From their names, you can correctly assume that two hosts are necessary for the disease to occur. The chemical options for control center around protecting the apple, hawthorn, or crabapple hosts with a fungicide. If you have worked with these diseases in the past, you know that hawthorns are particularly troubled by cedar-quince rust, which causes stem galls on the hawthorn.
Timing is the critical factor.
Chemical companies tell us to spray when the new growth appears and flower buds begin to open. Now is the time to spray the alternate hosts to protect against spore release from those galls. Hawthorns are generally slower to leaf and flower, so watch hawthorns closely for signs of bud break. Also refer to Report on Plant Disease No. 802, Cedar-Apple and Related Rusts.