**Disease and Pest Management in Cabbage Cultivation**
1. **Viral Diseases**
Viral diseases are often transmitted by aphids and can affect cabbage plants at various growth stages. In the seedling stage, leaf veins may lose their green color, leading to uneven green patches or mosaic patterns. Adult plants may show stunted growth, with leaves that are curled, brittle, and covered in small brown spots. The plants appear significantly smaller than healthy ones.
Control measures include:
- Choosing resistant varieties or hybrids.
- Keeping the field clean and free from weeds or other cruciferous crops.
- Planting at appropriate times.
- Avoiding continuous cropping of cruciferous plants.
- Proper fertilization and irrigation.
- Early prevention: Apply 50% thiamethoxam wettable powder diluted 2000–3000 times or 10% imidacloprid WP at 2000 times during the seedling stage. Alternatively, use 500-fold dilution of virus No. 1 oil emulsion, 500-fold of 20% virus A, or 500-fold of 5% bacterial agent. Spray every 7–10 days, up to 2–3 times.
2. **Downy Mildew (Fungal Disease)**
This disease affects cabbage from the seedling to bulb formation stage. Symptoms include yellowing of cotyledons and tender stems, with water-soaked spots on the lower parts of true leaves. As the disease progresses, a white mold appears, especially under high humidity or dew conditions. Leaves may develop polygonal lesions, and severe cases lead to wilting and death of infected foliage.
Control methods:
- Use disease-free seeds and resistant varieties.
- Treat seeds with 0.3% metalaxyl WP or thiram before sowing.
- Practice crop rotation, proper irrigation, and balanced fertilization.
- Apply fungicides like 58% metalaxyl MnZn WP, 64% oxadixyl WP, or 75% mancozeb at 500 times dilution at the first sign of infection, repeating every 7–10 days for 2–3 applications. Alternatively, use Green Hyun No. 6 (50% chlorobromoisocyanuric acid) at 1500–2000 times dilution.
3. **Soft Rot (Bacterial Disease)**
Soft rot is caused by bacteria and commonly occurs from the rosette to heart-filling stage. Infected plants show wilted outer leaves, with a foul smell of hydrogen sulfide. The tissue becomes soft, and a viscous, grayish-brown fluid oozes out. Under dry conditions, the leaves become thin and paper-like.
Control strategies:
- Select resistant varieties.
- Remove and destroy diseased plants, disinfect soil with quicklime.
- Improve irrigation and fertilization, avoid plant injuries.
- Control pests like diamondback moth and cabbage worm to reduce wounds.
- Apply 3000 times diluted agricultural streptomycin or neomycin, spray every 10 days for 2–3 times. Root drenching with 72% streptomycin solution or neophytin can also be effective.
4. **Cabbage Wilt (Root Tumor Disease)**
This disease causes root tumors and leaf discoloration, especially in sunny weather. In advanced stages, soft rot bacteria may infect the damaged areas, leading to plant death.
Control method:
- Apply 40% pentachloronitrobenzene powder at 0.4–0.5 kg per acre to the roots.
5. **Bacterial Leaf Spot**
Common in seedlings, rosette, and early heading stages. Initial symptoms include water-soaked spots on the leaf back, which expand into irregular, angular, membranous lesions. High humidity leads to bacterial exudate, and dry conditions cause the lesions to crack and become brittle.
Control:
- Spray 72% agricultural streptomycin at 3000–4000 times dilution or neophytin at 4000 times, every 7–10 days for 2–3 applications.
**Pest Management**
1. **Yellow Striped Armyworm**
Affects seedlings, eating cotyledons and damaging roots. Control with 5% frits (1500 times), 90% trichlorfon (1000 times), or 50% phoxim EC (1000 times).
2. **Cabbage Worm**
Larvae bore into leaves and hearts. Spray fenvalerate (3000 times), Bt emulsion (40 kg water + 50 g), or 48% chlorpyrifos (2500 times) during early larval stages.
3. **Cabbage Butterfly (Pieris rapae)**
Larvae feed on leaves, causing holes and damage. Use Bt emulsion (500–800 times), 50% phoxim EC (1000 times), or Green Hengheng (2000–2500 times).
4. **Cutworm (Spodoptera litura)**
Larvae attack leaves and burrow into the head. Spray Bt or 10% imidacloprid (2500 times), 80% dichlorvos (1000 times), or 90% trichlorfon (1000 times) at early hatching stages.
5. **Aphids**
Suck sap, causing wilting and spreading viruses. Use 20% Fungicide (6000 times) or 10% imidacloprid (10g/acre in 40–50kg water) or Green Hen Stable (2000–2500 times).
By implementing these integrated management practices, farmers can effectively reduce disease and pest losses, ensuring healthier and more productive cabbage crops.
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