What follows is opionated and perhaps heretical but useful nonetheless, at
least, I think it's useful:
First I totally agree that spacing to allow for circulation and starting
with and growing healthy plants and choosing varieties carefully can help
and are good things to do....still....it is wortwhile to remember that:
Well, here's the thing about "common" fungi such as most rusts and
mildews, they are ALWAYS around. Always. Fungi Are. In certain climates
this one or that one is really always around. And, not surprisingly,
where a plant thrives *often* so too will fungi who like it as a
host...not always, but often. (Again a healthy plant is the best
prevention ever since a health plant can coexist with a lot.)
For instance, here in portland, oregon powdery mildews (I mean the 's'
since we're talking about a loose group :-) are just about
always going to make an appearance in mid to late summer because they love
our climate. Knowing this. I mean really understanding that:
(1) Fungi are,
(2) Plants always co-exist with a fair amount (just like we do too),
(3 a) Most fungi are from-our-point-of-view good and (3b)Finally, as is
axiomatic with the notion of 'cides (posions whether orgo or not)
'cides are general. They don't just go for the one thing you want them
to....you may not know all their effects but they are myriad...
Knowing/believving 1-3 gives me a slightly different take:
For one, when I realize that for common fungi if I don't want them around
I'm going to have to every season "take action", e.g., spray...and
spraying is something I really don't like ("organic" or otherwise) I
relaize I don't want to spray.
I think gardening smart is the way to go. Here are a few examples from my
micro-climate in portland, oregon:
Cucurbits just do get pm around here. Most years, weather cooperating, if
you've grown them healthily you get a good crop even though the plant
eventually peeters our as the weather gets less favorable and the pm (and
other things) take hold. (Cucurbits aren't a cash crop for me so I
don't worry too much, maybe if they were and I got an early case of pm
I would consider spraying but not likely...) Some perennials of mine,
e.g., aquilegias, just seem to get pm every year and get it good. They are
a cash crop for me. But, I still DON'T spray. They are naturally
short-lived perennials and I've found I can just cut the foilage back when
they've gotten pm bad and it's the end of the summer and they grow back
fine...again I'm considering the fact that I'm not expecting super
longevity and we've got mild falls/winters which permit regrowth. Another
story I love to share is about a snapdragon which lived
for three years (they are perennials in their native climes and
short-lived ones here when our weather is mild). Every year it got rust,
not surprisingly given the omnipresence of rust(s). But it just grew along
anyways, co-existing with the life cycles of the rust for those three
years.
In repetition:
I think the best "prevention" for common things like powdery mildews is
smart gardening and coexistence. That is, rather than look to sprays or
"sterlizing" soils or ??? which don't work well with these ubiquitous
fungi (or work well with much, for that matter, imnso) take advantage of
your climate, the plant's life cycles and the life cycles of the fungi
where you live. This sort of knowledge is very localized and really, what
I do in portland, oregon may not work for you. But, you're sure to light
on things that work for you in your local clime.
Again not to downplay the importance of spacing and selection of
varieties...
And, that is my very opinionated two cents,
:-)
eliza
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