Gray Mold

Gray mold makes itself known when current-season shoots on conifers and susceptible ornamentals curl, twist, wither, and turn brown, often with a distinctive fuzzy gray fungal growth visible in moist conditions. The infection may start in lower foliage and move upward, killing needles and woody portions of the shoot. Unlike frost damage, which causes similar wilting, gray mold leaves a telltale gray fungal coating over infected areas when humidity is high, making diagnosis straightforward. This disease affects a wide range of plants from Douglas fir to kiwi, and establishes wherever humidity, moisture on foliage, and dead or wounded plant parts converge.

The reason gray mold thrives in Western Washington is our naturally humid springs and falls, and controlling it hinges entirely on managing moisture and air movement rather than fungicides. Remove all dead and dying plant parts (especially flowers and fallen debris) from your greenhouse or growing area, space plants generously to ensure air flows freely around foliage, and maintain humidity below 90% through venting and heating if necessary. Avoid wetting foliage during watering, particularly in evening hours when moisture lingers, and clean and sanitize growing areas before each production cycle to eliminate fungal spores overwintering in crop debris.