A contributing factor to problems with fruit color this fall has been
late arrival of minimum temperatures below 42F, A "rule of thumb" from a
Cornell bulletin is that optimum coloring conditions require two days with
low temperature below 42F, followed by a day with high temperature over 68F
AND over 80% sunlight on that day.
The Ag-Radar estimate for Sanford 9 miles away from you (far enough
that I wish we had closer data site, working on that) shows that the two
days below 42F requirement was not met until September 26, and Sept. 27 had
a high temperature over 68F. But the requirement for a day with high
temperature over 68F AND over 80% sunshine was not met until October 6.
I don't see this formula as a powerful predictor, esp. since I've seen
some good color improvement while checking traps and doing fall scab index
over the past few weeks. And even if it was a robust predictor, it wasn't
based on Jonagold. Still it gives some numbers to possibly help explain
late coloring conditions this fall.
Easy to suspect the drought as a contributing factor. I'm also
wondering if you used ReTain on these Jonagold. If so, do you think that
had any effect on coloring?
University of Maine Cooperative Extension
Pest Management Office
Voice: Office 207-581-3882, Cell 207-485-0918
491 College Avenue, Orono, ME 04473
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On Wed, Oct 12, 2016 at 2:19 PM, kellyorchards <kellyorcha...@gmail.com>
> Why are my Jonagolds not coloring? Can this be an issue if they have a
> heavy crop?
> Art Kelly
> Kelly Orchards
> Acton, Maine
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