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seasonal variation

Posted by Michael Phillips 
seasonal variation
April 01, 2021 10:39PM
Most of us probably reckon bloom time from year to year as the means of saying its an early spring or a late spring. Or even that mythical notion of an average spring! The pace of bud development in accord with accumulating warmth – the whole degree day thing – determines bloom timing at a given site. Some of you are beyond bloom now while those north of here may wait till as late as the first week of June. Amazing to ponder that, eh?

Anyway, I'm wondering about the margin of variation fruit growers experience in different regions with bud development. Asking about "green tip" is nebulous as that takes place in the cooler part of spring when a full week (or even more) may not amount to much observable growth. Asking about actual bloom hinges on the variety and microclimate factors. So I'm going to phrase this question "holistically" in terms of the timing of the Spring1 application recommended to be made at average tight cluster. Anyone tracking scab development could pinpoint this even more exactly by degree days, as I see in past spray records that I make Spring1 either side of 300 DD. The range of this event over the past five seasons is telling: May 4 in 2017 and May 21 in 2020. That's a two-and-a-half week spread from one year to another. Does that fit generally speaking in most other places?

And remember .. we're not actually talking calendar dates here but rather bud stage on equivalent varieties of apple. That could mean an early apple or a mid-season apple (as in my case) or even an ornery bittersweet blooming later than anything else in the orchard. Consistency counts to participate in this talk.

Lost Nation Orchard
Zone 4b in New Hampshire



Edited 1 time(s). Last edit at 04/02/2021 12:44AM by Michael Phillips.
Re: seasonal variation
April 02, 2021 02:59AM
300 DD with what base temperature?

Broomholm Orchard
Zone 5b in Nova Scotia
Re: seasonal variation
April 02, 2021 02:16PM
Please ignore the degree day bit if you're not already tracking scab and simply focus on tight cluster. (The scab countdown starts at first smile of green on a MacIntosh fruit bud in New England, with 32F being the threshold temp for pathogen development). Choose some other consistent bud development stage if that's happier. To be honest, David, this query is simply meant to encourage more people to chime in about something they surely know something about. No deep science intended!

Lost Nation Orchard
Zone 4b in New Hampshire
Re: seasonal variation
April 02, 2021 03:59PM
I don't track degree days specifically, bu let the models track them for me in as much as it relates to scab spore maturity. 15% scab spore maturity is "go time" in my book and that lines up pretty closely - usually - with tight cluster. There is also pressure, past history, susceptibility, etc. that play into the equation. You can have an infection before tight cluster and before 15%, but its rare and for most of us on this forum irrelevant. So there you go.

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: seasonal variation
April 02, 2021 06:57PM
I don't track degree days for scab either. (Indeed, I don't do anything in particular for scab, relying instead on growing scab-resistant cultivars.) But I do do so for European Apple sawfly spray timing, (which is closely tied also to bloom time). And this uses a different base temp and biofix date than most other monitoring programs.

Broomholm Orchard
Zone 5b in Nova Scotia
Re: seasonal variation
April 02, 2021 07:13PM
And my season varies by as much as two-and-a-half weeks... which I thought might be interesting to compare between regions.

Lost Nation Orchard
Zone 4b in New Hampshire
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