Controlling disease in organic seedlings

摘要

Downy mildew is a financially damaging, common disease in seedlings. Some treatments are available for conventional growers but how can organic producers overcome and prevent the problem? The downy mildew pathogens Peronospora parasitica (downy mildew of brassicas) and Bremia lactucje (downy mildew of lettuce) are both economically damaging seedling diseases. Losses of 10-12 percent during seedling transplant production have been reported in brassicas. Both diseases (Figure 1) ace most damaging toseedlings grown in protected environments because high plant densities combined with warm, humid atmospheres in glasshouses provide ideal conditions for both pathogens to infect seedlings. In conventional production, control of both diseases is by application of metalaxyl (Folio), phosphonic acid-based products (Aliette) anddichlofluanid (Elvaron WG). As these control measures are not open to organic growers, new methods or new organically acceptable active ingredients (natural compounds) for downy mildew control in organic transplant production are required.