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It is very important to remember that a
correct diagnosis is the most important step in the eventual control of a plant
disease. Most diseases have a fairly well established control protocol. Most
often, failure to control the disease happens because the problem was
misdiagnosed in the first place.
This is a list of the most important general strategies for management of plant diseases:
These methods will be discussed further with examples. Cultural methods for disease control refer to those growing methods that reduce pathogen levels or reduce the rate of disease development. These include:
Fig. 58. How are the tomatoes is in this photo being watered? How does this help to reduce disease?
Fig. 59. Note the tall sugarcane planted between rows of much shorter pepper. The sugarcane serves as a windbreak to reduce windblown sand injury that might create wounds for entry of pepper pathogens. The cane also traps winged aphids that might harbor and transmit several important pepper viruses. This is another excellent example of a cultural control.
Fig. 60. What is the obvious cultural control in this picture?
Fig. 61. What control method is being conveyed in this picture?
Fig. 62. Do these cabbage seedlings, bought at a suburban garden center look completely healthy?
Crop resistance The following terms are important in a discussion of crop resistance:
Immunity is the rule in the plant kingdom; most plants are immune to most pathogens. Therefore, one does not have to worry that the black spot on roses will appear next year on the garden tomatoes. Resistance, strictly speaking, refers to the lower disease levels seen in some cultivars or varieties of a particular crop species compared to other susceptible cultivars. Always choose resistant varieties when available. Tolerance refers to varieties or cultivars that appear to be just as heavily diseased as standard varieties, but which manage to be more productive or vigorous.
Fig. 63. Check out these seed packets. Where is disease resistance mentioned?
Fig. 64. Note this cucumber variety. How many diseases is it resistant to?
Create an environment unfavorable to the pathogen and favorable to the crop.
Fig. 65. There are many theories and ideas on the best time of the day to water. From a plant pathology point of view, it is preferable to water late morning, after the dew dries from leaves, but early enough to allow leaves to dry before evening. Of course, ideally, you would water only the soil surface because the roots are the water-absorbing organs.
Next: Module 8 -- Chemical Methods for Disease Control
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