Spraying roses with milk

I read about this with interest as I have just planted a new rose garden. Should I start spraying the new growth now, or wait until the leaves are more mature?

 

I don't think it will do any harm at all if you start now but it might be a bit
unnecessary at present as temperatures are still a bit on the low side for the development of fungal problems. However there is a school of thought that suggests that milk can contribute a foliar feeeding effect, so in essence you've nothing, apart from a pinta, to lose.