Current study was conducted to evaluate some plant oils (clove, spearmint and orange);
plant powders (clove, spearmint and orange); two inert dusts (silica and katelsous) and the insecticide
(malathion) as recommended standard reference against one of the most important stored grain insects,
Rhizopertha dominica. Three methods of application, mixing with medium, residual and repellent
activity were used to determine some criteria (toxicity, emergence, progeny reduction, which measure
the susceptibility of the tested insect). In addition, the study included the damage of grains (% wheat
loss) and the side effect on the germination. Results showed that toxicity of the tested materials were
depending on insect species and bioassay methods. This variation may be regarding to feeding habit of
tested insects and the vapor pressure and molecular weight of each compound, which influence the
level of toxicity. Moreover, insecticidal activity in the tested materials was related to their chemical
composition, and activity decreased with the time depends on the component volatility for oils.
Moreover, clove oil showed to has the best effects among the oils in the present study, where it
reduced the emerged adults, the percent of weight loss and increased the percent of reduction.
However, the clove oil inhibited the percent of germination of R. dominica. Results also showed that
the percent of germination did not influence by the method of mixing.