First Report of Downy Mildew of Sunflower in Greece. C. C. Thanassoulopoulos, Aristotelian University, Faculty of Agriculture, Plant Pathology Laboratory, 540 06 Thessaloniki, Greece. C. B. Mappas, Aristotelian University, Faculty of Agriculture, Plant Pathology Laboratory, 540 06 Thessaloniki, Greece. Plant Dis. 76:539. Accepted for publication 26 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0539B.
Sunflower (Helianthus annuus L.) cultivation in Greece is limited to northeastern Thrace, mainly in Rodopa Prefecture. During a survey in June 1991, more than 50% of plants in a O.4-ha field of a local cultivar were found to have symptoms typical of downy mildew. Healthy plants had seven to nine true leaves and were 1-1.2 m tall, whereas diseased plants were dwarfed (a few centimeters to 70 cm tall), with thicker than normal leaves that curled downward and showed extensive epiphyllous mottling. Downy growth of the fungus covered the abaxial surface of symptomatic leaves and also appeared on the adaxial surface of some leaves. The fungus showed monopodial branching of conidiophores at nearly right angles, with five or six terminal branches 6-9 µm long and bearing single elliptic, papillate zoosporangia, 15-25 X 12-17 µm. Sporangiophores were 260-450 µm. The fungus was identified as Plasmopara halstedii (Farl.) Berl. & De Toni in Sacc. The disease has long occurred in the neighboring countries of Yugoslavia, Bulgaria, and Turkey, but this is the first report in Greece. Weather conditions were favorable for disease development in 1991, with continuous rain during the sunflower seeding period in North Greece.