Abstract: Taking Hemerocallis fulva as the test material, the effect of combination of fertilizer and pesticide on the disease index of daylily leaf streak of Hemerocallis was studied. The results showed that the disease index of leaf streak increased with the prolongation of time after treatment, whether it was old leaves or new leaves, showing an obvious time effect; the combined treatment of pesticides and fertilizers could significantly reduce the disease index of leaf streak. Compared with the control (CK), the disease index of daylily leaf streak of old leaves treated by the fertilizer and carbendazim significantly decreased by 27.80%, 39.35%, 48.96% and 37.53%, respectively, and the disease index of the new daylily leaf streak treated by the joint action of carbendazim with fertilizers of 0, 240, and 320 kg/hm² significantly decreased by 40.07%, 53.31% and 55.02%, respectively. Compared with the control treated by carbendazim only, the development of daylily leaf streak was inhibited significantly by the mixed use of carbendazim and fertilizers, and the significant increase time of the disease index of old leaves and new leaves was delayed by 7 and 14 days respectively. The results of this study offer significant implications for the promotion and application of Hemerocallis in landscaping practice, as well as the research on the use of the pesticide reduction.