TheNaturePlanet

Are the leaves of your tomatoes suddenly turning yellow and withered during the fruiting period? Don't panic! Here are the causes and corresponding symptoms:


### 1. Improper Watering

- **Waterlogging and root rot**: The potting soil remains wet for a long time, causing roots to rot due to lack of oxygen. Old leaves turn yellow first, spreading from the bottom upwards, feeling soft and limp. In severe cases, the entire plant wilts.

- **Drought and water shortage**: If you forget to water for a long time, leaves will first wilt and curl, with edges gradually drying and yellowing, feeling brittle—especially noticeable on new top leaves.

**Remedy**: For waterlogging, immediately remove the plant from the pot to dry the roots, cut off rotten roots, and replace with dry soil. For drought, slowly water thoroughly along the pot edge; avoid directly pouring ice water to avoid stimulating the roots.


### 2. Nutrient Deficiency

- **Nitrogen deficiency**: Old leaves turn yellow evenly, fading gradually from the leaf tip to the base. The plant grows short and stunted, with fewer fruits.

- **Iron deficiency**: New leaves have yellow mesophyll but green veins, resembling a "yellow net pattern," while bottom old leaves remain normal temporarily.

- **Magnesium deficiency**: Yellowing occurs between the veins of old leaves, but leaf edges and tips stay green. In severe cases, yellow spots expand and merge.

**Remedy**: For nitrogen deficiency, water with腐熟 soybean cake water. For iron or magnesium deficiency, spray foliar fertilizers such as chelated iron or magnesium sulfate solution for faster absorption.


### 3. Disease Infection

- **Leaf mold**: Irregular yellow spots appear on the upper leaf surface; the undersides have gray or brown mold, which thickens in high humidity. Leaves gradually curl and dry out.

- **Viral disease**: Leaves turn yellow, shrink, and become deformed (e.g., narrow, twisted). New leaves grow small and yellow, and fruits may also be deformed.

**Remedy**: For leaf mold, spray carbendazim or thiophanate-methyl. For viral disease, promptly remove infected plants to prevent spread, and spray antiviral agents around nearby plants as prevention.


### 4. Pest Infestation

- **Spider mites**: Dense tiny pests hide on leaf undersides, leaving pinhead-sized yellow-white spots on leaves. Severe infestations cause fine webbing, with leaves turning yellow and falling off.

- **Whiteflies**: Clusters of small white flies gather on leaf undersides, flying when disturbed. Leaves turn yellow and curl, and black secretions may appear, leading to sooty mold.

**Remedy**: For minor infestations, rinse leaf undersides with water or wipe with soapy water. For severe cases, spray imidacloprid or abamectin, ensuring the undersides of leaves are covered.


### 5. Environmental Issues

- **Insufficient light**: Kept in dark areas for a long time, new leaves turn pale yellow, stems grow thin and leggy, and the plant may lodging after fruiting due to poor support.

- **Abnormal temperature**: Sudden cold (below 10℃) or heat (above 35℃) causes irregular leaf yellowing, metabolic disorders, and even scorched edges—especially noticeable in plants with heavy fruiting.

**Remedy**: Move to a well-lit area (at least 6 hours of light daily). For low temperatures, cover with a bag for warmth; for high temperatures, provide shade and ventilation.


### 6. Potting Soil Problems

- **Soil compaction**: Hardened soil slows water penetration, blocking root respiration. Leaves gradually turn yellow, and the plant grows weak due to poor nutrient absorption.

- **Soil salinization**: White frost forms on the soil surface, with an odor after watering. Leaf edges turn brown and scorched, spreading from old leaves, while new leaves fail to thrive.

**Remedy**: Loosen compacted soil and add leaf mold to improve drainage. For salinization, water with fermented and diluted rice washing water to gradually adjust soil pH.