SIXTEEN YEARS OF OAK WILT SUPPRESSION IN LAKEWAY, TEXAS

Transcription

1 SIXTEEN YEARS OF OAK WILT SUPPRESSION IN LAKEWAY, TEXAS Carrie Jean Burns, Forester City of Lakeway, Texas

2 SIXTEEN YEARS OF OAK WILT SUPPRESSION IN LAKEWAY, TEXAS Abstract. Lakeway, a rapidly developing central Texas community of 10,000, has been battling oak wilt since The city has installed twenty-three oak wilt suppression trenches with technical and financial assistance from the Texas Forest Service. Ten of the twenty-three trenches are holding and thirteen have broken out, resulting in a 43% success rate. Nine of the city s nineteen oak wilt centers are presently contained, four are partially contained and six are not yet contained. The cost of trenching has risen from $1.50 per linear foot in 1989 to $43 per linear foot in October Despite the high rate of breakouts and rapidly rising costs, the city plans to continue trenching. Key words: oak wilt, Ceratocystis fagacearum, urban forestry

3 LAKEWAY, TEXAS LAKEWAY, TEXAS Population 10,000

4 WORKING RANCH IN 1962 Lakeway was founded in 1963 as resort and retirement village. Before that, it was a working ranch with several thousand goats, a few ranch hands, some cedar choppers.

5 BARE HILLTOPS Hilltops cleared for pasture Hilltop trees small and scattered Bare hilltops were first sites developed Now dense with oaks Oak wilt in these areas today

6 LAKEWAY TODAY

7 FROM BARE HILLTOPS TO URBAN FOREST

8 WE LOVE OUR OAKS! Undeveloped lots are dense thickets of competing cedar and oaks. When lots are cleared for building, cedars are removed and oaks are preserved for their landscape value. Almost a monoculture of live oaks in some neighborhoods.

9 19 OAK WILT CENTERS One new oak wilt center per year on average

10 MOST MORTALITY IN LIVE OAKS through root transmission

11 NEIGHBORHOODS DEVASTATED

12 A FEW SURVIVORS

13 LAKEWAY S S OAK WILT SUPPRESSION PROGRAM Started in 1989 TFS foresters identified oak wilt centers, wrote up trench plans and applied for cost share refunds. City officials signed up homeowners and paid for trenching with tax dollars. 14 trenches installed

14 A PARTNERSHIP IS BORN IN 2001 Texas Forest Service awarded grants that helped Lakeway hire its first urban forester. Oak wilt program expanded: More emphasis on prevention Tree protection ordinances rewritten and enforced Information sharing and sick tree calls Trench installation is still the core of the program.

15 WHAT ABOUT REPLANTING? Homeowners are on their own. Value of mature trees is higher.

16 TRENCHES PROTECT MORE OAKS Putting the money where it will do the most good. Without trenches, more and more oaks would die each year. Benefit: Cost ratio of 6:1 for urban trenches that hold for 5 years (TFS )

17 CHALLENGES OF URBAN TRENCHING

18 TREATED TREES Fungicide does not prevent the movement of oak wilt through roots to the oaks beyond.

19 TIGHT FIT!

20 UNDERGROUND UTILITIES

21 LANDSCAPES TORN UP

22 STREET REPAIRS

23 RISING COSTS! Cost of trenching has skyrocketed from $1.50 per foot in 1989 to $43 per foot in October 2005!

24 OUCH!

25 HOW IS IT WORKING?

26 MILES TO GO 9 centers contained - 4 partially contained - 6 not yet contained 23 trenches installed in 16 years Some spots trenched 2 or 3 times

27 SUCCESS RATE TFS 2002 statistics ( ): 66% success for urban trenches statewide Lakeway 2005 statistics (1989-present): 43% success rate since out of 23 trenches are holding : 2 of 14 trenches holding : 8 of 9 trenches holding but most have not yet been challenged!

28 POSSIBLE REASONS FOR BREAKOUTS Pressure from homeowners to trench too close (difficulty lining up cooperators) Gaps in trench line Utility lines used as barriers Insufficient trench depth (30 in early days) Deep roots under limestone Roots grafting back in oldest trenches?

29 WHAT DOES THE FUTURE HOLD? Oak wilt symptoms and mortality still visible in 18 out of 19 oak wilt centers. Trench lines often not challenged for many years Concern about possible root grafting in older trenches. We know we ll be fighting oak wilt for years to come.

30 WE HAVE TOO MUCH TO LOSE!

31 CREDITS All photos, maps and text by Carrie Jean Burns, Lakeway City Forester unless otherwise noted below. Author s photos may be used for educational, non-commercial purposes only. Historical information in slides 3 and 4 from Varner, Byron D Lakeway, the first 25 years. Austin, Texas: Capital Printing Co., Inc aerial photos in slides 3 and 4 by Flint Sawtelle, published in Lakeway, the first 25 years. Original photos archived at the Varner History Center in Lakeway, Texas.

32 CREDITS 1996 aerial digital orthophoto from Texas Natural Resources Information System website ( aerial digital orthophoto from City of Austin CAPCOG website ( Benefit to Cost Ratio in slide 15 from Texas Forest Service presentation Oak Wilt in Texas and the Texas Oak Wilt Suppression Project, slide 41 (