Downy Mildew of sorghum

Whitish growth on the undersurface of the leaves.

The fungus invades the growing points of young plants and as the leaves unfold they show various types of symptoms. The first few leaves that show symptoms normally are only partially infected (the lower portion) with a lighter green or yellow coloration of the infected portion. Abundant downy white growth is produced on the under surfaces of infected portions of leaves during humid weather (Fig.).

                    Streaks of bleached leaves

Systemically infected plants show progressively more of a complete bleaching of the leaf tissue, sometimes in streaks or stripes (Left Fig.) and sometimes over the entire leaf surface (Bottom Fig.).

Leaf shredding

As the infected bleached leaves mature they become necrotic and the interveinal tissues disintegrate to give the typical shredded leaf symptom (Fig.).

Management

The eradication of wild hosts near sorghum fields. Removal of infected sorghum plants in the field. Destruction of plant debris by deep ploughing and other methods. Growing resistant varieties and hybrids like CSV5, CSV 6 etc.Seed treatment with Metalaxyl at 4 g/kg of seed or with Redomyl MZ @ 6 g/kg seed before sowing of sorghum. Foliar spray of Mancozeb 2.5 g/liter or Metalaxyl MZ at 2g/liter is recommended if standing crop is infested with downy mildew.