Stemphyllium purple spot
S. vesicarium infects herbaceous plants (onion, garlic, asparagus, lucerne, tomato and soybean) and trees (pear, mango). The symptoms that develop on each host are quite different. Initial symptoms appear on the leaves as brown spots, often surrounded by a purple halo. In garlic and onion, infection usually remains restricted to the leaves and does not extend to the bulb scales. In other hosts, young stems (asparagus, pear) and fruits (pear, tomato and mango) are also infected. Sometimes fruiting bodies (pseudothecia) may appear as small, black, pinhead-like, raised bodies in infected tissue. Pseudothecia of Pleospora allii develop during the winter on plant debris infected by S. vesicarium.
On asparagus, S. vesicarium causes lesions on spears and ferns and defoliation of fern. Tan to brown lesions with purple margins usually appear on the lower half of new spears and ferns, and small, slightly sunken, purple spots are observed just before harvest.