"Rod" wrote
- but

Yes, it's almost certainly Basamid or Dazomet. It's neither a powder
or granules btw, it's a prill - that is very tiny lumps of the
material of uniform size - like a powder but nothing small enough to
get airborne and too small to be called granules so it's very easy to
distribute evenly.
I used it in the greenhouses at work for sterilising the beds used
for early veg and salads. Also for replant problems in the rose
garden. I've heard of it's potential use for white rot but never tried
it. We tried it for rose replant disease on a 5 acre field on the
nursery where I worked in the '60s - it worked but it made growing
roses on that field a very expensive proposition. In the rose garden
here we felt it wasn't quite as effective as replacing the topsoil -
but in either case the treatment only lasts as long as it takes for
the rose roots to get down into the untreated soil below but the hope
is that by then the plants will be sufficiently well established to
withstand whatever it is that's causing the problem (and we still
don't know)

So with White Rot it should work as the onions are shallow rooted and even
cabbages roots don't go down too deep.
Interesting.

--
Regards
Bob Hobden
W.of London. UK