Physiological disorders

2.1. Drought — Moisture Deficiency

Causes. Prolonged absence of rainfall, insufficient or irregular watering, light sandy and sandy loam soils with low water-holding capacity. Drought can also occur during strong winds that increase evaporation from leaves and soil surfaces (Hall & Sobey, 2013).

How to Recognize. The first signs of moisture deficiency appear on the leaves:

• Leaves become small, pale green, and lose turgor (wilt);
• Leaf edges turn yellow and dry out, then yellowing spreads toward the center;
• In severe drought, leaves curl and prematurely drop;
• Shoots slow growth, internodes shorten, stems become thin;
• Berries become smaller, dry out, lose juiciness and flavor;
• Yield decreases; berries may dry out directly on the bushes (Yaroslavtsev, 2003; Buckingham, 2010).

Why This Happens. With water deficiency, the plant closes its stomata to reduce evaporation. This leads to decreased photosynthesis—carbon dioxide stops entering the leaves. Additionally, nutrients enter the roots only in dissolved form, so when the soil dries out, raspberries experience not only water stress but also nutrient starvation (Hall & Sobey, 2013). Pollination and fruit set are disrupted: at high temperatures and moisture deficit, pollen loses viability, and ovaries drop.

Critical Periods. Raspberries are most sensitive to moisture deficiency during the following phases (Trunov, 2012):

• Active shoot growth (May – June);
• Flowering and fruit setting (late June – July);
• Berry filling (July – August).

Irrigation is essential during these periods, especially in dry weather.

What to Do:

1. Ensure regular watering. In dry periods, water raspberries at least 1–2 times a week, soaking the soil to a depth of 30–40 cm. The watering rate is about 30–40 liters per 1 m² (roughly 3–4 buckets per square meter). It is better to water less frequently but deeply, rather than often and superficially—this way moisture reaches the main root mass (Trunov, 2012).

2. Use drip irrigation. This is the most effective method: water is delivered directly to the root zone, evaporates little, and does not wet the leaves, reducing the risk of fungal diseases. Drip irrigation is particularly beneficial on light soils and in arid regions (Hall & Sobey, 2013).

3. Mulch the soil. A layer of mulch (compost, straw, sawdust, black or dark film) 5–10 cm thick significantly reduces evaporation, retains moisture in the root zone, and protects roots from overheating in hot weather. Mulch also suppresses weed growth, which competes with raspberries for water (Yaroslavtsev, 2003).

4. Improve soil permeability. On sandy soils that dry out quickly, adding organic fertilizers (manure, compost, peat) helps—they increase water-holding capacity. On clay soils, it is important to avoid compaction and regularly loosen the rows.

5. Choose drought-tolerant varieties. For regions with insufficient moisture, prefer varieties with a robust root system and heat resistance. Varieties originating from southern or continental regions generally tolerate drought better (Hall & Sobey, 2013).

2.2. Waterlogging — Excess Moisture

Causes. Prolonged rains, watering without considering weather, high groundwater levels (closer than 1.5–2 m from the surface), heavy clay soils with poor drainage, stagnation of meltwater in spring (Trunov, 2012; Yaroslavtsev, 2003).

How to Recognize.

• Leaves turn yellow, starting from the lower ones, and drop prematurely;
• Shoots become weak and may wilt even when the soil is moist;
• Signs of rot appear at the base of the stems;
• When dug up, roots are dark brown or black, break easily, and rot;
• Plants lag in growth, bushes appear stunted;
• Yield drops sharply, berries are small, watery, and poor-tasting;
• Waterlogged areas often develop root rots (Phytophthora) and fungal diseases (Yaroslavtsev, 2003; Buckingham, 2010).

Why It Is Dangerous. In waterlogged conditions, water displaces oxygen from soil pores. Roots, deprived of respiration, stop absorbing water and nutrients. In anaerobic conditions, pathogenic fungi causing root rots (Phytophthora, Pythium) actively multiply. The situation is especially dangerous in cold weather when decomposition processes slow down, and reduced compounds (ferrous iron, hydrogen sulfide) accumulate in the soil and poison the roots (Trunov, 2012). Long-term flooding (over 20–30 days), even during dormancy, can kill the root system (Trunov, 2012).

What to Do:

1. Ensure drainage. When planting raspberries on heavy soils or in areas with high groundwater, create drainage trenches or plant raspberries on raised beds (15–20 cm high). Place a layer of crushed stone (8–10 cm) and sand in planting trenches to drain excess water (Yaroslavtsev, 2003). In areas with stagnant moisture, drainage pipes can be used.

2. Choose the site wisely. Avoid lowlands where cold air and water accumulate. Prefer sites with a slight slope ensuring natural water runoff or flat, elevated areas.

3. Do not water unnecessarily. Stop watering during rainy periods. Check the soil moisture at a depth of 10–15 cm—if it is excessively wet, postpone watering.

4. Loosen the soil. After rains and watering, loosen the surface layer (5–8 cm) in rows and between rows to break the crust and improve root aeration. Loosening helps excess moisture evaporate and saturates the soil with oxygen.

5. Improve soil structure. Regular application of organic fertilizers and compost makes heavy clay soils more loose and water-permeable, preventing water stagnation (Buckingham, 2010).

6. In case of severe waterlogging with signs of root rot — remove diseased plants, do not plant raspberries in that spot for 4–5 years, and carry out soil rehabilitation (liming, adding organic matter, green manures).

General Recommendations for Watering Raspberries

• In spring (before growth starts), winter moisture reserves are usually sufficient. Additional watering is only needed in a dry spring.
• In May – June, water raspberries 1–2 times a week if there is no rain, especially during shoot growth.
• In July – August, during berry filling, watering should be regular—moisture deficiency at this time directly reduces berry size and quality.
• In late August – September, reduce watering so that shoots ripen and prepare for winter. Excess moisture at this time prolongs vegetation and reduces winter hardiness (Trunov, 2012).
• The optimal watering method is drip irrigation or furrow watering (along the rows). Overhead watering is undesirable during flowering, as it washes away pollen and impairs pollination; it also promotes the spread of fungal diseases (Yaroslavtsev, 2003).
• In hot weather, water early in the morning or evening to avoid leaf scorch and excessive evaporation.

