Plant diagnostics in the nursery: Putting together the puzzle

Understanding plant symptoms and its pattern, onset timeframe and appearance is critical for diagnostics.

“What’s wrong with my plant?” is a common question among commercial nursery growers. According to Michigan State University Extension, abnormalities on plants can be caused by a plethora of biotic (biological) and abiotic (environmental) factors and even a combination of many factors. Context and history of the plant can be one of the most informative clues to the symptoms that the plant is demonstrating. Examining the conditions and surrounding plants to those affected is critical for diagnosis. Even the most experienced diagnostician may misdiagnose the true problem without understanding the whole picture: Are plants around it experiencing similar symptoms? Where are they located in the nursery? What were the plants directly treated with? There are four key steps in starting the plant diagnostic process:

  1. Keep accurate records.
  2. Define the problem.
  3. Look for patterns.
  4. Determine if it is a result of a biotic or abiotic factor.

Keeping accurate records of when the plants and neighboring plants were moved to the production area, what types of chemicals have been applied and how fast plants demonstrated symptoms is critical to an accurate diagnosis. For example, spray records may provide insight to an over-application in frequency or rate of a product.

Understand the problem before proceeding forward with the diagnostic process. New plant varieties can demonstrate an appearance that is atypical for other varieties of the species while it might be perfectly normal for that variety. For example, a chlorotic leaf margin may be interpreted as a magnesium deficiency, but it might just be a new variegated variety. For more information on nutrient deficiencies, check out the Center for Applied Nursery Research article “Container Nursery Crop Nutrient Deficiencies” and an article on conifer nutrition by MSU’s Bert Cregg.

Patterns of symptoms on the plant and between plants in a crop can give clues to the cause of the problem. Patterns on a plant, such as chlorotic foliage on the new growth or the old growth, can indicate a nutritional deficiency or toxicity, for example. Recognizing a pattern of symptoms within the production area can also provide insight. If symptoms are seen sporadically throughout the crop, likely the cause is a biotic factor, such as the presence of a pest, bacterial wilt, virus or fungus on nursery crops. If the symptoms are seen uniformly on all plants in a row or area, the cause is likely due to abiotic factors including environmental conditions, such as drought stress, or chemical applications, such as herbicide drift. In addition, the timeframe in which the symptoms appear may indicate a biotic or abiotic factor. If plants expressed symptoms very rapidly, the cause is likely environmental while if the problem continues to get worse, the cause is probably due to a pest or disease.

Lastly, if you encounter a problem in your own crop, consider sending it to MSU Diagnostic Services. Be sure to provide full details about the crop and three photos of the plant: a close up of the symptom, one of the whole plant and one of the plant amongst others. Diagnostic tests, such as tissue or media samples, may be indicators of a pathogen or pest, but may not always indicate more complicated, difficult problems. Providing extensive details helps them diagnose your problems more quickly and accurately.

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