TheNaturePlanet

Suddenly found the stem of your tomato plant turning black? Don't panic! This could be caused by diseases. Today, we'll guide you step-by-step on how to address the issue with targeted solutions.


### Stem Base Rot (Big Seedling Blight)
**Symptoms**: Light brown to dark brown patches appear at the stem base, constricting as they circle the stem. In later stages, spider-web-like mycelium forms, leading to wilting and death of the entire plant.
**High-risk period**: Prone to occur in high-temperature and high-humidity environments.
**Solution**: Use a mixture of 1200x diluted 20% methyl立枯磷 (methyl tolclofos-methyl) EC and 3000x diluted 95% 恶霉灵 (hymexazol) solution. Drench 300ml per plant, once every 7 days for 2 consecutive times.


### Phytophthora Root Rot
**Symptoms**: Dark brown sunken patches form at the stem base. Cutting the stem reveals browned vascular bundles, with rotted roots and wilting/dying plants.
**Early signs**: Leaves yellow from the edges first, then gradually dry out.
**Solution**: Drench the root soil with a combination of 800x diluted 72.2% 普力克 (propamocarb) SC, 500x diluted 50% DT WP, and 750x diluted 80% 金纳海 (thiram) WP.


### Late Blight
**Symptoms**: Water-soaked dark brown spots appear on the stem or branching areas. In high humidity, white mycelium covers the spots, and the stem may break and lodge severely.
**Outbreak conditions**: Continuous rainy days and poor ventilation.
**Solution**: Spray 800x diluted 68% 金雷多米尔 (metalaxyl + mancozeb) WP, focusing on the stem and undersides of leaves. Apply once weekly for 3 consecutive weeks.


### Stem Rot
**Symptoms**: Elliptical sunken ulcer spots form on the stem, later invading the vascular bundles and causing dry rot and shrinkage of the stem.
**Easy to misdiagnose**: Similar to late blight; distinguish by observing spot shape.
**Solution**: Evenly spray the entire plant with 1000x diluted 50% 扑海因 (iprodione) WP, applying extra to affected areas.


### Streak Virus Disease
**Symptoms**: Dark brown patches appear on the stem surface, but only the epidermis discolors without invading vascular bundles. Leaves often show yellow-green mottling.
**Transmission source**: Piercing-sucking pests like aphids and whiteflies.
**Solution**: In the early发病 stage, spray 500x diluted 2% 宁南霉素 (ningnanmycin) AS or 500x diluted 20% 病毒A (virus A) WP for 2-3 consecutive times.


### Bacterial Disease
**Symptoms**: Dark brown streaks on the stem; cutting reveals hollow pith with gray-white bacterial ooze. Leaves turn yellow and wilt.
**High-risk scenarios**: Greenhouses with excessive watering and poor ventilation.
**Solution**: Spray 300x diluted 细菌必清 (bacterial control agent) every 3-4 days for 3-4 consecutive times, focusing on the stem and lesions.


### Daily Prevention
1. Treat soil with carbendazim or calcium cyanamide before planting to kill pathogens.
2. Maintain ventilation in greenhouses/balconies to avoid high-temperature and high-humidity environments.
3. Hang yellow sticky traps to trap aphids and whiteflies, blocking viral transmission.
4. Avoid continuous cropping with Solanaceae plants to reduce soil-borne diseases.


By identifying symptoms and applying targeted solutions promptly, you can protect your tomato plants from stem blackening! 🍅