Orange tree - Rust leaf disease ?

We have a small orange tree that has been growing superbly during the recent very hot weather.

However unfortunately it has started to develop what appears to be a rust like disease on some of the leaves.

I wondered if somebody may be able to confirm my suggested diagnosis?

I also wondered somebody may be able to recommend a way to resolve specific to orange trees ie a pesticide or fungicide spray or similar ?
Any advice greatly appreciated.

 

Does it rub off to some extent?
Rust usually does.
Just wondering if it's brown spots on the leaves.

 

My apologies I meant to upload these photos.

In answer to petes question, no it does not brush off.

maybe my self diagnosis is incorrect?

 

Personal thoughts are its probably not rust then.
It looks more like these problems perhaps.
Pests & Diseases - Citrus.com.

 

Blimey, that link is the stuff of nightmares! I woudn't worry unduly, @Borischelski. Just take off the affected leaves and make sure you feed the tree well. Citrus are greedy feeders. AFAIK there are no longer any effective fungicidal treatments available, although Bordeaux mixture is better than nothing, and I see that 'copper' treatments are recommended for a lot of the nasties in the link. Then again, would you want to eat the fruit of chemically-impregnated trees? The real pest to watch out for is scale insect...that needs to be removed physically and as soon as it's spotted, because once it gets a hold, it's a horror!