I have four three-year-old apple trees, all planted on a north-facing slope in a valley in East Cornwall. I gave them all deep mulch (including old carpet), cleared the pervasive bracken away and erected seven-foot-high wire netting cages around each to ward off deer (I have seen roe deer around). This year for the first time three of them cropped and look healthy.
Sadly, the remaining one – although the same variety as one of the others – briefly showed leaflets and buds in the spring, which then withered and died. I could see no telltale bites, scrapes or insect infestation, or any canker so I left it alone to see whether it would regrow the leaves (we had a very dry April, which might have had an effect).
This week, with no signs of growth, I scraped bark away and then snapped twigs off and it's all brown inside. I'm no expert so I can't be sure but I suspect the tree is dead.
Somebody suggested either honey fungus as the cause (what does this look like?) or voles burrowing underground and nibbling the roots. I have removed all the old carpet and mulch but can see no holes. We do have holes in a bank about 30 feet away and the cat has caught a few rodents in the garden, so it is quite possible.
I have three questions: 1. How do I check to see if voles are the culprit? 2. How do I get rid of them? 3. How do I stop reinfestation? 4. What else could it be if not voles? I am convinced the cause is either airborne or underground, as there is nothing visible topside. I do have a black mulberry about 40 feet away which has canker, but one of the other apple trees is closer to it and appears fine.
It is a damp climate but the trees are two old local varieties so shouldn't suffer. The soil is on the acidic side but otherwise fine. I had a soil expert from a local university analyze the soil before I bought the land and she produced a long list of ingredients and pronounced it highly suitable (she also has an orchard so I trust her knowledge). Unfortunately I have lost touch with her!
Thanks for any tips and suggestions.