Don't let the presence of cedars three miles away prevent you from planting an apple tree. The rust spores can travel that far, yes, but such a distance would cause a good percentage of spores to fall out along the way, essentially dilution by distance. I would be more concerned about cedar trees growing within 1/4 mile. This is a one-time per year disease, in other words, the spores go one way, from cedar-to-apple or from apple-to-cedar, not from apple-to-apple. Any infection on apple does not continue to multiply and reinfect other leaves on the apple tree. And there are a number of apple varieties that have very good rust resistance.
I copied the following text on resistant varieties from an Iowa State University extension website at http://www.ipm.iastate.edu/ipm/hortne....
An easy way to avoid this disease is to plant disease resistant apple or crabapple varieties. Fortunately, there are many varieties available now that show good disease resistance. Redfree, Liberty, William's Pride, and Freedom are examples of new apple varieties that are immune to cedar-apple rust. These varieties are also immune to apple scab and show good resistance to powdery mildew and fire blight. Examples of apples that are susceptible to cedar-apple rust include Jonathan, Rome, Wealthy, York Imperial, and Golden Delicious.
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