Remember the key point: Raspberries need constant but moderate moisture. Regularly check the soil moisture at a depth of 20–30 cm: if the soil is dry there, water immediately; if it is too wet and sticky, stop watering and ensure air reaches the roots. Moisture balance is the key to health and a bountiful harvest.

3.1. Frost Damage

Frost stress in raspberries manifests in two forms: winter dieback of stems and buds, and damage to flowers and ovaries from spring frosts. Both forms can deprive you of your harvest, but the damage mechanisms and protection methods differ.

3.2. Heat and High Temperatures

The optimal temperature for raspberry photosynthesis is 18–21 °C. When it rises above 25 °C, photosynthesis intensity begins to decline, and at 30–35 °C, growth and fruiting are seriously compromised (Hall & Sobey, 2013).

How to Recognize. Heat stress manifests in a complex way:

• Leaves become pale, lose turgor, edges dry out (leaf scorch);
• In extreme heat (above 40 °C), leaves can completely dry out, turn black, and drop;
• Shoots slow growth, internodes shorten;
• Berries become smaller, soft, lose aroma and juiciness;
• Fruit set decreases due to pollen sterilization (pollen loses viability above 27–30 °C) (Hall & Sobey, 2013);
• White, discolored patches appear on berries under direct sunlight—this is sunburn (Hall & Sobey, 2013).

Why This Happens. At high temperatures, the enzyme Rubisco (a key enzyme in photosynthesis) loses activity, and stomata partially close to reduce water loss through evaporation. This limits carbon dioxide intake and consequently sugar production. Additionally, during overheating, cell proteins denature, and chloroplast membranes are damaged. Fruits, where pigment and sugar accumulation occurs, are particularly affected—this process slows down sharply, and in severe heat, berries can "cook" on the bush (Hall & Sobey, 2013).

What to Do:

1. Ensure abundant watering. Good water supply is the main factor for raspberry resistance to heat. Water frequently (2–3 times a week in intense heat), but avoid water stagnation. Roots supplied with water cool the above-ground parts better through transpiration.

2. Mulch the soil. A thick layer of mulch (sawdust, straw, compost, black film) protects roots from overheating and retains moisture. The soil temperature under mulch can be 5–10 °C lower than on the open surface (Yaroslavtsev, 2003).

3. Use shading nets. In regions with extreme heat (southern latitudes, subtropics), stretch shading nets (30–50% light permeability) over the raspberry plantation to reduce solar radiation intensity and protect leaves and berries from scorching. This is particularly relevant for fruits during ripening (Hall & Sobey, 2013).

4. Choose heat-tolerant varieties. Prefer varieties bred in warm regions or originating from Asian species, which are genetically more resistant to high temperatures. Such varieties often have a more powerful root system and dense leaf structure, reducing water loss (Hall & Sobey, 2013).

5. Increase row spacing and ensure good ventilation. Timely removal of fruited canes and shoot thinning improve air circulation, which helps cool the bushes. Avoid overcrowding in heat—it creates a greenhouse effect within the canopy.

3.3. Sunburn on Fruits and Leaves

Sunburn is a direct consequence of the combination of high temperature and intense ultraviolet radiation. It manifests on fruits as white or pale-yellow patches on the berries (so-called "white drupelets"), and on leaves as dry spots or browning of edges (Hall & Sobey, 2013).

Causes. Burns are most severe during sudden weather changes: after rain or heavy watering, when water droplets remain on berries and then bright sun comes out. Droplets act as lenses, focusing sunlight and causing local tissue overheating. Burns also occur where foliage has been removed (e.g., during pruning), leaving fruits unprotected from direct rays (Hall & Sobey, 2013).

How to Recognize. Whitened, discolored drupelets appear on berries; they do not ripen, remain hard, and taste bitter. On leaves—dry brown or whitish spots, often on edges or tips.

What to Do:

1. Protect fruits from direct sunlight. In hot regions, use shading nets or plant raspberries so that during the hottest hours they are in partial shade (e.g., near tall trees or structures that provide filtered shade).

2. Avoid overhead watering during sunny hours. Water at the root (drip irrigation, furrow) or in the evening when the sun is setting. If using sprinkling, do it only early in the morning so leaves dry before peak solar activity.

3. Leave enough foliage. When pruning and thinning shoots, try not to expose the tips, especially in varieties with large berries. Leaves create natural shade for the fruits.

4. Choose sun-tolerant varieties. Some varieties (especially Scottish breeding) develop a dense waxy bloom or heavy pubescence on berry surfaces, protecting them from burns. Study variety descriptions before planting (Hall & Sobey, 2013).

5. In hot and sunny weather, water regularly to maintain leaf turgor, which creates a "microclimate" for the fruits and reduces heating.

Preventing Temperature Stress: General Principles

• Choose the right site. Avoid lowlands (where cold air stagnates) and south-facing slopes with excessive heating. Level areas with a slight southwest slope or sheltered from wind are optimal (Trunov, 2012).
• Choose the right varieties. Consider your zone's climate: winter hardiness, heat tolerance, and resistance to return frosts.
• Prepare for winter promptly. Do not delay with bending down and covering with snow.
• Regular care (watering, mulching, pruning) increases the overall resilience of plants to any adverse factors.
• Monitor the weather forecast. A few days before severe frosts, heatwaves, or frosts, have time to implement protective measures.

4.1. Nutrient Deficiencies

Almost all deficiencies manifest through changes in leaf color, shape, and shoot growth patterns. It is important to remember: external symptoms are merely a reflection of internal disturbances. The same symptom (e.g., chlorosis—leaf yellowing) can be caused by different reasons. Therefore, observations should be supplemented with soil analysis.

4.2. Excess of Nutrients (Toxicity)

Excess of elements is less common than deficiency, but in some regions and conditions, it can cause serious damage.

Diagnosis and General Nutrition Recommendations

1. Conduct soil analysis (preferably every 2–3 years)—this is the basis for calculating fertilizer doses. Without analysis, you are working "blindly."

2. Use balanced complex fertilizers specifically designed for fruit and berry crops. They contain macro- and microelements in optimal ratios.

