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PLANT PATHOLOGY |
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KEY CONCEPTS
I. Definition of Plant Pathology
III. Diagnosis of Plant Diseases
IV. Disease Control
A. AvoidC. Use resistant or tolerant plants
G.Chemical Treatment of Plant Diseases
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DISEASE CONTROL
By the time disease symptoms appear, disease pathogens are inside the plant and usually beyond control. Therefore, it is important to prevent penetration of pathogens. Consider the following methods of disease control:
Avoid certain diseases through choice of appropriate site and planting time, purchase of disease-free stock and cultural practices that do not favor disease infection. Insect control can be important for controlling spread of viruses, mycoplasmas, bacteria and fungi. Mulching can help control diseases by preventing the contact of foliage with soil.
Exclude insect vectors with row covers. Don't bring diseased plants into the garden.
USE RESISTANT OR TOLERANT PLANTS
Appropriate selection of species or cultivars will avoid or minimize problems.
Remove all diseased plants, including alternate hosts. Immediate removal of diseased plants or plant parts reduces the chance of the disease spreading. Selective pruning and careful sanitizing of pruning equipment can prevent spread of disease. Rotate crops to avoid soil-borne diseases.
Use best cultural practices. Follow recommended cultural practices.
Treat plants with recommended chemicals to prevent infection. Some treatments will stop the spread of the pathogen.
CHEMICAL TREATMENT OF PLANT DISEASE
To use fungicides and bactericides effectively, follow these 4 steps:
1. Be sure that the diagnosis is correct.
2. Choose a recommended control. Remember, a fungicide controls fungal diseases and bactericides only control bacteria. Read the product label and follow the instructions precisely. Make sure the plant you will be treating is listed on the label.
3. Apply the control correctly following all label instructions. To be effective, fungicidal sprays must be applied properly. They work by creating a barrier that pathogens cannot penetrate. Good coverage is important. Give special attention to the underside of leaves, especially lower leaves. The barrier's effectiveness is affected by how well the spray spreads and sticks. Many fungicides have SPREADER-STICKERS added to the product. If you are not sure about coverage, observe the pattern spray deposits.
4. Apply at the recommended time. In many cases, fungicides are a protectant and must be applied just before the pathogen is able to infect the plant. As the plant grows, additional sprays may be necessary to protect the new growth.
Fungicides are developed so that they degrade fairly rapidly. They are affected by rain, sun, and microbial activity. Excessive rainfall or growth will require shorter intervals between spraying. New shoots should be treated. Product label guidelines usually indicate a range of 7 to 14 days. Fact Sheet 3038, "Using Fungicide Sprays Effectively has helpful tables for mixing and applying products, Reference Path.1.
Know exactly what disease pathogen or combination of pathogens and abiotic agents are causing a plant problem. Fungicides and bactericides are effective against specific diseases under specific conditions. In the past, general fungicides were used. Many pathogens developed resistance to these general pesticides.
Use common sense in analyzing a situation. If an expensive or sentimental plant is experiencing problems, seek the help of professionals at the Pest and Plant Diagnostic Clinic. The current procedures are in Reference Path.2.
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