INFLUENCE OF GRAIN TYPE ON THE EFFICACY OF SOME FORMULATIONS OF DIATOMACEOUS EARTH AGAINST THE RICE WEEVIL (Sitophilus oryzae L.)

The paper aimed to present the effect of grain type on the insecticidal efficacy of the diatomaceous earth (DE) formulations, applied on wheat, barley, maize and paddy rice against adults of the rice weevil, Sitophilus oryzae L. The formulations used in the bioassays were two local DEs deposits from Romania (Buzău Valey-Pătârlagele and South of Dobroudja-Adamclisi), two from Greece (Elassona region) and two comercial products (SilicoSec and PyriSec). The bioassays were done in laboratory conditions set at 25o C and 60±5%relative humidity in 3 series with 3 replicates. The DEs were applied at the dose rates of 100, 300, 500 and 900 ppm (mg DE per Kg of grain), while mortality of the exposed adults was recorded after 7, 14 and 21 days of exposure. Among the tested DEs, the most effective of all, was the commercial formulation of PyriSec witch manage to total control the adults of S. oryzae in half of the tested grains (wheat and maize) after 7 days of exposure in dose rates above 100 ppm. Between the tested grains, DEs were most effective when applied on wheat and totally ineffective on paddy rice. Furthermore for wheat, the two DEs from Romania and one from Greece (Elassona 1), at the highest dose rate, had the same high performance with the commercial formulation of SilicoSec, while for the other grains all of the no commercial DEs was ineffective and performed the same with SilicoSec formulation. These findings lead us to conclude that our no commercial DEs are competitive with the SilicoSec formulation, and can sufficient protect wheat in doses above 900 ppm.