Insecticidal and antinutritional effects of the fixed oil from Syagrus coronata (Mart.) Becc. Seeds on Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae)

• S. coronata seed fixed oil (FOSc) was evaluated for insecticidal activity against T. castaneum . • FOSc caused mortality via indirect contact (LC 50 : 16,41 µg/cm 2 ). • Ingestion of FOSc (350 mg/g of corn flour) resulted in 52% mortality in 14 days. • FOSc reduced biomass gain and food conversion efficiency, showing antinutritional effects. • FOSc increased α-amylase but inhibited endo- and exoglucanases, affecting carbohydrate digestion. • FOSc shows promise as a natural insecticide against stored-product pests. Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae), the red flour beetle, is a major pest of stored products, responsible for the loss of millions of tons of food annually. The drawbacks associated with synthetic insecticides have prompted the search for natural alternatives to control this insect. Seed oil from Syagrus coronata has been reported to exhibit insecticidal activity against disease vectors and agricultural pests. This fixed oil is rich in fatty acids, particularly lauric acid. This study investigated the insecticidal activity of the fixed oil from S. coronata seeds (FOSc) against T. castaneum adults. Indirect contact toxicity (13.75–55.0 µg/cm 2 ) and ingestion toxicity (90–350 mg/g of cornmeal) were evaluated. Additionally, the in vitro effects of FOSc on midgut glycosidase activities were assessed. FOSc induced significant mortality on T. castaneum adults through indirect contact, with LC 50 of 16.41 µg/cm 2 . Ingestion of artificial diets containing FOSc at 350 mg/g of cornmeal resulted in mortality rates of 31% and 52% after 7 and 14 days, respectively. The artificial diets containing FOSc exhibited weak feeding deterrence, impaired biomass gain and reduced the efficiency of food conversion. Enzymatic assays showed that FOSc stimulated α -amylase activity while reducing endoglucanase and exoglucanase activities. In conclusion, FOSc demonstrated both lethal and antinutritional effects on T. castaneum adults, supporting its potential as a sustainable botanical insecticide for managing stored-product pests.