Bud-based conidia have you again, my friend. The mantra where temps drop down well below freezing in the winter months is
no need to worry about the first three or so wetting events of early spring. This in a "clean orchard" with good leaf decomposition, between green tip and tight cluster and even up to earliest pink. I'm going to venture there was significant conidia production in late fall (when California trees hold on to leaves far too long) and that a warmer winter assured a greater percentage of these survived. You were set up bad . . . and accordingly whatever green tissue was showing got infected with one of your first "green tissue rains". I know you think about such things, and maybe even attempted a dormant version of the fatty acid knockdown. It would be nice to know how dormant copper impacts conidia--Terrence Welch south of the Bay Area goes about this with lime sulfur. Not that the question of "conidia toughness" compared to "ascospore toughness" is the concern at this point. The relevance is that
holistic spring sprays go on to target the entry mechanisms of ascospores in the regular scab season by boosting immune function and putting a competitive crowd in the way. Conidia take a much shorter path but I never have looked fully into the details.
The thing I've been contemplating about secondary scab season is how some varieties seem even more susceptible to conidia released from established primary lesions but others seem to dry up and cruise along to harvest. TRANSLATION: We keep scab minimal throughout the orchard but then certain "scab magnets" really should have additional protection when things appear to let off. Another observation during this time period is that scab spreads more on leaves than on fruit in general. I acknowledge varieties like Pink Pearl, Gravenstein, and Gala seem to be "conidia prone" here in my orchard.
Using sulfur has definite impact on good organisms in the short-term so you need to give some consideration to compost tea/ em renewal, if that's the direction you go. I have definitely tightened things up in the "fruit sizing window" being those 30-40 days beyond petal fall when I make the
holistic comprehensive sprays with the calcium and silica teas. The CCB utilizes only karanja oil rather than the synergistic mix with neem (because during bloom protecting bees from azadiractins) so not sure why you'd continue with CCBs beyond bloom.
BOTTOM LINE: I support a sulfur app or two for "yuge wetting events" that close off the primary window, given the great pressure you are facing.. Beyond that, no, unless you want to trial summer sulfur on "conidia prone" varieties only. Allopathic merged into holistic is a very gray area. I feel a holistic summer would do you good, mon.
And if several others contribute what they have observed, this post could actually turn into something useful.
Lost Nation OrchardZone 4b in New Hampshire