The insecticidal effect of the azadirachtin-based insecticide, NeemAzal,
was examined against adults of Rhyzopertha dominica (F.), Sitophilus
oryzae (L.), and Tribolium confusum Jacquelin du Val in rye, whole oats,
and peeled oats. The insecticide was applied at three dose rates, which
were equivalent to 50, 100, and 200 ppm of azadirachtin A. Adults of the
above-mentioned species were exposed to the treated grains at 25 degrees
C and 65% RH, and mortality was assessed after 24 h, 48 h, 7 d, and 14
d of exposure. Then, all adults were removed, and the treated substrate
remained at the same conditions for an additional 45 d. After this
interval, the grains were checked for progeny production. In all species
and commodities tested, mortality increased with the increase of dose
and exposure interval, except for T. confusum on whole and peeled oats.
For R. dominica, NeemAzal was more effective on oats than on rye and
peeled oats. In contrast, at rates >= 100 ppm, azadirachtin was equally
effective against S. oryzae on whole rye and oats, where mortality was
100% after 7 and 14 d of exposure, respectively. NeemAzal was not very
effective against T confusum where adult mortality was low, even after
14 d of exposure at the highest rate. For all species, significantly
less progeny were recorded in the treated grains than in the untreated
grains, with the exception of T confusum on oats where offspring was
significantly reduced only at the highest rate