Spots on apple leaves?

[Actingfan11]

I have an apple orchard and have been noticing these spots invading my leaves on several trees. Is this serious? Is there anything I can spray to prevent this from spreading to more trees? Also, is there anything I can do now? We're about to harvest so I don't want to harm our crop. Thanks, everyone!

[JONA]

Hi Actingfan,
Are there any Cedar trees near you?. This looks like Red Cedar Rust..
If so...you can spray a Rust Fungicide as a preventative from spreading. In the Autumn rake the leaves up and burn.
Cedars are the carriers though. The spores are produced from galls on the cedar trees.