North Humberside,
United Kingdom 
The trunk of my old apple trees has turned bright orange and the bark is coming off. There are some very tiny black insects on the trunk which appear to be dead. What is it and what do I do?The tree fruited OK last year and the leaves seemed uneffected, but the orange colour is creeping up the trunk.
The actual colour is deeper than the photograph and you can see what seems to be small dead insects on the detail picture.
23 Apr, 2010
Previous question
The mites are either just that, mites, or else they're some form of bark beetle - these things don't kill trees, but they aid its decline, and usually only go for dead or dying trees. I'm interested in whether the orange deposit can be rubbed off at all - it looks like rust more than anything else. I thought at first maybe it was fireblight, but now I've seen the pics, it doesn't look like it. It may be that your old trees are getting ready to depart - you could try spraying with a fungicide to see if that clears the rusty deposits, but the tree is probably old ailing anyway.
23 Apr, 2010