More Canker! This Time on a Cordon Apple Tree

At the weekend, as I was checking over our cordon apple trees – growing along a post-and-wire support on our main allotment plot – I sadly spotted the tell-tale signs of another dose of apple canker (see Winter Pruning to Control Apple Canker for details of my previous encounter with this infectious menace).

To be honest, it wasn’t entirely unexpected. I’d already found canker on this tree during my winter pruning sessions back in February and March and had taken off a main stem in the hope of preventing the disease from spreading. No such luck, as here was clear evidence of ongoing infection, as demonstrated by the darker, sunken tissue around the main branch junction:

This certainly explained the relatively weak top-growth that was all the tree had been able to put on this year, which is often a fairly reliable indicator of possible canker problems further down a branch:

Naturally, my first thought was “how can I save this tree?” and I opted for a major emergency pruning; removing all the top-growth above the lowest growth-point, which was hopefully far enough below the canker-affected tissue:

There was a small amount of dark staining in the wood (just about visible in the pic above), which could indicate that the canker had spread further down, but I decided it was worth allowing the tree to re-grow in the hope that the infection was now checked, as there was a minimal risk of spores developing and spreading to the other cordon trees nearby.

It turned out I needn’t have bothered. After re-checking the tree from a different angle to make sure the cut was clean, I spotted another patch of canker damage, this time on the rootstock section of the tree:

Looking at that photo again, there might even be a third infection point further down. In any case, that sort of damage to the rootstock meant only one thing: the tree had to be removed. Garden fork in, roots out, and off to the incinerator you go.

Two silver linings: firstly this tree was a ‘Howgate Wonder’ and, checking my records, it turned out that so was the tree next to it. So I’m down a tree, but not a cultivar, and have the opportunity to re-plant another cultivar next winter, although I will have to be mindful of possible re-plant disease if I replace with another apple, so might opt for a dwarfing pear or plum instead.

Secondly, removing the tree offered a rare opportunity to take a good look at the root system of a relatively young cordon:

This tree was planted in April 2019, after a year in the ground and, presumably, another year’s worth of rootstock growth before that. So it was a three-year grafted, tree on four-year-old rootstock. Shown above in the same configuration in which it came out of the ground, it’s interesting to note that the tree developed stronger anchor roots on the side with the more acute main stem angle (this section of cordons were all planted on an angle and trained to a diagonal support cane) so they were in effect on the inside of the lean, whereas I would have thought it might have stronger roots on the obtuse-angled side. But then there is a slight downward slope from left to right, so maybe the roots were responding to that?

Anyhow, there you have it. A drastic but necessary solution to an unfortunately intractable problem. And a future opportunity to plant a new cordon – along with another to replace a grafted tree that failed to establish, plus another row of 12 on the opposite side of this section of the plot – which is something to look forward to.

How about you? Have you had any canker problems this year? Do you find particular cultivars or varieties are more susceptible? Would you have taken the same action, or left the tree to its own devices? Do let me know, via the comments.

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