Physiological disorders

2.1. Moisture Deficiency (Drought)

How to recognize it?

This condition is often called "physiological drought." Symptoms develop gradually as stress intensifies:

1. Leaf wilting: Leaves lose turgor, become limp, and droop to the ground.

2. Color change and marginal burn: Leaves begin to yellow, and their edges and tips turn brown and dry out (Hill & Perry, 2011).

3. Growth retardation: The formation of new leaves and runners ceases.

4. Small and tasteless berries: Fruits become smaller, less sweet, and less aromatic, as sugar accumulation is disrupted.

5. Increased susceptibility to diseases: Plants weakened by drought become easy prey for fungal root diseases.

What is the cause?

Water deficit in the soil directly affects all life processes of the plant:

• Nutrient uptake disruption: Water is the main transport channel for dissolved minerals. Without water, roots cannot absorb nutrients, even if they are present in the soil (Agustí, 2010). Therefore, drought symptoms often resemble signs of starvation.
• Overheating: Strawberries evaporate water through leaves, cooling themselves (Westwood, 1993). With insufficient moisture, this mechanism is disrupted, and the leaf apparatus overheats in the sun, leading to burns and tissue death.
• Reduced photosynthesis: Due to water shortage, leaf stomata close to avoid further water loss. This stops the intake of carbon dioxide needed for photosynthesis, and the plant starves.

What to do and why it works:

1. Set up drip irrigation (the best method). This is the most effective method for berry crops, as water is delivered directly to the root zone, without spraying into the air and wetting leaves and berries (Krivko, 2014).

• "Why it works": First, it saves up to 50% of water compared to overhead sprinkling. Second, dry leaves are the main prevention against fungal diseases (Bowling, 2000). Water goes precisely to the roots where it is needed and does not create a greenhouse effect within the planting.
• Use mulching. After watering or rain, mulch the soil around the bushes with straw, mown grass, compost, or black agricultural fabric (Hill & Perry, 2011).
• "Why it works": Mulch creates a protective layer that significantly reduces moisture evaporation from the soil. It also prevents weed growth—the main competitors of strawberries for water and nutrients. Straw mulch also protects ripening berries from soiling and rotting.
• Ensure deep and infrequent watering. Instead of watering the bed a little bit every day, water deeply but less frequently (e.g., once a week, depending on the weather). Water should penetrate the soil to a depth of at least 20–30 cm.
• "Why it works": Shallow, frequent watering encourages the growth of shallow surface roots, which suffer even more in hot weather. Deep watering "forces" roots to grow deeper, making plants more resistant to short-term droughts.

2.2. Overwatering (Flooding and Waterlogging)

How to recognize it?

Symptoms of overwatering are often confused with drought or root rots, as they are similar:

1. Sudden wilting: Leaves may wilt despite the soil being moist. This happens because damaged roots cannot pump water.

2. Leaf chlorosis: Leaves turn yellow, starting with the lower ones.

3. Reddening of petioles and veins: This is a characteristic sign of root system stress.

4. Root rot: Roots darken, become slimy, and die off. The plant pulls out of the soil easily.

5. Growth arrest: Plants look stunted, new leaves are small and pale.

6. "Hollow" berries: Berries may be watery, tasteless, or contain cavities (Westwood, 1993).

What is the cause?

Excess water in the soil completely changes the root environment:

• Oxygen starvation: Strawberry roots need oxygen for respiration. Water displaces air from soil pores, and roots begin to "suffocate" (Agustí, 2010).
• Disrupted respiration and nutrition: Without oxygen, root cell function is impaired. Roots lose the ability to absorb nutrients, especially nitrogen and potassium. This leads to yellowing and weakening of the plant.
• Pathogen activation: In anaerobic (oxygen-free) conditions, dangerous pathogens that cause root rots actively multiply: Phytophthora (Phytophthora root rot), Verticillium (Verticillium wilt), and Rhizoctonia (black root rot) (Kirtbaya & Shcheglov, 2003).

What to do and why it works:

1. Choose the right location. The main rule—never plant strawberries in low areas where water stagnates after rains or snowmelt (Bowling, 2000; Hill & Perry, 2011).

• "Why it works": Strawberries cannot tolerate prolonged flooding, even for 1–2 days. Waterlogging is a sure path to plant death. The best location is a site with a slight slope or on higher ground.
• Improve drainage on heavy clay soils. If you have heavy clay soil that retains water for a long time, the solution is to create raised beds (20–30 cm high) (Hill & Perry, 2011).
• "Why it works": Raised beds ensure natural drainage of excess water. In addition, they warm up faster in spring, promoting earlier plant development. It is also recommended to incorporate coarse river sand and organic matter (compost) to improve soil structure (Krivko, 2014).
• Follow a watering schedule. During rainy periods, drip irrigation should be turned off or reduced to a minimum. Constant wetness is not a blessing, but the main enemy of strawberry health.

Remember the main rule of water management: strawberries tolerate a slight moisture deficit better than any, even short-term, overwatering (Husaini & Neri, 2016).

In the next part, we will discuss how to protect plants from spring frosts and summer heat.

