Hi Susan,

Thank you for your inquiry (and picture) about your crabapple on your property. Here is a CSU fact sheet about crabapples in Colorado to help guide the diagnosis.

Flowering Crabapple Trees – 7.424

The pictures look like the leaves could be suffering from Cedar Apple Rust. Here is a fact sheet to help you determine if it is a good fit.

CEDAR-APPLE RUST

If Cedar Apple Rust does not seem like a good fit, please respond back with more information about your tree's location/exposure (east, west, south, north facing). If the tree is near any buildings, structures or sidewalks and what other plants are nearby. Along with your regular maintenance schedule, watering, fertilizing, and pruning.

Hope this helps.

Happy Gardening!

Sincerely,

Amy