The red flour beetle (Tribolium castaneum), shown here on bleached flour, is a significant pest of stored products. In new research, very few red flour beetles normally developed to adults after exposure to insecticidal pyrolysis oil derived from biofuel production. (Photo by Rob Morrison, Ph.D.)

By Rob Morrison, Ph.D.

The past 30 years have seen significant advances in the production of biofuels—liquid fuels such as ethanol and biodiesel that can be derived from renewable, nonfood, bio-based feedstocks such as lignocellulosic biomass or algae. Part of these advances is discovering uses for byproducts of the biofuel production process, and new research shows that some of these byproducts show promise as insecticides targeting stored product pests.

In a multimillion dollar project funded by the U.S. Department of Energy’s Bioenergy Technologies Office, my fellow researchers and I from the USDA-ARS Center for Grain and Animal Health Research (CGAHR), National Renewable Energy Laboratory (NREL), and Michigan State University set out to determine whether byproducts from cellulosic biofuel production could be used to manage an array of important agricultural and stored product insects. These byproducts—or “coproducts” as they’re deemed when found to also be of value—are poorly suited for fuel streams, but they could increase the cost effectiveness and sustainability of biofuel production by being applied for other purposes rather than going to waste.

One of the primary biofuel production processes is pyrolysis, in which biomass is deconstructed through high heat in the absence of oxygen. Our team of researchers examined coproducts heated to specific temperature ranges, also called “fractions,” from this pyrolysis process and found that they successfully mimic insect growth regulators when applied to a range of stored product insects, including the red flour beetle (Tribolium castaneum) and the confused flour beetle (Tribolium confusum). Our findings are published this month in the Journal of Economic Entomology.

Even at low concentrations, the oils were found to cause deformities in normal development such as incomplete metamorphosis or only partial hardening of the pupal case. In the end, many of the exposed larvae never matured to adults. At higher concentrations, there was 100 percent population suppression of both red flour beetle and confused flour beetle larvae. By contrast, adults were relatively unaffected.

Furthermore, the price point for the intermediate pyrolysis oil was very reasonable at less than $1 per kilogram (kg) to produce, while the final pyrolysis oil cost between $1.41 and $1.70 per kg. That’s just 0.9 percent of the cost of the commercially available insect growth regulators for stored product insects.

Finally, a greenhouse gas (GHG) emissions lifecycle assessment was also performed, and the team found the use of the pyrolysis oil could reduce GHG emissions associated with the insecticide production supply chain by 25–61 percent relative to that of a fossil-fuel based insecticide or pyrethroid.

Thus, the pyrolysis oil is incredibly inexpensive to produce, highly effective against insect larvae, and more sustainable than conventional alternatives. We are encouraged that adoption of such bio-oils as pest management tools in agriculture will help enhance the sustainability of using biofuels to source at least some of society’s energy, while contributing to global food security.

“A Biomass Pyrolysis Oil as a Novel Insect Growth Regulator Mimic for a Variety of Stored Product Beetles”

Rob Morrison, Ph.D., is a Research Entomologist at the USDA-Agricultural Research Service, Center for Grain and Animal Health Research, in the Stored Product Insects and Engineering Research Unit, in Manhattan, Kansas. Web: www.ars.usda.gov/pa/cgahr/spieru/morrison. Twitter: @morrisonlabUSDA. Email: william.morrison@usda.gov.

Enter your email address to subscribe to Entomology Today. You'll receive notifications of new posts by email.

Insect pests are of immense economic importance, more importantly stored grain insect pests and developing novel means of control tools is need of the hour. The pyrolysis oil, after reading this research seems effective tool to minimize the use of chemical toxins.

Nice article, Rob. I did not know anything about pyrolysis oil. Thank you for sharing this with us! I would be curious to hear more about how DDGs from biofuel production can be biotransformed from contaminated grain in to safe and viable animal feed. There is a lot of work being done in the insect agriculture industry to study T. molitor intake of mycotoxin contaminated grain. However, to bring this into the animal feed supply would require a significant amount of public investment in conducting safety studies suitable enough for a food additive petition to the FDA. I am wonder what NREL and USDA would be able to contribute in sparking this investment.

Thanks for the feedback and question! I know there have been researchers that have actively looked at whether stored product insects can infest DDGS, for example some of that research has been done at Kansas State University and Purdue University. I also know DDGS emits a unique blend of volatiles that is attractive to red flour beetle, and may also be attractive to other species. We have looked at that in my lab, and I know others have assessed it, too. Here’s a couple article’s from Purdue on how red flour beetle responds to DDGS: 1) https://doi.org/10.1016/j.jspr.2012.12.001, 2) https://doi.org/10.1016/j.jspr.2018.11.008, but there are also others. Certainly DDGS as safe and viable animal feed is an important area, and my hope is USDA and US DOE would be willing to fund research along these lines to help meet societal grand challenges.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Enter your email address to subscribe to Entomology Today. You'll receive notifications of new posts by email.

Subscribe to Entomology Today via Email Enter your email address to receive an alert whenever a new post is published here at Entomology Today. Email Address Subscribe

Enter your email address to receive an alert whenever a new post is published here at Entomology Today.