For the home grower, try Growing apples naturally, a webpage which covers not only rust but organic apple growing in general.

 

 

For something more indepth, suitable for the commercial grower, try Management techniques for organic apple production in Canterbury, New Zealand, a paper from HortResearch which "reviews results obtained on many facets of orchard management and demonstrates especially that the vegetative understorey is the key component in organic apple production, influencing tree nutrition and growth, disease levels and pest infestations".

 

 

For still more, try some of the many links on the University of Reading's HorTips page on organic fruit production: