The four basic requirements for management of plant diseases are clean & healthy seeds, clean field or pathogen free soil, prevention of entry of and infection by a pathogen in a standing crop & precautions during harvesting & storage of the produce. An ideal schedule for controlling a disease is to integrate measures covering these four requirements.
In an integrated diseased management programme in an annual crop (potato, cereals etc.) the first step is the choice of healthy seed of a resistant variety. In potato, the seed tubers carry pathogens of late blight of potato, bacterial wilt, and almost all the viruses. In wheat, seed is the only source of loose smut. In sugarcane, seed setts carry the red rot, wilt & smut pathogens and also the viruses. The healthy clean seed can be obtained as a certified seed from a reliable agency. The next step is to treat the seed chemically if the supplier has not done the same.
The healthy, pathogen free seed is then planted in relatively clean field. In potato, the field should be free from old crop debris. If root knot nematodes are a problem, furrow application of a systemic granular nematicide should be given. Crop rotation is another precaution. During growth of the crop periodical rouging of diseased plants, if any, should be done. The inoculum of a pathogen may arrive from external sources. This inoculum should be prevented from causing infection by sprays of suitable chemicals. At the time of harvest, care should be taken, to discard diseased plants, do the harvesting in a clean weather, and store the produce in proper storage conditions.