Biofuel byproducts mimic insect growth regulators at inducing lethality of immature but not adult stored product insects

In an effort to reduce greenhouse gases, the production and integration of biofuel into our transportation systems has been increasing. However, there are some shortcomings in biofuel technology including the by-products produced in the biofuel conversion process. One possibility is to develop these by-products as value-added, biologically-derived insecticides. With resistance on the rise, as well as consumer demand for natural products, it is vital to diversify chemistries for mitigating stored product pests. The extract from the lignocellulosic biomass was fractionated by boiling points (e.g., 115–170°C, 200–255°C, etc.) and then each fraction was tested as a putative bioinsecticide against adult or immature red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and confused flour beetle, Tribolium confusum (L.) (Coleoptera: Tenebrionidae) on concrete arenas. Immatures were also tested on concrete arenas and checked for adult emergence. To determine if there was any long-distance repellency, fractions were tested against adult stored product pests in a wind tunnel assay. While lethality of the potential bioinsecticides to adults was minimal, larval mortality was high compared to controls with many molting deformities, suggesting that the bioinsecticides act as insect growth regulators. Minimal repellency was found in only a couple species. An LD₅₀ calculation was attempted using the fraction with the most insecticidal activity, but doses up to 3.25X of the original formulation proved ineffective against adult store product pests. While insecticidal activity against adult stored product species is minimal, there is potential in the chemistry of some fractions to disrupt emergence from the larval stage.