Effects of fungicides on the occurrence of winter wheat eyespot caused by fungi Oculimacula acuformis and O. yallundae

The aim of this study was to estimate the effect of fungicides on the occurrence of Oculimacula spp. on winter wheat stems using real-time polymerase chain reaction (Real-time PCR) method. The ratio of Oculimacula yallundae and Oculimacula acuformis in the population was assessed from 2009 to 2011 in the winter wheat crops after 2, 3, and 4 years of use of fungicides prochloraz, cyprodinil, prothioconazole, metrafenone, and boscalid. After 4 years of fungicide use, the highest relative reduction of DNA of both fungi, compared with the unsprayed control, was detected in the samples from cyprodinil-applied plots. Relatively less O. yallundae DNA was identified in the samples from prochloraz- and that of O. acuformis from prothioconazole-applied plots. Metrafenone and boscalid had little effect on the changes in Oculimacula population. Fungicide effect on O. acuformis and O. yallundae pathogenesis slightly differed. In Oculimacula population under the fungicide treatment, 10 days after application (BBCH 37), the ratio of O. acuformis in all treatments was reduced, but the ratio of O. yallundae was increased in prevalence compared to O. acuformis in cyprodinil and prothioconazole treatments. Later in the season (BBCH 75), the ratio of O. acuformis increased in metrafenone and O. yallundae in prochloraz treatments. The effect of fungicides used for eyespot control on winter wheat productivity was inconsistent. Prochloraz use led to a significant grain yield increase in 2010, while prothioconazole use showed a similar increase in 2009 and 2010. Cyprodinil, boscalid, and metrafenone did not have any effect on the yield in any of the experimental years. A significant increase in thousand grain weight was obtained in prochloraz, prothioconazole, and boscalid treatments.