12th International Working Conference on Stored Product Protection (IWCSPP) in Berlin, Germany, October 7-11, 2018 Julius-Kühn-Archiv 463 829 OLOTUAH, O.F., OFUYA, T.I. AND ALADESANWA, R.D. 2010: Effect of particle size on insecticidal activity of dusts of Eugenia aromatica and Piper guineense against Callosobruchus maculatus. Nigerian Journal of Plant Protection 24, 34-39. PERISIC, V., VUKOVIC, S., PERISIC, V., PESIC, S., VUKAJLOVIC, F., ANDRIC, G. AND KLJAJIC, P. 2018: Insecticidal activity of three diatomaceous earths on lesser grain borer, Rhizopertha dominica F. and their effects on wheat, barley, rye, oats and triticale grain properties. Journal of Stored Products Research 75, 8-46. SADEGHI, G.R., POURMIRZA, A.A. AND SAFARALIZADE, M.H. 2012: Lethality impact of diatomaceous earth (Sayan®), bran, sawdust and clay on adult of six stored-product insects. Archives of Phytopathology and Plant Protection 45, 986-999. SHAH, M.A. AND KHAN, A.A. 2014: Use of diatomaceous earth for the management of stored-product pests. International Journal of Pest Management 60, 100-113. STATHERS, T.E., RIWA, W., MVUMI, B.M, MOSHA, R., KITANDU, L., MANGRARA, K., KAONEKA, B. AND MORIS, M 2008: Can diatomaceous earth have potential as grain protectants for small-holder farmers in Sub Saharan Africa? Crop Protection 27, 44-70. TEE, S.P. 1981: Powdered paddy husk ash for grain protection against stored product beetles. MAPPS Newsletter 5, 2-3. TOFEL, K.H., NUKEINE, E.N., STAHLER, M. AND ADLER, C. 2015: Insecticidal efficacy of Azadirachta indica powders from sun- and shade- dried seeds against Sitophilus zeamais and Callosobruchus maculatus. Journal of Entomology and Zoology Studies 3, 100- 108. Effects of different inert dusts on Sitophilus oryzae and Plodia interpunctella during contact exposure Sonja Gvozdenac 1 , Tanasković Snežana 2 , Krnjajić S. 3 , Prvulović D. 4 , Ovuka Jelena 1 , Sedlar A. 4 1 Institute of Field and Vegetable Crops, Novi Sad, Serbia 2 University of Kragujevac, Faculty of Agronomy, Čačak, Serbia 3 Institute for Multidisciplinary Research, Belgrade, Serbia 4 University of Novi Sad, Faculty of Agriculture, Novi Sad, Serbia e-mail: sonja.gvozdenac@ifvcns.ns.ac.rs DOI 10.5073/jka.2018.463.179 Abstract The use of natural inert dusts against storage insect pests is increasing recently, as an alternative to conventional insecticides. Laboratory study was carried out to evaluate the contact effect of three inert dusts, diatomaceous earth (DE), kaoline (KA) and vermiculite (VE), at rates 5, 7.5, 10, 15 and 20 gm -2 , against adults of Sitophilus oryzae (L.) and larvae of Plodia interpunctella (Hubner). Insect mortality was evaluated 1, 2, 3 and 7 days after the exposure. Insect mortality varied depending on the species, concentrations and exposure periods. The DE and KA caused 86.7-98% mortality of S. oryzae after 2 days of exposure at the highest rates, while at 5 and 7.5 gm -2 , 100% mortality was achieved only after 7 days. The highest rates of inert dusts caused 42-50% (DE) and 60-75% (KA) mortality of P. interpunctella larvae only after 7days. The mortality of moths increased gradually with the concentration and 100% was achieved 3 days after the contact with DE and KA (10, 15 and 20 g m -2 ). However, inert dusts induced faster pupation of P. interpunctella, while adult emergence was reduced and adults had smaller body-sizes, compared to control. The VE caused relatively low mortalities (7-11% of S. oryzae adults and 5-8% of P. interpunctella larvae) at all tested rates during the entire experiment. Our results have shown good insecticidal effect of DE and KA against S. oryzae and P. interpunctella at 10, 15 and 20 gm -2 . These products could therefore be used by small-scale farmers to protect stored grains against insect pest infestation. Key words: Inert dusts, Sitophilus oryzae, Plodia interpunctella, contact exposure, diatomaceous eartth Introduction In recent years, the use of contact insecticides and fumigants for controlling storage pests is under increasing restriction due to the presence of residues in food and development of insect resistance (Collins, 2000; Kljajić and Perić, 2005). These shortcomings have stimulated the need for testing and evaluation of non-toxic methods that can replace conventional insecticides in stored grains (Arthur, 1996). Recently, physical control methods, like the use of inert dusts, have become prominent (Field and Korunić, 2002). These materials are classified into different groups depending on their composition and particle size and include materials such as diatomaceous earth, silicophosphate, rock phosphate, sand, kaolinite, clay etc. (Golob, 1997). There is a growing interest especially in desiccant or absorptive dusts, among which, diatomaceous earth is the most widely used in practice worldwide (Golob, 1997; Korunić, 1998a; Subramanyam and Roesli, 2000) and in commercial storages in the developed world. On the other hand, non-silica dusts and those composed of coarse grain silicates, such as kaoline and sand, have been used traditionally as grain protectants by small-