Many people believe that control of plant diseases always mean the use of chemicals , but many diseases can be controlled by cultural practices. Selection of plant material will greatly affect the amount of disease problems.
Some plants are very susceptible to diseases while others have very few, if any, disease problems.
The use of native plants can reduce the incidence of plant diseases. Some diseases such as the powdery mildews and Botrytis blights are encouraged by high humidity in plantings. Losses can be reduced by not crowding plants. Thin the plants to permit free air circulation and allow sunlight to reach the lower parts of the plants and soil. Diseased branches and shoots should be removed and discarded before a disease can spread.