The control of plant disease depends on an accurate estimate of the symptoms shown by the affected plant so as to arrive at the exact cause of the trouble. Even with parasitic diseases the cause is usually microscopic, requiring a careful examination and often laboratory tests on the diseased tissues. Similarly with non-parasitic troubles the environment must be studied as well as the plants and the details of cultivation carefully considered. There may have to be a careful soil analysis as well as a study of the drainage and soil texture and there may also be an analytical test of some of the foliage or fruits which could reveal a shortage of some essential plant food. The goal of plant disease management is to reduce the economic and aesthetic damage caused by plant diseases. When a plant is infected or an area is infested with a plant pathogen, eradication can eliminate or reduce the disease threat. Rotation, sanitation, heat treatment, eliminating the alternate host, and certain chemicals can be used to reduce or eliminate diseases. Crop rotation is a common method in both commercial agriculture and home gardens. It is necessary to know the pathogen and its host range. Rotation reduces soil populations of fungi or nematodes only if nonhost plants are used. Plant disease management practices rely on anticipating occurrence of disease and attacking vulnerable points in the disease cycle.  Specific management programs for specific diseases are not intended since these will often vary depending on circumstances of the crop, its location, disease severity, regulations and other factors.