The first step in managing plant diseases is to determine which diseases and pathogens are causing the problem. Once a diagnosis has been determined, growers can take the appropriate steps to manage the disease.
Plant diseases in Colorado are caused by viruses, bacteria, nematodes, fungi and higher plants (such as dodder). The majority of diseases seen in the state are caused by fungi. Fungicides have been implicated in the suppression of beneficial fungi in many cropping systems.
- Use clean seed and vegetative propagating material. Some disease-causing organisms are seed-borne and others are associated with seeds.
- Select cultivars that are resistant or tolerant to pathogens.
- Destroy or remove infected crop residues, culled fruits or prunings. Crop residues, which may be reservoirs of disease organisms, can be burned, composted, buried or shredded.
- Rotate crops to avoid or reduce the build-up of disease organisms in a field. Note that some plants have shown to have a suppressive effect on diseases.
Scientists are learning more about the role of the microbes associated with plant roots. Soil microbes can improve soil fertility, break down toxic wastes and contribute to the general health of soil and plants. New technology has made it possible for microorganisms to be formulated as bio-pesticides.
Compost teas are actively brewed to produce beneficial microbes.
- Provide plants with good nutrition. A properly nourished plant can withstand or tolerate the attack of plant pathogens better than a stressed plant.
- Avoid injuring or bruising plants because many pathogens can enter a plant through an injury or wound.
- Use proper spacing to allow air movement between plants and reduce the amount of time that leaves are wet.
- Schedule timing and duration of irrigation to satisfy the crop requirements without over-watering. Too much water can be as detrimental as not enough.
- Select the appropriate control method — biocontrol (using microorganisms) or chemicals (fungicides, bactericides, fumigants and nematicides).
Nematodes: Alternative Controls, National Sustainable Agriculture Information Service
Notes on Compost Tea, National Sustainable Agriculture Information Service
Sustainable Management of Soil-borne Plant Diseases, National Sustainable Agriculture Information Service
Use of Baking Soda as a Fungicide, National Sustainable Agriculture Information Service