Hello,

Based on your single image of the leaf from the apple tree – The condition is Cedar apple rust (Gymnosporangium juniperi-virginianae). More information is at these links:

Cedar apple rust - Integrated Pest Management (msu.edu)

Cedar-apple rust - Integrated Pest Management (msu.edu)

CedarRust.pdf (msu.edu)

Cedar apple rust (Gymnosporangium juniperi-virginianae) is a fungal disease primarily limited to eastern North America where Juniperus species occur.

Here are some key points about cedar apple rust:

Hosts:

Evergreen host: Mainly junipers (red cedar).

Rosaceous host: Various fruit trees, including apple, crabapple, hawthorn, quince, and mountain ash.

Symptoms:

On junipers, gelatinous telia (orange masses) form on twigs. These overwinter and produce spores during warm, wet spring weather.

On rosaceous hosts, symptoms include rusty orange leafspots, premature leaf drop, and deformed fruits. ‘Cluster cups’ form on the backs of leaves, carrying spores that infect junipers.

Management:

Prune galls (cedar apple rust) from junipers before spore horns develop.

Apply fungicides to rosaceous hosts when orange telial horns are visible on junipers.

Consider resistant cultivars for new or replacement plantings.

Red Cedar Trees:

Eliminating red cedar trees near orchards helps reduce disease pressure.

Pruning “cedar apples” from cedar trees is an alternative to tree removal.

More information is at these links:

Cedar apple rust - Integrated Pest Management (msu.edu)

Cedar-apple rust - Integrated Pest Management (msu.edu)

Remember, managing cedar apple rust involves a combination of cultural practices, fungicides, and host selection.

I hope this helps!