APPLE canker is a fungal disease my two mature trees have battled with for years.
The Cox’s Orange Pippin is particularly affected, to the point where I can see having to take it out.
This upsets me, as it’s the tree I grew from a pip when I was eight.
The James Grieve/Golden Delicious duo tree is only affected on the James Grieve side!
Red Falstaff, the two-year-old sapling planted in a barrel, is all clear so far.
A fungus, Neonectria galligena, attacks the bark, causing a sunken area and, eventually, death of the branch. New cankers form from mid-spring, and once formed, are present all year.
Sorbus species are also attacked as are ash, beech and some other trees.
On small branches and fruiting spurs, the infection may girdle the stem and kill it in a season.
On larger branches, cankers are perennial, with the affected area covered with dead bark showing concentric rings. Older cankers lose the bark, exposing dead wood in the centre.
Eventually the branch will die above the canker, being progressively weakened as the bark is killed.
Developing fruits are sometimes attacked and will rot and fall.
Canker is more serious on wet, heavy and/or acid soils, so pay attention to drainage and raise the soil pH by liming if needed.
I’ve just sent for a soil-testing kit to see if my soil needs liming – only about £8.
Completely cut out all affected smaller branches and spurs. With the larger branches, try to cut out all infected material. Pruning should remove all brown, infected bark and wood, cutting back to fresh green tissue. Paint immediately with a protective wound paint, to prevent the wounds becoming reinfected.
No variety is completely resistant, but the following show some resistance: Alfriston, Annie Elizabeth, Brownlees Russet, Cockle Pippin, Crawley Beauty, D’Arcy Spice, Emneth Early, Grenadier, John Standish, Katy (Katya), Lane’s Prince Albert, Lord Derby, Merton Russet, Newton Wonder, Orleans Reinette, Reverend W Wilkes, Rosemary Russet and Winston.
Unfortunately, most of these are uncommon varieties that you’ll only find at a specialist nursery.
Some popular varieties are particularly susceptible, including Cox’s Orange Pippin, Lord Suffield, James Grieve, Ribston Pippin, Worcester Pearmain, Ellison’s Orange and Spartan.
You can control it chemically with copper-containing fungicides such as Bordeaux mixture, spraying once after picking but before leaf fall and a second time when about half the leaves have fallen.
I’m not keen on this – studies have shown copper compounds build up in the soil and adversely affect helpful predators such as ladybirds and earthworms.