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Avoiding Plant Diseases

Posted Jun. 1, 2000

This time of year we receive calls dealing with plant disease problems, mostly turfgrass, ornamental plants and trees. The call usually begins with a homeowner describing some type of abnormal growth pattern. (And my grandmother said I'd never get anywhere with my vivid imagination.) Even when horticulturists have a working understanding of the plants and knowledge of the different diseases that affect them, they can easily misidentify some diseases. It is always hard to diagnose and prescribe over the phone. Diagnoses are less difficult when plants are sent in with a note describing their history, including fertilizer and pesticide applications. Having the plant and this type of information on hand allows close observation and a more accurate diagnosis.

Often plants are placed close to each other and receive plenty of rainfall or irrigation, much like agronomic crops. High humidity and moderate temperatures can cause some plant disease symptoms. When you add little or no air movement to the high humidity and moderate temperature, plant diseases have an ideal opportunity to set up housekeeping.

Sometimes improper cultural practices, including misapplication of a herbicide, can foul up the plant's growth pattern and cause symptoms that look like disease.

Stress to plants can take the form of dry weather, long spells of excessive heat, or prolonged wetness from rain or irrigation. Wind damage, hail damage, or anything else that injures the plants can encourage stress-related problems. Let's look at the recent past in the life of most plants in this area. It has been rather stressful for them the last two years because of the long periods of heat and lack of rainfall. It is our job to lessen the forms of stress, which in time will lessen the stress in our lives.

How can we control plant protection? Some things we can do before planting will help alleviate many problems: selecting plants adapted to the area and specific sites, lowering the number of plants in one area to increase air flow, and practicing transplant aftercare. By carefully watching plants' growth and development, potential problems can be detected earlier. When chemical control of a problem is required, proper chemical selection and application rate are a must to ensure the safety of the plant or crop.

Both Oklahoma and Texas extension services have a publication dealing with proper plant selection for most plants. Both states also participate in a program of determining the adaptability of plants in different areas. Each publishes a "best plant list." In Oklahoma it is called "Oklahoma Proven"; in Texas, "Texas Superstar." These programs take a lot of the guesswork out of gardening.

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