Botrytis Bunch Rot Gray Mold

Botrytis bunch rot affects fruit clusters of Oregon grape and mahonia, particularly during wet springs in the maritime Pacific Northwest. Gray mold develops on fruit touching fruit and on injured berries that provide entry points for spore germination. The fungus thrives in dense canopies where moisture lingers, making it most visible around harvest time and in years with humid weather.

The vulnerability window is narrow but critical: disease establishes during fruit set and flowering when dense canopy conditions trap moisture around developing fruit. Your prevention strategy is straightforward; space plantings generously and prune to open the interior for air movement, avoid overhead irrigation, and prevent any fruit damage that could invite fungal entry. Clean up all debris including mummified fruit at season's end.