3. Apply organic fertilizers (manure, compost, well-rotted manure) annually or every 2 years—they not only feed plants but also improve soil structure, increase moisture capacity and buffering, reducing the risk of both deficiencies and toxicity (Buckingham, 2010).

4. Use foliar feeding (leaf spraying) for rapid correction of acute microelement deficiencies (iron, boron, magnesium, manganese, zinc). They act faster than soil applications but do not replace basic root nutrition.

5. Consider the development phase: spring—focus on nitrogen; during flowering and setting—on boron and phosphorus; during berry filling—on potassium; autumn—on phosphorus and potassium for maturation and winter hardiness.

6. Observe the plants. Regular inspection of leaves and shoots will help notice early signs of disorders. Compare the appearance of healthy and problematic bushes—this makes deviations easier to spot.

5.1. Unsuitable Acidity (pH)

Soil acidity (pH) determines the availability of almost all nutrients. With unfavorable pH, even abundant fertilization will be ineffective because elements become unavailable to plants.

5.2. Soil Salinity

Causes. Accumulation of soluble salts in the soil occurs in arid and semi-arid regions when irrigating with mineralized (brackish) water, with insufficient drainage, under drip irrigation without leaching irrigation, and with excessive application of mineral fertilizers (especially chloride forms). In dry climates, salts are not leached by precipitation but accumulate in the topsoil (Trunov, 2012).

How to Recognize. With mild to moderate salinity, leaves turn yellow, edges and tips dry out and become brown (marginal burn). Leaves may be small, plants appear stunted. With severe salinity, leaves dry up completely, shoots die, and the bush dies. Salinity is often accompanied by reduced root growth and impaired water supply—even with moist soil, leaves wilt (Buckingham, 2010).

Why It Is Dangerous. High salt concentration in the soil solution creates high osmotic pressure. Roots cannot absorb water because water tends to move from roots to the soil (osmosis). Physiological drought occurs. Additionally, excess chlorine and sodium are toxic to cells, disrupting enzymatic processes. Raspberries are moderately sensitive to salinity: the maximum permissible chloride concentration in the root zone is 0.3 mg-eq/100 g of soil, sulfates—2.0 mg-eq/100 g (Trunov, 2012).

What to Do.

1. Use quality water for irrigation. If water from a well or borehole is brackish, mix it with rainwater if possible or use desalination systems.

2. Ensure a regular leaching regime. In regions with drainage, periodically conduct abundant irrigation with clean water (rate—800–1000 m³/ha, i.e., about 80–100 l/m²) to leach salts from the root zone. However, without drainage, this can worsen the situation.

3. Apply organic fertilizers. Peat, compost, manure improve soil structure, increase its moisture capacity and buffering, and partially bind salts.

4. Use drip irrigation cautiously. With drip irrigation, salts concentrate in the wetting zone, especially without leaching irrigation. Alternate drip irrigation with sprinkling or abundant watering to flush the profile.

5. Choose tolerant varieties and rootstocks. Some raspberry forms tolerate salinity better. In saline regions, prefer varieties with a powerful root system.

6. Avoid applying chloride-containing fertilizers (potassium chloride, potassium salt). Use sulfate forms—potassium sulfate, magnesium sulfate.

5.3. Soil Compaction and Oxygen Deficiency

Causes. Compaction occurs on heavy clay soils, with excess moisture followed by drying, with frequent cultivation in wet weather, with foot traffic between rows, and with lack of organic fertilizers that loosen the structure. Raspberry roots need constant oxygen access for respiration and nutrient absorption (Trunov, 2012).

How to Recognize. With compacted soil, raspberries grow slowly, leaves become pale and yellow (often from the lower tiers). Shoots are weak, root system is superficial and poorly developed. When dug up, roots may be brown with signs of rot. In hot weather, plants wilt even with sufficient moisture, as roots cannot function properly. Root rots often develop on compacted soils, especially in wet weather (Buckingham, 2010; Trunov, 2012).

Why This Happens. In compacted soil, pore space is reduced, and oxygen content drops to critical levels (less than 5–8% by volume). Roots switch to anaerobic respiration, which is inefficient and leads to accumulation of toxic products (alcohols, organic acids). Absorption of water and nutrients is impaired. In anaerobic conditions, pathogenic fungi (Phytophthora, Pythium) become active, causing root rots. Compaction combined with waterlogging is particularly dangerous (Trunov, 2012).

What to Do.

1. Loosen the soil regularly. Surface loosening (to a depth of 5–8 cm) in the root zone and between rows breaks the crust and improves aeration. However, deep cultivation (more than 10–15 cm) should be done carefully to avoid damaging the shallow raspberry roots.

2. Apply organic fertilizers. Manure, compost, peat, green manures improve the structure of heavy soils, making them more loose and water-permeable. On loamy and clay soils, the recommended organic dose is 8–12 kg/m² for digging or as mulch (Yaroslavtsev, 2003).

3. Create drainage and raised beds. On heavy soils and in areas with high groundwater levels, plant raspberries on beds or ridges 15–20 cm high to drain excess water and ensure aeration.

4. Avoid walking and working on wet soil. Do not loosen or walk between rows when the soil is wet—this leads to severe compaction.

5. Use mulching. A layer of mulch (straw, sawdust, compost, black film) not only retains moisture and suppresses weeds but also protects the topsoil from compaction and overheating, promotes the development of soil microflora that loosens the soil (Yaroslavtsev, 2003).

6. Periodically perform deep loosening (chiseling) between rows (to a depth of 20–25 cm) to break the plow pan if it has formed. This is done in autumn, after harvest, when roots are no longer actively growing, but before severe frosts.

5.4. Complex Soil Problems and Their Prevention

Often, several factors combine on one site: acidic or alkaline reaction, salinity, and compaction simultaneously. Therefore, the approach should be systematic:

• Conduct soil analysis (pH, salt content, major elements, granulometric composition). This is the only reliable way to determine exactly what is wrong with your soil.
• Improve the soil at the site preparation stage: dig deeply, add organic matter, carry out liming or acidification according to the analysis (Yaroslavtsev, 2003).
• When establishing a new plantation, consider the site's suitability: avoid lowlands with stagnant water, saline and rocky soils. If the soil is heavy, prepare drainage or plant raspberries on ridges.
• Regularly maintain the topsoil in a loose state using mulching and surface loosening.
• Monitor the water regime—excess water is as harmful as its deficiency and contributes to compaction and salinity.

