This greatly differs from most insect control. Some of the newer fungicides, however, do have curative or eradicant action, that is they can stop further growth and development of the pathogen, or even kill pathogens already infecting the plant. Even though they have curative action, it may not be wise to use them as curatives because of increased probabilities of resistant strains developing. Also, most fungicides possessing curative action have narrow modes of action, and thus, control only a few diseases of the target crop. Applications of protective fungicides must be done well to be successful under strong disease pressure.
Coverage is a critical issue with fungicides.
Equally important, however, is timing of the application in relation to when the disease develops. For most fungicides, the applications must be made before the disease begins because the materials control by prevention and not by eradication of the pathogen after the organisms are inside the plant. Lower volumes and lower pressure can be used, but are not usually as effective. Kentucky's vegetable growers, as a whole, need to pay more attention to this area. Sprayer nozzles should be those made for fungicide use, clean, and without excessive wear.