Plant diseases can reduce the quantity and quality of food, fiber, and ornamental products from the time of planting to harvest, usage or storage. Spraying with a chemical is not the key to disease prevention. Controlling plant diseases takes a little preplanning, but can go a long way to prevention.
Eliminating plant diseases is nearly impossible. Controlling measures focus on preventing the diseases from occurring or at least minimizing their effect. Disease control is achieved by understanding the organism that is causing the problem, the condition of the crop, and the tactics available to control the disease.
Plant selection is one of the best disease management tools available. Choosing disease resistant species or varieties can prevent homeowners from having disease problems at all. Consideration should be given to those varieties that have shown a resistance to the common diseases of the area. For instance, tomato varieties are normally labeled “VFN,” “VFNA”, “VFNT”, etc. This indicates that the plants are resistant to Verticullium Wilt (W), Fusarium Wilt (F), Southern Root Knot Nematodes (N), early blight (A), or tobacco mosaic virus (T).
Using plants that will thrive under local growing conditions will mean that these vigorous growing plants will be less susceptible to most diseases. Many varieties of plants that are adapted to Oklahoma already have a defense mechanism built into the plant’s genetic.
Cultural practices that promote the overall health of the plant are another important tool in controlling diseases. Appropriate site selection, establishment procedures, fertilization, pruning and watering all contribute toward making plants more resistant to infection by plant diseases. Healthy, vigorous plants are more likely to tolerate or overcome diseases once infection has taken effect than unhealthy, less vigorous plants. Planting new plants in affected areas will only increase the chances of the disease attacking the new plant.
Pathogen control is another option to preventing the development of diseases. Exclusion of disease plants from the area is a very effective way of assuring that diseases do not become a problem. Early detection through regular inspection is another. Removal of diseased plants and plant parts can eliminate diseases from an area and prevent the spread to other susceptible plants.
Controlling stress and damage is another way to prevent diseases from entering plants. Damaged plants are more susceptible to plant diseases either because plants are weakened or pathogens can enter through a wound. Sheltering or supporting plants that are likely to be damaged by wind can minimize damage. Protecting less cold hardy plants during the winter can prevent winter injury. Protecting plants from damage by weedeaters, lawn mowers, pets and people also helps prevent diseases.
Then there is the environment. Gardeners are quite limited on the ways they can manipulate the environmental factors that influence the infection and disease development. Most of these factors such as moisture, temperature, and wind are due to the weather, especially when they are extreme.
There are a several ways gardeners can alter these factors so that diseases can be avoided. Many diseases need water on plant surfaces to cause infection. Watering carefully to avoid wetting the foliage and watering early in the morning so that plants dry off quickly are good disease control measures. Pruning and spacing of plants to allow better air movement and drying are also effective.
Avoid transporting soil or tools from known disease areas to disease-free areas. Rotate the garden site to disease-free areas or if space is limited, rotate crop placement within the garden from year to year will help control diseases.
Protection of healthy plants by applying a protective fungicide is the last resort for controlling plant diseases. The chemical protective treatment can only be effective if the fungicide is applied before the pathogen has a chance to infect the plant.