Crown rot of lucerne in Queensland caused by Colletotrichum trifolii

Abstract

A detailed description of a crown rot of lucerne caused by Colletotrichum trifolii is given for the first time in Australia. The characteristic symptom of the disease, which causes serious losses in Queensland, is an internal black discolouration extending from the base of infected tillers, through the crown and often into the tap root. The fungus spreads internally into the crown tissue from anthracnose lesions produced on the stem bases. Field trials at Gatton and Biloela have shown that the cultivars Denmat, African, Siro Peruvian, and Gabes are particularly susceptible. High levels of field resistance are available in the cultivars Rhizoma, Lahontan, and the experimental lines ESI, BDSI, and ECRSI. The common commercial cultivar, Hunter River, was less susceptible than many of the cultivars tested.