SAYED M. MOAWAD , SHAHIRA S. MAREI , MAMDOUH M. MATTER AND MOHAMED R. SALEH
Plant Protection Dept., National Research Centre , Cairo , Egypt .

ABSTRACT

The relative. pathogenicity of the microsporaidian Vairimorpha (Nosema) ephestiae to the second and fourth - instar larvae of Heliothis armigera (Hubner) was investigated . The results indicated that the larval mortality increased with the increase of the protozoan concentration in the diet Younger Iavae of the second instar were more susceptible than elder ones of the fourth instar . On the other hand, the latent effects, expressed as mortality or deformity of pupae and adults, were more pronounced among treated fourth instar larvae . The expression of CLD50 ( cumulative median lethal dose was used to calculate all deleterious effects of any protozoan concentration on all stages (larvae, pupae and adults) and averaged 7.2 x10 6 and 12.0 x 10 6 spores / ml for the second and the fourth larval instars , respectively . Larvae survived after infection showed an obvious reduction in pupal formation and adult emergence . The results revealed that V. ephestiae is an efficient biological agent against H. armigera.

Key Words: Protozoa, Vairimorpha (Nosema ) ephesriae , Helior his armigera