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