Hello Tim, after reading your post, I read my post again and realized
that someone could interpret that I suggested that blight can occur
in "any" weather. Of course, that's not what I meant. We have
"somewhat favorable" to "very favorable" conditions for blossom
blight every year. So at least a bit risky every year. Of course, we
see a lot more blight on "very favorable" years, but we have a few
orchards with fireblight despite "relatively benign" infection
conditions.
We also have a huge number of orchards that are NEVER sprayed with
streptomycine and NEVER get fireblight despite extremely favorable
weather. I always assumed sanitation could explain this difference.
Obviously, relying exclusively on sanitation is a risky game. A bit
of blight "next door" followed by a extremely favorable year =
potential disaster on a large scale. Some growers learned this the
hard way in 2002.
Since then, they kept on pruning out disease, but thanks to your work
many growers now spray Streptomycine when the Cougarblight model
stresses very risky conditions.
One subject which was not mentioned in this thread is that there's a
huge difference in risk between growing McIntosh on old standard
trees and Gala on M9 !!!
Accounting for every factor (weather, inoculum levels, cultivar,
rootstock, age) before deciding to spray means work, but worth every
penny...
7. I have never documented a blight outbreak where infection was
initiated during a period of cool weather, however wet. If this
was possible, why don't we see blight everywhere, every year?
Timothy J. Smith
WSU Extension,
Chelan, Douglas & Okanogan Counties
Vincent Philion, M.Sc. agr.
IRDA
Laboratoire de production fruitière intégrée
335, Chemin des vingt-cinq Est
Saint-Bruno-de-Montarville
J3V 4P6
téléphone: 450-778-6522 poste 233
courriel: [EMAIL PROTECTED]
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