| Houttuynia cordata Thunb belongs to Saururacese and Houttuynia. It is many-year-life grass plant. It is a kind of uncultivated edible and official vegetable.The purple spot of heartleaf hourtuynia is a new disease of cropping base in Sichuan, Ya'an 'SanJiu' company. It has become the primary disease of heartleaf houttuynia. The percentage of diseased plant and leaf reached 100% and 58%, respectively. It not only affects growth and output, but reduce quality. This dissertation included the symptom characteristics , the identification of pathogen, the biology characteristics, the disease cycle and the control of disease.1. The symptom characteristics of purple spot of heartleaf houttuyniaThe disease mostly harm to leaf. The symptom of the disease is as follows: at first, there is a red spot, then, little spots become circular or irregular spots, which diameter reaches 1.5~ 10.0 mm, 0.5~19.2 mm long and 0.5~10.5 mm wide. The purple brown edging is indistinct. The center withered even break, and the disease spot is a little bit hollow.The spot on lower leaf is purple brown and there is purple and black mould in damp circumstance.2. Isolation and cultural characteristics of purple spot of heartleaf houttuyniaIsolate the diseased leaf, and gain the pathogen. The pathogen were cultured on PDA medium, the colony is hoary, circular, brown later.3. Inoculation and identificationThe diseased symptom and the pathogen characteristics of inoculated plant, were similarly to the diseased plant in field. The conidiophore wide 3.75~6.25 μm , and there is constriction on septum. The apical cell is vesicle. The vesicle wide 6.25~ 11.25 μm . Conidiospore is acrogenous, globular or approximate globular, black, diameter reaches 12.50~21.25 μm. So by these, the pathogen of purple spot of heartleaf houttuynia was identified to Nigrospora sp..4. Biological characteristics of Nigorspora sp.The best medium for the mycelia growth and spores formation was PDA and PYA. The optimum temperature and pH for the mycelia growth and spores formation were 25℃ ~30℃ and pH 5~7, respectively. Effect of illumination on the mycelia growth is insignificant. Gluocose is the best carbon sources, and Yeast extract is the best nitrogen sources for the mycelia growth and spores formation. The optimum temperature and relatively humidity (RH) for spore germinationwere 25, 90%~ 100%, respectively. But the best spore germination condition was drops of water. The spore couldn't germinate at lower than 10癈 or RH50%. The optimum pH was 6~7, and the light was unfavorable for the spore germination.5. Disease cycle ofNigorspora sp.Nigorspora sp. over-wintering through conidiospore and mycelium on the diseased plant and leave in field . The pathogen disseminated on wind and rain, it infected host through intercellular space. When mean temperature 24.9 16.6 and 7.6, it's latent period were 2 d 3~4 d and 4~5 d, respectively. There is reinfection in field.6. Select medicaments and field trial6.1 Select medicamentsThe inhibiting effects of 7 medicaments ( Carbendazim, Cercobin M, YangKang bio-active organic fertilizer, BA, BY, extracting solution of two plants ) on Nigorspora sp. . The results demonstrated that the best medicaments of inhibiting the mycelia growth and spores formation is Carbendazim and Cercobin M, BA is better. Carbendazim and Cercobin M strongly inhibited spore germination , the inhibitory rates were more than 96%. The extracting solution of two plants were better, the inhibitory rates was 89% and 92%.6.2 Field trial5 medicaments (Carbendazim, Cercobin M, YangKang bio-active organic fertilizer, BA, BY) were put in field trial. The results of field trial demonstrated that Carbendazim and Cercobin M were the best medicaments , control effects were more than 53%. The BY was better, control effect 31.0%. The control effects of YangKang bio-active organic fertilizer and BA were more than 22.14%...
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