Introduction Late blight caused by Phytophthora infestans severely threatens potato production, necessitating novel natural fungicide. Methods Ethanol extracts from 11 wild plants were screened for anti-oomycete activity. Active extracts from Artemisia lavandulaefolia and Clinopodium repens were fractionated. The petroleum ether fraction and aqueous fraction were evaluated for effects on mycelial growth, morphology, spore germination, pathogenicity, stress response, and synergy with fungicide Infinito. Components were analyzed by LC-MS. Results A. lavandulaefolia and C. repens extracts showed the highest inhibition (88.3% and 81.3%). the petroleum ether fraction of A. lavandulaefolia and the aqueous fraction of C. repens exhibited strong activity (IC 50 : 115.78 and 649.59 μg/mL), inhibited diverse isolates, and altered hyphal morphology. Spore germination reduced to 27.19% and 31.80%. Both fractions reduced tuber pathogenicity and showed stress tolerance. Combined with Infinito (IC 50 ), enhanced inhibition was observed. LC-MS tentatively identified 20 components each, primarily flavonoids and phenolics. Discussion This study elucidated that the petroleum ether fraction of A. lavandulaefolia and the aqueous fraction of C. repens are potential natural anti-oomycete resources, providing a basis for the development of environmentally friendly inhibitors against late blight.
Chang et al. (2026) studied this question.