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Poster: Biology & Disease Mgmt: Mycology


Ray blight disease (Stagonosporopsis tanaceti) development in pyrethrum
M. BHUIYAN (1), T. Groom (2), M. Nicolas (3), P. Taylor (3) (1) The University of Melbourne, Australia; (2) Botanical Resources Australia, Australia; (3) The University of Melbourne, Australia

Pyrethrum (Tanacetum cinerariifolium) is commercially cultivated in Australia for pyrethrins which are used as natural pesticides. Ray blight caused by S. tanaceti is considered as the most devastating fungal disease and is recognized as one of the limiting factors of pyrethrum production. The pathogen is known to infect the flowers and leaves however, little is known about the mechanism of infection and process of tissue colonisation. Therefore, this study was undertaken to identify disease development within the whole plant using traditional culturing and histopathology, and elucidate the life cycle of S. tanaceti. Ray blight disease development in pyrethrum plants was the result of colonisation of the parenchyma cells in the hypodermis and cortex with no infection of the vascular tissues. Pycnidia developed in severely infected tissues which developed a deep brown discolouration due to necrosis caused by intra- or inter cellular colonization. Secondary infection of upper flower stems, flower buds and flower tissues most likely occurred from pycniospores released from the pycnidia in the infected leaves and petioles and being disseminated through wind, rain or water-splash. The pathogen did not infect roots of plants with infected crown tissue. This process of infection and colonisation of pyrethrum plants provides a better understanding of the complete life/disease cycle which will lead to improved control measures through the strategic use of fungicides.