Plant Diseases

Control of plant disease begins with good soil management. The best soil for most plants is loamy, with good drainage and aeration. This minimizes diseases that attack the roots and allows the roots to feed nutrients from the soil to the rest of the plant. Organic methods, such as the addition of compost, can improve soil quality, and fertilizers can be added to the soil to enrich the nutrient base. Soil pH measures the degree of acidity or alkalinity of the soil. Gardeners and farmers must be aware of the pH needs of their plants, since the right pH balance can help reduce susceptibility to disease, especially root diseases like club root or black root rot.

Other important factors in the control of plant disease are the selection of disease-resistant plants (cultivars), proper watering, protection of plants from extreme weather conditions, and rotation of crops. Disposal of infected plants is important in the control of diseases, as is the careful maintenance of tools and equipment used in farming and gardening. Many plant diseases can easily be spread by hand and by contact with infected tools, as well as by wind, rain, and soil contamination. Plant diseases can also be spread by seeds, and by transplants and cuttings; careful attention to the presence of disease in seeds, transplants, and cuttings can avoid the spread of pathogens.

Crop rotation is an important part of reducing plant diseases. Pathogens that favor a specific crop are deprived of their preferred host when crops are rotated. This reduces the virulence of the pathogen and is a natural way to reduce plant disease. Soil solarization is another natural method used by gardeners to reduce diseases.

Barriers or chemical applications to eliminate pests that may carry pathogens to plants are another method of disease control. The use of chemical pesticides has become standard practice among home gardeners and commercial growers alike. Among the organic chemicals used today are copper, lime-sulfur, Bordeaux mixture, fungicidal soap, and sulfur. After World War II, DDT, a synthetic insecticide, was used to destroy plant pests. Today, the use of this and a number of other pesticides has been banned or restricted because they were found to present hazards to the health of human, wildlife, and the environment.