Turcicum leaf blight (TLB) is a major disease that causes losses up to 98% in cool and humid conditions. Disease management depends upon resistant sources. However, nonavailability of a foolproof technique makes it difficult to locate resistant sources. Among the existing techniques, the hypodermic method is better but tedious, and causes injury to plants. To find a better alternative technique for inducing field infection, a modified treatment of actual lesion powder was compared with existing methods in glasshouse conditions with a susceptible control (CM 202). The treatment was tested in the field for refinement at a hot-spot location (Barapani, Meghalaya, India; 1000 m msl). Infected leaves were collected from a TLB-affected maize field and actual lesion area was collected. The collected portions of leaves were dried in the shade and pulverized. Two pinches of powder were applied in the central whorl at four growth stages from 2-3 to 5-6 leaf. Both single and repeated applications were tried with two susceptible controls, RCM 1-2 (local) and CM 202 and a resistant control, CM 104. Powder applied at various stages of growth had a significant difference. However, repeat application of powder had no significant difference from single application. Final disease data were recorded on an individual plant basis at the silk drying stage. Powder applied at the 3-4 leaf stage was found effective in inducing field infection abundantly, reaching the score of 5.0 (on a 1-5 rating scale). Hence, a single application of powder collected from the lesion area and applied to maize leaf whorls at the 3-4 leaf stage was found sufficient to induce a full field infection.

Global Maize Program

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INT2823