I have had siome very serious problems with downy mildew during this
and last years wet summers.I have plant onions from sets and seed
grown on the same patch for 21 years previously with little sign of
trouble,but the last two years have seen the crop crippled with downy
mildew.I even changed to a new onion bed this year so as not to be
infected by the previous years spores,but I have had a similar
problem.I have not used any nitrogen during the growing period,just
fish blood and bone at planting time,as I understand lush growth
encourages attack from mildew.My onions were very healthy until about
the middle of June,but then it came,and despite spraying with wettable
sulphur and copper oxychloride,the onions did not grow much more,and
are already rotting in store.
The only thing I may do next year is start spraying from late May,when
the onions are smaller,as I read this advice in an old book (1944) by
Arthur Hellyer.The other problem in spraying onions is that the spray
does not seem to give good coverage,but just collects in
globules.Perhaps I should add some lime to make it stick more,but I am
not sure this is correct.
I would very much welcome any advice,since we are very fond of our
onions,and believe they have similar health advantages as garlic.
Michael