Answer: Cucumber and squash plants are susceptible to powdery mildew, generally towards the end of the season here in the contiguous states, when the nights are cold enough to stress the plants. In your tropical gardening region I suspect the development of the disease has more to do with humidity and poor air circulation around the plants, than cool night air. You might try removing the older leaves, especially when they begin to show signs of distress. Give your plants as much direct sunshine as possible and increase the space between the plants to provide excellent air circulation.
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