3.1. Frosts (Low-Temperature Damage)

Unlike many fruit trees, strawberries flower and fruit very close to the ground, making their flowers and young fruit particularly vulnerable to late spring frosts (Hill & Perry, 2011). Even a brief drop in temperature below -2…-3 °C can destroy the crop.

How to recognize it?

The effects of frost are easy to identify:

1. Flower damage: The center of the flower (pistil) turns black or dark brown. Such a flower will not produce a berry.

2. Fruitlet damage: Small green berries darken, become watery, and dry up.

3. Leaf damage: Leaf edges and tips become water-soaked, then turn brown and die. Young leaves may become deformed, with a crinkled blade, because damaged tissues cannot expand properly (Sharma et al., 2019).

4. Root damage (winter): During snowless, frosty winters, the shallow root system can be damaged. In spring, such plants appear stunted with delayed growth.

What is the cause?

Low temperatures cause ice crystals to form in the intercellular spaces and inside cells (Westwood, 1993). This leads to rupture of cell membranes and tissue death. Actively growing tissues (flowers, fruitlets, young leaves) contain more water and are therefore the first to suffer.

What to do and why it works:

1. Protective covering. For small plots, the most reliable method is to cover the beds at night with any row cover material (spunbond, lutrasil), old sheets, or several layers of newspaper (Hill & Perry, 2011).

• "Why it works": The covering creates a buffer air layer that traps heat rising from the soil. The soil, as a heat accumulator, continues to radiate warmth at night, and this layer of warm air protects the plants from frost.
• Sprinkler irrigation. This method is effective during light frosts (down to -2 °C). It involves continuously spraying the plants with water until dawn (Krivko, 2014).
• "Why it works": When water freezes on the plant surface, it releases heat (heat of crystallization). This heat prevents the temperature inside the plant from dropping below 0 °C, protecting tissues from death. Important: Do not stop watering until the sun rises and the temperature begins to rise.
• Site selection. Do not plant strawberries in low-lying areas, as cold air flows and stagnates there, creating "frost pockets" (Hill & Perry, 2011).
• "Why it works": Cold air is heavier than warm air and accumulates in depressions. Planting on higher ground or flat surfaces minimizes the risk of frost damage.

3.2. Heat (High Temperature)

Strawberries tolerate prolonged heat poorly, especially when combined with low air humidity. Temperatures above +30 °C inhibit the plant, disrupting basic physiological processes.

How to recognize it?

Symptoms of heat stress:

1. Wilting: Leaves lose turgor and droop, even if the soil is moist.

2. Leaf marginal burn: Dry, brown leaf edges that may later curl inward.

3. "Albinism" (white berries). Upon ripening, berries do not develop normal red color, remaining pinkish or almost white. The flesh becomes loose and sour (Sharma et al., 2019; Husaini & Xu, 2016).

4. Growth cessation. Plants stop producing new leaves and runners, entering a state of summer dormancy.

5. Increased susceptibility to diseases. Plants weakened by heat are easily infected by powdery mildew and spider mites.

What is the cause?

High temperature directly affects the enzymes controlling all life processes (Westwood, 1993):

• Impaired photosynthesis: Plant respiration accelerates, and it begins to consume more energy than it produces. Productivity drops.
• Protein stress. At high temperatures, proteins can denature (lose their structure), halting crucial reactions, including the synthesis of pigments (anthocyanins) responsible for the red color of berries (Husaini & Xu, 2016).

What to do and why it works:

1. Ensure regular watering. In hot weather, strawberries need to be watered more frequently, ensuring the soil does not dry out. It is best to do this in the morning or evening to avoid water evaporation under the scorching sun.

• "Why it works": Abundant soil moisture allows the plant to actively evaporate water through leaves (transpiration), which cools the leaf apparatus and protects it from overheating.
• Provide shade. During the hottest midday hours, beds can be shaded with lightweight row cover (agrospan) or special shade netting.
• "Why it works": Shading reduces direct solar radiation and leaf surface temperature, reducing evaporation and preventing photoinhibition (cessation of photosynthesis due to excess light).
• Mulching. Light-colored mulch (straw, grass) reflects sunlight and prevents soil overheating.
• "Why it works": Strawberry roots are sensitive to overheating. Mulch maintains soil temperature 5–7 °C lower than in open sun, providing comfortable conditions for the root system.

3.3. Sunburn

This is a type of heat stress where not leaves but the berries themselves are damaged.

How to recognize it?

Depressed, pale, brownish or whitish spots appear on the berries. The tissue under the spot becomes dry, hard, and tasteless (Sharma et al., 2019). Sunburn most often occurs on berries exposed to the sun, especially in the afternoon.

What is the cause?

Direct sunlight strongly heats the berry surface. Dark, ripe berries absorb solar heat particularly intensively. Protein structures in the pulp cells break down, and the berry ceases to develop normally.

What to do and why it works:

1. Maintain a healthy leaf canopy. Avoid leaf burns and do not remove all foliage during the berry ripening period.

• "Why it works": Leaves create natural shade for the berries, protecting them from the scorching sun. Excessive pruning or leaf damage makes berries vulnerable.
• Drip irrigation. If you use overhead sprinkling in sunny weather, water droplets on berries can act as lenses and intensify sunburn. Drip irrigation solves this problem.
• Use shading nets. As with heat protection, shading is effective.

