Extension agents and growers may occasionally receive diagnostic reports from the University of Kentucky Plant Disease Diagnostic Laboratory that indicate “no disease was found.”
One possible cause for “no disease” diagnoses is insufficient sample size. This occurs when the sample size is too small or does not represent the affected area. Often leaves, small twigs, or dead plant material (Figure 1) provide little information to determine potential causes of problems.
When symptoms are inconclusive, diagnosticians may recommend an agent or grower re-examine the entire plant to provide additional information or additional sample material.
Another reason for “no disease” diagnoses is that symptoms may be caused by an abiotic factor as opposed to a plant pathogen. Many environmental or cultural conditions can cause symptoms that are similar to those of infectious diseases.
For more information on a “no disease” diagnosis, refer to the publication Diagnosis of “No Disease” (PPFS-GEN-11).
Additional Information
- Diagnosis of “No Disease” (PPFS-GEN-11)
- Submitting Plant Specimens for Disease Diagnosis (PPFS-GEN-09)
- Plant Pathology Publications (Website)
By Kimberly Leonberger, Plant Pathology Senior Extension Associate, and Nicole Gauthier, Plant Pathology Extension Specialist
Kentucky Pest News 
