Laboratory experiments were carried out at 28±2°C and 55±5 % RH. to
evaluate the efficiency of katel- sous (KS), diatomaceous earth (DE) and their
joint action against three species of stored product insects, namely the rice
weevil, Sitophilus oryzae (L.), the lesser grain borer, Rhizopertha dominica (F.)
and the red flour beetle, Tribolium castaneum (Herbst).
The grain protectants katel-sous and diatomaceous earth,when used
separately, gave relatively lower percentages of insect mortalities as compared
with those resulted from the application of the different mixtures of the two
dusts. The effectiveness of KS and DE alone or in combinations was
concentration- and exposure period-dependent. Adults of T. castaneum were less
sensitive to the tested dusts than the other two insect species.
Additionally, when the two dusts were mixed together and applied to
the grains against S. oryzae- adults, additive effects were noticed for all the
tested combinations at different concentrations and various exposure periods of
2, 3, 5, 7 and 14 days.
Similar result was also obtained in case of R. dominica, except for the
two mixtures, which showed a potentiation effect at 2 days exposure-period.
In case of T. castaneum, two mixtures showed negative effects at shorter
exposure periods of 2 and 3 days, but these effects turned to additive effects at
longer exposure periods, and the other combinations indicated additive effects at
all exposure periods.
In general, the obtained results revealed that the effectiveness of katel
sous against the insect species under study was obviously improved by adding it
to the diatomaceous earth dust.
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