In the next part, we will look at how to properly feed strawberries and avoid problems related to nutrient deficiency or excess.

4.1. Nutrient Deficiencies

Each element performs a unique function in the plant, so symptoms of deficiency are specific.

Nitrogen (N)

• How to recognize: Leaves become pale green or yellowish (chlorosis), starting with the older lower leaves. Plant growth slows, shoots and petioles thin out, few runners are produced. Berries become smaller, and their color becomes less intense.
• What is the cause: Nitrogen is the main element for building proteins and chlorophyll. With its deficiency, the plant cannot synthesize enough proteins, leading to a slowdown in all growth processes. Young leaves get nitrogen by redistributing it from old leaves, so old leaves yellow first (Agustí, 2010).
• What to do and why it works: Apply a nitrogen fertilizer—urea (0.5–1% solution, i.e., 5–10 g per 1 L of water) or ammonium nitrate at the beginning of the growing season (Krivko, 2014). "Why it works": Nitrogen is quickly absorbed by plants, restoring green leaf color and stimulating the growth of new shoots. Important: Do not overdo it; excess nitrogen is as harmful as deficiency (see below).

Phosphorus (P)

• How to recognize: Leaves become dull, bluish-green or with a purplish tint. Shoot growth slows, flowering is weak, and fruit set is poor. Leaves may become small and drop prematurely.
• What is the cause: Phosphorus is involved in energy metabolism (ATP) and is a building material for cell membranes. Its deficiency slows down all energy-consuming processes, including flowering and fruiting (Agustí, 2010).
• What to do and why it works: Apply phosphorus fertilizers (superphosphate) to the soil in autumn or spring, as they are immobile in the soil (Krivko, 2014). "Why it works": Superphosphate dissolves slowly, creating a long-term reserve of phosphorus in the root zone. On acidic soils, phosphorus is poorly absorbed, so prior liming is required.

Potassium (K)

• How to recognize: Edges and tips of old leaves turn brown and dry ("marginal burn"). Leaves may curl upward. Berries become small, sour, and poorly colored. Plants become more susceptible to drought and fungal diseases.
• What is the cause: Potassium is responsible for water balance, stomatal opening and closing, sugar synthesis, and strengthening cell walls. Its deficiency disrupts water and nutrient transport, making the plant vulnerable (Westwood, 1993).
• What to do and why it works: Apply potassium fertilizers (potassium sulfate, potassium magnesia) in spring and during berry formation. "Why it works": Potassium improves berry quality, increasing their sugar content and shelf life. It also increases plant drought resistance.

Magnesium (Mg)

• How to recognize: Interveinal chlorosis: veins remain green, but the tissue between them turns yellow, red, or brown. Symptoms appear first on old lower leaves.
• What is the cause: Magnesium is the central element of the chlorophyll molecule. With its deficiency, the photosynthesis process is disrupted. Magnesium also activates many enzymes (Agustí, 2010).
• What to do and why it works: Apply a foliar spray with 0.2% magnesium sulfate solution (200 g per 100 L water). "Why it works": Foliar feeding is the fastest way to deliver magnesium to the leaves. You can also apply dolomite flour to the soil, which simultaneously supplies both magnesium and calcium.

Calcium (Ca)

• How to recognize: Young leaves become deformed, their edges curl upward. Leaf tips die off. Calcium deficiency is especially dangerous for berries: "tipburn" appears—the tips of the berries darken and die, fruits become soft and spoil quickly (Agustí, 2010; Sharma et al., 2019).
• What is the cause: Calcium is a building material for cell walls. It practically does not move within the plant (is not reutilized), so young growing tissues suffer first. Poor calcium uptake is often associated with uneven watering (drought or overwatering) or excess potassium and magnesium, which are antagonists of calcium (Agustí, 2010).
• What to do and why it works: Ensure even watering. Carry out preventive foliar feeding with 0.5–1% calcium chloride or calcium nitrate solution during the fruit set period. "Why it works": This delivers calcium directly to the tissues where it is most needed.

Iron (Fe)

• How to recognize: Chlorosis of young upper leaves—they become pale yellow or almost white, with veins remaining green.
• What is the cause: Iron is a component of enzymes involved in chlorophyll synthesis. On alkaline soils (pH > 7), iron becomes unavailable to plants (Agustí, 2010).
• What to do and why it works: Apply a foliar spray with iron chelate. "Why it works": In chelated form, iron is in a plant-available form and easily penetrates through leaves. Soil acidification can also help in the long term.

Zinc (Zn)

• How to recognize: "Rosette" growth—leaves at shoot tips become small, narrow, deformed, and cluster into a dense rosette. Leaves may show interveinal chlorosis.
• What is the cause: Zinc is involved in the synthesis of auxins (growth hormones) and proteins. Its deficiency is particularly common on soils high in phosphorus (Agustí, 2010).
• What to do and why it works: Foliar spray with 0.05–0.1% zinc sulfate solution. "Why it works": Zinc moves poorly within the plant, so foliar feeding is the most effective way to correct the deficiency.