Remember: healthy soil is a living, structured environment with developed microflora and sufficient organic matter content. Such soil provides raspberries with everything they need and makes plants resilient to diseases and pests.

6.1. Herbicide Damage

Causes. The most common case is herbicide drift by wind from neighboring fields treated with agricultural machinery. Herbicides from the groups 2,4-D, dicamba, and other phenoxyacetic acid derivatives are particularly dangerous. Raspberries are extremely sensitive to these substances: even microscopic doses (as vapors or droplet "mist") can cause characteristic deformations. Damage is also possible during careless weed control within the raspberry plantation itself (if the gardener uses herbicides without considering crop sensitivity) or when using garden tools that have herbicide residues (Buckingham, 2010).

How to Recognize. Symptoms depend on the herbicide type, but are most characteristic for growth regulators (2,4-D, dicamba):

• Leaves become narrow, thread-like, curled, wrinkled, with uneven edges;
• Shoots become distorted, thickened, or conversely, brittle;
• Leaf veins may be deformed, thickened; sometimes leaves take on a "crinkled" appearance;
• Growth slows significantly, flowers are underdeveloped, ovaries drop;
• In severe cases, shoot tips die off, and the bush may die (Buckingham, 2010; Yaroslavtsev, 2003).

Why This Happens. Herbicides from the 2,4-D and dicamba groups are synthetic auxin (growth hormone) analogs. They disrupt the plant's hormonal balance, causing abnormal cell division and elongation, resulting in tissue distortion and damage to vascular systems. Raspberries are highly sensitive, so even fractions of a gram of active ingredient per hectare can cause visible deformations (Buckingham, 2010).

What to Do.

1. Prevention is the main defense. If agricultural fields are nearby, try to plant raspberries on the leeward side or create windbreaks (tall shrubs, trees) that will intercept airflow. Agree with neighbors on treatment times so they do not spray in windy weather towards your property.

2. React immediately. At the first signs of herbicide drift, water the raspberries abundantly with clean water—this will help wash some substance off the leaves and reduce absorption. You can also carry out foliar feeding with complex fertilizer (with microelements) and growth stimulants (e.g., humates, epin)—this stimulates the growth of new healthy shoots and helps the plant restore normal hormonal balance faster.

3. Remove severely damaged shoots to avoid exhausting the bush and allow new, healthy replacement shoots to develop. If only the tops are damaged, cut them back to undamaged buds.

4. In case of systematic herbicide drift, consider moving the raspberry plantation to protected cultivation (e.g., under a plastic tunnel) or changing the planting site.

6.2. Excess Fertilizers ("Salt Burn" of Roots)

Causes. Application of excessively high doses of mineral fertilizers, especially dry or without sufficient watering; placing fertilizers too close to roots; using poor-quality fertilizers with high chlorine or other harmful impurities; applying fertilizers to dry soil (Buckingham, 2010; Yaroslavtsev, 2003).

How to Recognize. Excess fertilizer manifests similarly to soil salinity:

• Leaves turn yellow and dry out, starting from the edges (marginal burn);
• Brown spots appear on leaves, edges curl;
• Roots darken, become brittle, rot (when dug up);
• Shoots are weak, growth slows, leaves may drop;
• In severe cases, the bush dies.

Why This Happens. High salt concentration (nutrient elements) in the soil solution creates high osmotic pressure; roots cannot absorb water—physiological drought occurs. Additionally, some elements (e.g., ammonia nitrogen) in high concentrations are toxic to cells. Dry granular fertilizers that fall into the root zone in pure form and cause chemical burns are particularly dangerous (Buckingham, 2010).

What to Do.

1. Strictly adhere to doses. Always follow recommendations based on soil analysis, not "average" rates. For young plants, fertilizer doses should be lower than for fruiting ones.

2. Distribute fertilizers evenly and incorporate them into the soil, but no closer than 10–15 cm from the stem base to avoid localized overdosing.

3. Water abundantly after application. This helps dissolve fertilizers and distribute them evenly in the soil, reducing the risk of root burn.

4. At signs of overfeeding, stop fertilizing and carry out several abundant waterings with clean water to leach excess salts from the root zone (if drainage exists and soil is permeable). You can also mulch the soil with organic matter, which will bind some salts and buffer the concentration.

5. In the future, use slow-release fertilizers (e.g., organo-mineral granules with slow release)—they reduce the risk of sharp concentration spikes.

6.3. Salt Stress (General)

This type of stress is closely related to the previous ones, but its causes are broader: it can be caused by irrigation with brackish or hard water, long-term use of drainage water with high salt content, shallow saline groundwater, as well as natural soil salinization in arid regions (Trunov, 2012; Buckingham, 2010).

How to Recognize. Symptoms are similar to excess fertilizers: marginal leaf burn (yellowing and browning along edges), yellowing and premature dropping of lower leaves, growth inhibition, reduced yield. However, unlike localized fertilizer burn, salt stress usually manifests uniformly across the entire plantation or over large areas, especially during dry periods (Buckingham, 2010).

Why It Is Dangerous. Salts (especially sodium and calcium chlorides and sulfates) disrupt the plant's water balance, hinder water absorption by roots, and chloride and sodium ions are toxic to cells. Potassium and calcium metabolism is disrupted, further weakening the plants. Raspberries are moderately sensitive to salinity (Trunov, 2012).

What to Do.

1. If possible, use low-salt water for irrigation. If water from a well or borehole is brackish (electrical conductivity above 1.5–2 mS/cm), mix it with rainwater if possible or use reverse osmosis systems.

2. Carry out leaching irrigations (abundant watering with clean water) during periods when drainage is available to leach salts from the root zone. However, without drainage, this can lead to flooding and worsen the problem—in that case, switch to drip irrigation with moisture control and combine it with mulching.

