Using Trunk Injections Sustainably

Using Trunk Injections
Sustainably
Mark Harrell, Ph.D.
Forest Health Program Leader
Nebraska Forest Service
University of Nebraska
“I have seen trees that have died from injections
and implants!”
– Alex Shigo. 1991. Modern Arboriculture.
Injections and
tree damage
“The substances or chemicals put into or forced into the hole with
pressure are the most important factors affecting internal injury.”
“Large deep holes that touch other columns of infected wood cause
the greatest amount of injury.”
– Alex Shigo. 1991. Modern Arboriculture.
Photo credit: USDA Forest Service - Northeastern Area Archive,
USDA Forest Service, Bugwood.org
Key objectives
• Explain how trunk injections damage trees
• Explain how damage from injections can
be reduced
Vascular tissues
Phloem
•Movement up and down
•Mostly sugars and hormones
Xylem
•Movement up (roots to leaves)
•Mostly water and minerals
•Most pesticide movement
•Large amount of food storage
© Shigo and Trees, Associates LLC
Sapwood
• Contains parenchyma cells
used for storing food (starch;
stained black in the photo)
• Stored food provides energy
for growth and defensive
chemicals
Heartwood
• No living cells
• No food stored
© Shigo and Trees, Associates LLC
Open vessels
Closed vessels
Vessels are
closed by tyloses
or gums after
air enters.
APSnet.org
Air enters by cavitation,
freezing, wounding,
drilling, etc.
© Shigo and Trees, Associates LLC
Wounding and compartmentalization
Barrier zone:
A protection
boundary formed in
the wood by the stillliving cambium after
a tree is injured.
© Shigo and Trees, Associates LLC
Contains suberin
(cork) and protects
new wood produced
after the wounding.
Reaction zone: A protective chemical boundary that separates
wood infected by pathogens from healthy wood present at the time
of injury and infection. Also uses plugging of the vessels.
Dutch elm
disease – an
example of
compartmentalization
Dutch elm disease kills trees only after
multiple infections.
“The barrier zone walls off… wood that normally stores energy reserves.”
– Alex Shigo. 1986. A New Tree Biology.
Dutch
elm
disease
Only the
current ring
has food the
tree can use
and is
available for
food storage.
© Shigo and Trees, Associates LLC
“The beetles and fungus reproduce in living but defenseless tissues.”
– Alex Shigo. 1986. A New Tree Biology.
Injury from
injections
and
implants
© Shigo and Trees, Associates LLC
“Injection wounds do the same thing to the tree as the pathogens
[Dutch elm disease], the storage space for energy reserves is
drastically reduced.”
– Alex Shigo. 1986. A New Tree Biology.
Tree Decay: An Expanded Concept
─ Alex Shigo. 1979.
1. Healthy tree/ strong compartmentalizer
• Short, vertical, compartmentalized columns
•
1
Little or no lateral spread
2. Moderately healthy tree/ moderate
compartmentalizer
• Long vertical columns
•
Some lateral spread
2
3. Weak tree/ weak compartmentalizer
• Long vertical columns
•
Complete lateral spread
Images: © Shigo and Trees, Associates LLC
3
Where does ash fit in this?
1
• All of them
• Strong to weak compartmentalizer
• Healthy to weak trees
2
Images: © Shigo and Trees, Associates LLC
3
American elm after injection treatments
Age at the most
recent injection
Barrier zone
is failing
Initial reaction
zones
Decay
Reaction
zone from a
previous
injection
Additional
compartmentalized areas
© Shigo and Trees, Associates LLC
Many holes are
not closed after
3 years
Shigo’s comments on injections
and damage:
─ 1991. Modern Arboriculture.
•“Small shallow holes cause the least injury.”
•“Large deep holes that touch other columns of
infected wood cause the greatest amount of injury.”
•“Large columns of discolored wood decrease
greatly the energy storage capacity of the tree.”
•“The substances or chemicals put into… the hole… are the most
important factors affecting internal injury.”
•“When holes do not close, that is a sign of serious internal injury.
The tree should not be injected and injured again.”
Image: © Shigo and Trees, Associates LLC
The best way to keep trees healthy, to limit
compartmentalization and the problems it causes,
and to use trunk injections over the long term:
• Use small shallow holes
• Use small amounts of product
• Make sure the previous holes have closed
(gives the tree time to recover)
Mark Harrell
Nebraska Forest Service
University of Nebraska
402-472-6635
[email protected]
The University of Nebraska-Lincoln
is and equal opportunity educator and employer.