Apple Canker is a common disease that affects apples in Scotland. Here is what it looks like, the conditions it needs, and the controls that actually work.
What does it look like?
Round or oval patches of dead, sunken bark, often starting at a wound or a bud. On small branches and fruiting spursWhether a fruit tree carries its fruit mainly on short side-shoots along older wood (spur-bearing) or at the tips of the previous year's growth (tip-bearing). Full definition →, the infection can girdle and kill the stem in a single season, with bark flaking off. On larger branches and the trunk, cankers are perennial: the affected area sometimes shows concentric rings marking periods of active spread, older cankers lose their bark to expose dead wood underneath, and raised edges form as the tree tries to grow bark back over the damage. Developing fruit can be attacked too, and will rot and fall.
What causes it
Wet, heavy or acid soil makes this genuinely worse, which is why drainage and soil pH are worth checking alongside anything you do at the tree itself.
Is this disease active now?
New cankers form from mid-spring, and once they’ve formed they stay visible all year round.
Symptoms
A canker on a small branch can kill it outright within a season. On a larger branch or the trunk, it’s a slower fight: the canker spreads in some periods and the tree’s bark grows back over it in others, and it can genuinely go either way. Left alone, the usual outcome is the branch eventually dying above the canker, or breaking once it’s weakened enough.
Life cycle
The fungus produces water-dispersed spores from the edges of lesions in summer, and airborne spores from small red structures in winter and spring. Both can start new infections, almost always through a wound: a pruning cut, a leaf scar, frost damage, or damage from scab disease or woolly aphid all count. Once a canker is established on a larger branch, it settles into a slow back-and-forth between the fungus spreading and the tree’s own bark trying to grow back over it.
Why this matters in Scotland
A lot of Scottish garden ground is wet, heavy or acid, and that’s exactly the soil profile that lets this canker take hold most easily. A tree here starts at a real disadvantage before pruning or hygiene even come into it.
Controls: what actually works
All the methods below are backed by real evidence, not just repeated folklore.
Improve drainage, and lime the soil if it’s acid
Addresses the growing conditions that let canker take hold in the first place, not just the symptoms once they’ve already appeared.
Cut out all infected wood, completely, back to clean green tissue
Smaller affected branches and spurs should come out entirely. On larger branches, remove every trace of infected bark and wood you can reach.
Choose a resistant cultivarA plant variety that arose or was bred under cultivation and is kept true by deliberate propagation, rather than a naturally occurring wild species. Full definition → where you’re planting new
No variety is fully resistant in every condition, but some show real resistance, including ‘Lord Derby’, ‘Winston’ and ‘Crawley Beauty’. Others are particularly susceptible and worth knowing before you plant, including ‘Cox’s Orange Pippin’, ‘James Grieve’ and ‘Worcester Pearmain’.
Myths about apple canker
7 common claims about apple canker, checked: 2 busted2 disputed0 untested3 hold up
“Spraying a copper fungicide on your apple tree will control apple canker”
Apart from wound paints applied to fresh cuts, no products are available to gardeners for controlling apple canker, so there's no spray that clears an existing infection.
What to do: Cut out cankered wood back to clean tissue, improve drainage, and pick resistant varieties for new plantings — don't look for a copper spray solution.
1 source
- RHS: Apple cankerApart from the wound paints described above, no products are available to gardeners for the control of apple canker
“Apple canker only affects apple trees, not pears”
RHS names apples as the most important host but explicitly states pears and Sorbus species (rowan, whitebeam) are also attacked by the same canker fungus.
What to do: Check pear trees and ornamental Sorbus for the same sunken, target-ringed cankers, especially on wet or poorly drained ground, not just apples.
1 source
- RHS: Apple cankerApples are the most important hosts, although pears and Sorbus species are also attacked
“Cutting cankered wood out back to clean, green tissue gets rid of apple canker for good”
RHS treats complete removal of infected wood, cut back to fresh green tissue, as the primary control for apple canker. Virginia Tech's extension guide to the same disease agrees that pruning out and destroying cankered wood cuts down the amount of infectious material available, but frames it as one tactic among several, stating plainly that no single strategy is sufficient on its own. The two don't contradict each other outright, but they weight the same practice very differently: one as the real control, the other as necessary but incomplete.
Our read Removing infected wood is worth doing every time a canker is found, but treating it as a permanent fix rather than one part of an ongoing programme looks like the weaker reading of the two sources.
What to do: Cut well beyond any visible browning into clean green wood, disinfect tools between cuts, and pair this with drainage, resistant stock and wound protection rather than relying on pruning alone.
2 sources
- RHSRecommends completely cutting out all affected wood back to fresh green tissue as the main control.