Boron (B)

• How to recognize: Cessation of growth at growing points, dieback of shoot tips. Young leaves become thickened, brittle, and crinkled. Flowers may dry and drop without setting berries (Agustí, 2010).
• What is the cause: Boron is essential for cell division and pollination. It is not reutilized, so young tissues suffer.
• What to do and why it works: Foliar spray with 0.1% boric acid solution during budding and flowering. "Why it works": Boron stimulates pollen germination and fruit set, preventing the formation of hollow and deformed berries.

4.2. Excess Fertilizer

Excess fertilizer is as dangerous as deficiency. Overfed plants become lush, vulnerable to diseases, and produce poor yields.

How to recognize it?

• Nitrogen overload: Leaves become dark green, large, and succulent. Plants grow vigorously, but flowering and fruiting are delayed; berries color poorly ("albinism"), become watery, and are easily affected by gray mold (Sharma et al., 2019). Plants have a "fat" look and overwinter poorly.
• Salt burn (overfeeding with any mineral fertilizer): Leaf edges turn brown, dry, and die. Roots can be burned when fertilizers are applied to dry soil.
• Element antagonism: Excess potassium and magnesium blocks calcium uptake, provoking berry tipburn. Excess phosphorus can lead to zinc deficiency (Agustí, 2010).

What is the cause?

Excess salts in the soil create high osmotic pressure, preventing roots from absorbing water. This leads to plant dehydration—"physiological drought." Additionally, element imbalance disrupts normal metabolism.

What to do and why it works:

1. Carefully follow the dosages on the package. It is better to under-fertilize than to over-fertilize.

• "Why it works": Fertilizers are chemically active substances. A lower dose often gives better results than a higher one.
• Apply fertilizers to moist soil and water thoroughly after application.
• "Why it works": This prevents root burn and promotes even distribution of nutrients in the root zone.
• Use balanced complex fertilizers. Prefer fertilizers with micronutrients in chelated form.
• "Why it works": Chelated forms of micronutrients (iron, zinc, copper) are more available to plants than ordinary salts and do not antagonize other elements (Krivko, 2014).

In the next part, we will discuss problems related to soil acidity, salinization, and compaction.

5.1. Inappropriate Acidity (pH)

Soil acidity (pH) is one of the key factors determining nutrient availability. For strawberries, the optimal pH range is 5.5–6.5 (slightly acidic soil) (Bowling, 2000; Hill & Perry, 2011).

How to recognize it?

Symptoms most often manifest as a complex nutrient deficiency:

• On alkaline soils (pH > 7.0): characteristic chlorosis of young leaves (yellowing) with green veins—a sign of iron and manganese deficiency. Boron and zinc deficiencies may also be observed (Agustí, 2010).
• On acidic soils (pH < 5.0): symptoms of calcium and magnesium deficiency may appear, as well as aluminum and manganese toxicity, which inhibits root growth.

What is the cause?

Nutrient availability directly depends on the pH of the soil solution (Westwood, 1993). In alkaline environments, iron, manganese, zinc, and copper become insoluble forms that roots cannot absorb. In acidic soils, conversely, some elements (aluminum, manganese) become too mobile and toxic, blocking calcium and magnesium uptake.

What to do and why it works:

1. Conduct a soil test. This is the only way to accurately determine pH. Laboratory analysis at an agrochemical lab or using a pH meter/test strips on site is a mandatory first step (Bowling, 2000).

• "Why it works": Diagnosis by appearance is unreliable, as similar symptoms can be caused by other reasons. Analysis provides accurate knowledge.
• To lower pH (on alkaline soils): Apply elemental sulfur, ammonium sulfate, or use acidic peat moss as mulch and a component of the planting mix (Krivko, 2014).
• "Why it works": Sulfur is oxidized by soil bacteria to sulfuric acid, which gradually acidifies the soil. This process is slow, so sulfur is applied several months before planting.
• To raise pH (on acidic soils): Apply dolomite flour or lime (chalk, slaked lime). Dolomite flour is preferable because it not only neutralizes acidity but also enriches the soil with magnesium and calcium.
• "Why it works": Dolomite and lime contain carbonates that bind excess hydrogen ions (H⁺), raising pH. They are applied in autumn, 2–3 months before planting, as the neutralization process is gradual.

5.2. Soil Salinization (Salt Stress)

Strawberries are considered salt-sensitive. Excess soluble salts (especially chlorides) in the soil disrupt water balance and plant nutrition (Gulen et al., 2016; Sharma et al., 2019).

How to recognize it?

• Leaf marginal burn: Leaves, especially old ones, begin to brown and dry from the edges, then die.
• Growth inhibition: Plants become stunted, leaves are small and dark green.
• Reduced yield: Berries become smaller, and the number of flower stalks decreases.
• In severe cases: Leaves may become glossy and stiff, then brown and drop.

What is the cause?

Excess salts (NaCl, CaCl₂, sulfates) in the soil solution create high osmotic pressure. Roots cannot absorb water, even if it is present in the soil—this creates "physiological drought" (Gulen et al., 2016). In addition, chloride and sodium ions can be toxic to cells, damaging their membranes. Salts can also block the uptake of potassium and calcium.

