Impact of diatomaceous earth on adults and larvae of the yellow mealworm, Tenebrio molitor L

Abstract

Although the efficacy of diatomaceous earths (DEs) against most major stored product insects has been extensively evaluated, studies on the effect of DEs on the yellow mealworm, Tenebrio molitor, are rather limited. Apart from being a secondary colonizer of stored commodities, T. molitor is currently one of the most promising species reared to obtain protein sources. In order to update the available information on the tolerance of T. molitor to DEs, we carried out a series of laboratory bioassays with both adults and larvae of T. molitor at a range of DE doses (20, 50, 100, 250 and 1000 ppm). Briefly, 10 g of treated bran were placed in plastic cylindrical vials together with 10 T. molitor adults, 10 large or 10 small larvae. Untreated bran served as control. Mortality was recorded after 7, 14 and 21 d of exposure. After this interval, vials with larvae were examined for adult emergence once a week. Based on our results, adult survival was not significantly affected by DE application. Similarly, mortality of small and large larvae was low, regardless of the exposure interval and the DE dose. Finally, adult emergence was in most cases not significantly affected by the DE treatment in both bioassays with small and large larvae. In general, the results of the present study clearly illustrate that the DE doses used here do not drastically affect adults and larvae of T. molitor. Considering the increased interest for the production of T. molitor at a global scale, and given that this species is typically reared on commodities that are suitable for the development of other major stored product insects, the addition of small doses of DEs in rearing material may be used as a means to mitigate the “cross-infestation” in T. molitor-producing lines by other storage insect species.