If there is a late freeze or even cold weather during bloom time, check the flowers and young fruit for the presence of Botrytis blight. If Botrytis is present, there will be a gray-green fuzzy growth on the plant tissues. Botrytis will usually cause losses early in the growing season, but a lot of rainy weather during the spring may also lead to Botrytis problems. It is not recommended to treat preventatively for this disease. Treat only if there is a frost that damages blooms or if there has been a significant cold spell.
There are two options for good Botrytis blight control. One is to use a fungicide with the active ingredient fenhexamid and is in the chemistry group hydroxyanilides (FRAC code 17). Another option is to use a fungicide in the multi-site mode of action chemistry group (FRAC code M). This fungicide will be most effective if applied as a preventative spray.
Consult your local Cooperative Extension Service office for current fungicide recommendations. Information also can be found in the Southeast Regional Blueberry Integrated Management Guide.
Bill Cline, North Carolina State University Cooperative Extension Service.
Harmon, Philip F. Botrytis Blossom Blight of Southern Highbush Blueberry. University of Florida. IFAS Extension.