If soil drainage is poor, you may want to consider raised beds to avoid excess soil moisture. Finally, avoid fluctuations of too little water and then too much. Blossom end rot of tomato is an example of a problem that may develop when such moisture fluctuations occur. Control insects and weeds. Certain insects, especially aphids and leafhoppers, may transmit virus and bacterial diseases to healthy plants.
Perennial weeds can serve as overwintering spots for disease organisms, especially viruses.
Consequently, keeping weeds and insects under control also may pay dividends in reduced disease pressure. Clean up garden at season's end. Removing dead plants from the garden during the growing season and in the fall will reduce the chance of pathogens surviving over the winter. Fall tillage will bury and help to speed up the breakdown of any remaining plant residue. Weeds also should be removed because they can harbor pathogens until spring.