[Apple-Crop] Jonagold

[Glen Koehler]

Hi Art
    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?

- Glen

Glen Koehler
University of Maine Cooperative Extension
Pest Management Office
Voice:  Office 207-581-3882,   Cell  207-485-0918
491 College Avenue, Orono, ME  04473
UMaine Apple IPM <https://extension.umaine.edu/ipm/programs/apple/>
Ag-Radar <https://extension.umaine.edu/ipm/ag-radar-apple-sites/>

On Wed, Oct 12, 2016 at 2:19 PM, kellyorchards <kellyorchards at gmail.com>
wrote:

> 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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