Physiological Decline and Recovery of Eastern Hemlock to Hemlock Woolly Adelgid (HWA)

Kelly McDonald1, John Seiler1,Scott Salom2,Rusty Rhea 3

1Department of Forest Resources and Environmental Conservation2Department of Entomology3 USDA Forest Service Forest Health Protection Department

Overall Goal

Characterize the physiological response of eastern hemlock to HWA

with a particular emphasis on the impact on carbon

uptake

Heavily infested tree recovering after treatment

WHY DO WE CARE?

William M. Ciesla, Forest Health Management International, Bugwood.org

Predicted Range Expansion of HWA

Map produced by: USDA Forest Service

Randall MorinNortheastern Research Station

1. Determine the impact of HWA in hemlock needle physiology at sites with varying levels of HWA infestation.

2. Examine initial changes in needle physiology in response to treatment with imidacloprid.

3. Examine the impact of HWA on hemlock chlorophyll fluorescence.

4. Examine percent bud break on treated and untreated trees.

Specific Objectives

Study Locations

Elevation ~3825

Elevation ~2010 ft

Elevation ~2000 ft

•Six replications

•Three tree size classes

•Treated and untreated with imidacloprid

•Treated plots 15m+ away from untreated plots Smallest size class tree being treated with

imidacloprid in summer of 2011

Design at Fishburn Forest & Mountain Lake

Imidacloprid Treatment

•Kiortz Soil Injection of imidacloprid (Merit® 2 F, Bayer)

•Rate of 1.2 g (a.i.)/ 2.5 cm dbh

•Treatment Dates:-Fishburn Aug 2011-MLBS Nov 2011-Twin Falls Oct 2011 Medium size class tree being treated with

imidacloprid in summer of 2011

DBH Distribution

Small Medium Large0

7

14

21

28

35

DBH

(cm

)

Small Medium Large

TreatedUntreatedMLBSFishburn

•Ten replications

•Treated and untreated with imidacloprid

•No size classes

Hemlock in serious decline due to HWA

Design at Twin Falls State Park

DBH Distribution

Treated Untreated0

5

10

15

20

25

DBH

(cm

)

Methods

Leaf Gas ExchangeLi-Cor 6400 Open Portable Photosynthesis System

CO2R= 385 ppm Temp= ambient PAR= 1200 µmol m-2sec-1

Gas Exchange•Fishburn & MLBS- measurements are taken on fully mature, attached foliage

•Twin Falls- measurements are taken on detached foliage

Branch Removal

Attached Detached0 6 12 18 24 300

1

2

3

4

5

Time Since Removal (min)

Phot

osyn

thes

is (µ

mol

CO

2 m

-2 s-

1)

Chlorophyll Fluorescence•Hansatech Handy PEA Meter

•15 min dark adaption

•Fv/Fm- Quantum Efficiency of PSII

% Bud Break•5 randomly selected branches on each side of tree

•~20 buds counted per branch

•Recorded Y/N for each bud

Results

9/15/11 11/15/11 1/15/12 3/15/12 5/15/12 7/15/12 9/15/12 11/15/12 1/15/130

3

6

9Twin Falls

*

0

3

6

9MLBS

0

3

6

9

FishburnUntreatedTreated

Phot

osyn

thes

is (µ

mol

CO

2 m-2 s

-1 )

* **

****

*

=2.92 =3.16

=3.18 =3.31

=3.87 =4.10

0.760000000000001

0.790000000000001

0.820000000000001

0.850000000000001

0.880000000000001Fishburn Not

TreatedTreated

0.760000000000002

0.790000000000002

0.820000000000002

0.850000000000001

0.880000000000001MLBS **

**

Fv/F

m

Fishburn MLBS0.760000000000001

0.790000000000001

0.820000000000001

0.850000000000001

0.880000000000001

TreatedNot Treated

Fv/F

m

Quantum Efficiency of PSII

Fishburn MLBS0

20

40

60TreatedUntreated

% B

ud B

reak

Percent Bud Break

*

50%

Conclusions

1. Determine the impact of HWA in hemlock needle physiology at sites with varying levels of HWA infestation.

• Ps rates similar between sites-Twin Falls averages highest Ps rates-MLBS averages lowest Ps rates

Conclusions

2. Examine initial changes in needle physiology in response to treatment with imidacloprid.

• Treated trees tend to have higher Ps rates than untreated trees

• Treated trees:-highest average rate @ Twin Falls-lowest average rate @ MLBS

• Untreated trees:-highest average rate @ Twin Falls

-lowest average rate @ MLBS

3. Examine the impact of HWA on hemlock chlorophyll fluorescence.

• No difference between treated and untreated trees overall

• No difference in Fv/Fm between Fishburn & MLBS

4. Examine percent bud break on treated and untreated trees.

• % bud break much lower at Fishburn compared to MLBS• % bud break significantly higher for treated trees at

Fishburn

Conclusions

Future Work

•Continue with gas exchange measurements through March

•Develop methods to use a Sunscan Plant Canopy Analyzer to get LAI estimates

-Correlate with: Hemiview photograph analysis Crown class score based on % foliage

•Run statistics in JMP- time series analysis-Covariates: soil moisture, tree age/size, min temps

Acknowledgements

•John Peterson•Tom McAvoy•Tom McNamara•US Forest Service

Schedule

Complete fieldwork: April 15Organize data for statistical analysis: May 1Run Statistics: May 15Submit first draft: June 1Submit second draft: June 15Defend: July 1