---
title: Canker: Sunken Dead Patches on Bark and Limbs
url: https://battleborntreeservice.com/glossary/canker/
business: Battle Born Tree Service
address: 6301 US Highway 50 East, Carson City, NV 89701
phone: 775.232.8243
hours: Office Monday-Friday 8:30 am-5:00 pm; phones answered seven days a week; 24-hour emergency service
credentials: ISA Certified Arborist WE-11728A on staff; Nevada Business License # 20131580674; fully insured
type: Tree service (removal, crane work, pruning, stump grinding, defensible space, snow removal, firewood)
---

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- [Arborist glossary](https://battleborntreeservice.com/glossary/)
- Canker

# What is canker?

A canker is a localized area of dead bark and the tissue beneath it on a trunk or branch, often sunken, cracked or swollen at the edges. Cankers can come from fungi, bacteria, sun, cold or mechanical injury, and the size of the canker against the size of the limb decides how serious it is.

## How to recognise a canker

Look for a patch of bark that is sunken, discolored, peeling or cracked, sometimes with oozing sap or a ring of raised callus around the edge. On a thin-barked tree such as aspen the patch may be dark and slightly sunken; on a limb it may end in a dead tip beyond it.

Walk the tree and notice whether the dead patch is on one side only. A canker that has reached around most of the circumference of a limb is cutting off the flow of water and sugars to everything beyond it.

## Why it matters in Northern Nevada

Dry air, deep winter cold, intense sun on bare bark and sudden freezes after warm spells all injure bark here, and a damaged spot is an easy place for a canker fungus to start. Trees already short of water have less to defend with. Aspens, cottonwoods, poplars and willows are among the species that commonly show cankers. See [quaking aspen](https://battleborntreeservice.com/tree-guide/quaking-aspen/) and [drought stress and dieback](https://battleborntreeservice.com/tree-guide/drought-stress-and-dieback/).

A canker does not always spell the end of a tree. A small one on a side limb may be pruned out, while one on the main trunk is a structural concern.

## What an arborist does about it

The arborist looks at where the canker is and how much of the trunk or limb it has girdled, then checks the wood around it for decay and the crown above it for dieback. The options are the usual ones: remove an affected limb back to healthy wood, keep watching a small canker, or remove the tree if the trunk is compromised and it stands over a target. Battle Born does not spray or treat trees; we diagnose and handle the pruning or removal. See [arborist consultation](https://battleborntreeservice.com/tree-services/arborist-consultation/).

Bring photographs to the estimate if you can, taken in good light from a few feet away and from the ground up to the dead tips. The pattern of dieback above a canker helps the arborist tell a limb problem from a trunk problem.

### Sources

- [International Society of Arboriculture, Trees Are Good: Recognizing Tree Risk (brochure)](https://www.treesaregood.org/Portals/0/TreesAreGood_Recognizing%20Tree%20Risk_0721.pdf) (read October 17, 2026)
- [University of Nevada Cooperative Extension: Gardening Guide for High-Desert Urban Landscapes](https://naes.agnt.unr.edu/PMS/Pubs/2013-3170.pdf) (read October 17, 2026)

### Talk to the office

[775.232.8243](tel:775.232.8243)

| Monday to Friday | 8:30 am - 5:00 pm |
|---|---|
| Saturday and Sunday | Office closed, phones answered |

Phones answered seven days a week. 24-hour emergency service.

[Free estimate](#quote)

### Keep reading

- [Arborist glossary](https://battleborntreeservice.com/glossary/)
- [Quaking aspen](https://battleborntreeservice.com/tree-guide/quaking-aspen/)
- [Root and trunk decay](https://battleborntreeservice.com/tree-guide/root-and-trunk-decay/)
- [Arborist consultation](https://battleborntreeservice.com/tree-services/arborist-consultation/)

## See also

[Cavity](https://battleborntreeservice.com/glossary/cavity/) [Conk](https://battleborntreeservice.com/glossary/conk/)

## Read it in context

[Cytospora canker](https://battleborntreeservice.com/tree-guide/cytospora-canker/) [Sunscald and frost cracks](https://battleborntreeservice.com/tree-guide/sunscald-and-frost-cracks/) [Quaking aspen](https://battleborntreeservice.com/tree-guide/quaking-aspen/)