What to do and why it works:

1. Use quality irrigation water. Do not use water with high mineralization (more than 1 g/L salts) and high chloride content for irrigation (Krivko, 2014).

• "Why it works": This prevents the accumulation of harmful salts in the root zone. If water quality is questionable, it should be analyzed.
• Leaching the soil. In irrigated regions with high evaporation, periodically apply abundant irrigation (more than the normal rate) to wash excess salts deeper into the soil (Krivko, 2014).
• "Why it works": Soluble salts are removed with water beyond the active root layer. This method is effective only with good drainage.
• Use organic fertilizers (compost, manure). They improve soil structure and help bind excess ions.
• "Why it works": Organic matter increases the cation exchange capacity of the soil, allowing it to retain nutrients and reduce the toxic effect of harmful ions.

5.3. Soil Compaction and Oxygen Deficiency

Strawberry roots, like all living tissues, need oxygen for respiration. Compacted soil (especially after heavy machinery or prolonged rains) suffers from air deficiency.

How to recognize it?

• General suppression: Plants grow poorly, leaves yellow (chlorosis), even with normal watering.
• Poor root system development: Roots are small, shallow, and easily damaged.
• Water stagnation on the surface: Water after rain or watering does not soak in for a long time.
• Crust on the soil surface.

What is the cause?

In compacted soil, there are few large pores filled with air. Roots experience oxygen starvation, disrupting their respiration and absorption capacity. In addition, under anaerobic conditions, pathogens causing root rots are activated (Hochmuth & Sideman, 2023).

What to do and why it works:

1. Regular loosening between rows. After watering and rains, carry out surface loosening (to a depth of 3–5 cm) to break the crust (Krivko, 2014).

• "Why it works": Loosening restores soil aeration, providing oxygen access to roots. It is important not to loosen deeper to avoid damaging shallow roots.
• Applying organic matter (compost, manure). Regular application of organic substances improves the structure of heavy clay soils, making them more friable and breathable.
• "Why it works": Organic matter binds clay particles into larger aggregates, between which air-filled pores are formed.
• Creating raised beds (ridges). On heavy soils or in regions with excessive moisture, planting on ridges 20–30 cm high solves both compaction and overwatering problems (Hill & Perry, 2011).
• "Why it works": Soil on ridges dries and warms faster, is less prone to compaction, and roots get more air.

In the next part, we will consider problems related to crop formation: poor pollination, berry deformation, and other disorders.

6.1. Poor Pollination

Strawberries are self-pollinating, but for a full harvest, high-quality pollination is critically important. Poor pollination is one of the main causes of berry deformation and size reduction (Sharma et al., 2019).

How to recognize it?

• Small berries with underdeveloped seeds (achenes). On the berry surface, there are areas where achenes are small, inconspicuous, and not swollen. The tissue around such achenes does not develop, leading to deformation.
• Asymmetrical, misshapen berries. The fruit develops unevenly, resembling a "beak" or "saddle" in shape.
• "Nubbins." Very small, underdeveloped berries, often with a few large achenes at the tip (Sharma et al., 2019).
• Reduction in total number of set berries. Flowers wither and dry without forming ovaries.

What is the cause?

The pollination process in strawberries is a complex mechanism. Each achene (the true fruit—a seed) secretes auxins—growth hormones that stimulate the enlargement of the receptacle (the edible part of the berry) (Westwood, 1993). If an achene is not fertilized, auxins are not released, and the tissue around it does not grow. The more unfertilized achenes, the more deformed the berry (Sharma et al., 2019).

Main factors disrupting pollination:

• Bad weather during flowering: Rain, strong wind, fog, and low temperatures (below +10…+12 °C) reduce the flight activity of pollinating insects (bees, bumblebees) and can sterilize pollen (Krivko, 2014).
• Lack of pollinating insects: In small isolated plots or greenhouses without access to bees, pollination may be insufficient (Bowling, 2000).
• Very high temperatures (above +30 °C) during flowering: Pollen becomes sterile, and stigma receptivity decreases (Sharma et al., 2019).
• Unbalanced nutrition, especially boron deficiency, which is necessary for pollen tube germination (Agustí, 2010).

What to do and why it works:

1. Attract pollinating insects. Plant nectar-producing plants near strawberry beds (phacelia, buckwheat, dill, coriander) that bloom at the same time as strawberries (Bowling, 2000).

• "Why it works": These plants attract bees and other pollinators, providing additional food resources. Bees will work more actively on strawberry flowers, ensuring high-quality pollination.
• Carry out hand pollination (for small areas or greenhouses). In the morning hours when flowers are open, use a soft brush or cotton swab to transfer pollen from flower to flower.
• "Why it works": This guarantees pollination even in the absence of insects. For greenhouses or tunnels, this is a mandatory technique.
• Ensure balanced nutrition. Apply complex fertilizers with micronutrients, especially boron, during budding and flowering (Agustí, 2010).
• "Why it works": Boron stimulates pollen germination and pollen tube growth, increasing the percentage of fertilized achenes.

6.2. Berry Deformation

This is the most common problem related to pollination disturbances. However, there are other causes.

How to recognize it?

