Study On Fungal Leaf Spot Of Gingko Biloba In Sichuan Province And Gingko Ring Spot Caused By Pestalotiopsis Gingko Hori

This paper reports the main kinds of fungal leaf spot of Gingko biloba in Sichuan Province.The bionomics, infection cycle, occurrence dynamics and fungicides screening of gingko ring spot were studied.From 2007 to 2008, occurrence and kind of leaf spot diseases were surveyed in main cultivated field in Sichuan Province. The results showed that the main disease including gingko black spot, anthracnose, leaf spot and ring spot were caused by Alternatia tenais Ness, Colletotrichum sp., Phyllosticta gingko Brunand and Pestalotia gingko Hori., respectively.The appropriate growth temperature for P. gingko Hori was 10-30℃, and the fit temperature was 15-35℃. Conclusively, the optimum temperature was 25℃.The appropriate pH for mycelial growth and sporulation was 2-11, and the optimum pH was3-4 and 5, respectively. Illumination was helpful for mycelial growth and sporulation. The best carbon source and best nitrogen source for mycelial growth were lactose and ammonium nitrate. Sporulation was promoted by glucose, fructose and potassium nitrate, and inhibited by urea. The optimum temperature and pH for conidia germination were 25℃and 7. Conidia germination was better in the juice of Gingko biloba and failure to germinate when the relative moisture was lower than 85%.Conidia began to germinate at 2 hours after inoculation with P. gingko Hori. Then, from 12 to 24 hours, the leaf surface was infected by appressorium and hypha. The germ tube erupted from one end of the third colored spore, and then formed globose appressorium by means of ultimate swelling, and hypha grew on appressorium, which was the way of conidia germination mostly. Stomata and leaf surface were main paths of pathogen penetration. At 25℃, Optimum wetness period for infecting leaf of Gingko biloba by the pathogen was 48 hours, with the incubation period of 4 days.From 2007 to 2008, results of investigation in the fielde showed that, the disease first appeared in early June and with a peak in September, while the highest rate of diseased plant and leaf were up to 100%,85.00% respectively, and the disease index was 55.50. In October, the disease development began to slow down. In November, the development of the disease stopped.Conidia from indoor diseased leaf, outdoor piles of fallen leaves and diseased tissue were the primary source of infection. However, the leaves debris of 10cm depth down from the ground, became rotten after 15 days'buried by the pluvial autumn, and couldn't be through the winter. The conidia were spreaded through raindrop splash and air current.Mycelial growth velocity and spore germination were used to screen effective fungicides inhibiting the growth and reproduction of P. gingko. The results showed that 50% carbendazole WP exhibited the best effect, while the worst effect was 15% trazodone WP. EC5o was 0.3341ug/ml, and followed by 70% topstn-methyl.60% mancozeb WP was lower than 70% topstn-methyl WP.