North American Fruit Explorers mailing list at ibiblio

["Mark Garrison" <pawpaw1@cox.net>]

Bryan,

It is helpful and encourages me to try to develop a model, which could be
helpful in planning, e.g. putting up netting, advertising, etc.  What
started me thinking along these lines was the New England Apple Pest
Management Guide, which provides a graph showing when scab ascospores
mature, depending on cumulative degree-days beginning from silver tip/green
tip.  Degree days for that purpose are defined as the number of degrees each
day the average temperature is above freezing.  I guess I'll have to figure
out a starting point, whether a calendar date or a certain stage in the
blueberries' bud or shoot development.  A neat little puzzle.  Thanks for
your input.  (And greetings from a former fellow Hoosier, I grew up in
Kokomo, up the road from you.)

Mark

Bryan wrote:

Mark,

I reread your message below and it triggered something that I worked on in
Grad school.

My professor was trying to see if I could create a growth model for potatoes
which would help predict the emergence of the potato out of the ground.
Potato emergence was a key period to apply a herbicide spray over the top of
a potato row after hilling (hill-spray treatment).  The key was finding a
potato growth model from study out of Australia that found that potatoes
start growing at about 50 F, and stop growing after 90 F.  The model also
assumed that 3 hours of the 24 hr day was at the low temperature of the day,
and 3 hours of the day was at the high temperature for the day.  The rest of
the time was assuming a combination calculation of the high and low
temperature of the day.

The result was that we were able to predict potato emergence for 4 locations
in the state using four key potato varieties (Russet Burbank, Norland,
Norchip, and Superior).  The model was able to predict emergence at over a
98% accuracy rate that was a tremendous help to farmers that planted over a
wide timeframe and farm locations.  In some of the locations of the state,
the planting date was all you need to predict an emergence date.  In some
locations, you need to input the high and low temperature for about 10 days
after planting to predict the emergence date.

Once that was done, we tried and successfully predicted harvest yields using
the same model after correlating final yields to degree days per day (I
believe you could quite accurately predict final yields by June 30th of the
same growing season).  We did not use the model for harvest dates because
the vines are usually burned down with a desiccant.  I'm not sure what
parameter a farmer (or researcher) would use to say it was time for the
burndown.

In summary, I believe it is possible to use a model like this to help
predict things like blossom emergence, harvest dates, yield prediction,
etc... It a matter of capturing yield data, harvest dates, and high/low
temperatures to develop a model for blueberries.

Hope that helps,

Brian
Sheridan, IN  zone 5b

Mark wrote:

I've been wondering about degree days as a way of predicting harvest time,
specifically in my case blueberries.  Whether I could build up a record
year-to-year that would enable me to say that I can expect fruit to begin
ripening after x number of degree days from Jan 1, Feb 1 or whatever.  Is
that feasible?  Also, I wonder if there is available a historic record of
degree days.  I see the weather service on its website shows heating degree
days, cooling degree days, and corn ripening degree days for locations
around the country.  Are any of these measures the same as what we are
discussing here?

Mark Garrison, RI zone 6