Integrated control of garlic leaf blight caused by Stemphylium solani in China

Leaf blight caused by Stemphylium solani is a major fungal disease of garlic (Allium sativum) in central China where it has caused severe crop losses during the winter growing season from the end of autumn to the middle of spring. Epidemiology, cultivar resistance, and chemical controls were investigated during the 2006 to 2008 growing seasons in Dangyang County to improve disease control methods. Disease severity monitoring revealed that the activity of S. solani was variable between growing seasons, and this may have been due to weather conditions. Disease severity was positively correlated with increasing temperatures, but no consistent relationship was found between total rainfall and disease. Additionally, the study demonstrated that conidia and mycelium of S. solani could survive in garlic debris for long periods and serve as the primary inoculum source for the subsequent season. Relatively few of the commonly grown cultivars had high levels of resistance to leaf blight. Garlic cultivars 'Qingganruanye', 'Ruanruanye' and 'Zixuan-2' were among the most resistant, but except for 'Zixuan-2', did not produce sufficient harvestable bolts as would be desirable for the local market. All fungicide treatments applied to cloves used as planting material seemed to promote seedling emergence, but significant effects (P = 0.05) were observed only with fludioxonil (0.05 g kg-1) and thiram (1.25 g kg-1). Fungicide applications in the field were effective in controlling leaf blight, and flusilazole (50 g ha-1), flusilazole plus famoxadone (50 g plus 104 g ha-1) or mancozeb (350 g ha-1) had the highest efficacy in reducing leaf blight severity.