• "Beak-shaped" or "sickle-shaped" berries. One end of the berry is elongated, while the other remains underdeveloped.
• "Fused" berries. Two or more receptacles grow together, forming a misshapen fruit.
• Berries with "bald spots" (without achenes). Areas of the berry are smooth, without achenes, and uncolored.

What is the cause?

Deformation is a direct consequence of uneven pollination (Sharma et al., 2019). Where achenes are fertilized, tissue grows; where they are not, tissue remains underdeveloped. In addition, deformation can be caused by:

• Pest damage to flowers (e.g., strawberry blossom weevil or thrips), disrupting normal ovary development (Kirtbaya & Shcheglov, 2003).
• Herbicide stress (see Ch. 7). Herbicide exposure to flowers can cause severe berry deformation (Hill & Perry, 2011).
• Boron deficiency. Boron is critical for cell division and pollination, and its deficiency often leads to misshapen fruits (Agustí, 2010).

What to do and why it works?

• All measures to improve pollination (see above) are the best prevention of deformation.
• Control pests during flowering using biological or permitted chemical agents (Kirtbaya & Shcheglov, 2003). "Why it works": This prevents damage to the reproductive organs of the flower.
• Regularly apply boron fertilizers. "Why it works": This ensures normal cell division and achene development.

6.3. Reduction in Berry Size

Every gardener dreams of large berries. Berry shrinking is a signal that the plant lacks resources or is under stress.

How to recognize it?

Berries become significantly smaller than typical for the variety, even with abundant flowering. The number of berries may be large, but all are small.

What is the cause?

Berry size is determined by the number of fertilized achenes and the plant's carbohydrate supply (Westwood, 1993). If there are few achenes, the berry will be small regardless of nutrition. If there are many achenes but the plant lacks water, light, or nutrition, it cannot "feed" all the berries, and they will be small. This is often observed:

• During crop overload: The plant spends too much energy forming a large number of berries (Krivko, 2014).
• In heat and drought: Photosynthesis and carbohydrate transport to berries are disrupted.
• With nitrogen and potassium deficiency: There is a lack of building materials and energy for fruit growth (Agustí, 2010).

What to do and why it works?

1. Crop thinning (removing flower stalks). In the first year after planting, remove all flower stalks to allow the plant to establish a strong root system and leaf rosette (Hill & Perry, 2011). On mature plants, you can remove some of the first flower stalks so that the remaining berries are larger.

• "Why it works": The plant stops wasting energy on forming all berries and channels it to the remaining ones, making them larger and sweeter.
• Ensure adequate watering and nutrition. Large berries require a lot of water and nutrients. During berry filling, watering should be regular, and fertilizing balanced (with an emphasis on potassium).
• "Why it works": This ensures a continuous supply of resources for fruit growth.

6.4. Hollow Berries ("Cavity")

Sometimes, when cutting a large berry, a cavity is found inside. This is a serious defect that reduces marketability and shelf life.

How to recognize it?

An internal cavity (hollow) in the center of the berry, which may be small or occupy a significant volume. The tissue around the cavity is often dry and hard.

What is the cause?

The exact causes are not fully understood, but it is believed to be related to:

• Poor pollination: If achenes in the center of the receptacle are not fertilized, the central tissue does not receive growth stimulus and tears as the berry enlarges (Westwood, 1993).
• Sharp temperature fluctuations: Rapid berry growth after a cold period can lead to tearing of internal tissues.
• Excess nitrogen: Nitrogen overfeeding causes vigorous but loose tissue growth, which may then tear (Sharma et al., 2019).

What to do and why it works?

• Improve pollination (see above). This is a key factor.
• Avoid excessive nitrogen fertilization. Apply nitrogen only in early spring at the start of the growing season, and use potassium-phosphorus fertilizers during flowering and fruiting.
• "Why it works": This prevents overly rapid and loose tissue growth, making their structure denser.

6.5. "Nubbins" (Button Berries)

This is the extreme form of underdeveloped berries.

How to recognize it?

Very small, hard, round berries without achenes. They practically do not grow, have a pale color, and are tasteless.

What is the cause?

This is the result of complete lack of pollination. Without pollination, no auxins are released, and the berry does not develop at all (Sharma et al., 2019). Causes can include:

• Absence of pollinators.
• Extremely cold or hot weather during flowering.
• Damage to flowers by pests or diseases.

What to do and why it works?

Prevention of "nubbins" is the same as prevention of poor pollination—attracting bees and creating optimal conditions for flowering. It is useless to fight such berries; they should be removed.

In the next part, we will discuss how chemicals (herbicides, fertilizers) can cause physiological disorders in strawberries.

7.1. Herbicide Stress (Damage from Weed Control)

Herbicides are preparations for killing weeds. However, many are not selective and can damage cultivated plants. Particularly dangerous for strawberries are systemic herbicides that penetrate the plant through leaves and roots (Krivko, 2014).

How to recognize it?

Symptoms depend on the type of herbicide, but there are common signs:

• Leaf deformation. Leaves become narrow, twisted, crinkled, and their shape changes. This is characteristic of herbicides from the 2,4-D group (dichlorophenoxyacetic acid) (Hill & Perry, 2011).
• Chlorosis and yellowing. Leaves may yellow, especially along the edges or between veins.
• Growth arrest. Plants stop developing, new leaves are small and misshapen.
• Berry deformation. Berries may be malformed, misshapen, with "beaks" or "bald spots" (Sharma et al., 2019).
• Flower and fruitlet drop. In severe cases, herbicides can cause bud and flower drop.

