In the ternary system of Podosphaera pannosa, Spodoptera exigua, and Rosa chinensis, volatiles from infected roses suppress S. exigua oviposition, but the non-volatile-mediated resistance mechanism remains unclear. This study investigated mildew-induced resistance in roses by assessing larval feeding responses to leaf extracts. Infected rose leaf extracts significantly inhibited larval feeding (68.55% inhibition; t = 4.742, df = 28, p = 0.0002). Untargeted LC-MS metabolomics identified 1046 metabolites in R. chinensis. P. pannosa infection altered the rose metabolome, yielding 64 differentially accumulated metabolites (47 up, 17 down). Among these, five compounds were markedly upregulated: dehydro(11,12) ursolic acid lactone (A), maslinic acid (B), trametenolic acid B (C), betulonic acid (D), and ganolucidic acid B (E). All five inhibited larval feeding. Compound A showed the strongest activity (80.99% at 0.1 mg/mL), with an EC50 of 0.015 mg/mL. EC50 values for compounds B–E were 1.256, 0.067, 1.189, and 0.014 mg/mL, respectively. This study elucidates a resistance mechanism of mildew-induced roses and suggests that compounds with low EC50 values (e.g., A and E) warrant further investigation as potential candidates for eco-friendly pest management under laboratory conditions.
Chen et al. (Thu,) studied this question.