Alan, fireblight is one fickle beast. Most years I had it easily
under control with pruning out the strikes; I also left galls around
if I thought I would have to take too much of the tree out to get
one. Last spring here however was the perfect storm -- it absolutely
ravaged my apples in spite of diligent pruning of strikes and several
streptomycin sprays. I think the weather was just right for the
infection. Now the funny thing is pears are 20' from the apples but
they didn't get any strikes last year at all (and the quinces got
nailed, I lost one of them).
This year? Its at the lowest level I have seen in five years. Three
blossom strikes and not a single flagged limb. We recently had two
weeks where it seemed to rain all the time, but these rains came a
little later and with cooler weather than last year and I think that
made all the difference.
So, don't let your guard down, if the weather is just right for
infection it could come back with a vengeance.
Scott
[NAFEX] Last years fireblight discussion,
Scott Smith, 05/11/2009