Cytospora Canker
A sunken dead patch of bark on a trunk or limb with thick amber gum oozing out of it on stone fruit, or white and purplish resin patches on spruce. On spruce the lowest branches brown and die first and the damage climbs the tree year by year, which separates it from needle diseases that thin the whole canopy at once.
Disease checklist
Four things to look for. If most of them match what you are holding, you are in the right place.
What gets rid of it
Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.
1Prune out cankers in dry late winter
Cut well below the canker into clean wood, and prune only when the weather has been dry for several days.
pruning saw foldingTry this first2Avoid wounding the trunk
Keep the string trimmer and mower away from the base, and prune stone fruit late in the dormant season rather than in autumn.
tree trunk protector guard3Prevent winter and sunscald injury
Wrap or paint young stone fruit trunks going into winter, since freeze cracks are the usual entry wound.
tree wrap for winter trunk protection4Water spruce in drought
Deep watering during dry spells and a mulch ring reduce the stress that makes spruce vulnerable.
soaker hose 50 ft5Control borers on stone fruit
Peach tree borer wounds open the door for the fungus, so manage borers on the trunk base.
peach tree borer trap6Skip the wound paint and the fungicide
Neither sealing compounds nor sprays control this disease, so do not spend money on them.
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Which plants get cytospora canker
Every plant we cover that gets cytospora canker, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same disease can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.
Plant families hit hardest
Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Rosaceae, with 4 of the 8 affected plants.
- Rosaceae4 plants
- Pinaceae2 plants
When to treat
No fungicide controls this once it is in the tree, and there is no reliable spray timing, so the honest answer is to prune the cankered wood out in dry late-winter weather and prevent the wounds and stress that let it in.
Timing only — the label is the law
This page tells you when to watch for cytospora canker and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.
- Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
- Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
- Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
- Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.
Other problems on the same plants
If a plant gets cytospora canker, these are the problems it most often gets as well, so they are worth checking for while you are out there. They tend to appear together; one does not cause another.