Tree Branches Dying? It Might Be Bot Canker – Here’s What to Do
Arizona’s desert climate is tough on trees. When heat and drought stress set in, a hidden fungal disease can take advantage. Botryosphaeria canker, commonly called Bot canker, is one of the most widespread and destructive tree diseases in the Phoenix area.
If you’ve noticed sudden limb dieback, peeling bark, or dark sap oozing from your tree’s trunk or branches, Bot canker could be the culprit.
At Adaptive Plant Health & Weed Solutions, we diagnose and treat Bot canker in residential and commercial landscapes across the Valley every day. Here’s what you need to know to protect your trees.
What Is Bot Canker?
Bot canker is a fungal infection caused by Botryosphaeria species. These pathogens attack stressed trees, especially those struggling with:
- Extreme heat
- Inconsistent watering
- Drought stress
- Bark wounds or improper pruning
Once inside the tree’s vascular system, the fungus blocks water movement, causing branches to die back and, in severe cases, the entire tree to decline.
Common Trees Affected in Phoenix
Bot canker targets many of the ornamental and desert-adapted trees commonly found in Arizona landscapes, including:
- Olive
- Ash
- Palo Verde
- Mesquite
- Citrus
- Bottle Tree
- Texas Ebony
If you have any of these species on your property, they’re at higher risk, especially during hot, dry summers.
How to Spot Bot Canker
Early detection is critical. Look for these warning signs:
Dark Sap or Oozing Resin
Sticky, dark-colored sap leaking from cracks or wounds on the trunk or branches.
Sunken or Blackened Bark
Cankers often appear as dark, depressed patches on the bark surface.
Bark Peeling Easily
When bark lifts away, the tissue underneath typically appears brown or discolored, not healthy and green.
Random Branch Dieback
Even with adequate watering, infected limbs suddenly collapse or dry out.
If you’re unsure, our certified technicians can perform an on-site diagnosis.
What Causes Bot Canker in Arizona Trees?
Bot canker thrives in the exact conditions Phoenix landscapes struggle with:
- High summer temperatures
- Drought or shallow watering
- Improper pruning during hot months
- Mechanical wounds from mowers, string trimmers, or storm damage
Trees under stress have reduced ability to defend themselves, allowing the fungus to take hold.
How to Treat Bot Canker
While there is no “cure” once the fungus moves into woody tissue, professional care can slow the progression, improve the tree’s vigor, and prevent future infections.
Professional Treatment Options
- Prune out infected limbs well below visible symptoms
- Sterilize tools between cuts to avoid spreading the fungus
- Deep-root soil treatments to increase water uptake and reduce stress
- Targeted nutrient support to improve natural disease resistance
Adaptive Plant Health uses advanced soil biology and plant-health treatments to strengthen trees from the inside out.
Prevention: Your Best Defense
Keeping your trees healthy is the most effective way to avoid Bot canker.
Water Deeply & Consistently
Shallow irrigation is one of the leading stressors in desert landscapes.
Avoid Heavy Pruning in Extreme Heat
Open pruning wounds during summer create prime entry points for the fungus.
Improve Soil Structure
Products like humic acid, seaweed extract, and biochar help improve root efficiency and reduce stress levels.
Remove Infected Wood Properly
Always cut at least 6–12 inches below the last visible sign of the canker.
Protect your trees with professional Care
Bot canker often goes unnoticed until severe damage has already occurred. If your tree is showing symptoms, or you just want a preventative evaluation, schedule a no-obligation consultation with one of our expert arborists. We’ll check out your trees and ideally, we’ll provide peace of mind knowing that your tree is safe and healthy.
If work needs to be done, we can recommend the best course of action. Call 602-777-7764 or fill out a short form to get in touch.
Our team specializes in diagnosing and treating tree diseases throughout the greater Phoenix area, including Scottsdale, Mesa, Chandler, Gilbert, and Peoria.