3. Apply organic fertilizers (manure, peat, compost). They improve soil structure, increase its buffering capacity, and promote binding of salts into immobile complexes.

4. Create a drainage system. In areas with salinity due to capillary rise of salts from groundwater, it is necessary to divert them from the root zone using deep drainage and regular loosening to break capillary rise.

5. Avoid applying chloride-containing fertilizers (potassium chloride, potassium salt). Prefer sulfate forms (potassium sulfate, ammonium sulfate), which do not contain chlorine and are less toxic.

6. In saline regions, choose varieties and rootstocks with increased salt tolerance. Although breeding for salt tolerance in raspberries is less developed than in some other crops, some raspberry genotypes may tolerate moderate salinity better.

6.4. Pesticide Poisoning (Insecticides, Fungicides)

Although pesticides are used to protect against diseases and pests, their improper use (overdose, violation of treatment timing, application in heat) can cause chemical damage to leaves and fruits—the so-called phytotoxic effect (Buckingham, 2010).

How to Recognize. Symptoms depend on the preparation and concentration:

• Brown spots appear on leaves, edges curl;
• Leaves may turn yellow and drop;
• Young shoots become distorted, growth slows;
• Flowers and ovaries drop;
• Berries become covered with necrotic dots or spots.

What to Do.

• Follow the instructions for the preparation precisely: dose, concentration, treatment timing, recommended interval between treatment and harvest.
• Do not apply in hot weather (above 25–27 °C) and in bright sun—this increases tissue damage.
• Check the compatibility of preparations in tank mixtures—some pesticides increase phytotoxicity when mixed.
• At the first signs of burn, spray the raspberries with clean water and stop using the preparation.

General Preventive Measures Against Chemical Stress

• Follow regulations—always read instructions on fertilizer and pesticide packaging carefully.
• Apply fertilizers in split doses—better several times in small doses than once in a large one.
• Water after fertilizer application and in dry weather—this prevents salt accumulation in the root zone.
• Use mulch to protect roots from sharp fluctuations in salt concentration.
• Be mindful of neighbors. If field work with herbicides is being carried out nearby, try to limit the airflow to your raspberry plantation.
• Keep a treatment log so that in case of a problem, you can quickly identify the potential cause.

Remember: chemical stress is one of the most unpleasant problems because it can appear suddenly and severely affect bush health. However, most such cases can be prevented by simple attention to dosages and application conditions.

7.1. Biennial Bearing (Alternating High and Low Yields)

The Problem. Many raspberry varieties are prone to biennial bearing: in one year, bushes give a bountiful harvest ("on" year), and the next year, a very meager or zero harvest ("off" year). This is one of the most common complaints among gardeners (Trunov, 2012).

Causes. In a high-yielding year, the plant spends an enormous amount of assimilates on forming berries. By the time the crop matures, reserves of carbohydrates and nutrients are depleted. Flower bud initiation for the next year occurs in July–August, when the bush is still feeding the ripening crop. As a result, few flower buds are initiated, and the next year's yield drops sharply. This is a vicious cycle: abundant yield → depletion → weak bud initiation → low yield → resource accumulation → abundant yield (Trunov, 2012; Yaroslavtsev, 2003).

The expression of biennial bearing varies among varieties. Some varieties show sharp periodicity (high-yield years alternate with nearly zero ones), some are weakly periodic, and some varieties bear fruit annually (regularly) (Trunov, 2012).

What to Do.

1. Shoot thinning. Remove excess young shoots in May–June, leaving 6–8 of the strongest per bush, and 10–12 shoots per 1 m of row (for ribbon cultivation). This reduces competition for light and nutrients, improves flower bud initiation, and allows a full crop to form without depletion (Yaroslavtsev, 2003).

2. Double pruning. For varieties with drooping tips (Novost Kuzmina, Alyy Parus, Malakhovka), shorten the canes in spring at the bending point—this enhances branching and increases the number of fruiting laterals. For upright varieties, summer pinching (pinching out) of young shoots in June, when they reach 60–90 cm, can be done—this induces branching and increases the next year's yield (Yaroslavtsev, 2003).

3. Timely removal of fruited canes. Immediately after harvest (in July–August), cut out all fruited canes at the base. This improves light and nutrition for the remaining young shoots, promoting better flower bud initiation. The earlier you remove fruited canes, the better the conditions for initiating the next year's crop (Yaroslavtsev, 2003).

4. Balanced nutrition. During flower bud initiation (the second half of summer), provide plants with phosphorus and potassium (apply superphosphate and potassium sulfate). Nitrogen at this time is excessive—it stimulates shoot growth at the expense of bud initiation. In autumn, apply organic matter during digging.

5. Using remontant varieties. Remontant raspberries fruit on current-year shoots (in August–September). After the autumn harvest, all above-ground parts are cut down, eliminating the problem of wintering and biennial bearing. The crop forms on annual shoots, and periodicity does not occur (Yaroslavtsev, 2003).

6. Timely plantation renewal. On old, overloaded, and depleted plantations, biennial bearing becomes more acute. Renew the raspberry plantation every 8–10 years, moving it to a new site.

7.2. Insufficient Pollination and Poor Fruit Set

Causes. Raspberries are cross-pollinated plants. For successful pollination and fruit set, insect pollinators (bees, bumblebees) are necessary. Unfavorable weather during flowering (rain, strong wind, heat above 27 °C) reduces bee flight and pollen viability. Problems also arise from a lack of pollinator varieties (if only one variety is planted) or improper selection of varieties with incompatible pollen (Hall & Sobey, 2013; Yaroslavtsev, 2003).

How to Recognize. Flowering is abundant, but few ovaries set; flowers drop without forming berries. Berries that do set may be small, misshapen, with underdeveloped drupelets ("crumbly"). Yield is low.

Why This Happens. Many raspberry varieties exhibit partial self-sterility—pollen from the same variety does not ensure adequate pollination and fruit set. Even in self-fertile varieties, cross-pollination significantly increases yield. Bees and bumblebees are most effective for raspberry pollination, as raspberry flowers have nectar that attracts insects. At temperatures below 15 °C and above 30 °C, insect flight decreases, and pollen loses viability (Hall & Sobey, 2013).

