Effect of Serbian-originated diatomaceous earths on Acanthoscelides obtectus (Say)adults on treated beans

Abstract: Based on current IPM programs for the protection of stored products, as well asgeneral food safety concerns, a preliminary study was conducted to test the potential of naturaldiatomaceous earths originating from Serbia (roughly purified at the Institute of Technology ofNuclear and Other Raw Materials, Belgrade) in protecting beans against Acanthoscelidesobtectus (Say). Using modified methods OEPP/EPPO (2004), three dust products with differentSiO2 contents, i.e. DE S-1 with 79.8%, DE S-2 with 63.2% and DE S-3 with 46.5%, were testedagainst A. obtectus in the laboratory at 24±1°C and 55±5% r.h. All three diatomaceous earthswere applied at the rates of 0.5, 1.0 and 1.5g/kg of beans. Lethal effects on weevils weredetermined after three and seven days of contact with treated beans. The effects of dusts onprogeny production/reduction in F1 generation were also determined. A. obtectus mortality afterthree days of exposure was not significant, while maximum mortality after seven days was 52.5and 57.5% on beans treated with the highest rates of DE S-1 and DE S-2, respectively. However,progeny reduction after three days of parent exposure to beans treated with all three rates of DES-1 and DE S-2, and with 1.0 and 1.5g/kg rates of DE S-3 achieved a high level of 97.5-100%and 100%, respectively. Progeny reduction after seven days of parent contact ranged 86.8-100%(DE S-1), 72.8-99.3% (DE S-2) and 17.6-97.1% (DE S-3). The results indicate that the testeddiatomaceous earths have weak direct insecticidal effect on bean weevil adults, but a high impacton progeny production.