Evaluation of Tetraconazole efficacy in controlling sugarbeet powdery mildew in comparision with some commonly used fungicides.

Powdery mildew is one of the most important diseases of sugarbeet in Iran.The trial was carried out in Kermanshah, Razavi Khorasan and western Azarbijan provinces during 2007 and 2008. The experimental design was randomized complete block with four replications and six treatments. The treatments included the recently produced fungicide Eminent 125 ME (E125) (common name, tetraconazole) at three rates (1, 0.8 and 0.6 lit/ha), Opus at 1 lit/ha, wettable sulfur (WS) at 11 kg/ha and control (water spraying at 300 lit/ha). Disease index (DI) was estimated 15 days after utilization of the treatments. Root yield, DI and white sugar content (WSC) were applied to evaluate fungicide efficacy. Duncan's test was used to compare means of treatments. Results showed that all of the fungicides compared with the control reduced DI significantly (at á= 0.01). In Kermanshah trial E125 (at 0.8 lit/ha) and WS increased root yield significantly (at á= 0.05) as much as 13.5% and 12.4% respectively. In western Azarbijan all of the treatments in comparison with control increased root yield significantly (at á= 0.01) so that E125 at 1 and 0.8 lit/ha had the most effect on it and they promoted the root yield as much as 25.2% and 19.8% respectively. The effect of them was statistically identical. In Razavi Khorasan difference between effects of treatments compared with control on root yield was not significant. In western Azarbijan the treatments increased the amount of WSC from 0.4 to 2.5 unit but in this aspect just the effect of E125 at 1 and 0.8 lit/ha was significant (at á= 0.05). Although in two other locations the amount of WSC was increased a little by some of the treatments, their effect in comparison with control was not significant. The results reveal that E125 at 0.8 lit/ha can be applied against Sugarbeet powdery mildew in our condition. This study confirmed the results of previous studies that had shown the effectiveness of sulfur for controlling powdery mildew disease in sugarbeet. ____________________________________________________________