What is Plant Pathology?
Plants make up the majority of earth’s living environment as trees, grass, flowers etc. Directly or indirectly plants also make up all the food on which humans and all animals depend. Plants are the only higher organisms that can convert the energy of sunlight into stored, usable chemical energy.Plants grow and reproduce well as long as the soil provides them with sufficient nutrients and moisture, sufficient sunlight reaches their leaves, and the temperature remains within a certain range. Plants however do get sick. Sick plants grow and reproduce poorly, exhibit a range of symptoms, and often parts or whole plants die due to disease.
The causative agents of disease in plants are similar to those causing disease in humans and other animals. They include microorganisms such as viruses, bacteria, fungi, protozoa, and nematodes, and unfavorable environmental conditions such as lack or excess nutrients, moisture, light and the presence of toxic chemicals in the air or soil.
Plant pathology is the study of the microorganisms and the environmental factors that cause disease in plants; the mechanisms by which these factors induce disease; and the methods of preventing or controlling disease and reducing its damage. Plant diseases can result in less food, higher prices for food, food of poor quality, and/or that is unfit for consumption due to toxic contamination from the pathogens.
Management practices that result in plant disease prevention or control include using resistant varieties, disease-suppressive cultural practices, biological agents antagonistic to disease, and chemical pesticides. The use of pesticides to control plant disease usually includes fungicides, bactericides, fumigants (both soil and post harvest treatments), and sometimes insecticides that control insect vectors of a pathogen.
Integrated disease management involves first diagnosing that in fact a disease is the problem and that a pathogen is present and is the causal agent. Second, monitoring the extent of the disease (in space and time) and determining whether it makes economic sense to take any additional curative actions. Third, determining that the environmental conditions exist currently, or may occur, that will contribute to further disease. Fourth, developing a plan of action, including appropriate preventative and curative measures.
The choice of what pesticide to use should be based on efficacy, use of least toxic chemicals whenever possible, rotation of chemicals to reduce potential resistance developing in the pathogen population, and environmental fate concerns. The timing of pesticides, and any other intervention for disease control, should be based on knowledge of the, 1). pathogen and it’s most susceptible growth stages, 2). host and its growth and reproductive stages, and, 3). environmental factors such as temperature and plant surface wetness conditions resulting from rain, dew, and/or irrigation events.