Efficacy of Nigella sativa L. and Trigonella foenum-graecum straw ethanolic extracts against some tomato pests in a greenhouse

The tomato (Lycopersicon esculentum) is a crucial vegetable crop worldwide, but various pests threaten its yield. Excess food and agricultural waste create health and environmental issues. This study evaluated the pesticidal activity of ethanolic extracts from Nigella sativa and Trigonella foenum-graecum straw ethanolic extracts against Amrasca biguttula biguttula, Liriomyza trifolii, and Tuta absoluta under greenhouse conditions. Tomato leaflets were collected from treated plots before spraying and examined in the lab for pests. Then, infestation rates were assessed 7 days after spraying by comparing the number of larvae to that of an untreated control. All treatments showed significant differences in the mean number of recorded pest infestations after the first and second sprays compared to the control. The 5% T. foenum-graecum extract was the most effective, reducing pests by 78.98%, 81.94%, and 28.03%, respectively, while N. sativa extract caused an 88.75% reduction in A. biguttula. The high-performance liquid chromatography analysis identified 18 phenolic compounds in N. sativa straw extract, with the predominance of catechol (330.14 µg/mL), chlorogenic acid (169.23 µg/mL), catechin (94.07 µg/mL), naringenin (91.99 µg/mL), and rutin (78.16 µg/mL). A similar profile was observed for the ethanolic extract of T. foenum-graecum straw, with some quantitative differences, where ellagic acid (287.13 µg/mL), gallic acid (188.89 µg/mL), naringenin (48.71 µg/mL), rutin (34.99 µg/mL), and catechin (33.97 µg/mL) were the major phenolics in the extract. In line with the above findings, rutin, chlorogenic acid, and daidzein showed the highest in-silico docking scores against AChE, GABA_(A), and RyR enzymes compared to the controls. These results suggest that agricultural waste from N. sativa and T. foenum-graecum can serve as novel, environmentally friendly bioinsecticides.