Biochar Ingestion Is Associated with Hindgut Symbiotic Disruption and Mortality in Coptotermes formosanus: A Proposed Protist-to-Bacterial Cascade

Abstract

Simple Summary Termites cause billions of dollars in damage to wooden buildings each year. Current control methods often involve poisons that need to be shared among nestmates to work. This study tested whether a charcoal-like material called biochar, made from burnt rice straw, could be a safer alternative. We fed termites pine wood powder containing 0%, 5%, or 20% biochar. The 5% diet was not deterrent in a choice test, whereas 20% reduced intake. Over 30 days, both biochar diets were associated with reduced body weight and survival. Our data suggest that biochar ingestion is associated with a sequence of hindgut symbiont disruption: major cellulolytic protozoa declined, bacterial community structure changed, and host transcriptome showed exploratory stress/catabolic trends. However, because these responses were measured in parallel and no continuous causal or rescue experiment was performed, we cannot establish a definitive cascade. Reduced intake at the high dose and unmeasured biochar physicochemical properties remain alternative or contributing explanations. Because 5% biochar acted slowly and was not deterrent, it may be a promising candidate ingredient for termite baits, but mechanism and field tests are needed.