Multiple Fruit tree disease or pest?

[FB.]

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On the subject of pests and diseases; have a look at the severity of the leaf-curling aphid attack on a young apple tree (and notice that being on a strong rootstock allowed it to outgrow the aphid attack without assistance). Some of the small brown spots on the leaves may have been scab - but, again, it didn't concern me.

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[Ben1030]

I've just noticed the ants on the base of almost every leaf! They seem to have covered the small red lumbs at the start of the leaf. Hopefully not doing any harm?