U. virens was cultured in PSB medium at 28˚C for 8 days, the culture was filtered with three-layer of lens papers to exclude hyphae, U. virens conidia were collected and adjusted to the concentration of 1 × 107 conidia per milli-liter. Panicles at booting stage were peeled out and rinsed in the filter-treated conidia solution for 10 minutes. After the treatment, the panicles were cultured in 1/2 MS medium for 5 days, spikelets were used to observe conidium germination and examine the early infection process of U. virens.