06Fungal diseases
Fungi spread through wet leaves, still air and wet soil, so dry leaves and good airflow prevent most of them. Remove infected leaves first, then spray.
How to identify them
| Disease | What you see | Where and when | Common on |
|---|---|---|---|
| Powdery mildew | White or grey flour-like powder on the top of leaves. It rubs off with a finger | Older leaves first. Dry days with humid nights | Cucumber, gourds, pumpkin, okra, roses |
| Leaf spot and early blight | Brown spots with rings like a target, often with a yellow halo. Spots join and the leaf dies | Lower leaves first, moving upward. Warm, wet weather | Tomato, brinjal, chilli, potato |
| Downy mildew | Yellow patches on top of the leaf with grey-purple fuzz underneath | Cool, wet, cloudy weather | Gourds, cucumber, spinach |
| Damping-off | Seedling stem turns thin, watery and brown at soil level, then the seedling falls over | Seedlings in wet, crowded trays | All seedlings |
| Root and collar rot | Plant wilts and yellows even when soil is wet. Base of stem is dark and soft. Roots brown and smelly | Overwatered pots, poor drainage | Chilli, tomato, curry leaf, succulents |
| Rust | Small orange-brown raised dots on the leaf underside. Rub off as rusty powder | Humid weather | Beans, roses, marigold |
If the spots have no rings, no fuzz and no powder, and new leaves are affected, check the nutrient table first.
Prevention
- Water the soil, not the leaves, and water in the morning so the surface dries by evening.
- Space pots so leaves do not touch. Prune crowded inner branches.
- Mulch the soil with dry leaves or straw so soil does not splash onto lower leaves.
- Never reuse soil from a diseased plant, and clean scissors with alcohol between plants.
- Add Trichoderma to the soil at planting: 1 tsp per medium pot mixed with a handful of compost.
Organic cures
| Remedy | Recipe per litre | Use against | How often |
|---|---|---|---|
| Baking soda spray | 1 tsp baking soda + ½ tsp liquid soap + 1 tsp vegetable oil | Powdery mildew, early leaf spot | Every 7 days, 3 rounds |
| Milk spray | 300 ml milk + 700 ml water | Powdery mildew. Spray on a sunny morning | Every 7 days |
| Sour buttermilk spray | 100 ml buttermilk fermented 5–7 days | Leaf spot, powdery and downy mildew | Every 7–10 days |
| Neem oil spray | 1 tsp neem oil + ½ tsp liquid soap | Mildews, rust, leaf spot | Every 7 days |
| Trichoderma drench | 1 tsp Trichoderma viride powder | Damping-off, root and collar rot | Pour 1 cup per pot every 15 days |
| Pseudomonas spray | 1 tsp Pseudomonas fluorescens powder | Leaf spot, blight, root rot | Spray or drench every 10–15 days |
| Cinnamon powder | Dust directly | Damping-off on seedlings, cut stems after pruning | Once, on the soil surface or cut |
For blight or downy mildew that keeps spreading, a copper spray (copper oxychloride, ½ tsp per litre) is allowed in organic farming. Use it at most 2 times, 10 days apart.
07Viral diseases
A virus cannot be cured, in organic or chemical farming. You can only stop it spreading by removing sick plants and controlling the insects that carry it.
How to identify them
| Disease | What you see | Carried by | Common on |
|---|---|---|---|
| Leaf curl | New leaves small, thick, curled upward or downward, puckered. Plant bushy and stunted, few fruits | Whitefly, thrips, mites | Chilli, tomato, papaya |
| Mosaic | Irregular light and dark green or yellow patches like a jigsaw, leaves crinkled or twisted | Aphids, hands and tools | Cucumber, gourds, beans, tomato, papaya |
| Yellow vein mosaic | Veins turn bright yellow in a net pattern, then whole leaf yellows. Fruits pale and hard | Whitefly | Okra (bhindi), beans |
Virus or nutrient shortage?
- A virus pattern is uneven and patchy. Nutrient yellowing is even and repeats the same way on every affected leaf.
- Virus-affected leaves are usually distorted (curled, crinkled, narrow). Nutrient-short leaves keep their normal shape.
- Virus symptoms do not improve after feeding. If new leaves stay mottled 2 weeks after the right remedy, suspect a virus.
- Look for the carriers: tiny white flies rising when you shake the plant, or aphids on the shoots.
Management
- Uproot the infected plant, put it in a sealed bag and bin it. Do not compost it or leave it in the garden.
- Wash hands and clean tools with soap or alcohol after touching it. Avoid handling plants right after smoking, since tobacco can carry mosaic virus.
- Control the carriers on the remaining plants: yellow sticky traps plus a neem oil spray (1 tsp per litre) every 7 days.
- Remove weeds around the pots. They hide whitefly and aphids.
- Buy healthy seedlings, and choose varieties labelled resistant to leaf curl or yellow vein mosaic where you can.
- Do not replant the same crop in that pot for one season. Reuse the Leihaao medium for a different crop family instead.
08Safety and weekly care checklist
Spray safety
- Test any new spray on 2–3 leaves first and wait 24 hours. Skip it if leaves burn or spot.
- Spray in the early morning or evening, never in hot midday sun.
- Use one spray at a time. Do not mix soap, neem, baking soda and copper sprays together.
- Wait at least 3 days after a neem or garlic spray before harvesting, and wash produce well.
- Label every bottle, keep it away from children and pets, and wear gloves for copper, borax and alcohol.
- Never go above the doses in this guide. More fertiliser burns roots faster than it helps.
Weekly checklist
- ☐ Check soil moisture with a finger before watering
- ☐ Match a leaf to the leaf colour chart and note the shade
- ☐ Turn over 5 leaves and check stem joints for insects
- ☐ Do the white paper tap test on 1–2 plants
- ☐ Remove yellow, spotted or dead leaves and bin them
- ☐ Check yellow sticky traps and replace when full
- ☐ Feed or spray only if a section of this guide says so