Acaricidal Effect of Different Diatomaceous Earth Formulations Against Tyrophagus putrescentiae (Astigmata: Acaridae) on Stored Wheat

Abstract

Laboratory bioassays were conducted to evaluate the effect of different diatomaceous earth (DE) formulations against adults and immature stages of the stored-product mite species Tyrophagus putrescentiae (Schrank). Five DE formulations were used in the tests: SilicoSec, PyriSec, Insecto, Protect-It, and DEA-P. The tests were conducted at 25 degrees C and 75% RH, on wheat, Triticum. aestivum L., treated with DEs at two close rates, 0.2 and 0.5 g/kg. The mortality of mite individuals was measured after 5 d of exposure, and after 30 cl the treated wheat was checked for T putrescentiae offspring. Significant differences were noted among the DEs tested. Application of the lowest dose rate (0.2 g/kg) provided mortality of both adults and immatures that exceeded 78%, whereas the respective data for 0.5 g/kg were almost in all cases 100%. The adults of T. putrescentiae were more tolerant to DEs than the immature stages. Generally, PyriSec was the most effective against adults. Progeny production was dramatically reduced with the increase of dose. The results of the present work indicate that T. putrescentiae call be effectively controlled by DEs on wheat, at dose rates as low as 0.2 g/kg.