Irrigating plants with salty well water can cause yellowing around the edges of leaves and leaf-drop starting from the bottom part of the plant's canopy. When a plant does have a disease, the problem may be merely cosmetic rather than truly damaging to the plant. Examples are minor leaf spots or other damage to select leaves. Such minor aesthetic concerns are no cause for alarm or treatment. There are serious diseases, however, that can damage or kill plants they affect.
Examples are mushroom root rot on woody ornamentals, fire blight on loquat and brown patch on turf.
Such diseases can seriously damage the plant's appearance or yield. Because diseases are difficult to identify, it is not recommended to assume a disease is in the works just because of a plant's appearance. The home gardener can use a magnifying glass to look for insect pests that may be causing the damage and also analyze maintenance practices for causes related to visible symptoms. If a disease is still suspected, it is best to contact your local Cooperative Extension Service for advice on how to collect and submit plant samples for disease diagnosis and recommendations on the least-toxic methods of treatment.