Protection of Oak Stands from Powdery Mildew (Microsphaera alphitoides Griff. et Maubl.)

Protection of oak seedling plants has been performed on regular basis in the whole area of pedunculate oak (Quercus robur) and, to a smaller extent, of sessile oak (Quercus petraea). From numerous fungicides, in the last 10 years our experts have been testing the effectiveness of fungicides, i.e. preparations from triazole group (Folicur 250, Sumi-8, Vectra, Anvil 5 SC, Artea Plus, Artea 330 EC, Impact SC 250, Punch 10 EW) and from strobilurin group Stroby DF, Amistar Xtra 280 SC i Amistar 250 SC. The following fungicides proved to be very effective: Artea Plus, Artea 330 EC, Amistar Xtra 280 SC and Amistar 250 SC. In the last two years, these were the most frequently used agents for the control of powdery oak mildew.Oak protection was carried out in 11 Forest Offices. 12 types of preparations were used, but mainly the four ones mentioned above. Some of the used preparations are not used in Croatia any more (Anvil, Sumi-8, Vectra, Rotondo, Alvin etc.).In the period from 2006 to 2009, oak trees were treated on the area of 29,869.04 ha. The annual average was 7,467.26 ha. Compared with the past years, the annual average of the treated areas decreased by more than 1,600 ha. Treatments were performed from airplanes and by tractor sprayers. Most areas were treated once and only some were treated twice. Dosage was 0.3, and mainly 0.5 l/ha. All treatments gave good results.M. alphidoides is very harmful for young oak plants. The safety of growth and development of oak young plants is almost impossible without protection from powdery mildew. Therefore it is a continuing task of everyone involved in the management of oak forests.