The Biology and Management of Hydrilla

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The Biology and Management of Hydrilla

  1. 1. The Biology and Management of Hydrilla Michael D. Netherland US Army Engineer Research and Development Center Gainesville, FL BUILDING STRONG®
  2. 2. Does Hydrilla Pose a Greater Threat to Missouri Waters Than Other Invasive Plants ?Hydrilla Eurasian Milfoil Curlyleaf Pondweed BUILDING STRONG®
  3. 3. Overview Hydrilla ► Life history ► The “Perfect Weed” ► Invasion History Factors Impacting Establishment & Spread ► Abiotic contraints Control Methods Feasibility of Eradication BUILDING STRONG®
  4. 4. Hydrilla verticillata L.f. Royle Hydrilla is a monocot - Hydrocharitaceae family ► Elodea, Egeria, and Vallisneria ► Early detection ? Native to tropical SE Asia ► Found on 6 Continents as far North as Poland Dioecious and Monoecious Biotypes ► Separate Introductions to the US ► Worldwide – Monoecious is tropical and Dioecious is temperate BUILDING STRONG®
  5. 5. Hydrilla - “The Almost Perfect Weed”* Ability to cover thousands of contiguous acres* propagates by fragments, turions, tubers, crowns - tubers can remain quiescent for years (seed)* Low light and CO2 compensation points* Clonal plant - but high genetic diversity BUILDING STRONG®
  6. 6. Why Plant Biology Matters ? What is it about Hydrilla that Allows it to Grow to Such Abundance ? 6 BUILDING STRONG®
  7. 7. Does Hydrilla Grow an Inch per Day ? Data often presented in terms of biomass ► E.g. 400 grams dry wt. /square meter Single 4” shoot grown for 35 days 1.2 M BUILDING STRONG®
  8. 8. 3500 Hydrilla change in Week 1 Week 2 Week 3 Week 4 Week 5 inches over 35 d 3000 Laterals 2±2 13 ± 6 43 ± 11 109 ± 29 127 ± 38 191.7 New Stems 2±0 6±1 34 ± 13 71 ± 16 110 ± 63 Runners 0±0 1±1 3±2 9±6 35 ± 20 2500Total Length of New Growth (in) 2000 -A single 9 inch shoot resulted in over 3200 inches of growth in 1500 182.3 5 weeks 1000 500 58.8 2.9 11.5 0 7/23/09 7/30/09 8/6/09 8/13/09 8/20/09 8/27/09 Harvest Date BUILDING STRONG®
  9. 9. Hydrilla BUILDING STRONG®
  10. 10. Dioecious Hydrilla Southern Distribution in the US ► Clonal female population Tubers produced - day length < 12 hr ► Fall production (short window in North) ► May switch to axillary turions in North (rapid process) Rapid Canopy formation ► Internodes measured in feet Fluridone Resistant Populations are in FL BUILDING STRONG®
  11. 11. Monoecious Hydrilla Northern Distribution in the US Tubers produced in summer Dies Back in Winter (propagules) Rapid lateral expansion ► Competitive interactions not documented Multiple Eradication Programs Ongoing BUILDING STRONG®
  12. 12. Greatest Threat to Missouri ? Monoecious Biotype May be Well Suited to Missouri ► Tolerates much higher disturbance ► Reservoir fluctuations ► Found in Reservoirs throughout the S.E. ► Becoming well established in TVA reservoirs • Expansion westward ► We know much less about monoecious hydrilla 12 BUILDING STRONG®
  13. 13. Significant Milfoil or Hydrilla Presence Natural Lakes Reservoirs Ohio River – Hydrilla Expanding where no SAV Was previously noted High Energy Reservoirs / Turbid with water level fluctuationsGenerally not conducive to SAV (Monoecious hydrilla ? ) BUILDING STRONG®
  14. 14. Progression of Hydrilla Spread Year Number States of States1960 – 1969 1 FL (1953)1970 –1979 6 AL, CA, DE, GA, LA1980 – 1989 13 CT, MD, MS, NC, SC, TX, VA1990 – 1999 17 AR, PA, TN, WA2000 – 2010 29 ID, IN, KY, MA, ME, NJ, OK, WI, WV, NY, KS, OH BUILDING STRONG®
  15. 15. Water Bodies in Wake County, NC with Hydrilla 70Number of Water Bodies 60 58 50 40 30 20 12 10 10 1 2 0 1980 1982 1984 1986 1989 Year Surveyed BUILDING STRONG®
