Evaluation of natural diatomaceous earth deposits from south-eastern Europe for stored-grain protection: the effect of particle size

BACKGROUND: The use of diatomaceous earths (DEs) provides a promising alternative to the use of contact insecticides in stored-product IPM. Geographical origin and the physical properties of a given DE may affect its insecticidal activity. in the present study, DE samples were collected from different locations of south-eastern Europe, and their efficacy was evaluated in the laboratory against Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujiidae), Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). In addition, three fractions comprising particles of different size were obtained from each DE sample and assessed with regards to their effectiveness against the above stored-product insect pests. RESULTS: DE from the Greek region of Elassona was the most effective against C. ferrugineus and S. oryzae, whereas the DE Kolubara 518, mined in the Serbian region of Kolubara, was the most effective against R. dominica. Smaller particles were more effective than larger particles against the three tested species, although significant differences in the efficacy of fractions containing particles of 0-150 mu m and particles with sizes of <45 mu m were not always recorded. CONCLUSIONS: Deposits from south-eastern Europe appeared to be very effective against the tested species, and therefore this region should be further evaluated as a source of development of commercial products. Particle size is a physical property that should always be taken into account during the DE manufacturing process, as it can strongly influence the insecticidal action of a given product. (C) 2009 Society of Chemical Industry