Epidemiology and control of grape black rot in southern Switzerland

Guignardia bidwellii, the causal agent of black rot of grape, appeared in 1988 in a restricted area in Switzerland. Ascospores discharged mainly at the beginning of and during flowering in correspondence with initiation of rain. Leaf infections had little correlation with disease on bunches. Secondary infections seemed to play no major role in disease on bunches. Loads of primary inoculum must be consistent to cause problems. We suggest that in the vine growing systems used traditionally (hand pruning), black rot disease can be avoided by sanitation measures.