| Apple canker is one of the important constraints in current production of apple in China. The pathogen can infect trunk, main branch, fruit and many other parts of the plant, causing die back, yield loss, tree die off and even destruction of the whole orchards. Durrently apple canker is a serious threat for the healthy development of the apple industry in China. The pathogen infection is the first step towards the occurring of the disease, it is also an important period for disease management. In this paper, the conditions for conidia germination, survival and infection of V. mali Miyabe et Yamada were studied. The main findings are as follows:1. Conidia of V. mali Miyabe et Yamada can germinate from 0℃to 35℃. 25℃is the optimum temperature and conidia germination percentage reached 90% after being treated for 12 hours. From 25℃to 0℃, the lower the temperature the longer period required for the conidia germination. When the temperature was 5℃, the spores began to swell after treated for 60 hours and the germination rate reached 90% after 144 hours (6 days). The spores could also germinate at 0℃. After treated for18 days the spore germination rate reached 67%. From 25℃to 35℃the germination rate gradually decreased. The lethal temperature of V. mali was 49℃.2. Different culture medium has different influence on conidia germination of V. mali. The results in our study showed that PDA, ABA, RA were fit for the spore germination and after 24 hours the germination rate reached over 80%, followed by PMA and PSA, the worst one was LB medium.3. Ultraviolet radiation has a greate impact on the germination of V. mali conidia. When the UV intensity was 800μW, the germination rates were 80%, 38% and 23% after being treated for 2 , 4 and 6 minutes respectively. The germination rate was 46 %, 1% and 0 when the UV intensity was 1200μW and treated for 2, 4 and 6 minutes respectively. The germination rate was 19% under 1600μW UV for 2 minutes, while no germination was observed after treated for 4 and 6 minutes.4. The survival time of V. mali is quite different under different situations. On indoor in vitro branches, the conidia survived longer, which had germination ability after 9 weeks. The conidia on indoor in vitro barks could survive for 4 weeks and the germination rate reached 17%. The conidia had a short survival time on outdoor in vitro barks. In shady conditions the survival time was 2 weeks and the conidia germination rate was 8% at this time. Under sunlight the survival time was only 1 week; The conidia in indoor water could survive for 4 weeks, while no spore germination was found after being treated for 5 weeks.5. The infection ability of V. mali to apple leaves was tested. Apple leaves were inoculated by a patent inoculator. It showed that the fungi infected the leaves from the upper side easier than from lower side. Fungal disk was the best form to inoculate, followed by spore suspension in fruit juice and the last was the suspension in sterile water which could not provide enough nutrient for spore germination. Gala is more susceptible for the infection, followed by Rattan Wood No. 1, Fuji, and Wang Lin.6. The infection ability of V. mali in different season was measured in our study. We found that fresh wounds were more easily infected by the pathogen in the four seasons and old wounds were difficult comparatively due to the formation of callus. In terms of infection period, winter is easy for the pathogen to infect comparing with the other three seasons.
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