On the 26th March 2006 The Western Mail newspaper published an article featuring Professor Derek Knottenbelt.
It started with the scary statement,
"HUMANS may face a growing threat of liver cancer and other ailments unless the rapid spread of a flowering plant is checked, an expert warned yesterday."
In fact Professor Knottenbelt had been claiming, with no proper evidence, that ragwort had been increasing. There is an offcial government survey covering this period showing a significant decrease.
The article quotes him :-
"He said the poisonous pyrrolizidine alkaloids (PAs) contained in ragwort could spread to humans through several routes ............ In South Africa they had been found in bread, possibly through ragwort growing unseen among crops and being included in the flour."
However, the South African National Biodiversity Institute which includes their National Botanic Garden says there are no specimens of this species in their herbarium apart from a few from Europe and it appears to be unknown there.
The example from the scientific literature shows that it was a different set of plants that were responsible not our ragwort under the agricultural practices of nearly a hundred years ago when seed cleaning practices in the harvesting of grain had not been perfected.
These plants are annual and grow and produce seed in one year like wheat. Our ragwort is biennial, flowering in its second year.and coould not survive the plouging at the end of the first season of growth to any significant degree.
See also an account of a letter with similar claims that Professor Knottenbelt wrote in the Yorkshire Post for more comprehensive details.
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