I had the same problem recently with leaf spots appearing on my Indian Hawthornes ( a few different dwarf varieties). I also have problems with scale, euonymus and possibly also tea types, so I assumed that they had migrated over to the hawthornes.

I sprayed them (as well as my camellias and euonymus) with horticultural oil (not neem, one of the refined petroleums) a few weeks ago and was planning to follow up starting this weekend with neem oil (garden safe 3-in-1) to try to get the crawlers. Don't know if this will work, but this is what im doing anyway.

Id be curious if anyone had a better plan as well.

Here's a good link. Looks like fungicide treatment is recommended because the cause is a fungus. While neem oil is said by some sources to be a fungicide, it appears to primarily be used to combat insect pests.

I've not used neem oil myself, this is just what I found by searching around based on your problem.

Hope that helps.

Here is a link that might be useful: Indian Hawthorn leaf spot

Thanks for your responses.

Esh-GA, are you familiar with any of the fungicides on the list? Banner sounds familiar. Our local Pikes closed last year and it was the place I could depend on to find the various oils or other garden treatments we sometimes need. Other local options for me are Lowes and Home Depot. I find often they don't carry some of the fungicides or things like horticultural oil concentrate. What they offer often comes only in premixed, small bottles. Very expensive way to go. (I REALLY REALLY miss Pike's.)