After cloudy weather, connect a disease warning with the affected crop and tissue. Weather can make a problem plausible; the observation needed to identify it is more specific.
What a historical pansy case showed
UMass reported a Botrytis diagnosis on pansy blossoms in April 2017. Tannish irregular petal spots enlarged, while no other plant symptoms were reported. The greenhouse had been poorly ventilated, and the plants had been overwatered before a cold, cloudy day. These were reported circumstances of the case, not a controlled test isolating weather as the cause. (UMass case)
Look at the tissue and sequence
UMass's cut-flower guidance describes aging flowers as susceptible and notes that blossom or bud blight may precede less conspicuous leaf spots or stem cankers. That sequence helps explain why a flower observation matters even without obvious symptoms elsewhere. It does not establish a fixed number of days from cloudy weather to disease. (UMass cut-flower guidance)
Turn the warning into a useful crop question
Keep three observations separate: the recent weather and greenhouse conditions, where symptoms first appeared, and how they changed. For example, “spots began on blossoms after a cloudy period” gives an advisor more to assess than “humidity caused disease.” Record unaffected tissues too; they help describe the pattern without ruling a disease in or out.
Bring unresolved symptoms to a crop advisor or plant pathologist. Use the leaf-wetness guide for environmental context. A later normal room reading does not identify the cause of an earlier crop symptom.
Related project questions
To distinguish disease-specific exposure routes, compare Botrytis infection routes and crop-specific downy mildew conditions. For the wider project context, return to agricultural humidity control.
