1Associate Director of Research (Retd.) APAU, Hyderabad, A.P.
Regional Agricultural Research Station, Lam, Guntur, 522034, A.P.
Field experiments conducted under caged condition to assess the extent of damage and yield loss in MCU-5 cotton variety due to varied larval densities of Helicoverpa armigera (Hubner) indicated results in one larva per 8 plants recorded lowest percent Heliothis damage in respect of squares (8.63), shed squares (39.38) bolls (13.43) and locules (8.91) followed by treatment with two larvae per 8 plants. It was found that percent yield losses varied from 9.32 with one larva per 8 plants to 72.30 with 6 larvae per 8 plants. The economic injury levels based on the regression equation was worked out to be 2.52 and 3.06 larvae per 10 plants during 1988–89 and 1989–90 crop season respectively.
