Treating Currant Diseases

1. Make an accurate diagnosis. Not all spots on the leaves are anthracnose, and not every coating is powdery mildew. An incorrectly chosen drug will not help and may even harm. Compare the symptoms with the descriptions from the previous chapters.

2. Treat systematically, not sporadically. A single treatment rarely yields results. Usually, 2–3 treatments are required with an interval of 10–14 days (Hessayon, 1993; Hill & Perry, 2011).

3. Consider the development phase of the plant. Preparations permitted before flowering may be dangerous during flowering (for bees) or during berry ripening (for the consumer) (Potapov et al., 2000).

4. Chemistry is not the only tool. In some cases, biopreparations and agrotechnical measures are effective. Combine methods.

5. Do not hope for a miracle. Viral and phytoplasma diseases cannot be cured. Diseased bushes are removed. The sooner this is done, the lower the risk of infecting neighbors (Hessayon, 1993).

6.2. Treatment of Fungal Diseases

Fungal infections are the only group where chemical treatment is really effective, especially in the early stages.

6.3. Treatment of Bacterial Diseases

Bacterial diseases are much more difficult to treat. Most bactericides do not penetrate the vascular system and cannot destroy bacteria inside tissues (Hill & Perry, 2011).

Bacterial crown gall:

• There is no treatment. If galls are found on the roots, the bush is dug up and burned.
• The soil is disinfected (2% copper sulfate solution—200 g per 10 L water, poured over an area of 1–2 m²). Currants are not planted in this place for 3–5 years (Potapov et al., 2000).

Bacterial blight (Pseudomonas):

• At the first signs (blackening of shoots), cut out the affected branches, capturing 15–20 cm of healthy tissue. Disinfect the tool after each cut.
• Spray the bush with 1% Bordeaux mixture or a copper-containing preparation ("Hom", "Oksihom").
• Repeat treatments every 10 days until symptoms cease (Trunov et al., 2012).
• In case of severe damage (more than 50% of the crown), the bush is removed.

Bacterial wilt (Erwinia):

• Similar to bacterial blight—removal of diseased shoots and copper-containing treatments.
• Effectiveness is low, often the bush dies (Hessayon, 1993).

6.4. Treatment of Viral and Phytoplasma Diseases

The only "treatment method" is removal and destruction of the diseased plant. All attempts to "cure" reversion, mosaic, ring spot, or witches' brooms with chemicals or folk remedies are useless (Kurennoi et al., 1985; Potapov et al., 2000).

Algorithm of actions when a virus/phytoplasma is suspected:

1. Carefully inspect the bush. Compare symptoms with descriptions from Chapter 4.

2. If only one branch is affected, cut it out with a margin of 30–40 cm of healthy tissue.

3. If symptoms are on several branches or throughout the bush, the bush is dug up entirely, leaving no stumps.

4. Immediately burn all removed parts—viruses and phytoplasmas persist in plant residues.

5. Disinfect tools with alcohol or potassium permanganate solution.

What to do with the soil after removing a diseased bush:

• Viruses and phytoplasmas do not persist in the soil for long (unlike fungi and bacteria), but their vectors (mites, aphids, leafhoppers) may remain.
• Do not plant currants in this place for 3–4 years (Hill & Perry, 2011).
• If there are healthy bushes nearby, treat against insect vectors.

6.5. Biological Preparations as an Alternative

More and more gardeners are switching to biopreparations—they are safe, environmentally friendly, and do not accumulate in berries (Trunov et al., 2012; Hill & Perry, 2011).

Advantages of biopreparations:

• Do not cause resistance in pathogens.
• Safe for bees, birds, soil microflora.
• Can be used during berry ripening (waiting period 0–3 days).

Disadvantages:

• Act more slowly than chemical fungicides.
• Require more frequent application (every 7–10 days).
• May be ineffective in case of severe disease development (Hessayon, 1993).

6.6. Safety Precautions When Working with Chemical Preparations

When using pesticides and fungicides, be sure to follow safety precautions (Potapov et al., 2000):

1. Use protective equipment: rubber gloves, safety glasses, mask or respirator, long sleeves.

2. Work in calm weather (morning or evening)—avoid drift of the preparation onto neighboring crops and water bodies.

3. Strictly observe the dosage according to the instructions. Overdose causes burns to plants, while insufficient concentration is ineffective.

4. Do not treat during flowering—this is dangerous for bees and other pollinators (Buckingham, 2010).

5. Observe the waiting periods—the minimum interval between the last treatment and harvest (indicated on the package, usually 7–30 days).

6. Prepare the solution in a special container, do not use food utensils.

7. Do not pour the remaining solution into water bodies or sewers—bury it in the ground away from wells (Hill & Perry, 2011).

6.7. Comparison Table: What Is Treated and What Is Not

6.8. Brief Practical Tips

• Start treatment at the first signs of the disease. The earlier, the better the chances.
• In dry weather, contact preparations work better. Systemic ones—in any weather except rain (Hessayon, 1993).
• Alternate preparations with different mechanisms of action to avoid resistance of pathogens.
• Do not mix untested components—tank mixtures can give unpredictable reactions.
• After treatment, intensify care—fertilizing with potassium and phosphorus helps the plant recover.
• Restore immunity—use growth stimulants ("Epin-Extra", "Zircon") after the stress of disease and treatments.

7.1. Typical Gardener Mistakes

Even experienced gardeners sometimes make mistakes that weaken plants and contribute to the development of diseases. Here are the most common ones.

7.2. Frequently Asked Questions (FAQ)