Canker: scourge of apples & pears​

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APPLE canker is a fungal disease my two mature trees have battled with for years.

 

The Cox's Orange Pippin is badly affected. 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 three-year-old in a barrel, is all clear so far.

 

The fungus Neonectria galligena attacks the bark, causing a sunken area and, eventually, death of the branch. New cankers form from mid-spring.

 

Sorbus species are attacked as are ash, beech and some other trees. On small branches and fruiting spurs, the infection may girdle the stem and kill it.

 

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, progressively weakened as the bark is killed.

 

Test your soil's pH

 

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 used a soil-testing kit, about £8 and a worthwhile purchase. My soil turned out to be pH7 - neutral.

 

You can try to control it chemically with copper-containing fungicides such as Bordeaux mixture, 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.

 

I've learned to live with the canker on the old tree, cutting out the worst and making sure it is in the best health possible - any parasite/predator will attack the weak.