Management of red flour beetles, Tribolium castaneum, using eggshell nano-powder

Red Flour Beetles (RFB) are a major stored product pest that can damage milled grain and baked goods. They contaminate wheat flour with insect fragments, and can cause mold and color changes in flour. This presentation explores the use of eggshell nano-powder and eggshell nano-powder plus Spinosad as a natural insecticide for RFB adults and larvae. Spinosad has been labeled organic by the EPA since 1997 and has an organic label rating by the USDA since 2003 as it is extracted from a bacterium cultured on simple sugar. Spinosad at a rate of 1 ppm has a mortality rate of 54% and 56% to RFB adults and larvae, respectively, after 7 days. In an attempt to increase the mortality rate higher, Spinosad was added to Eggshell nano-powder, with an average size of 117 nm (measured via TEM).

Surprisingly, eggshell nano-powder alone caused mortality of the RFB adults at 94±5% at 0.04 mg/mm2 on a glass surface after 7 days. Although eggshell nano-powder alone was very effective in killing adults, eggshell nano-powder only had a mortality rate of 50% when RFB larvae were exposed for 7 days. However, when the eggshell nano-powder was combined with 1 ppm Spinosad applied to the surface of the bioassay tube, the mortality of the RFB larvae increased to 98±2% after 7 days. Thus, eggshell nano-powder alone caused good control of RFB adults. Larvae of RFB were very tolerant to eggshells alone, but the addition of Spinosad with eggshells increased the RFB larvae mortality.