What to Do.

1. Plant several raspberry varieties with coinciding flowering periods. The distance between varieties should be small (up to 20–30 m) for effective cross-pollination. Variety mixtures (e.g., red and yellow varieties) have proven effective.

2. Attract pollinating insects. Sow honey plants near the raspberry plantation (phacelia, buckwheat, mustard, sweet clover). During flowering, do not use insecticides toxic to bees. In protected cultivation (greenhouses, tunnels), you can place bee hives or bumblebee colonies.

3. Create favorable conditions for pollination. Pollination worsens in light wind and rain—in this case, artificial supplementary pollination (gentle shaking of branches in the middle of the day) or installing windbreaks can be used.

4. Choose varieties with a high degree of self-fertility for regions with unstable weather during flowering (continental climate, rainy summers). However, even in self-fertile varieties, cross-pollination increases yield.

5. Protect flowers from frost (see Chapter 3). Frost-damaged flowers are not pollinated and drop.

7.3. Aging of the Rootstock and Reduced Shoot-Bearing Capacity

The Problem. Raspberries have a perennial root system but a biennial cycle for the above-ground part (a cane lives for two years). The rootstock (underground part) lives for 8–12 years, but with age, its ability to produce vigorous replacement shoots decreases. Old bushes produce many weak, thin shoots that bear fruit poorly (Yaroslavtsev, 2003).

How to Recognize. On plantations older than 8–10 years, many weak, low-growing shoots appear, leaves become smaller, berries become small, and yield decreases. Bushes look "thinned out" even with good care.

Why This Happens. The rootstock gradually ages: toxic metabolic products accumulate, the number of active buds decreases, and nutrient supply worsens. Additionally, specific diseases and pests accumulate in the old location, and the soil is depleted (Yaroslavtsev, 2003).

What to Do.

1. Timely plantation renewal. The optimal productive lifespan of a raspberry plantation is 8–10 years. Then it should be grubbed out and a new one established in a different location, preferably after 3–4 years of other crops (not after solanaceous plants, strawberries, or raspberries themselves). This prevents disease accumulation and soil depletion (Cornell Guide, 2003; Yaroslavtsev, 2003).

2. Rejuvenation of bushes. If you do not want to establish a new plantation, you can try to rejuvenate old bushes: in spring, dig up and remove the old central part of the rootstock (4–5 years old), leaving young lateral shoots and roots. After rejuvenation, the bush recovers faster, but this method is not as effective as complete replacement.

3. Using own-rooted plants. In varieties prone to producing suckers, you can form new bushes from young suckers appearing 1–2 m from the old bush. Gradually, old bushes are removed, and the plantation "moves" using the young plants (the "walking rows" technique, according to Yaroslavtsev, 2003).

4. Regular application of organic fertilizers (compost, manure) throughout the plantation's life slows down aging and maintains soil fertility.

7.4. Competition Between Young Shoots and Fruiting Canes

The Problem. In traditional raspberry cultivation (bush or ribbon method), a single bush simultaneously supports fruiting canes and young replacement shoots (which will bear fruit the following year). They compete for light, water, and nutrients. As a result, fruiting canes receive fewer resources, berries become smaller, and young shoots grow weaker, reducing future yields (Yaroslavtsev, 2003).

How to Recognize. In dense plantings (more than 20 shoots per 1 m of row), a reduction in berry weight and quality is observed, along with weak development of young shoots. Bushes are poorly ventilated, which also promotes diseases.

What to Do.

1. Shoot thinning. Regularly (in May–June) remove excess young shoots, leaving 6–8 of the strongest per bush (or 10–12 per 1 m of row). This reduces competition and ensures better nutrition for the remaining shoots (Yaroslavtsev, 2003).

2. Separate cultivation (regulated fruiting periodicity technology). The essence: on one part of the plantation in a given year, only fruiting canes are grown (removing all young shoots), while on another part, only young shoots for the future crop are grown (removing flower stalks). The roles are reversed the following year. This allows significant reduction of competition, improved lighting, and increased yield by 2–2.5 times. Particularly effective on varieties with high shoot-forming ability (Yaroslavtsev, 2003).

3. Timely removal of fruited canes. Immediately after harvest, cut out fruited canes so they do not shade young shoots and compete for nutrients.

4. Use of trellis. Tying canes to a trellis improves light and air access to all parts of the bush, reducing density and competition.

7.5. Disruption of Flower Bud Initiation

The Problem. Flower buds in raspberries are not initiated in spring, but in the previous year—in July–August. If the plant experienced stress during this period (drought, lack of light, crop overload, disease), bud initiation will be weak, and the next year's yield will be low (Trunov, 2012; Yaroslavtsev, 2003).

How to Recognize. In spring, there are few fruiting laterals on the canes, buds are weak, many do not open. Yield is reduced, even if plants look healthy externally.

What to Do.

1. Ensure good canopy lighting. Do not overcrowd plantings, timely remove excess shoots and fruited canes. The more light leaves receive in summer, the better the flower bud initiation.

2. Maintain optimal water regime in July–August. Drought during this time is particularly detrimental to bud initiation. Water regularly (see Chapter 2).

3. Provide balanced nutrition in the second half of summer. Apply phosphorus-potassium fertilizers (superphosphate and potassium sulfate) in July–August. Nitrogen is not applied or applied minimally at this time, to avoid stimulating shoot growth at the expense of bud initiation.

4. Do not allow crop overload. If you see that the current year's crop promises to be very abundant, carry out partial removal of ovaries (manually or chemically)—this will reduce the load on the plant and improve bud initiation for the next year.

5. Remove fruited canes in a timely manner (immediately after harvest) so they do not shade young shoots on which buds are initiated.

7.6. Ovule Drop (Physiological)

Causes. Even after successful pollination, some ovaries may drop. This is a physiological self-regulation process: the plant "sheds" excess fruits it cannot "support" due to resource shortages (water, light, nutrition) or stress (drought, heat, frost, disease). Drop is particularly severe during the "June drop" (when ovaries the size of a pea drop) and during pre-harvest drop (when berries fall before ripening) (Trunov, 2012; Buckingham, 2010 – from general principles).

