Pseudomonas syringae pv. tagetis
on Cirsium, etc.
Cirsium arvense, Ooijpolder, 26.v.2011.
The tips of the shoots are chlorotic. The cause is the compound tagetitoxin, that is produced by the bacterium and and interferes with the development of chloroplasts.
distribution within Europe
The well known phenomenon of chlorotic thistle tips formerly, also on this site, was associated with the rust fungus Puccinia punctiformis. Still unexplained is why this phenomenon in the field seems to be limited to creeping thistle: according to the literature the pathovar tagetis infests several more Asteraceae.
Gronwald, Plaisance, Ide & Wyse (2002a), Lydon, Kong, Murphy & Zhang (2011a), Rhodehamel & Durbin (1985a).