How can you access if a plant is under heat stress or diseased?

Yesterday I visited my field and found some wilted and curled leaves. I thought it was a disease and planned to treat them. But then another thought popped up in my mind that if a sprayed my plant without identifying the disease it will damage my plant. Then I started observing my plants keenly and realized that I am WRONG. This is not a disease at all in fact that it is heat stress stimulating plants to curl their leaves to decrease transpiration rate under elevating temperatures.
Now, I will explain the difference between a disease and heat stress.
Your plants will let you know if they have a disease problem or not. Growth decreases down, sometimes stunts or becomes spindly; leaves turn yellow, show white powdery blotches, or develop spots. Infected leaves eventually drop. Plant stems may become soft and mushy, with black discoloration near the soil.
While Heat stress of a plant will show itself by wilting, which is a sure sign that water loss has taken place. The plants will eventually dry up, turning a crunchy brown before dying. In some cases, yellowing of the leaves may occur.

What is the treatment for recovery?

1. First water your plants deeply in the morning, if possible.
2. Do not fertilize during times of heat stress.
3. If your plants are in pots, move them indoors or to an area with shade.
4. Place temporary shading, such as shade cloth, over plants to keep them cool and block out the sun’s rays.