What is the cause?

Systemic herbicides mimic or block the action of plant hormones (auxins). This leads to uncontrolled cell division, disruption of normal tissue growth, and organ deformation (Westwood, 1993). Strawberries are particularly sensitive to herbicides during active growth and flowering.

What to do and why it works?

1. Use herbicides with extreme caution. It is best to apply them spotwise on weeds or in calm weather to avoid drift onto cultivated plants (Krivko, 2014).

• "Why it works": Herbicide drift by wind is a common cause of damage to neighboring plots. Selective application reduces risk.
• Apply herbicides before planting or after harvest. On a strawberry plantation, if you are not sure of the herbicide's safety, it is better to use mechanical weed control methods (weeding, mulching).
• "Why it works": This eliminates the risk of direct herbicide contact with strawberries.
• For mild damage: Water the plants abundantly with clean water and apply a foliar spray with a complex fertilizer containing micronutrients.
• "Why it works": Watering will help wash off herbicide residues from leaves, and feeding will support the weakened plant and stimulate the growth of new healthy tissues.
• For severe damage: Affected plants, unfortunately, will have to be removed. Strawberries should not be planted in that spot for 1-2 years, as some herbicides persist in the soil (Krivko, 2014).
• "Why it works": This prevents herbicide accumulation in the soil and protects future plantings.

7.2. Damage from Pesticides (Insecticides and Fungicides)

Even products intended to protect against diseases and pests can cause leaf burns and other damage if used incorrectly.

How to recognize it?

• Leaf burns. Appearance of brown, dry spots on leaves, especially along edges and tips. This most often occurs when the working solution concentration is too high or when spraying in hot, sunny weather.
• Chlorosis and yellowing. Leaves may yellow, especially old ones.
• Russeting (bronzing). A brown, net-like roughness appears on fruits and leaves, resembling sandpaper.
• Growth inhibition. Plants stop developing.

What is the cause?

Many chemical products are salts or organic compounds that, at high concentrations, can damage cell membranes and disrupt photosynthesis. Particularly dangerous are:

• Application of products in heat (above +25 °C). Drops of the solution on leaves evaporate quickly, the concentration of the active substance rises sharply, causing chemical burns (Westwood, 1993).
• Exceeding the dosage. "More" does not mean "better." Exceeding the recommended dose almost always leads to damage.
• Incorrect treatment timing. Spraying during flowering can not only kill bees but also burn the delicate tissues of the flower.

What to do and why it works?

1. Strictly follow the instructions. Always read the label and observe recommended dosages and pre-harvest intervals (Hochmuth & Sideman, 2023).

• "Why it works": Dosages are calculated for specific conditions; exceeding them leads to phytotoxicity.
• Spray in the morning or evening hours. Avoid treatments in hot, sunny weather (above +25 °C).
• "Why it works": In cooler weather, evaporation is less, and droplets have time to spread over the leaf without causing burns.
• Use tank mixtures with caution. Do not mix several products without checking for compatibility (Krivko, 2014).
• "Why it works": Some products, when mixed, can undergo chemical reactions that increase phytotoxicity.
• If burns appear: Rinse the plants abundantly with clean water from a hose with a spray nozzle.
• "Why it works": This reduces the concentration of the chemical on the leaf surface and minimizes damage.

7.3. Excess Fertilizers and Salt Stress (Repetition and Deepening)

We have already touched on this topic in the chapter on mineral nutrition disturbances, but here it is worth saying a few words about "salt burn."

How to recognize it?

• Marginal leaf burn. Brown, dry edges of leaves, which then die off.
• White crust on the soil surface. Especially noticeable after watering.
• Wilting and growth arrest. Plants look stunted, even with adequate watering.

What is the cause?

Excess mineral salts in the soil create high osmotic pressure; roots cannot absorb water (physiological drought). In addition, individual ions (chlorine, sodium) can be toxic (Gulen et al., 2016).

What to do and why it works?

1. Do not exceed fertilizer dosages. Follow the principle "better to under-fertilize than over-fertilize."

2. Leaching the soil. Carry out abundant watering (more than the normal rate) to flush excess salts from the root zone (Krivko, 2014). Important: This method is effective only on soils with good drainage.

3. Apply fertilizers to moist soil. Before applying dry or liquid fertilizers, be sure to water the bed with clean water (Krivko, 2014).

• "Why it works": Moist soil distributes salts better, preventing local accumulation that could cause root burn.

7.4. General Principles for Working with Chemicals

To avoid chemical damage, follow these simple rules:

1. Always read the label. It indicates dosages, waiting periods, temperature restrictions, and compatibility.

2. Use protective clothing. Work in gloves, protective goggles, and a respirator to avoid contact with chemicals (Hochmuth & Sideman, 2023).

3. Do not exceed the dosage. This is not only harmful to plants but also dangerous for consumers due to possible pesticide residues in the berries.

