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

Attention, watermelon growers! White leaves are no 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 what is going on+the solutions so you can check against your own plants right away.

Symptoms of White Leaves
 
1. The leaves are covered with"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 slippery 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 stages of the disease, spray with a mix of hymexazol solution and propineb solution, or a suspension concentrate of ethirimol, once every10 days, for2-3 consecutive sprays. If you are worried about chemical agents, you can also spray filtered water mixed with plant ash or baking soda water,3-5 days apart, suitable for small areas with mild disease.

2. The leaves have"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 a greenhouse is ventilated too late, causing the temperature to spike at midday, or if irrigation is delayed 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 excessive temperature swings inside; add plastic film mulch, which both conserves 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 - keep the soil moist but not waterlogged so the plants can recover gradually.

3. Leaves turn white along with wilting and softness

If you have recently applied fertilizer, especially organic fertilizers like 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 little brittle to the touch.

Emergency measures: stop fertilizing immediately! Slowly flush the soil around the roots with clean water to dilute the excess fertilizer; once the plant no longer looks so wilted, apply a small amount of diluted weak fertilizer to help it"regain its strength""as a remedy"

Precautions
 
1. The treatments for different causes are worlds apart. For example, powdery mildew requires a fungicide spray, while root burn requires watering to dilute the fertilizer - mix them up and you will make the problem worse. If you are not sure yourself, 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, sensible fertilization and stable temperature and humidity are the key. This is especially true for greenhouse growing - observing frequently and adjusting early saves far more effort than trying to rescue the plants after problems appear!