Phomopsis Fruit Rot and Rachis Blight
Pathogen:
Phomopsis viticola
(Sacc.) Sacc.
Impact on grapevine:
Rots berries, shrivels up and kills rachis.
Symptoms: Berries turn brown first and develop small black pustules only
when the entire berry has been spoiled. Affected berries remain round, but
occasionally fall off the rachis. When infected, the rachis shrivels up and dries
out.
Susceptible growth stages:
Rachis infection can take place from cluster
emergence until ripening; fruit infection can happen from bloom to pea-size
berry stage, but symptoms develop only after veraison.
Favorable conditions:
Cool, rainy weather during ripening; heavy rains
appear to be important.
Preventive fungicides:
mancozeb, captan, and ziram.
Rescue fungicide:
No fungicide is known to provide eradicative control of
Phomopsis fruit rot once rot symptoms have developed.
Cultural practices:
Sanitation (excision of old wood, removal of diseased
plant material).
Susceptible cultivars:
Vignoles, Seyval Blanc, Vidal Blanc, Chardonel, Concord and Delaware.
