Codiaeum rust

A rust affecting Codiaeum variegatum (‘Croton’, Euphorbiaceae) imported into the UK from Ivory Coast in 1978 was originally identified as Aecidium codiaei H. Sydow. However, studies on germination of spores, pathogenicity tests and examinations of sori under light microscope and scanning electron microscopy (SEM) revealed that the rust belonged to the tribe Pucciniosireae (a diverse group of mostly tropical microcyclic rust genera characterised by their stages being telescoped into aecidioid telia). Attention was drawn to the transfer of this Aecidium species to Dietelia (a member of the Pucciniosireae) following imports of the disease into the Netherlands from Ghana in 1978. Dietelia codiaei (H. Sydow) Boerema was subsequently confirmed as the causal agent of Codiaeum rust on recent imports into the UK and Italy. It is believed to be distinct from D. emasculata recorded on Breynia, another euphorbiaceous host.