Mortality and suppression of progeny production of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) in seven different grains treated with an enhanced diatomaceous earth formulation
DEBBM, an enhanced diatomaceous earth (DE) formulation consisting of a mixture of DE and the plant extract bitterbarkomycin, was applied to seven different grains (wheat, barley, oats, rye, triticale, paddy rice and maize) at two dose rates 50 ppm and 150 ppm. Unsexed, 7d old adults of Sitophilus oryzae (Coleoptera: Curculionidae) and Tribolium confusum (Coleoptera: Tenebrionidae) were exposed to the DEBBM treated commodities and their mortality was assessed after 7d and 14d of exposure at 25 oC and 65% r.h. Furthermore, progeny production of the tested species per treated commodity was also assessed. Sitophilus oryzae appeared to be more susceptible than T. confusum to DEBBM. Performance of DEBBM was better in barley, wheat and oats compared to the remainder of the tested commodities. DEBBM performed better in rye and triticale than in paddy rice against both species although in many cases, significant differences among these grains were not recorded. Despite that DEBBM reached its highest efficacy levels on barley, wheat, and oats it did not suppress progeny production of the treated species in any of the grains. A significant reduction in progeny production of the treated species was recorded in the DEBBM treated grains in comparison with the untreated ones. This reduction in progeny production was expressed more vigorously to S. oryzae rather than T. confusum. In commodities with high DEBBM performance such as barley, oats or wheat, > 9-fold less progeny of S. oryzae were recorded at 150 ppm of DEBBM than in the untreated commodities. Although significantly less progeny of T. confusum were recorded in DEBBM treated grains than untreated grains, progeny suppression of this species was neither dose nor commodity dependant. Keywords: Diatomaceous earth, Bitterbarkomycin, Tribolium, Sitophilus, Mortality, Commodit
