Insecticidal Effect of Beauveria Bassiana and Paecilomyces fumosoroseus alone and in Combination with Diatomaceous Earth Against Rice Weevil (Sitophilus oryzae) and Red Flour Beetle (Tribolium castaneum)

The virulence {bioassay tests) of two fungal entomopathogens such as Beauveria
bassiana and Paecilomyces fumosoroseus alone and in combination with 250 and 500 ppm of
Diatomaceous earth (DE) was evaluated at laboratory scale. The results demonstrate that
50% relative humidity (RH) is more suitable to kill the insects than at 70% RH. Further,
combined in inocu1ation treatments of both entomopathogenic fungi under test, along with
higher doses of DE (500 ppm), recorded greater mortality than any other treatments followed
by combined treatments of DE at 250 ppm. Nevertheless, the control treatments have recorded
from 10-18% mortality. Although higher % mortality was observed with single treatment of
Beauveria bassiana and Paecilomyces fumosoroseus over controls, greater differences were
not observed compared to combined treatment of Beauveria bassiana with 250 ppm of DE.
However. simultaneous use of DE with the fungus resulted an additive effect. Therefore, from
the practical point of view, this substance {DE} is very good alternative to traditional
insecticides.