RUST(note rust colored spore patches on leaf undersides)

It seems Rust (fungal disease) is becoming more of a concern every year.  In 2010 and 2011 I thought the high infection levels might be attributable to the cool growing seasons we experienced those years.  This year the temperatures warmed back up to a near average valley summer.  Additionally, we treated all of the bearing orchards with a rust fungicide early in the season. Despite these factors the disease has been present at low levels all year, and is really taking off now in the late season.