Surveys between 1989 and 1993 in the major garlic production areas of Spain
identified a new leaf spot disease, characterized by white and purple lesi
ons followed by extensive necrosis. Isolation and pathogenicity tests with
fungal isolates taken from these spots indicated that Stemphylium vesicariu
m was the causal agent. Pseudothecia of the teleomorph stage, Pleospora sp.
, were found on leaf debris from affected plants. Inoculation of garlic and
onion plants with residues carrying mature pseudothecia, or with ascospore
suspensions obtained from the pseudothecia, resulted in the development of
white and purple leaf spots. Wetness periods longer than 24 h were require
d for symptom development under controlled conditions. Isolates of S. vesic
arium from garlic, onion and asparagus caused disease in all three hosts. I
n garlic, cv. Blanco de Vallelado was most susceptible, while lines B4P17 a
nd B6P1, and cvs Iberose and Golourose were less susceptible to the disease
.