What disease causes watermelon leaves to turn white? Causes and pesticide control methods

Watermelon growers, pay attention! White leaves are not a small problem - different symptoms point to different causes, and getting it wrong can make things worse the more you try to fix them! Today I will explain how to tell them apart+the solutions, so check them against your plants right away.

Symptoms of white leaves
 
1. Leaves covered in"white powder" 
 
The most typical sign is white powdery patches on the leaves. At first there may be just a few scattered spots, but they gradually spread across the whole leaf and even onto the stems, feeling smooth to the touch. This is powdery mildew at work, and it breaks out especially easily in hot, humid, poorly ventilated conditions!

Treatment steps: in the early stage of the disease, use hymexazol solution mixed with propineb solution, or ethirimol suspension concentrate, spraying once every10 days, for2-3 consecutive sprays. If you are worried about chemical pesticides, you can also spray filtered wood ash mixed with water or baking soda water, once every3-5 days, suitable for small areas with mild disease.

2. Leaves with"scattered small white dots"

If the white dots are scattered like stars rather than powdery, it is most likely a physiological disorder related to sudden temperature changes. For example, if the greenhouse is ventilated too late, causing the temperature to rise sharply at noon, or if irrigation is not timely during drought so the roots cannot take up water fast enough, the leaves are prone to this kind of"stress response"

Solution: adjust the greenhouse ventilation schedule right away, ventilating promptly once the temperature rises in the morning to avoid too great a temperature difference inside the greenhouse; add plastic film mulching, which both preserves moisture and stabilizes soil temperature, reducing the impact of environmental fluctuations on the roots; do not wait until the soil is too dry before watering, keeping the soil moist but not waterlogged, so the plants can recover gradually.

3. Leaves turning white along with wilting and softening

If you have just fertilized recently, especially with organic fertilizers such as uncomposted chicken manure or sheep manure, or if you applied too much chemical fertilizer, it is very likely root burn causing the abnormal leaf color. Besides the leaves turning white, the leaves may also wilt and droop, feeling a bit brittle to the touch.

First-aid measures: stop fertilizing immediately! Slowly rinse the soil around the roots with clean water to dilute the excess fertilizer; once the plants no longer look so wilted, apply a small amount of diluted weak fertilizer to help them"regain their strength""fix"

Points to note
 
1. The treatments for different causes are worlds apart. For example, powdery mildew requires a fungicide spray, while root burn requires watering to dilute it, and getting it wrong will make the problem worse. If you are not sure, contact your local plant protection department right away and let the professionals help you judge.

2.If the number of diseased leaves exceeds30%

3. No matter which problem it is, ventilation, reasonable fertilizing, and stable temperature and humidity are all key. Especially for greenhouse growing, observing frequently and adjusting early saves far more effort than waiting until problems appear and then rescuing them!