- Virginia Cooperative ExtensionStates sanitation pruning reduces available inoculum but that no single strategy, pruning included, is sufficient to control the disease alone.
“Painting a pruning cut with wound sealant stops apple canker getting in”
RHS recommends painting a fresh cut with a protective wound sealant straight away, describing it as the one product-based measure available to gardeners against reinfection. Virginia Tech's extension guide to the same disease, aimed at commercial growers, doesn't recommend wound sealant at all, instead focusing on pruning during dry weather and disinfecting tools between cuts as the practical defences against wound infection.
Our read The gap may come down to gardeners versus growers having different tools available rather than one source being wrong, but two institutional sources giving wound paint such different weight means it isn't a settled point.
What to do: Painting a fresh cut is cheap and worth doing, but don't treat it as a substitute for pruning in dry weather and keeping tools clean between cuts.
2 sources
- RHSRecommends painting fresh pruning cuts with a protective wound sealant immediately to prevent reinfection.
- Virginia Cooperative ExtensionDoes not recommend wound sealant, focusing instead on dry-weather pruning and tool disinfection to limit wound infection.
“Wet, heavy or poorly-drained soil increases the risk of apple canker”
RHS names wet, heavy or acid soil directly as conditions that make apple canker worse, and recommends improving drainage and liming acid ground as genuine risk-reducing steps rather than just symptom management. Virginia Tech's extension guide independently identifies cool, wet climates and prolonged wet conditions as favouring the disease's spread, discussing this in terms of weather rather than soil drainage specifically, but pointing the same direction.
What to do: Improve drainage before planting or as an ongoing fix around an established tree, and lime acid soil. This addresses a real underlying risk factor, not just the cankers once they've already appeared.
In Scotland: Much of Scotland's garden ground runs wet, heavy or acid, which puts an apple tree here at a real disadvantage before pruning or hygiene even come into it.
2 sources
- RHSNames wet, heavy and acid soils as risk factors and recommends drainage improvement and liming.
- Virginia Cooperative ExtensionIdentifies cool, wet climates and prolonged wet conditions as favourable for disease spread.
“Choosing a resistant apple variety meaningfully cuts canker risk”
RHS names varieties showing real resistance, such as 'Winston', against particularly susceptible ones like 'Cox's Orange Pippin', 'James Grieve' and 'Worcester Pearmain'. A peer-reviewed screening of 55 apple cultivars found considerable, genuine differences in how fast the fungus colonised different varieties, with 'Santana' progressing much more slowly than susceptible types including 'Cox's Orange Pippin' and 'James Grieve'. No cultivar showed complete immunity in that research.
Our read Variety choice is a real lever, not folklore, but it reduces risk rather than removing it.
What to do: Check a variety's known susceptibility before planting, particularly in wetter Scottish gardens, but keep up drainage and pruning hygiene regardless of variety since nothing is canker-proof.
2 sources
- RHSNames specific resistant and susceptible apple cultivars.
- International Society for Horticultural Science (ISHS), cultivar resistance screening studyFound significant, quantifiable differences in colonisation rate across 55 screened cultivars, with no cultivar showing complete resistance.
“Apple canker fungus mainly gets in through wounds, pruning cuts, leaf scars or damage from other problems like scab”
Infection is usually through wounds, including pruning cuts, plus leaf scars, frost damage, scab disease and woolly aphid damage. The fungus gets in through natural openings or wounds of all kinds, including fruit picking injuries and frost cracks as well as leaf scars and pruning cuts.
What to do: Treat pruning cuts, frost damage and scab lesions as canker entry points: prune in dry weather, disinfect tools, and control scab separately since it opens a second route in.
2 sources
- RHSStates the fungus usually infects through wounds including pruning cuts, leaf scars, frost damage, scab and woolly aphid damage.
- Virginia Cooperative ExtensionStates the pathogen enters through natural openings or wounds, including leaf scars, pruning cuts, fruit picking injuries and frost cracks.
Frequently asked questions
What should I do first if I find apple canker in my garden?
Start with improve drainage, and lime the soil if it’s acid. After that, cut out all infected wood, completely, back to clean green tissue. Work through the rest in order of how well-evidenced they are if the first two aren’t enough on their own.
Is there a spray that works?
No. There are no amateur chemical treatments available for apple canker. The controls that work are cultural: the measures listed above.
When are apple canker most active in Scotland?
Check the seasonal activity section above. Scottish timings can run a few weeks behind the UK-generic figures.
Sources
1 source, recorded with what each was used for
- RHS1: identification, symptoms, mechanism/biology, soil-condition trigger, active timing, drainage/liming and pruning controls, resistant and susceptible cultivars