Harris Lake Hydrilla Management Project

Rob Emens, N.C. Aquatic Weed Control Programrob.emens@ncdenr.gov or 919-707-9012https://deq.nc.gov

Presenter

Presentation Notes

A handful of hydrilla appears very harmless. Most people have never heard of it and would assume this plant to be native and benign.

Hydrilla – A Noxious Aquatic Weed

• Submersed perennial– Native to Asia– Brought to USA in 20th

century– 1980 – 1st report of it in N.C.

• Prohibited plant– Not legal to culture,

sell or transport• N.C.’s most costly aquatic

plant to control– Annual expenditures

exceeding $1.5 million• Reproduces through

fragmentation, turions, and tubers

Presenter

Presentation Notes

Upper right shows how leaves are arranged in whorls. 3-7 leaves per whorl. Lower right side shows the tip with flowers The dark structures are tubers Hydrilla will senesce in the winter, remaining only as tubers Tubers sprout in the spring..... Responding to warming water temperatures Some tubers can ‘hibernate’ for several years

Why is Hydrilla a Problem?

• Currently most invasive aquatic weed in N.C.• Interferes with ability to use lakes, reservoirs,

rivers, etc., as it impacts recreation and can clog water intakes.

• Strongly associated with a fatal disease that affects waterfowl and raptors.

• Hydrilla found for the 1st time in N.C.• Task Force assembled to recommend response.• Several lakes in Wake Co. were found to be infested with

Hydrilla.• Finding Hydrilla here was alarming:

– Florida had been dealing with rampant spread of Hydrilla and major impacts from its invasion for ~20 years.

N.C.’s Hydrilla History1980 – 1982

Take-Home Messages

1. Introduction of Hydrilla to N.C. waters was a serious concern: • Quickly caught attention from the highest level of state

government. • Governor tasked DEQ with aquatic weed management

responsibility.

2. Hydrilla is being moved by human and/or wildlife vectors.

N.C.’s Hydrilla History1983 – 1984

• Control efforts initiated by the Office of Water Resources (known today as DWR) in cooperation with NCSU-WRRI

• Various herbicides were used with mixed results.

Take-Home Messages

1. State was able to coordinate a quick response and implement management efforts, however; controlling Hydrilla was not a simple matter.

2. Realized the need to develop better tools and technology.

• Hydrilla spreads to lakes outside of Wake Co. – Lake Gaston (NC-VA border) and downstream to Roanoke

Rapids– Lake Rogers and Holt Reservoir (Granville Co.)

• Methods were developed to produce sterile grass carp.

• Large-scale aquaculture operations ramped up production which lead to sterile grass carp being more available and affordable.

N.C.’s Hydrilla History1985 – 1989

1. Hydrilla can be easily moved from one lake to another.

2. Fragments are likely ‘hitchhiking’ on equipment, or intentional introductions are occurring.

Take-Home Messages

N.C.’s Hydrilla History1990 – 1999

• Hydrilla becomes widespread in Lake Gaston. Surveys estimate 3,000-4,000 acres. – Integrated pest management using both herbicides and

triploid grass carp

• Several new infestations outside of Wake Co.– Catherine Creek (Hertford Co.)– Lake Orange (Orange Co.)– Randall Lake (New Hanover Co.)– Twin Lakes (Brunswick Co.)

Sterile Grass Carp Used to Remove Hydrilla1990s

Reservoir Size (Surface Acres)

Sorrell’s Grove Reservoir 29Shelly Lake 53Lake Lynn 56Fred Bond Lake 80Lake Rogers 140Lake Wheeler 550

Take-Home Messages

1. Hydrilla can spread very easily.

2. Hydrilla can expand to large areas within a N.C. reservoir.

3. Low turbidity allows the plants to grow in deeper water (10’ deep and deeper).

4. Triploid (sterile) grass carp have proven to be very effective at removing Hydrilla from N.C. reservoirs.

N.C.’s Hydrilla History2000 – 2004

• Hydrilla spread westward infesting impoundments within the Catawba River Basin:– Lake James– Lake Norman– Mountain Island Lake

