Watermelon diseases and pests include damping-off, anthracnose, blight, viral infections, aphids, leafhoppers, thrips, and the melon fly (L. sativae). Managing these issues requires a combination of agricultural, biological, and chemical methods to ensure healthy growth and high-quality yields.
**I. Agricultural Control**
1. **Field Cleanliness**: Removing weeds around watermelon fields is essential, as they can serve as hosts for pests and pathogens. This reduces the likelihood of pests like aphids and virus-carrying insects entering the field. Additionally, any diseased plants should be removed and destroyed by deep burial or burning, rather than being discarded in ditches or on roadsides.
2. **Foliar Fertilization**: While farmers often focus on base fertilizers, foliar sprays also play a key role in plant health. A 0.2% solution of potassium dihydrogen phosphate mixed with pesticides can boost plant growth and disease resistance. After fruit set, applying 0.3% potassium dihydrogen phosphate along with pesticide sprays enhances nutrient uptake, promotes early ripening, and increases sugar content. For weak plants, a 0.2–0.3% urea solution can be used. Foliar applications help slow down disease progression and improve overall plant vitality.
**II. Biological Control**
1. **Bio-pesticides**: Using 2% nanchangmycin at a dilution of 200–250 times can help control viral diseases before or at the onset of symptoms.
2. **Aphid Management**: Spraying 0.9% insecticide at a 3000x dilution effectively controls aphid populations, reducing the spread of viruses.
**III. Chemical Control**
1. **Damping-off and Vine Blight**: After seedlings emerge, spraying 66.5% propiconazole at 1000–1500x or 64% antivirus glutinous rice 8 wettable powder at 400–500x can reduce disease incidence. Mixing 200 times dry soil with antiviral agents and applying it around the base of seedlings also helps.
2. **Fusarium Wilt**: Applying 50% carbendazim wettable powder (2 kg per 100 kg fine soil) during planting prevents wilt. Root irrigation with 50% carbendazim (500x) or 70% thiophanate-methyl (1000x) at 250 ml per plant can cure the disease when detected early. Digging a circular pit around the root zone and applying the solution directly to the roots is effective.
3. **Bacterial Blight**: Spraying 70% thiophanate-methyl at 800x or 64% antivirus glutinous rice 8 WP at 500x helps manage bacterial blight.
4. **Viral Diseases**: Controlling vector insects like aphids is crucial. Spraying 20% imidacloprid at 1500x before peak infestation reduces virus transmission. Fumigation with 1.5% ziram smoke agent (300g per 667m²) or 80% dichlorvos (150–200g per 667m²) in greenhouses can also prevent outbreaks. Virus-infected plants should be sprayed with 20% virus A at 600x every 7 days for 2–3 applications.
5. **Anthracnose**: Early-stage infection can be managed with 80% mancozeb at 800x, 70% thiophanate-methyl at 500x, or 50% carbendazim at 400–600x. Fumigation with 45% chlorothalonil smoke agent (200–250g per 667m²) every 8–10 days also helps.
6. **Leafhoppers**: Spraying 40% green vegetable poison at 800x, 25% lindane at 1000x, or 40% dimethoate at 1000x controls both adults and larvae.
7. **Integrated Pest Management**: Combining fungicides, insecticides, and foliar fertilizers improves efficiency. However, avoid mixing anti-virus agents with other chemicals. Pesticides should be applied every 7 days under sunny conditions to maintain effectiveness and promote strong plant growth.
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