I just noticed this post. What makes captan difficult is that it washes off in rain and commercial growers reapply it after every heavy rain. Without rain I guess it protects for about 2 weeks because a 2 week sched is usually what’s recommended.
I use Indar but prop. is supposed to be about as effective and is available from two companies in smaller quantities. Both are locally systemic and don’t wash off in rain, which is huge.
At most sites here I actually get peaches in with a single early summer app of Indar and Cap at highest rates. It never takes more than two as long as the customer isn’t looking for pristine fruit.
Drew’s comment about two varieties being more effective is not really embraced by commercial fruit growers to my knowledge. The reason they don’t depend on Indar and other single mode pesticides alone is the possible development of resistance, but as I keep writing here and seem to be yelling into the night, resistance is a much larger problem when you are managing thousands of same species trees at a single site.
I’ve never seen a study, but I have a hunch it takes more than 10 times as long on average to develop resistance at a site with a tenth of the trees. I’ve yet to have a site I manage develop resistance to Indar after 20 years.
This guide tells what materials you can use to get sound fruit. Spray Schedule- Synthetic Materials - #17 by MES111