In article , Nick Maclaren
writes

Disease suvives the winter in infected potato tubers in the soil or on
compost heaps. The foliage which grows from these develops spores
which spread on the wind. Can come from many miles away.

As I said. This wasn't my source, incidentally.

Was your initial source a reliable one, i.e was it reliable enough to
negate the HDRA statement which is based on Govt. recognised guidance?
--
Alan & Joan Gould - North Lincs.