Where the Maxilla Meets the Meristem: An Examination of How Bark Beetles Kill Ponderosa Pine in Northern Arizona. By Stephen James Burr

Transcription

1 Where the Maxilla Meets the Meristem: An Examination of How Bark Beetles Kill Ponderosa Pine in Northern Arizona By Stephen James Burr

2 Acknowledgements Dissertation Committee Thomas Kolb, Ph.D. Richard Hofstetter, Ph.D. Monica Gaylord, Ph.D. Catherine Gehring, Ph.D. Field Assistants John Kaplan Ansley Roberts Yudith Reyes Clair Nash Additional Assistance Kristen Potter Nick Aflitto Kelsey Flathers Asier Herrero Jacob Baker & many others

3 Funding Primary Funding U.S. National Science Foundation McIntire-Stennis Mission Research Grant Additional Assistance C.R. Krimminger Forestry Scholarship John H. Stephenson Forestry Scholarship K.R. and Irene Hafen Forestry Scholarship

4 Bark Beetles Coleoptera: Curculionidae, subfamily Scolytinae Aggressive tree-killing bark beetles Outbreaks Hundreds of millions of acres of trees killed How do beetles kill tree hosts?

5 Primary Study Goals What is the effect of tree stress on beetle colonization success? What is the effect of tree stress on the growth of beetle associated fungi? What is the role of bark beetle associated fungi on beetle colonization success?

6 Experimental Design 2 Stress levels Trenched & Untrenched (intact root system) 3 Treatments 1) Attack treatment 2) Inoculation treatment 3) Control treatment

7 Experimental Design 2 Stress levels X 36 Treatments X 8 Blocks = 48 Trees

8 Trench Treatment Roots trenched on 20 & 21 May 2013 Ditch Witch trencher 0.3 m depth Lined with polyethylene sheeting Back filled

9 Attack Trees Lures attached 2 June, 2014 Lures (frontalin, endo-brevicomin and α-pinene) 2 trees/block (one trenched, one untrenched) Trees were checked twice a week Attacks were recorded and marked with push pins

10 Inoculation Trees 2 trees/block (one trenched, one untrenched) Beetle smash technique Inoculation trees paired with attack trees Inoculations were recorded and marked with push pins 2% Carbaryl Insecticide spray on Inoculation & control trees

11 Dissertation Chapter I: Introduction Chapter II: Impacts of Stress on Bark Beetle Colonization Success, Associated fungal Growth and Mortality of Ponderosa Pine in Northern Arizona Chapter III: Is Bark Beetle Colonization Success Dependent on Fungal Penetration of Tree Xylem, or Vice Versa? Chapter IV: Conclusions and Management Implications

12 Chapter II: Inoculations Assess differences in fungal growth with trees Primary Dendroctonus brevicomis D. frontalis Secondary D. valens Mycangia Sterile Control (no beetle)

13 Chapter II Beetle attacks (& fungal inoculations) 1st attack recorded on 4 June, 2014 Last attack 5 August, beetle attack 230 ± 13.2 attacks Lures pulled following 150 attacks

14 Chapter II: Canopy decline 15 August 1 October 10 September 75% Trenched Attack trees 16 September 3 more dead by 25% 1 May 27 November Untrenched Attack trees

15 Chapter II Beetle attack between untrenched & trench trees attacks/m 2

16 Chapter II Beetle attack between surviving & doomed attack trees

17 Chapter II: Beetle emergence

18 Chapter II: Fungal Inoculations Male D. brevicomis Female D. brevicomis Male D. frontalis Female D. frontalis D. valens Control

19 Chapter II Fungal inoculations between untrenched & trench trees No evidence of fungal penetration into tree sapwood Phloem lesions formed Trench treatments had no effect on lesion length

20 Chapter II Phloem lesion length by species gender from mycangial species

21 Chapter II: Phloem lesion length

22 Chapter II: Conclusions Mortality rates were higher in trenched (75%) compared to untrenched (25%) attack trees Tree stress had no impact of beetle attack densities or beetle emergence rates Minimum lethal beetle attack densities:76.7 attacks/m 2 for untrenched and 57.6 attacks/m 2 for trenched attack trees (Mean attack density on all doomed trees: 86.2 ± 8.5 attacks/m 2 ) No mortality recorded in inoculation or control treatments

23 Chapter II: Conclusions Secondary bark beetles (D. valens) produced longer phloem lesions compared to primary species (D. brevicomis and D. frontalis) Female beetles from mycangial species produced larger lesions compared to their male counterparts No difference was found between D. valens and female D. brevicomis and D. frontalis No evidence of fungal penetration of tree xylem in inoculation trees

24 Chapter III: Physiological Measurements Predawn & midday water potentials Scholander pressure chamber Photosynthesis & stomatal conductance Li-Cor 6400 IRGA Measurements taken at mid-canopy Fungal xylem penetration in all treatments Assess differences between surviving & doomed trees

25 Chapter III: 2013 Water Potentials

26 Chapter III: 2013 Gas Exchange 126 day post trench treatment

27 Chapter III: 2014 Photosynthesis 2 June Lures attached to attack trees 23 July Attack trt lower than other trts 23 June No difference found 2 May 9 June 7 July Trenched lower Trenched lower than than untrenched untrenched trees trees 5 August 18 September Trenched attack trees lower than other trts

28 Chapter III: 2014 Stomatal Conductance 2 June Lures attached to attack trees 23 July Attack trt lower than other trts 20 August Trenched lower than untrenched Attack trt lower than other trts No interaction 2 May Trenched lower 7 July than untrenched trees 5 August Trenched attack trt lower than other trts 4 September Trenched attack differed from trenched inoculation 18 September No differences

29 Chapter III: Predawn water potential 2 June Lures attached to attack trees 23 July Trenched lower than untrenched 2 May 23 June Trenched lower than untrenched trees 7 July Trenched attack differed from all but trenched inoculation 5 August 18 September Trenched attack trees lower than other trts

30 Chapter III: Midday Water Potential

31 Chapter III: Predawn water potential 2 June Lures attached to attack trees 11 September Beetles emerged Trenched and Untrenched 15 August Tree xylem positive for Fungi in attack trees

32 Chapter III: Fungal Penetration of Xylem July 2014 August 2014 June sample cores/ tree taken each month beginning July, cores total 3.0 cm Fungal penetration of tree xylem only found in doomed attack trees

33 Chapter III: Leaf Gas Exchange Fungi found in tree cores Fungi found in tree cores

34 Chapter III: Water Potential * * Fungi found in tree cores Fungi found in tree cores

35 Chapter III: Conclusions Bark beetles can disrupt tree water relations and gas exchange, but it is not necessary for successful beetle development Bark beetle fungal penetration of tree sapwood only occurred in doomed trees Tree physiological decline was recorded in trenched attack trees prior to finding fungal penetration of tree sapwood

36 Management Implications Fewer beetles to colonize stressed trees Possible future increase in the number of stressed trees across the Southwest Management: Focus on reducing tree stress Prepare for changes in stand composition and tree species distribution

37 Thank You