Terpenes’ role in plant protection. Four critical functions of terpenes in plant protection: (a) insecticidal role of terpenes, (b) antimicrobial activities of terpenes against rice blast disease and Fusarium head blight, and (c) allelopathy of root exudates of plants. Momilactone B inhibits the growth and development of Monochoria vaginalis. (d) Terpenes indirectly attract natural enemies of pests, e.g., (E)-β-caryophyllene attracts entomopathogenic nematodes on corn root borer. (Structures were drawn and analyzed with ChemDraw software, version 20.0.0.41, and uploaded on BioRender.com to create the illustration).