Influence of Temperature on Susceptibility of Tribolium Confusum (Coleoptera: Tenebrionidae) Populations to Three Modified Diatomaceous Earth Formulations (Report‪)‬

ABSTRACT The influence of temperature on the insecticidal effect of 3 commercially available modified diatomaceous earth (DE) formulations and their mixture against adults and larvae of Tribolium confusum Jacquelin du Val originating from different European geographical locations was evaluated in laboratory tests. The temperatures tested were 20, 25, and 30[degrees]C. The T. confusum populations (strains) originated from Greece, Italy, Portugal, United Kingdom, Germany, France, and Denmark. Mortality counts were carried out after 7 d of exposure of T. confusum individuals to DE-treated wheat. The 3 modified DEs tested were PyriSec, Insecto, Protect-It, and a mixture of the three. The dose rates tested were 500 and 1000 ppm. The strains from Portugal and France were the least susceptible to DEs, while the most susceptible one was the strain from the United Kingdom. The increase of temperature in many of the combinations tested increased the efficacy of DE formulations against both adults and larvae, but there were some cases in which temperature had no effect on DE efficacy. Moreover, adults were more tolerant than larvae to the DEs tested as well as to their mixture, regardless of the strain or temperature. The present study clearly indicates that there are serious variations in the efficacy of DEs against T. confusum individuals originating from different geographical regions, and several factors affect this efficacy, such as the type of formulation and the temperature level prevailing.