Impact of food source on survival of red flour beetles and confused flour beetles (Coleoptera : Tenebrionidae) exposed to diatomaceous earth

A series of experiments was conducted to determine the effect of a flour fo od source on survival of red flour beetle, Tribolium castaneum (Herbst), an d confused flour beetle, Tribolium confusum (DuVal), exposed to the labeled rate (0.5 mg/cm(2)) of Protect-It, a marine formulation of diatomaceous ea rth. Beetles were exposed at 27 degrees C, and 40, 57, and 75% RH in 62-cm( 2) petri dishes. When beetles were esposed for 1 or 2 d in dishes with the labeled rate (0.5 mg/cm(2), or 31 mg per dish) of diatomaceous earth or in dishes containing flour at varying levels from 0 to 200 mg mixed with the l abeled late of diatomaceous earth, survival of both species increased as th e amount of flour increased, and quickly plateaued at levels approaching 10 0%, In a second set of experiments, experiments, beetles were transferred t o dishes containing flour at varying levels from 0 to 200 mg after they wer e esposed for 1 or 2 d in dishes with the labeled rate of diatomaceous eart h alone. There were no significant differences in beetle survival among the levels of flour, however, survival in dishes with flour was usually greate r than survival in dishes with diatomaceous earth alone. In a third test, b eetles were exposed for 1, 2, and 3 d in dishes with tither the labeled rat e of diatomaceous earth alone (clean dishes),dishes with diatomaceous earth and empty straws, or dishes with diatomaceous earth and approximate to 300 mg of flour packed in the straws. Survival was not significantly. differen t between clean dishes or dishes with straws, but survival in dishes contai ning the str aws with flour was usually 100%, regardless of exposure interv al. In all experiments, confused flour beetles were less susceptible to dia tomaceous earth than red flour beetles. In addition, survival was negativel y related to exposure interval and positively related to relative humidity.