| Dipsacus leaf spot is considered as a new and destructive disease of Dipsacus asperoides in Sichuan in recent years.The symptom and pathogen identification, biological characteristics of the pathogen,infection process and conditions,disease occurrence and fungicides screening was studied first and systematically.The results are as follows:1.Symptom and pathogen identification of Dipsacus leaf spotDipsacus leaf spot mainly appears on the leaves as well as pedicel.The ealy appearance of its symptom is small dark green spot,spots gradually expand to be anomaly polygon restricted by nervure.The typical leaf spot is purple-brown in the edge and grey-white in the center,in diameter of 1～3mm.According to the symptom,cultivating characters,especially the shape and size of pycnidium and conidia,the pathogen of Dipsacus leaf spot was Septoria dipsaci.It was the spieces of new report in China.2.Biological characteristics of Septoria dipsaci.Results showed that the temperature and pH value rage for hypha growth and sporulation was 10～30℃,pH4～11,with the optimum at 25℃,pH 7.All kinds of carbon sources could be effectively used by the pathogen,and the most suitable nitrogen sources was inorganic nitrogen.It could grow and sporulate well on host juice medium.The light treatment hadn't remarkable effect on the hypha growth and sprulation.Conidia were able to germinate in 10～35℃,pH 3～10 and humidity of RH≥90%,the maximum rate of conidia germination was in 25℃,pH6 and water.The lethal temperature of conidia was 52℃. 3.Infection process and conditions of Septoria dipsaci.After inoculation,conidia of Septoria dipsaci began to germinate within 24 hours at the leaves surface,then formed the branched hypha which was the infection structure of Septoria dipsaci.The pathogen penetrated host only through epidermis after inoculation. The hypha avoided the stomata while happen to it.The appressorium was not formed before the penetration of the pathogen.After the hypha penetrated leaf cells,they could continue through the various cells.The cells that were infected by the pathogen could became empty,ultimately lead to the cells death.The infection of Dipsacus asperoides by Septoria dipsaci could be occured at 15～28℃,and the optimum temperature was 25～28℃.At 20℃and 25℃,the incubation period was the same shortest(8 days).The optimum wetness period rage for infecting leaf of Dipsacus asperoides by the pathogen was 24 to 36 hours.Septoria sp.infected the basal leaves firstly,then spreaded to the upper leaves.Old leaves were more conductive to the infection.4.Disease occurrence of Dipsacus leaf spotThe diseased leaves on the plants in winter and residue of infected leaves in the field were the primary infectious source.When the pathogen encountered high humidity,the conidia were released from pycnidium,then transmitted by rain as reinfection sources.By the mycelium and pycnidium in the residue of diseased plants and infected plants in winter were the overwintering methods of the pathogenic fungi.Results from the investigation in the field showed that,the disease first appeared in the middle of March and with a peak in June,while the highest percentages of diseased plant and leaf were up to 100%,51.83%respectively,and the highest disease index was 34.62. Thereafter,with the cessation of Dipsacus asperoides growth,the disease degree began to slow down and the development of the disease stopped.5.The fungicides screening in laboratoryThe five fungicides were tested in laboratory to determine the effect on the hypha growth and the germination of conidia.The results showed that carbendazim inhibited the hypha growth and the germination of conidia well,Thiophanate-methyl,diniconazole and Copper Sulphate were good fungicides on the inhibition of the hypha growth and the germination of conidia.Chlorothalonil almost had no inhibition on the hypha growth and the germination of conidia.
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