EFFICACY OF SOME FUNGICIDES ON CONTROLLING CERCOSPORA LEAF SPOT AND THEIR IMPACT ON SUGAR BEET YIELD COMPONENTS

Sugar beet leaf spot, caused by Cercospora beticola, is the most important and destructive foliar disease in North Nile Delta of Egypt. However, control of the disease in Egypt is mainly achieved by fungicide treatments. So, the control efficacy of two Sterol demethylation  inhibitors (DMI) fungicides, tetraconazol (Eminent) and difenoconazole + propiconazole (Montoro), and one Multi-site activity (MSA) fungicide, benalaxyl + copper oxichloride (Galben), against C. beticola  and their impact on sugar beet yield components were tested in this study. Fungicides were tested under natural field infection in four seasons (2008/2009, 2009/2010, 2011/2012 and 2012/2013) in commercial field at Sakha in Kafr El-Sheikh governorate. All the three fungicides suppressed Cercospora leaf spot significantly compared with untreated plots. However, there were significant differences in efficacy among them. The most effective fungicide was Eminint, which provided high levels of efficacy (from 95 to 96.5%) followed by Montoro which showed efficiency from 83 to 86%. Galben provided moderate control efficacy from 53 to 63%. Sprays with Eminint increased root yield, sucrose percentage and gross sucrose more than 90, 56 and 214 % respectively compared with the untreated plots. However, Montoro caused more than 70, 35 and 136% increases in yield respectively. Sprays with Galben provided less increases in yield components (up to 37, 30 and 80% respectively). Since fungicidal application considered as the main tool employed in sugar beet Cercospora leaf spot disease management in Egypt, the obtained results concluded that both DMI fungicides, Eminint and Montoro, were effective in controlling the disease. However, further studies are needed to determine the best application program to avoid appearance of DMI resistance strains of C.  beticola.