Botrytis (gray mold) on strawberries

Botrytis gray mold is consistently ranked as one of the most economically significant diseases of strawberries worldwide. The fungus attacks blossoms, developing fruit, and ripe fruit simultaneously, and in wet harvest seasons it can destroy 50 percent or more of a planting's yield. The challenge.

Botrytis gray mold is consistently ranked as one of the most economically significant diseases of strawberries worldwide. The fungus attacks blossoms, developing fruit, and ripe fruit simultaneously, and in wet harvest seasons it can destroy 50 percent or more of a planting's yield. The challenge is timing: the critical infections happen at bloom, weeks before the fruit is visible, and by the time gray mold appears on fruit, the protection window has passed.

I don't grow strawberries at my Long Island property, so this guide draws on University Extension research and UC IPM publications.

The pathogen

Gray mold on strawberry is caused by Botrytis cinerea. Per UC IPM, the fungus overwinters as sclerotia in soil and infected plant debris. In spring, sclerotia germinate and produce spores that are dispersed by wind and rain to open flowers. Infection primarily enters through floral tissue; petals that fall onto developing fruitlets provide additional infection sites.