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Address: P.O. Box 27552, Richmond, Va. 23261-7552
                             Phone: 804-290-1141 Agriculture Lessons: Plant Science 1 Plant Science 2 Plant Pathology Weed Science Horticulture Science Animal Science Basic Entomology Soil Science Activities Quiz Plant Pathology
All living organisms succumb to diseases and this includes plants. Anytime the normal anatomical structures or physiological functions are impaired, the plant is in the diseased state. Obviously, the signs and symptoms range from minimal disorders to death. The disorders that affect plants can be caused by infectious agents as well as environmental factors or lack there of. Some abiotic environmental factors are chemicals, mineral deficiencies, temperatures that are too high or too low, and not enough or too much water. All of these can make the plant susceptible to infectious organisms. Disease causing agents of the biotic community could be bacteria, viruses, fungi and nematodes (roundworms). Color changes, usually yellowing, are indicative of any of the general causes mentioned above. This is called “chlorosis” and we can observe it on sections of the leaf. Brown colors on the leaves can often be the result of a fungus, insect damage, or from the use of herbicides. Galls, tumors, and knots on leaves and stems are the sure signs of insect infestation. Bacteria. Virus. Fungi. Roundworms. Chlorosis.