Effect of diatomaceous earth-treated wheat on population growth of stored product mites under laboratory test

The suppressive effect of Detia diatomaceous earth (DE) was tested on the mites Acarus siro L., Tyrophagus putrescentiae (Schrank) and Lepidoglyphus destructor (Schrank) in treated wheat grain. Fifty mites were reared on DE-treated wheat in concentrations ranging from 0 to 250 mg kg(-1) in darkness at 25 +/- 1 degrees C, in 15 +/- 0.5% moisture contents. After 21 days, mites were counted and their growth rates calculated using a polynomial regression model. The DE suppressed population growth of all mite species. The fitted doses of DE for 50% suppression of population growth ranged from 8 to 24 mg kg(-1). The most sensitive was L. destructor, followed by A. siro and T. putrescentiae. The wheat treatment with the highest DE concentration (250 mg kg(-1)) did not eliminate mites completely, but their growth rate was negative. The applications of DE for the control of pest mites in the field condition are discussed in addition to other biological control agents.