4. Observe waiting periods. The waiting period is the minimum time between the last treatment and harvest. Never pick berries before the specified period (Krivko, 2014).

5. Avoid treatments during flowering. This kills bees and other pollinators and can damage the delicate tissues of the flower.

In the next, concluding part of the article, we will compile all the advice into a unified system for preventing physiological disorders.

8.1. A Comprehensive Approach: The Key to Strawberry Health

Strawberry health is the result of a proper balance of four main factors:

1. Water (proper irrigation and drainage).

2. Nutrition (balanced fertilization).

3. Temperature (protection from extreme fluctuations).

4. Soil (optimal pH, structure, and aeration).

These factors are closely interconnected. For example, lack of water makes the plant unable to absorb nutrients, and nitrogen overfeeding reduces frost resistance (Agustí, 2010). Therefore, prevention must be comprehensive.

8.2. Practical Steps for Prevention

1. Proper site selection and soil preparation (the key to success for years to come)

• Choose a sunny location. Strawberries require at least 6-8 hours of direct sunlight per day. In shade, they will fruit poorly, and berries will be sour and small (Bowling, 2000; Hill & Perry, 2011).
• "Why it works": Sunlight is energy for photosynthesis, which drives growth and sugar accumulation in berries.
• Avoid low areas and places with water stagnation. Cold air accumulates in low spots, increasing frost risk, while stagnant moisture leads to root rots (Hill & Perry, 2011).
• "Why it works": This prevents two of the most serious stress factors simultaneously—overwatering and frost.
• Conduct a soil test 2-3 months before planting. Determine pH and levels of major nutrients (phosphorus, potassium) (Bowling, 2000).
• "Why it works": This gives precise knowledge of what needs to be added to the soil. Adding lime (to raise pH) or sulfur (to lower it) requires time to take effect.
• Incorporate organic matter (compost, manure) and dolomite flour during digging. This will improve soil structure, provide slow release of nutrients, and normalize pH (Krivko, 2014).
• "Why it works": Organic matter makes soil loose and breathable, while dolomite flour supplies calcium and magnesium, which prevent tipburn and improve berry quality.

2. Proper watering (the key to healthy roots)

• Use drip irrigation. This is the most effective and safest method for strawberries (Krivko, 2014).
• "Why it works": Drip irrigation saves water, does not wet leaves (prevention of fungal diseases), and delivers moisture precisely to the root zone.
• Water infrequently but deeply. The soil should be wet to a depth of 20-30 cm. In hot weather, water 1-2 times a week; in cool weather, less often.
• "Why it works": Deep watering encourages roots to grow deeper, making the plant more drought-resistant.
• Mulch the soil. A layer of mulch (straw, grass, agrofabric) retains moisture, prevents root overheating, and suppresses weed growth (Hill & Perry, 2011).
• "Why it works": Mulch creates a stable microclimate in the root zone, protecting against temperature fluctuations and drying.
• Adjust watering during rainy periods. During prolonged rains, turn off drip irrigation and, if possible, cover the beds with film to protect against excess moisture.
• "Why it works": This prevents overwatering and the development of root rots.

3. Balanced nutrition (without overfeeding or starvation)

• Follow a fertilization schedule:
• Spring (start of growth): Nitrogen fertilizers (urea, ammonium nitrate) to stimulate leaf growth.
• Budding and flowering period: Complex fertilizers with micronutrients (especially boron) to improve pollination and fruit set (Agustí, 2010).
• Berry filling period: Potassium-phosphorus fertilizers (potassium sulfate, monopotassium phosphate) to improve flavor, size, and shelf life of berries.
• Autumn (after fruiting): Phosphorus-potassium fertilizers for flower bud formation for the next year and to increase winter hardiness.
• Apply fertilizers to moist soil and water thoroughly after application. This prevents root burn.
• "Why it works": Even distribution of salts in the soil ensures nutrient availability to all roots.
• Use foliar feeding (on leaves) to quickly correct micronutrient deficiencies. Chelated forms of micronutrients (iron, zinc, manganese) are absorbed faster and more effectively (Krivko, 2014).
• "Why it works": Foliar feeding is "first aid" for the plant when a particular element needs to be replenished urgently.

4. Protection from extreme temperatures

• Cover beds at night when frost is threatened. Use spunbond, lutrasil, or old sheets.
• "Why it works": Covering traps heat rising from the soil and protects flowers from damage.
• Provide shade during intense heat. Use shade netting or lightweight row cover during the hottest midday hours.
• "Why it works": Shading reduces leaf surface temperature and protects berries from sunburn.
• Choose varieties adapted to your climate. Some varieties are more frost-resistant, others more heat-tolerant (Hill & Perry, 2011).
• "Why it works": Genetic resistance is the most reliable protection.

5. Monitoring and regular inspection

• Inspect plants regularly (at least once a week). Pay attention to leaf color, berry shape, and overall condition.
• "Why it works": Early detection of symptoms allows you to quickly adjust care and prevent serious losses.
• Keep an observation diary. Record dates of watering, fertilizing, treatments, and weather anomalies. This will help identify patterns and avoid mistakes in the future.

8.3. Quick Diagnostic Table of Physiological Disorders

For convenience, we have summarized the main signs and causes of disorders in a table.