North American Fruit Explorers mailing list at ibiblio

[Alan Haigh <alandhaigh@gmail.com>]

"The bad news is the sensitivity to Sevin for thinning is different with
various varieties. What works with one variety may be too strong for others
and
no effect for another. Sevin attaches the apple stem and it may not be too
late depending on where you are. But it is normally done right after
blossoming."

And the rates vary greatly from season to season depending on weather- the
warmer the weather at time of application the less thinning agent is
needed.  All of this makes chemical thinning the most complex issue in
commercial production.

There are a couple of hormonal compounds like NAA that are mixed with Sevin
in the common approach, but none that do an adequate job by themselves- at
least none currently available, but probably coming soon.  Sevin alone will
probably cause an even more unpredictable amount of thinning.

This is not a subject that I have first hand experience with as I do all
thinning by hand in the non-commercial orchards I manage- often of the
blooms themselves if trees are stubbornly biennial.  I don't like using
Sevin at all because it tends to lead to mite outbreaks- this is something
I have experienced.

I have my help thin while I do more interesting work.