Identifying plant diseases and diagnostic tests
Infection and response • Plant disease (biology only)
Flashcards
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Key concepts
What you'll likely be quizzed about
Visible symptoms and reference guides
Plants show predictable symptoms such as stunted growth, spots, malformed leaves, discoloration and areas of decay; these symptoms guide initial identification. Gardeners and horticulturists compare symptoms with descriptions and photographs in gardening manuals or reputable websites to form a provisional diagnosis, because matching visible signs to known diseases provides a rapid first step in control and treatment.
Taking samples to a laboratory
Laboratories provide confirmatory identification through microscopic examination, culturing and biochemical tests. Culture techniques such as streak plates isolate bacterial or fungal colonies so that colony appearance and further tests identify the pathogen; accurate lab diagnosis allows targeted treatment. Limitations include time taken for cultures to grow, need for sterile technique and the possibility that some pathogens do not culture well.
Testing kits and monoclonal antibodies (Higher tier only)
Monoclonal antibodies bind specifically to antigens on pathogens and form the basis of many rapid test kits. These kits produce quick, specific positive or negative results for particular pathogens, reducing the need for time-consuming culture. Limitations include the kit’s specificity to particular pathogens (false negatives for untested pathogens) and cost; proper interpretation requires understanding of what the kit detects.
Cause → effect: identification leading to treatment
Correct identification of the causal agent (virus, bacterium, fungus, pest or nutrient deficiency) directs the appropriate control measure: antifungal spray for fungal infections, removal and burning of infected tissue to prevent spread, or nutrient amendment for deficiency. Misidentification produces ineffective treatments and wasted resources, so confirmation by laboratory tests or specific kits improves treatment success.
Practical limits and accuracy
Visual guides suit common, distinctive diseases but can mislead when symptoms overlap between causes (for example viral mosaic patterns versus fungal spots). Laboratory tests increase accuracy but require time, equipment and sterile technique. Monoclonal antibody kits are fast and specific but only detect the pathogens they are designed for; negative results do not exclude other infections.
Key notes
Important points to keep in mind