Most people carry the Fusarium Fungi on their body someplace
toe nails is a good place to start
also very popular with the USSR in the 1930's as a tool to make germ warfare ,...lol
as for weed, the spores like all fungi spores are everywhere, the soil is the best place to start
on commercial mixes by health laws soils got to 'cook' before being sold
in the vain 'hope' of killing these and other spores ..lol
if you suspect fusarium wilt see it as very serious and contain it
but like with all fungi attacks avoid over watering in the first place in cold temps
good luck