  16. 16. Each Water Body Requires an INTRODUCTION ! Lake Gaston, NC Plants move from large to small water bodies and vice versa Small Landscape Pond in NC BUILDING STRONG®
  17. 17. Hydrilla in Wisconsin Pond – Response by DNRPositive i.d. in fall of 07 Completely drained pond for winter drawdown Spring 08- refilled and treated with fluridone Why such a strong response ? Where did the hydrilla come from ? BUILDING STRONG®
  18. 18. Management Options Are Limited Grass Carp – SE Reservoirs Selective BiocontrolEnvironmental Extremes 18 BUILDING STRONG®
  19. 19. Hydrilla Management Grass Carp – ► “All or None control” in large systems ► generally non-selective or at least non- predictable ► Still no efficient means for removal of fish ► Limited use in northern lakes due to low preference for milfoil • Cold water can reduce feeding efficiency/predictability BUILDING STRONG®
  20. 20. 13 Herbicides Labeled for Aquatic Use (223 labeled for terrestrial use)Copper (1900’s) 2,4-D (1950’s)Endothall (1960) Diquat (1962)Glyphosate (1977) Fluridone (1986)*Amitrole, Dicamba, Dalapon Simazine, Fenac, Dichlobenil, Silvex (most cancelled in 1987)Triclopyr (2002)Imazapyr (2003) Carfentrazone (2004)Penoxsulam (2007) Imazamox (2008)Flumioxazin (2010) Bispyribac (2011) Blue = Plant Enzyme Specific Inhibitors BUILDING STRONG®
  21. 21. Thousands of Harvesters - Winter Biomass Control , FL 21 BUILDING STRONG®
  22. 22. California – Eradication Policy Ongoing Eradication efforts for 30+years ► concern = agricultural irrigation Aggressive and Immediate Action Clear Lake (~ 40,000 acres) ► Eradication policy ► Treat 5 acres around individual plant finds ► Poor Economics on an acre basis / Good overall Policy ? Nationwide Eradication projects > 6 years BUILDING STRONG®
  23. 23. Hydrilla and Ecosystem Services Increased water clarity Provides Structure and Food ► Hydrilla- low density = native plant Does Not Produce Toxins (e.g. golden algae) Valued by the Fishing and Hunting Communities ►“ Fishing the Edge” “Ringneck duck buffet” Growth Rate , Canopy formation, & “Just leave us a little” Ability to Occupy Vast Expanses ► Access, Flood Control, Fishery Mgmt. ► Native Plants, Water Quality BUILDING STRONG®
  24. 24. Hydrilla Expansion Initial Establishment – difficult step 2 to 10% may be the hardest step Once well established plant can easily go from 30 to >70% coverage - widespread cover and low biomass ! Hydrilla creates habitat for more Hydrilla • Water clarification and wave reduction in open fetches BUILDING STRONG®
  25. 25. Unintended Consequences of Hydrilla Growth Stignematalan algae – produces a novel toxin 25 BUILDING STRONG®
  26. 26. Kissimmee Chain of Lakes– Headwaters- C&SF Flood Control Project- Extensive hydrilla management In a cruel twist of irony – Florida DEP recently declared Lake Toho impaired for Excessive Macrophyte Growth (HYDRILLA) BUILDING STRONG®
  27. 27. What Limits Hydrilla Growth ? “It’s the light”, stupid ► Algal turbidity, suspended sediments Poor Sediment quality or nutrition Cyanobacteria blooms – toxins ? Herbivores – general and specialists ► Grass carp, snails, etc. Consistent Management ? ► Setting back the clock 27 BUILDING STRONG®
  28. 28. Unknowns for Hydrilla in MO What is the greatest environmental constraint to hydrilla growth in MO waters ? • Fluctuating Reservoirs • Seasonal Extremes (temp, flow, etc.) • Sediment Composition • Water Clarity Can hydrilla colonize & proliferate in MO Reservoirs ? • We will likely find out BUILDING STRONG®
  29. 29. 29 BUILDING STRONG®

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