Alternative Methods to Chemical Control 849 PS7-25 – 6240 Efficacy of a Chinese diatomaceous earth and purpose-built sprayer for control of stored grain insect pests in an empty warehouse Y. Cao 1 , Y. Li 1,2 , P. Wang 3 , L. Wei 4 , J. Su 3 1 School of Food Science and Technology, Henan University of Technology, Zhengzhou 450052, China 2 Academy of State Administration of China, Beijing, 100037 3 Linli Grain Depot, Linli 415216, China; 4 Henan Weilai Mechanical and Electrical Engineering Co., Ltd. Zhengzhou 4500, China Abstract The aim of these trials was to test the efficacy of an 85 % diatomaceous earth (Puliangtai TM ) sprayed at a rate of 3g/m 2 with a specially developed powder spraying machine. Efficacy was tested by placing 14 empty test dishes spread at intervals on the floor of the warehouse before spraying. Each dish contained 20 live adults of Oryzaephilis surnamensis (Linnaeus) and Sitophilus zeamais (Motschulsky). After application of DE, mortality of insects was counted every 24 h until endpoint. Complete mortality of both test species was obtained in 4~6 days. The spray powder machine successfully distributed the Puliangtai TM evenly across the floor of the warehouse. We recommend this treatment for control of insects infesting empty warehouses and grain handling facilities. Key words: diatomaceous earth, stored grain insect pests, spray powder machine, empty warehouse, Oryzaephilis surnamensis (Linnaeus); Sitophilus zeamais (Motschulsky). Introduction Application of residual insecticides such as malathion, fenitrothion, pirimiphos-methyl, deltamethrin has, for many years, been important component of pest management in empty grain storages and food processing facilities in China. These chemicals are applied to the structures of facilities to limit or prevent infestation. Despite the many advantages of chemical pesticides, such as good efficacy and relatively low vertebrate toxicity, there has been a move away from the use of synthetic insecticides because of growing concerns regarding the potential effects of residues on human health and the increasing numbers of stored-grain insects developing resistance. A potential alternative to the use of chemical pesticides for both treatment of grain and empty storages is insecticidal diatomaceous earth (DE). IDE is composed of the fossilized skeletons of siliceous marine or freshwater organisms, predominantly diatoms. These skeletons are made of amorphous silicon dioxide, which is nontoxic to mammals and is registered as a food additive. Before DE can be used as an insecticide, deposits must be milled to separate individual diatoms. DE is a kind of inert dust. It is used to dilute insecticide dusts, as a carrier, and as an insecticide to control stored grain insect pests. Four thousand years ago, observations of such natural phenomena probably led the Chinese to use diatomaceous earth (diatomite) to control pests (Allen, 1972). Since the 1960s, extensive research has been undertaken on the possibilities of using DE for the protection of stored agricultural products. Today, several commercial insecticidal DE formulations are available on the