So, you sprayed your tomato plants and they still got leaf blight. I have heard this statement several times this summer. You need the right kind of fungicide to control leaf blight on tomatoes. Overall, there may be confusion about what type of spray to use for what pest.
Diagnosis is the first step in eliminating the cause of a plant problem.
Only after making a correct diagnosis, can a gardener attempt any control measure. Select the appropriate method or methods of control. Three categories of controls are cultural practices, natural methods, and chemical controls. If the chemical control is selected, then you need to understand some basic information about pesticides. A pesticide is any substance or mixture of substances intended to prevent, control, or kill a pest.