Effect of temperature, relative humidity and light on conidial germination of oak powdery mildew (Microsphaera alphitoides Griff. et Maubl.) under controlled conditions

The influence of temperature, humidity and light on the conidial germination and germ tube elongation of oak powdery mildew (Microsphaera alphitoides Griff. et Maubl.) was studied in controlled conditions. The maximal germ tube length was attained at 25°C, whereas at lower and higher than optimal temperatures, germ tube growth was significantly lower. Germ tubes begin to develop at all values of relative humidity (10-100%), reaching the maximum length at 90%. The development of germ tubes was the most intense in full light and the lowest in total darkness. The artificial infection of floating leaves showed that an increasing age had an inhibitory effect on the mycelium development and spore formation. Since conidia play a crucial role in powdery mildew epidemiology, it is of particular importance to elucidate the influence of environmental factors in the complex relations that exist between the plant and its pathogen

First Appearance of White Mould on Sunflower Caused by Sclerotinia Minor in the Republic of Macedonia

Sclerottnia spp. a very destructive fungus causing "white mould" became one of the biggest problems in sunflower breeding in the Republic of Macedo­nia in 2010. Field monitoring in the region of Bitola show very high infection of around 20-30%. Two types of symptoms where observed during the field mon­itoring. First symptoms were observed on the leaves of the Infected plants in the form of wilting, prior to flowering stage. The most characteristic symptoms were observed. at the lower part of the stem in the form of a stem cancer. Big variable sclerotia in size and shape were observed inside the stem. The appear­ence of white mycelium on the infected lower parts of the plant was often observed during the wet weather. Other infected plants showed different symp­toms. The stem was longer and thinner than in uninfected plants and the pit was very small around 9 cm. Sclerotia observed inside the stem were not big­ ger than 2.5 mm. In vitro investigations confirmed the presence of ascomycetes Sclerotinia sclerattorum (Lib.) de Bary and Sclerotinia minor Jagger, for the first time In the Republic of Macedonia. In vitra Investigation of antifungal abillty of Pseudomonas mediterranea Cattara et al., 2002 against S. sclerottorum and S.minor showed that it can be a possible antifungal agent against these ascomycetes