Downy Mildew of Sunflowers in Tunisia and evaluation of four fungicides

Plasmopara halstedii, the downy mildew pathogen of sunflower (Helianthus annuus L.) causes significant economic losses world-wide, mostly through soilborne systemic infection of seedlings. Natural infection of sunflower with P. halstedii was monitored in sunflower fields cultivated in many regions of Beja, during a survey in the spring of 2010. P. halstedii were obtained from diseased sunflowers seeds in 2010 and characterized by virulence and by reaction to four fungicides: Ridomil MZ 58, Ridomil Gold 48%, Aliette 80% and Triziman 80%. These fungicides have significantly reduced the colony growth of the fungi compared to the control. The significant reduction of mycelia growth were obtained with Ridomil M, Triziman 80% and Aliette 80% with acompletely inhibition