How to prevent and treat yellow leaf disease in watermelon? Mastering these methods is key
Watermelon yellow leaf disease can be dealt with by rinsing with clean water, controlling the amount of fertilizer, and choosing high-quality organic fertilizer. For yellow leaf disease caused by different reasons, the methods needed also differ. Yellow leaf disease caused by excessive pesticide use can be relieved by the clean water rinsing method, washing away the pesticide remaining on the surface. Yellow leaf disease caused by excessive nitrogen fertilizer requires reasonable control of the amount used and the selection of high-quality organic fertilizer for application.
Watermelon Cultivation Techniques
1. Site selection
For planting watermelon, choose a location with relatively deep soil that drains easily; sandy loam is most suitable. Cultivate on plots where no cucurbit crops have been grown within 5 years on dry land or within 3 years on paddy fields.
2. Land preparation and fertilization
After land preparation is completed, apply base fertilizer and organic fertilizer as a foundation to supplement the soil with nutrients; inorganic fertilizer can be added in appropriate amounts. The combination of nitrogen, phosphorus, and potassium fertilizers should be reasonable, and the amount applied depends on soil fertility and the cultivated variety. Small-fruit watermelons and grafted watermelons can be given 20% less fertilizer, planted on high beds, with wide beds 4-4.5 m and narrow beds 2.0-2.5 m.
3. Transplanting
Early-maturing watermelon seedlings are about 1 month old and can be transplanted once they grow 2-3 true leaves. Mid-maturing watermelon seedlings can be transplanted at 20-25 days old, and late-maturing watermelon seedlings at 7-10 days old.
4. Pruning and vine pressing
A three-vine pruning method is generally used. When the main vine has 8-9 leaves, keep the main vine and two robust side vines, and remove all other secondary and tertiary vines. Pruning should not be done on cloudy or rainy days to prevent the spread of disease. When the vines grow to about 50 cm, press the vines with soil while pruning; afterward press once more every 3-4 nodes, for a total of 2-3 pressings per vine, and arrange the vines evenly. [19]
5. Fruit setting
The 2nd and 3rd female flowers on the main vine or the 1st and 2nd female flowers on the side vines should be selected for fruit setting. Fruit setting should be done in low-temperature weather as much as possible, as this ensures the fruit-setting rate.
6. Topdressing
When the young fruit grows to the size of an egg, apply fruit-swelling fertilizer according to the plant's growth vigor, generally 15-20 kg of 45% nitrate-sulfur-based or potassium sulfate-type controlled-release fertilizer per 667 sq m.
7. Water
During the seedling stage, water as little as possible; after the plants gradually grow larger, begin watering in appropriate amounts according to conditions. In the 7-10 days before harvest, watering should be avoided so the fruit can accumulate sugar. Drain field water immediately after irrigation and rain, otherwise root rot and vine rot are likely to occur.