Invasive Aquatic Plant Dynamics in North Carolina

Invasive Aquatic Plant Dynamics
in North Carolina
Rob Richardson
Crop Science Dept.
How Do Aquatic Plants
Spread?
• Human activities (wildlife plantings, boating,
fishing enhancement, aquarium dumping,
water gardens, dredging, mechanical
harvesting)
• Animals (wading birds, aquatic mammals)
• Water movement
• Transport by wind and rain (seeds, spores)
Why Are Some Aquatic Plants
Invasive?
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Large areas of clear, shallow water
High levels of nutrients, especially N and P
No natural enemies (introduced weeds)
Characteristics which make them more
competitive than native plants
– Adapted to low light or CO2
– Adapted to intense sunlight and high temperatures
Why Control?
Hydrilla in Lake Gaston
Focus on Hydrilla
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Called the “perfect aquatic weed”
#1 aquatic weed in U.S.
Leaves in whorls of 3-10+
Serrated leaf margins
Tubers can remain in sediment for over 7
years
• Very shade tolerant
• Low CO2 compensation
Hydrilla
Hydrilla verticillata
Egeria densa
Hydrilla verticillata
Hydrilla
HYDRILLA
ONLY
Egeria densa
(Brazilian Elodea)
Hydrilla Spread
1991
Lake McIntosh
Eno River
Chowan River
2002
Lake Tillery
Biotypes
• Monoecious
– Native to tropics
– Introduced 1980’s
– Invading NC north
– Less robust
– Herbaceous perennial
– May produce seed
– Tubers:
• Formed June – Nov.
• Weight 36 to 77 mg
• 200 – 1,228 / m2

Dioecious
Native to temperates
 Introduced 1950’s
 Invading SC south
 More robust
 Root crown persists
 No seed production
 Tubers:

 Formed
Oct. – April
 Weight 160 to 376 mg
 20 – 600 / m2
Avian Vacuolar Myelinopathy
• Disease complex associated with dead of
coots, bald eagles, and other birds
• Coots die within 5 days of first symptoms
• Bioaccumulates in birds
• Believed to be connection between hydrilla,
cyanobacteria, and waterfowl
• Documented throughout southeastern US
• No long-term impact on grass carp
Stigonematales sp. culture
100X Light
--Prime Suspect--
Stigonematales sp. culture 100X
Epifluorescence, Rhodamine filter
Stigonematales species-Morphologically similar to 3 genera:
Hapalosiphon, Fisherella, or
Thalpophila
Williams, S.K., S.B. Wilde, J. Kempton, and Alan J. Lewitus. (in prep) A novel epiphytic
cyanobacterium associated with reservoirs affected by Avian Vacuolar Myelinopathy. To be submitted
to Phycologia.
Stigonematales
on hydrilla
Toxin
Production
Diseased
primary feeders
(coots)
Bioaccumulation
Diseased
secondary
feeders (eagles)
Invasion
Hydrilla
Natural
Site
Hydrilla Turions
• Form main challenge to management
• Turion – an overwintering bud structure
• Hydrilla forms both axillary turions or
subterranean turions (tubers)
• Tubers more commonly formed than turions
• Tuber longevity estimated to be 4+ years, but
turions only 1 year
• Long-term management plans must consider
and monitor the tuber bank
Tar River Tuber Counts
Tar River Reservoir
600
P<0.0001; r2=0.994
Col 1 vs Col 2
5% reference line
500
Tubers per m2
Year 1
400
80
77% decline
60
Year 2
Year 3
55% decline
300
48% decline
40
200
20
100
0
0
0
200
400
600
800
Time (days after first sample)
1000
Tubers remaining (% of first sample)
100
Tar River Tuber Counts
Hypothetical Tuber Decline
100
Tuber decline over time
Yearly points
Tubers remaining (%)
80
60
40
99.5%
decline
99.95%
decline
20
0
0
2
4
6
Time (years)
8
10
Gaston Sample Site-Treatments
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Lakeview
Hamlin
Cotton
Cold Springs
Hawtree
Poe
Hubquarter
Lyons
Smith
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No public treatments
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Alternate year treatments
2007 – fluridone
2008 – No Treatment
Consecutive year treatments
2007 & 2008 – fluridone
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Lake Gaston Tuber Dynamics
Site
Density Spring
‘08
tubers/m2
Density Fall ’08
Gaston control
308
438
Gaston biennial
139
268
Gaston annual
137
82
Tar River
164
78
1,275
1,700
Shearon Harris
tubers/m2
Giant Salvinia
• Free-floating fern
• Descending spore capsules do not
produce viable spores
• Pubescent leaves with egg-beater shaped
hairs
• May double in biomass in 2 days
• About 10 A infested near Wilmington
Giant Salvinia
Salvinia molesta
Molesta vs. Minima
Characteristic Egg-Beater
shaped hairs of Salvinia
molesta
Leaf hairs of Salvinia
minima branch but do not
rejoin as do molesta
US Distribution and Range Prediction
Salvinia On Ice, 1/27/03
NC Salvinia History
1998: found in Wake County (NC State Fair)
2000: confirmed in Brunswick, New
Hanover, Pender, and Onslow counties
2004: Sampson and Craven counties added
to infestation list
• Maximum salvinia infestation reached 10 sites
and 40 acres
• The Southeast North Carolina Giant Salvinia
Task Force was formed to develop and
implement an eradication program
North Carolina
Fall 2007 Distribution
= eradicated
= present
* Currently 1 site with <5 acres
NC Giant Salvinia Task Force
• Cooperative effort of:
• NC Cooperative Extension
• NCDA
• NC Dept. of Environment & Natural Resources
• NCSU
• SePRO Corporation
• USGS
• Funding obtained from National Fish and
Wildlife Foundation – Pulling Together
Initiative
Salvinia Treatment
• Three methods used:
• Herbicides
• Biocontrol: salvinia weevil (Cyrtobagous
salviniae )
• Limited hand removal
• Infested sites were considered eradicated if
no salvinia was found for at least one year
after last treatment
Salvinia Weevil
• Weevils collected in TX and shipped to NC by
NCDA
• Infested pond adjacent to the Riverbend site
was selected for release
• Pond was not treated with herbicides for two
years after release
• The salvinia weevil survived and overwintered,
but failed to reduce salvinia populations
• Weevils were more effective in controlling
salvinia in full sunlight than in shade
Current Site
Questions?
Visit Us On The Web At –
www.cropsci.ncsu.edu/aquaticweeds