plant growth regulators - trees.umn.edu · • pbz was used to slow the growth of live oak near...
TRANSCRIPT
Plant Growth Regulators: Slow & Steady Wins the Race
MNLA Fall Pesticide RecertificationNovember 16, 2018
Chad P. GiblinDepartment of Forest Resources - University of Minnesota
Contacts & LinksChad Giblin
Urban Forestry Outreach, Research & Extension (UFore)
Nursery and Labtrees.umn.edu
Tree Pruning Cycles
• Typical Pruning Cycles– Every 5 to 10 years to NEVER!
• Fast growing young trees require more– Every 2 to 3 years for 10 Years is IDEAL
• Pruning cycles that are too long– Increased rate of tree failure– Lower permanent canopy– Smaller trees
The Cost of Waiting
Every Year
Every Two Years
Every Three Years
6 Years
4 Years
9 Years
4 Years
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Photo: Tom Zetterstrom
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Photo© Tom Zetterstrom
Two Case Studies of Storm Failure in Saint Paul, MN
Storm #1July 28, 2015
Failure at Genus Level
0
5
10
15
20
25
Tilia spp. Acer spp. Ulmus spp. Fraxinus sp. Celtis sp.
Aver
age
DBH
(in)
0%
5%
10%
15%
20%
25%
30%
35%
Tilia spp. Acer spp. Ulmus spp. Fraxinus sp. Celtis sp.
30%
25%24%
6%5%
12%
27%
7%
17%
5%
0%
5%
10%
15%
20%
25%
30%
35%
Tilia spp. Acer spp. Ulmus spp. Fraxinus sp. Celtis sp.
Storm %
Total %
Average DBH at Time of Failure
18.2
15.1
5.5
19.1
13.1
0
5
10
15
20
25
Tilia spp. Acer spp. Ulmus spp. Fraxinus sp. Celtis sp.
Aver
age
DBH
(in)
Number of Elm Failures by Cultivar or Variety
1
0
0
0
0
1
0
7
35
0 5 10 15 20 25 30 35 40
Accolade
American Elm (WT)
Cathedral
Commendation
New Harmony
New Horizon
Patriot
Princeton
Valley Forge
Elm Inventory Citywide
2006
1636
1102
730 680 640
202 191106
0
500
1000
1500
2000
2500
Elm Failure Percentage of Total Population
0.1%
0.0%
0.0%
0.0%
0.0%
0.5%
0.0%
0.3%
4.8%
0.0% 1.0% 2.0% 3.0% 4.0% 5.0% 6.0%
Accolade
American Elm (WT)
Cathedral
Commendation
New Harmony
New Horizon
Patriot
Princeton
Valley Forge
Storm #2July 5, 2016
Failure at Genus Level
36%
27%
19%
6%5%
7%
27%
12%
17%
5%
0%
5%
10%
15%
20%
25%
30%
35%
40%
Ulmus sp. Acer sp. Tilia spp. Fraxinus spp. Celtis spp.
Storm %
Total %
Average DBH at Time of Failure
5.5
16.9
21 20.8
13.1
0
5
10
15
20
25
Ulmus sp. Acer sp. Tilia spp. Fraxinus spp. Celtis spp.
Aver
age
DBH
(in)
Number of Elm Failures by Cultivar or Variety
5
5
1
1
3
0
1
53
123
0 20 40 60 80 100 120 140
Accolade
American Elm (WT)
Cathedral
Commendation
New Harmony
New Horizon
Patriot
Princeton
Valley Forge
Elm Inventory Citywide
2006
1636
1102
730 680 640
202 191106
0
500
1000
1500
2000
2500
Elm Failure Percentage of Total Population
0.3%
0.5%
0.5%
0.9%
0.4%
0.0%
0.2%
2.7%
17.7%
0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% 16.0% 18.0% 20.0%
Accolade
American Elm (WT)
Cathedral
Commendation
New Harmony
New Horizon
Patriot
Princeton
Valley Forge
How Can We Reduce Tree Failures?
… without getting rid of all the trees!
Utility Vegetation Management• $20,000,000 to $50,000,000 lost
annually to storm-related outages• Many outages are the result of downed
trees and/or branches• Maintenance of vegetation can be
extremely hazardous• Pesticides can reduce the need for
vegetation management
C₁₅H₂₀ClN₃O
Paclobutrazol(PBZ)
PBZ Blocks Gibberellin
• Gibberellins cause cell elongation• Cell elongation causes longer branches• Longer branches create more pruning• More pruning means more work• More work means more risk!
“Electricity is consistently one of the leading causes of
worker fatalities in the tree care industry…”
Tree Care Industry AssociationFive Year Analysis of Tree Care Accidents
(2009-2013)
Photo: Tomahawk Tree Service, Ltd.
Image: Pacific Gas & Electric Co.
Image: Rainbow Treecare Scientific Advancements
• PBZ was used to slow the growth of live oak near utilities.• PBZ reduced the time necessary to prune trees and
process pruned material.• Treatment produced shorter branches and less biomass.• Ideally applied 90 days before or after pruning• Overall this means easier pruning and processing
“The Efficacy of Paclobutrazol Soil Application as it Relates to the Timing of Utility Right-of-Way Pruning”
Haugen et al.Arboriculture & Urban Forestry 42(2): 95–101 (2016)
• PBZ applications were made to nine tree species• Trees were wounded to simulate pruning cuts• Two-thirds of the trees showed slower wound closer after
treatment with PBZ• One-third of the trees showed wound closure that was
unaffected after treatment with PBZ• Wood discoloration/decay was not affected by PBZ
“WOUND CLOSURE IN TREES AFFECTED BY PACLOBUTRAZOL”Bai et al.
Journal of Arboriculture 31(6): 273–279 (2005)
Next Steps
Reducing Maintenance in Municipal ROWs
Contacts & LinksChad Giblin
Urban Forestry Outreach, Research & Extension (UFore)
Nursery and Labtrees.umn.edu
Thanks!
• Environment & Natural Resource Trust Fund• Minneapolis Park & Recreation Board• City of Saint Paul – Parks & Recreation• Minnesota Turf & Grounds Foundation• Minnesota State Capitol• Minnesota Nursery & Landscape Association