Etiology, Dynamic Of Epidemic And Control Of Garlic Leaf Blight In Sichuan Province

As one of the most important fungal diseases occurred in Wenjiang, Garlic leaf blight caused a great loss in recent years. Pathogen separating and pathogenicity test were carried out; Stemphylium solani was turned out to be the pathogen. On this basis, etiology, epidemic dynamics and prevention and control technology were studied for the purpose of treating Garlic leaf blight.Tissue separation and single spore separation were used to isolate pathogen and8fungi were isolated.Typical strain in each species was selected to test Pathogenicity,1-1strain and1-3strain turned out to be the most pathogenic and the disease incidence was100%.However,1-3strain was confirmed to be Botrytis sp., not the pathogen of Garlic leaf blight. The culture morphology on PCA plate was as follows:colony flat, mycelium villous, mycelium light gray in the beginning and turned to be brown afterwards. Conidiophores solitary, sidelong diaphragm1-3, endlong diaphragm2-7, with constriction near the sidelong diaphragm. Mature conidia had the measurement about30-56.5×14-27μm, average45×21μm, L/W=1.6-2.5, average2.0. Combining morphological identification to ITS sequences analysis,1-1strain was identified to be Stemphylium solani.Experiment on inducing sporogenesis by4different medium, different illumination, temperature and vegetation damage showed that the treatment which used PCA medium, damaged vegetation,25℃temperature and cultured in the dark had the maximum spores-reached to422per horizons (10×).In the same condition GA medium produced389spores per horizons (10×). There were very little spores in PDA medium and PSA medium. The results showed that the best medium for sporogenesis were PCA medium and GA medium; The best temperature was25℃The best illumination was total darkness and vegetation damage could induce sporogenesis.The survey of two years indicated that there were two Garlic leaf blight peak in a growing season. The first peak appeared in November to January and the second peak continued from February to harvest. In2011-2012, the disease index was50.3in the first peak and the average apparent infection rate was0.0261.The disease index was the logistic growth for70days and rose from40.5to89.5; the average apparent infection rate was0.0361during this period. However, in2012-2013, the first peak lasted for70days and the highest disease index was52.4, the average apparent infection rate was0.0199. The second peak lasted for50days and the disease index rose from51.8to76, the average apparent infection rate was0.02166.Determination of virulence interior showed that pyraclostrobin had the best effect on restrain the growth of mycelium and the value of EC50was0.2199ug/ml; Following the azoxystrobin and difenoconazole and the value of EC50were0.8896ug/ml and1.0009ug/ml; The least effective fungicides was cyprodinil which had a EC50value of391.84ug/ml. Moreover, pyraclostrobin also had the best effect on the inhibition of spore germination, and the EC50value was0.0388ug/ml; The last still was cyprodinil and the EC50value was343.68ug/ml.Field efficacy experiments in2012indicated that all tested fungicides had effects on garlic leaf blight, azoxystrobin, prochloraz and pyraclostrobin had control effects above60%, the control effect of pyraclostrobin was71.25%. Various fungicides had a significant reduction in its control effect in the spring of2013because of the rising temperature. The control effect of pyraclostrobin was49.63%; Contrasting the result of control effect showed that pyraclostrobin was the best fungicides on garlic leaf blight, azoxystrobin and prochloraz also played a good role in controlling garlic leaf blight.