Success Story: Eradication of Hydrilla at Lake Murray (and continued success in the
rest of the State)
Western Regional Panel
La Jolla, CA
Sep 10, 2003
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Success Story
• CDFA legal authority to eradicate hydrilla
• Quick overview of hydrilla• Lake Murray (thanks to Jeffrey Pasek
from the City of San Diego Water Dept.)• Overview of current hydrilla eradication
projects
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Success Story: Lake Murray
• Why review Lake Murray ?– Good example of a successful large scale
eradication effort – Demonstrates essential components of a
successful eradication program
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CDFA Hydrilla Eradication Program
• Legal authority– California Food and Agriculture Code
• Section 6048: Secretary of Agriculture authorized to survey and eradicate hydrilla (1977)
• Section 405: Secretary of Agriculture authorized to prevent introduction and spread of noxious weeds
– California Code of Regulations • Section 4500: lists hydrilla as State noxious
weed
– Title 7, Code of Federal Regulations • Section 360: lists hydrilla as Federal noxious
weed (1974)
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Hydrilla: a Federal and State Aquatic Noxious Weed
• Two forms– Monoecious– Dioecious
• Forms impenetrable mats
• Tubers form a long term bank
• Spread mostly by human activity
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Lake Murray
171 surface acres65 feet, max water depth3.2 shoreline miles
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History of the Project
• Hydrilla first detected in Lake Murray in 1976• Limited quarantine imposed in 1977• Full quarantine imposed in 1979
Lake closed to water-based public recreationBoats, fishing, water contact prohibited
• Project goalsPrevent spread of hydrilla to other watersEradicate hydrilla in Lake Murray
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History of the Project - cont.• Eradication began in 1979
1977-1994: reservoir water level drawdown 1979-1984: herbicide applications1985-1991: mechanical removal using
SCUBA divers and suction dredge1992-1994: on-going inspections
• Water-based recreation gradually
re-established, beginning in mid-1980’s
• Last plant found July 1991• Declaration of eradication November 1994
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Initial Infestation: 1977
• Covered 80 acres(of a total of 170 surface acres)
• All of the lake area less than 20 feet deep
• Continuous mat along shoreline
• Probably introduced from aquarium
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Water Level Drawdown: 1977-1994
• Water level dropped 30 feet
• Late summer
• Exposed plants killed by drying
• Some roots and tubers survive
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Water Level Drawdown
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Vapam
Herbicides: 1979-1984
Komeen®
®
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Eradication: Initial Phase
• Combination of water level draw downs and herbicides reduced infestation by 90%
• By 1984 only isolated individual plants remained
• Herbicides and drawdown not effective for remaining infestation
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Underwater Inspections,SCUBA
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Suction Dredging: 1985-1991
• SCUBA divers removed individual plants
• Labor intensive
• Removed remaining 10% of infestation
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Suction Dredging
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Eradication Complete: 1994
1977
1994
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Success Story: Lake Murray
Eradication of Hydrilla from Lake Murray, 1976-1985; (arrow indicates greatly reduced density of plants)
0
10
20
30
40
50
60
70
1976 1981 1986 1991
Year
No
. o
f in
fes
ted
ac
res
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Success Story: Lake Murray
Eradication of Hydrilla at Lake Murray, 1985-1994; (arrow indicates start of large scale diver assisted
dredging)
0
500
1000
1500
2000
2500
3000
3500
1976 1981 1986 1991 1996
Year
No
. of
hy
dri
lla p
lan
ts
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Project Costs• Direct Costs $5,700,000
1979 – 1984: ~$200K per year – herbicide applications, quarantine, drawdown
1985 – 1991: ~$600K per year– mechanical removal, SCUBA inspections, drawdown
1992 – 1994: ~$90K per year– on-going surveys and draw downs
• ~$71,000 per acre of originalinfestation
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Project Costs• Indirect costs
Reduced use of Lake Murray as a water supply reservoir
Loss of revenue from public recreation program
Loss of use of Lake Murray for public recreation
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Lessons Learned• Quarantine can be effective
to prevent spread
• Methods used for initial eradication probably won’t work in final stages
• Eradication can be a long and costly effort
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Success Story: rest of the State
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Status of Hydrilla in California COUNTY
*YR WATER BODY SIZE STAT
USCALAVERAS 88
8896
Bear Creek/ and 3 pondsTwo ponds
Bear Creek, 2 ponded areas
23 acres0.6 acre26 acres
Survey ActiveActive
IMPERIAL 77
45 ponds/reservoirsImperial Irrigation System
270 acres600 miles of
canals, ditches
SurveyActive
LAKE 94 Clear Lake 1,440 acres /43,000 acres
Active
LOS ANGELES
808385
Eight pondsOne pondOne pond
2 acres<1 acre<1 acre
Erad.Erad.Erad.
MADERA/MARIPOSA
89 Eastman LakeChowchilla River
100/1,800 acres26 miles
ActiveActive
MONTEREY 78 Private pond 0.01 acre Erad.
RIVERSIDE 778485
One pondOne pond
Three ponds
<1 acre<1 acre<1 acre
Erad.Erad.Erad.
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Status of Hydrilla in California SAN BERNARDINO
88 One pond <.01 acre Erad.
SAN DIEGO 7777
Lake MurrayOne pond
160 acres<1 acre
Erad.Erad.
SAN FRANCISCO
88 One pond 2 acres Erad.
SANTA BARBARA
7793
One pondOne pond
0.12 acre<.01 acre
Erad.Erad.
SHASTA 85869496
Seven pondsFour pondsTwo pondsFour ponds
133 acres23.5 acres13 acres39 acres
Erad.Erad.
SurveyActive
SONOMA 84 Spring Lake 72 acres Erad.
SUTTER 85 One pond <.01 acre Erad.
TULARE 9396
Three pondsSeven ponds
0.6 acre20 acres
Erad.Active
YUBA 769097
Lake EllisOne pond
13 ponds andtwo spill basins
30.8 acres6.0 acres
20 acres and 3.1 miles of canal
Erad.Erad.Active
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Springville ponds, before/after
1996
2002
Komeen treatedlanes
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Chowchilla River, before/after
1989
Dec 2001
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Lake County Project• Surveys in Clear Lake
– Visual, Grappling hook– 2001, 1042 surveys– 2002, 790 surveys
• Treatments: aquatic herbicides– Fluridone slow release pellets– Copper ethylenediamine
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Clear Lake
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Success Story: rest of State
• Lessons learned– Eradication is feasible– Requires early detection and rapid
response– Requires long-term dedication of funds and
manpower– Requires technology appropriate to the
situation and phase of eradication
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Success Story: Lake Murray
• Many thanks to Jeffrey Pasek for his slides for this portion of presentation
• Thanks to City of San Diego and the San Diego County Agricultural Commissioner for their support in the eradication of hydrilla from Lake Murray.
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COOPERATORS• U.S. Department of the Interior-Bureau
of Reclamation• U.S. Department of Agriculture-Animal
and Plant Health Inspection Service• U.S. Army Corps of Engineers-
Eastman Lake• Dept. of Boating and Waterways• Dept. of Water Resources• Yolo County Flood Control and Water
Conservation District• County Dept.s of Agriculture