Another common cause of withering and scorching is shortage of water and nutrients. If these are short enough in supply the entire leaf area cannot be furnished with water. As the problem becomes more acute, scorching will progress toward the center of the leaf. Watering according to need with good quality water and fertilizing according to soil test represent the best means of prevention. Toxicity can also result in withering and scorching of foliage.
Toxic materials vary in the way they affect plants.
Excessive use of fertilizer burns roots and causes root failure described earlier. Certain herbicides may kill roots directly while others translocate to foliage tissue, with these often accumulating on leaf margins and scorching occurs. Many substances are toxic to plants and their modes of action differ. Atmospheric toxicity - Certain air pollutants may produce a scorching of the leaf surface. Several described pollutants are capable of causing damage and these are identified in the section on air pollution.