How to Recognize. A significant number of ovaries (more than 20–30%) drop without reaching maturity. Many small dried ovaries are found on the ground under the bushes.

What to Do.

1. Maintain optimal water regime. Lack or excess of moisture during ovary growth is a common cause of drop. Water regularly (see Chapter 2).

2. Avoid sharp temperature fluctuations. Protect plants from frost and intense heat (see Chapter 3).

3. Provide balanced nutrition during ovary growth (potassium, phosphorus, boron). Foliar boron applications (0.1–0.2% boric acid solution) during budding and early flowering improve fruit set.

4. Manage the load. If there are too many ovaries, they will compete with each other, and some will inevitably drop. Regulate the number of shoots and, if necessary, thin the ovaries (especially in large-fruited varieties).

5. Protect the leaf apparatus. Leaves provide fruits with carbohydrates. Diseases and pests damaging leaves increase ovary drop. Timely control diseases and pests (see the disease and pest chapter in other articles).

General Recommendations for Increasing Raspberry Yield

• Proper selection of varieties suited to your climate and goals (summer or autumn fruiting, resistant to diseases and stress).
• Balanced nutrition throughout the growing season (with an emphasis on nitrogen in spring, and phosphorus and potassium in the second half of summer).
• Regular pruning and shoot thinning—the key to managing yield and berry quality.
• Maintaining optimal soil moisture and protection from extreme temperatures.
• Timely plantation renewal (every 8–10 years) to maintain high productivity.
• Attracting pollinators and protecting flowers from adverse weather.

Remember: raspberry yield is the result of a complex interaction between external conditions and internal physiological processes. Understanding these mechanisms allows you to influence them purposefully and obtain stable, high yields.

8.1. Choosing the Right Site — The Foundation of Prevention

Mistakes in choosing a site for a raspberry plantation are difficult to correct later. Therefore, pay maximum attention to this stage.

Basic Site Requirements (Cornell Guide, 2003; Yaroslavtsev, 2003):

1. Sunlight. Raspberries should receive sunlight for most of the day. In shade, shoots elongate, fewer flower buds are initiated, berries become smaller, more watery, and less sweet. An exception is regions with very hot climates, where slight shading during midday hours may be beneficial to protect against sunburn (Hall & Sobey, 2013).

2. Wind protection. Strong winds desiccate shoots in winter, damage flowers and ovaries in spring, and reduce pollinator activity. Ideally, place the plantation along fences, building walls, or surrounded by windbreaks of tall shrubs. In northern regions, protection from cold winds is especially important (Yaroslavtsev, 2003).

3. Topography. Avoid lowlands—cold air stagnates there, increasing flower damage from spring frosts. Prefer level areas or gentle slopes (southern or south-western exposure) that provide good drainage of meltwater and natural ventilation (Trunov, 2012).

4. Groundwater level. Groundwater should be no closer than 1.5–2 m from the surface. Higher levels risk waterlogging and root rots (Trunov, 2012).

5. Predecessors. Do not plant raspberries after crops affected by verticillium wilt: tomatoes, potatoes, peppers, eggplants, as well as after strawberries and raspberries themselves. The best predecessors are green manures (lupine, mustard, phacelia), legumes, cucurbits, and root crops (Cornell Guide, 2003; Yaroslavtsev, 2003). The interval between raspberry plantings on the same site should be a minimum of 2–4 years, and 6–8 years if viral infections are present.

8.2. Soil Preparation — The Foundation of Health

High-quality soil preparation before planting lays the foundation for the health and productivity of the raspberry plantation for years.

1. Conduct soil analysis (pH, content of major elements, salts). This is the only reliable way to determine if your site needs liming, acidification, or high doses of organic matter. Take soil samples from a depth of 20–25 cm from 5–10 points on the site, mix thoroughly, and send to an agrochemical laboratory (Yaroslavtsev, 2003).

2. Adjust acidity. The optimal pH for raspberries is 5.5–6.5.

• On acidic soils (pH below 5.0) carry out liming 1–2 years before planting: apply dolomite flour (200–600 g/m² depending on soil type) during deep digging.
• On alkaline soils (pH above 7.0) use acidification: apply sulfur (30–100 g/m²) or acidic peat, use physiologically acidic fertilizers (ammonium sulfate, potassium sulfate).
• Dolomite flour is preferable to lime as it contains magnesium and does not cause a sharp pH spike (Buckingham, 2010; Trunov, 2012).

3. Apply organic fertilizers. During digging (in autumn or 2–3 weeks before planting), apply 10–12 kg/m² of well-rotted manure, compost, or humus. Organic matter improves soil structure, increases its moisture capacity, enriches it with nutrients, and promotes the development of beneficial microflora (Yaroslavtsev, 2003).

4. Improve drainage on heavy soils. If groundwater is high or the soil is clayey, create drainage. Place a layer of crushed stone (8–10 cm) and sand in planting trenches, or plant raspberries on raised beds 15–20 cm high (Yaroslavtsev, 2003).

5. Remove perennial weeds (couch grass, sow thistle, dandelion) before planting. This facilitates future care and reduces competition for moisture and nutrients.

6. If necessary, limit root spread. If you plan ribbon cultivation, you can bury barriers (slate, sheet metal, roofing felt) along the walls of the planting trench to a depth of 40–50 cm. This prevents uncontrolled raspberry spread beyond the row (Yaroslavtsev, 2003).

8.3. Choosing Healthy Planting Material

Using healthy, true-to-type, verified saplings is a critically important preventive element. Most viral and bacterial diseases are introduced with planting material (Cornell Guide, 2003; Yaroslavtsev, 2003).

Rules for Selecting Saplings:

• Buy planting material from nurseries with a good reputation or trusted suppliers.
• Saplings should be certified, free from viruses and diseases. The root system should be well-developed, fibrous, without swellings or growths (signs of crown gall).
• Shoots should be healthy, without spots, cracks, swellings (galls), or signs of pest damage.
• For regions with severe winters, prefer zoned varieties—adapted to local climatic conditions.
• If you collect planting material from your own plantation, take it only from absolutely healthy, highly productive bushes, not older than 3–4 years.

