Phoma exigua var. exigua
History in New Zealand
Some unusually sickly looking Californian thistles were noticed in the Manawatu in 1999 and phoma leaf blight was isolated from them. Since then, phoma leaf blight has been seen attacking a range of thistles all over New Zealand.
How does it damage californian thistle?
If you see plants over a wide area that are chlorotic (yellow looking) and later turn brown as they die, it is likely to be due to an outbreak of this pathogen.
How effective is it?
Research has shown that the impact of this fungus is highly variable with damaging systemic infection only occurring rarely.
