Disease cycle of Stagonosporopsis tanaceti in pyrethrum plants

Abstract

Pyrethrum (Tanacetum cinerariifolium) is commercially cultivated in Australia for the production of pyrethrins. Ray blight caused by Stagonosporopsis tanaceti is considered a major limiting factor for pyrethrum production. Histopathology of infected pyrethrum plants identified the importance of crown infection where the infection hyphae were confined to the parenchyma cells of the epidermis, hypodermis and cortex without infecting the vascular tissues. Throughout the growth of pyrethrum plants, no vascular infection occurred in the petioles, flower stems and crowns. In infected leaf petioles and flower stems, pycnidia and extra-cellular anthocyanin material developed within 1–2 weeks of infe..