8.4. Care System: Water, Nutrition, Mulching

Watering (see Chapter 2):

• In dry periods, water regularly, especially during active shoot growth, flowering, and berry filling.
• Use drip irrigation or furrow irrigation, avoiding wetting leaves and flowers.
• Maintain soil moisture in the root zone (30–40 cm) at 75–80% of field capacity.
• Reduce watering in the second half of August–September for shoot maturation.

Fertilizers (see Chapter 4):

• Apply fertilizers based on soil analysis and considering the growth phase.
• In spring—focus on nitrogen (urea, ammonium nitrate) for shoot growth.
• During flowering and fruit set—phosphorus and boron to improve fruit formation.
• During berry filling and in autumn—potassium and phosphorus for berry quality and winter hardiness.
• Annually or every 2 years, apply organic fertilizers (10 kg/m² of compost or humus) for digging or as mulch.

Mulching:

• A mandatory practice. A layer of mulch (straw, mown grass, sawdust, compost, black film) 5–10 cm thick:
• Retains soil moisture;
• Suppresses weed growth;
• Protects roots from overheating and cooling;
• Enriches soil with organic matter as it decomposes;
• Reduces soil compaction and improves its structure (Yaroslavtsev, 2003).
• In winter, mulch can be left, but in cold regions, in spring, it is lightly pulled back from the bush base so the soil warms up faster.

8.5. Pruning and Bush Formation

Pruning is a powerful tool for preventing physiological disorders and increasing yield. Proper pruning regulates light conditions, reduces competition for nutrients, improves ventilation, and stimulates flower bud initiation.

Basic Pruning Rules (Yaroslavtsev, 2003):

1. Removal of fruited canes. Immediately after harvest, cut out all canes that have fruited, at the base. This improves conditions for young shoots, reduces disease risk, and frees space for growth.

2. Thinning young shoots. In May–June, remove all weak, thin, diseased, and excess replacement shoots and suckers. Leave 6–8 of the strongest per bush (or 10–12 per 1 m of row for ribbon cultivation). Cut the rest at soil level—the earlier, the better, to avoid wasting assimilates (Yaroslavtsev, 2003).

3. Shortening canes. In spring, before bud break, shorten the canes left for fruiting to 1.6–1.8 m (or to the first well-overwintered bud). This stimulates branching and increases berry size.

4. Pinching (stopping) young shoots. In June, when shoots reach 60–90 cm, pinch their tips (remove 3–5 cm). This induces branching and increases the fruiting zone in the following year. Particularly effective for varieties with high shoot-forming ability and for upright blackberries (Yaroslavtsev, 2003).

5. Sanitary pruning. During the season, remove all suspicious shoots—those with spots, distorted, damaged by pests, or frostbitten. It is best to burn them to prevent the spread of infections (Buckingham, 2010).

8.6. Winter Preparation and Frost Protection

In regions with severe winters, preparing raspberries for winter is a critically important preventive measure (see Chapter 3).

1. Bend down the stems for winter in September–October, while they are flexible. Bend them along the row, fixing them at a height of 30–40 cm from the ground (you can tie them in a "braid" or pin them with hooks). This ensures snow cover (Yaroslavtsev, 2003).

2. Cover with snow. Stems should be completely covered with snow at least 30–50 cm thick. If there is little snow, bring it from between rows. Regularly break the ice crust to ensure gas exchange and prevent damping off (Yaroslavtsev, 2003).

3. For winter-hardy varieties with robust stems (which are not bent down), tie the stems in bundles (sheaves) in autumn to protect them from wind desiccation and mechanical damage, especially if winters have little snow.

4. In spring, after snowmelt, release the stems, assess their condition, and remove frozen ones, leaving only healthy ones.

8.7. Regular Monitoring and Quick Response

Regular inspection of the plantation allows early detection of physiological disorders when they are easiest to correct.

What to Check and When:

• In spring: bud break, stem condition (wood color on a cross-section), presence of chlorosis on young leaves.
• During flowering: pollinator activity, fruit set rate, presence of frost damage.
• During berry filling: berry size and quality, signs of water or heat stress.
• In autumn: shoot maturation, presence of diseases and damage.
• After each stressful event (drought, frost, heat, heavy rains)—check plant condition and take necessary measures: water, mulch, feed, spray.

Keep an observation journal. Record watering dates, fertilizer applications, treatments, and unusual weather events. This will help establish cause-and-effect relationships and avoid repeating mistakes.

8.8. Plantation Renewal (Renovation)

When to Renew. The optimal productive lifespan of a raspberry plantation is 8–10 years. By this time, diseases and pests accumulate, soil is depleted, rootstocks age, and yields decline (Yaroslavtsev, 2003).

What to Do:

1. Establish a new plantation in a new location in advance, 1–2 years before grubbing out the old one. Use healthy planting material of zoned varieties.

2. Practice crop rotation. Return raspberries to the original site no earlier than 2–4 years later, and 6–8 years if viral diseases were present.

3. If moving the plantation is impossible (small plot), use partial renewal: dig out and remove the old central part of the rootstock, leaving young lateral shoots and roots. However, this method is less effective than complete replacement.

4. Use the "walking rows" technique—raspberries gradually "move" across the site via suckers. Old rows are grubbed out and used for other crops (vegetables, green manures), while young plants form new rows (Yaroslavtsev, 2003).

8.9. Summary: A Systematic Approach to Prevention

Prevention of physiological disorders is not a single action but a system of interconnected agronomic practices.

Conclusion

Physiological disorders in raspberries are not a death sentence but a consequence of the mismatch between the plant's needs and its growing conditions. Most can be prevented or corrected by understanding what the plant needs and what hinders it.

The Main Principles of Raspberry Plantation Health:

• Light and air — do not overcrowd, remove excess shoots promptly.
• Water and nutrition — balance, not excess or deficiency.
• Heat and cold — protection from extremes.
• Soil — loose, fertile, with optimal acidity.
• Timeliness and regularity — prevention is effective when it is systematic.

Remember: physiologically healthy plants resist diseases and pests better, bear fruit longer, and produce higher-quality berries. By investing in proper care and prevention, you lay the foundation for stable yields for many years.