Studies On Primary Infection Sources, Occurrence Dynamics And Control With Fungicide Of Maize Curvularia Leaf Spot

Maize Curvularia leaf spot was an important disease which happended in maize in the north of China in recent years. The disease was reported in Sichuan in 1999. Therefore, the primary infection sources,occurrence dynamics and control with fungicide for maize Curvularia leaf spot were studied.The results are as follows:1, The conidia adhering to seeds and mycilia in infected seeds could overwinter successfully and infect the maize.The mycilia in infected seeds could influence the germination of seeds, but the conidia adhering to seeds couldn't affect the germination of seeds. Both mycilia in infected seeds and conidia adhering to seeds could infect the root and the bud of the seedlings so that the seedlings could grow weak.Under Yaan ecological conditions,conidia of C. lunata couldn't overwinter on disease leaves in the field ,but mycilia of C. lunata in leaves could overwinter successfully in the field.Conidia and mycilia of C. lunata in or on disease leaves could overwinter and survive at least 3 years in indoors condition.C. lunata isolated from rice and maize could infect leaves of wheat and C. lunata isolated from the disease wheat could infect maize.C. lunata isolated from rice and Echinochloa crusgalii (L.) var. mitis(pursh.) peterm could infect maize.The results indicated that the disease seeds and the disease leaves indoors and in field were primary infection sources of Maize Curvularia leaf spotunder yaan ecological conditions.The pathogen of C. lunata in disease wheat and Echinochloa crusgalii (L.) var. mitis(pursh.) peterm could infect maize, but it needs to be studied as initial infection souce.2, Under Yaan ecological conditions, The symptom of Curvularia leaf spot occurred in field in May 18. and disease index growed quickly from May 29 to July 5. The effect of growth potential of corn plant on the disease was tested.The leaf position and growth stage of corn influenced upon the amount of spore production and lesion size.Therefore, the upper leaves and seedling stage of corn were more resistant than under leaves and boot stage.3, Through bioasaays of five fungicides ,the results showed that mancozeb had strong inhibition to conidia germination and germ tube growth, with EC50 value of 1.86ppm and 0.49ppm respectively. And Difenoconazole showed strong refrain effect on the mycilia growth, with EC50 value of 0.68ppm. The results of indoors experiments suggested that mancozeb showed the best prevention effect and difenoconazole showed the best treatment effect ,and the effect period of mancozeb was the longest in the five fungicides.In the field experiments, mancozeb showed the best effect to maize Curvularia leaf spot.