Significance and need of powdery mildew control (Microsphaera alphitoides Griff. et Maubl.) in the process of regeneration of the pedunculate oak (Quercus robur L.) stands in the Ravni Srem area

Background and Purpose: Powdery mildew (Microsphaera alphitoides Griff. et Maubl.) was studied from the aspect of its influence on regeneration of the pedunculate oak stands in the Ravni Srem area. Possibility to control the funguswith chemical protection measures was also investigated.During the three-year research period (2006–2008), efficiency of eight fungicides (Microthiol special, Stroby DF, ZATO 50-WG, Cabrio Top, Quadris, Alert S, Duett Ultra, Sabithane) and their influence on the plant growth increase were tested. Material and Methods: The research was conducted on seedlings and juvenile oak plants in a newly regenerated pedunculate oak stand in the southwestern Srem area, in the Vini~na forest section (dept. 15a). Level of plants infection and evaluation of fungicide efficiency were determined by visual evaluation of the presence of powdery mildew on leaves of 25 randomly picked plants within each experimental field. Plant growth elements were determined on the basis of the length of multistage formed shoots and root neck diameter. Results and Conclusion: Suppression of powdery mildew on pedunculate oak seedlings and juvenile oak plants is an important protective measure which is essential for regeneration areas in the period of regeneration cutting. The observed fungicides showed high efficiency in control of the fungus. A biological feature of pedunculate oak to form multistaged shoots by activating terminal buds during the growing season came to the fore. Majority of plants formed 3 or 4 stage growths during the first year. Chemical protection of seedlings from powdery mildew should be conducted in the period of plant growth in height. In such proceedings, the application of fungicides is reduced to minimum and thereby provides a rational seedling protection. In the second and third year of oak development, applied fungicides had little effect. Under a canopy of herbaceous weed species, plants hadmore or less intense growth in height, depending on climatic conditions and the amount of moisture in the soil