Stemphylium leaf blight of garlic (Allium sativum) in Australia

Abstract

Stemphylium vesicarium was isolated from lesions on garlic (Allium sativum) leaves showing purple leaf blotch symptoms in commercial garlic farms at Tenterfield, New South Wales in 1994 and at Waikerie, South Australia in 1997 where an epidemic occurred. This is the first record of S. vesicarium on garlic in Australia. Isolates of S. vesicarium from garlic were pathogenic on onions and leeks. Disease incidence at Waikerie, on three commercially grown garlic cultivars, was 100% with severity of 10–30% leaf area diseased 1 week before harvest. The disease epidemic was influenced by prolonged periods (≥8h) of leafwetness. Most airborne conidia (950/m3) of S. vesicarium were trapped between 1100 and 1500 h. Under the same epidemic conditions five out of 26 garlic accessions grown in seed plots showed good resistance to stemphylium leaf blight.