Richard, there are some lower impact options out there that may (or
may not) work for you. I had kept brown rot away for several years by
spraying copper plus a sticker 3-4 times in the spring, up through
shuck split on the peaches. I only did two copper sprays this last
spring (and nothing later) and I ended up with bad brown rot for the
first time. So if you use copper you need lots of coverage. It
cannot be sprayed after shuck split due to phytotoxicity. This coming
summer I am going to be trying Serenade MAX and Saf-T-Side oil later
in the season. There was a study which found both of these moderately
effective against brown rot. The Saf-T-Side was more effective than
Captan in the study. Sulphur is also somewhat effective but based on
my limited experience you really need to be diligent on the coverage
to get efficacy. If you have lots of pathogen build-up in your
orchard you may need to use Indar or the like for a season or two just
to lower the pressure.
I would be interested in hearing what other organic growers are doing
about brown rot.
Scott
[NAFEX] Control of Brown Rot,
Scott Smith, 01/19/2009