SUSCEPTIBILITY OF THE AUSTRALIAN NATIVE, HELIOTROPIUM-CRISPATUM, TO THE RUST FUNGUS UROMYCES-HELIOTROPII INTRODUCED TO CONTROL COMMON HELIOTROPE, HELIOTROPIUM-EUROPAEUM

During host-specificity rests of the rust Uromyces heliotropii carried out in Europe against a range of cultivated and wild plants, two spec ies of European heliotropes closely related to the summer annual weed, common heliotrope (Heliotropium europaeum) and one native to Australi a, H. crispatum, were found to be susceptible. Detailed observations w ere made of the degree of infection the climatic requirements, the att enuation of virulence over time and the low probability of spore trans mission for infection. These results, in addition to the scattered, re latively uncommon occurrence of H. crispatum in the field, showed that the plant was unlikely to be adversely affected by the rust, which ha s been released in Australia to control common heliotrope infestations .