Anatoli, I use sulphur on my apricots even though you are not supposed to. Its interesting that this idea of not using sulphur on cots didn't make it down under, in Australia they spray sulphur on cots. So, I am somewhat doubtful if there is a reason for this restriction, or maybe only a few varieties are sensitive (I never noticed any sensitivity on my several dozen varieties). Anyway its your call on it in the end. I have also used Serenade but I don't think it works as well as sulphur.
Sulphur is a good organic spray for brown rot but needs many applications. If you are using synthetics try Monterey Fungi Fighter, it should zap any brown rot and it is one of the less toxic synthetic sprays. For the worms you need to use Surround clay to keep off the curculio, as soon as the fruits are bare (the shucks - flower remnants - have fallen off), or use pyrethrin spray. I don't like pyrethrin since it is a poison, Surround is non-toxic clay. You also need something to protect against moths, oriental fruit moth in particular. Either Surround or pyrethrin will do that. You need to protect against the curc until the cots are nickel sized and from dime sized to maturity you need to protect against the fruit moth.
Scott
Q