Catawba River Basin

Take-Home Messages

1. Hydrilla is being transported across major river basins.

2. N.C. infestations are leading to fragments flowing across the state line into S.C.

New Habitats Invaded2005 – 2008

• Hydrilla started to show up in Coastal Plain reservoirs. – Rocky Mount Reservoir (Tar River Basin)– Buckhorn Lake (Neuse River Basin)

• Hydrilla began colonizing flowing water systems.– Eno River– Neuse River

Buckhorn Lake (Wilson Co.)August 27, 2010

Sterile Grass Carp Used to Remove Hydrilla2000s

Reservoir Size (Surface Acres)

Lake Howell 1,200Lake Mackintosh 1,200Buckhorn Lake 2,424Mountain Island Lake 3,281Belews Lake 3,683Badin Lake 5,350Lake Tillery 5,697Lake Wylie 13,000Lake Gaston 20,300Lake Norman 32,475

Eno River at Cabes FordAugust 26, 2008

Eno River at Cabes FordAugust 26, 2008

New Habitats Invaded2008 – 2010

• Hydrilla found in areas adjacent to and within the estuary (Albemarle Sound):

- Chowan River- Bachelor Bay- Salmon Creek- Queen Anne Creek

& Filbert’s Creek (Edenton)

Chowan River & Albemarle Sound

Arrowhead BeachOctober 15, 2009

Batchelor Bay

Hydrilla History in N.C.2010 - present

• Hydrilla continues to be at the top of the list for “worst aquatic weeds”.

• Major reservoirs become re-infested.• Lake Waccamaw.

Lake Waccamaw

– Natural Lake (a Carolina Bay)– 9,000 surface acres– Average depth ~5’ (deepest part ~11’)– Endemic species

Hydrilla documented in October 2012

– Area infested = 608 acres– Herbicide treatment 2013 – 2018

• Cost = $2,549,956

https://deq.nc.gov/conservation/natural-resource-conservation

Harris Lake

• Full water level 1983• ~4,100 acres• Source of cooling

water for nuclear station

• Recreational use– 2 boat ramps– Harris Lake

County Park• Hydrilla 1st observed

in 1988

Hydrilla Management

History

• Hydrilla 1st observed in 1988

• Within the first couple years of observing Hydrilla, Progress Energy attempted to control with aquatic-use herbicides.

• No management has been implemented since that time.

2018 Survey of Submersed

Aquatic Vegetation

• Hydrilla is shown on map as red.

• Estimated 232 acres.• Other aquatic plants

found:– Chara– Lotus– Brittle Naiad– Cabomba

Why Remove Hydrilla from Harris Lake?

• Harris Lake is a source population.

• Harris Lake cannot continue to be a source of Hydrilla.

What Methods Will Be Used to Remove Hydrilla From Harris Lake?

Integrated Pest Management

1) Herbicide applications at the boating access area (boat ramp) as needed.

2) A multi-year sterile grass carp stocking program.

Monitoring efforts and aquatic vegetation surveys will provide the data needed to drive decisions.

• Nov. 2018 - 1,400 sterile grass carp will be released.

• Additional sterile grass carp will be released Spring 2019. The specific number will be based on the data collected from the recent survey.

What Methods Will Be Used to Remove Hydrilla From Harris Lake?

Questions?

Aquatic Weed Control Program

Contact:

Rob Emens

919-707-9012

rob.emens@ncdenr.gov

https://deq.nc.gov

Summary

• Hydrilla continues to spread in N.C. It is being introduced to more counties and to different habitats.

• Managing Hydrilla in rivers and natural lakes is more difficult and more costly compared to reservoirs.

• Leaving source populations in place only fosters continual spread and re-infestations.