Current Status of a Literature Review

on Monoecious Hydrilla for the NE

Aquatic Nuisance Species Council

Rob Richardson and Sarah True

Crop Science Dept., NCSU

Objective

• Review all scientific papers related to

monoecious hydrilla

• Work period: Aug. – Dec. 2012

• Deliver completed documents on Dec.

31, 2012

Review Document

• Currently 16 pages

• 66 references cited

• Review document is standard text summary of literature on

monecious hydrilla

• Approximately 500 articles evaluated, ~125 mentioned

monoecious, ~70 relevant

• Left to do:

– Add additional detail

– Add tables and figures

– Add some “softer” references, i.e. not mainstream peer-reviewed

journals

– Add some references on dioecious hydrilla that have relevance to

monoecious hydrilla in the monoecious hydrilla range of US

Citations Document

Allows Key Word Search,

Clickable Links

Authors, Title, Literature citation,

and abstract (if available)

Internet location (if available)

St. John Fisher College

• Michele Price, Science Librarian,

collaborated

• Provided educational opportunity for

Plant Biology Lab Students

• They sent outline of 47 articles in

November

• All relevant articles now included

Hydrilla

• Called the “perfect aquatic weed” (Langeland

1996)

• #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

Hydrilla

specimen

Dec. 9 1980

NCSU

herbarium

Monoecious

Biotypes - Summary

• Monoecious

– Linked to Korea

– Introduced mid 70’s

– Invading NC & north

– Less robust

– Herbaceous perennial

– May produce seed

– Tubers:

• Formed June – Nov.

• Weight 76 to 139 mg

• 430 – 1,700 / m2

Dioecious

Linked to China, India

Introduced 1950’s

Invading SC & south

More robust

Root crown persists

No seed production

Tubers:

Formed Oct. – April

Weight 188 to 290 mg

60 – 900 / m2

Hydrilla Biotype Phenology

Modified from Harlan et al. (1985. J. Aquat. Plant Manage. 23:68-71).

What is a Biotype?

• Biotypes are

distinct

reproducing

populations of the

same species that

exhibit different

reproducible

characteristics

Madeira et al. 2007. Aquatic Botany 87:176-180.

Madeira et al. 2007. Aquatic Botany 87:176-180.

Seoul Kashmir

Guangzhou

Bangalore

Other clusters

U.S. monoecious

U.S. dioecious

Benoit UConn Dissertation

• Examined 93 accessions of Hydrilla

• Reported 3 cryptic lineages that should be

considered separate species:

– Indian/Nepal/US dioecious

– Japan/Korean/European

– Indonesian/Malaysian

• US monoecious likely hybrid of Indian and

Indonesian lineages

Benoit UConn Dissertation

Hydrilla Northern Distribution

Les, D.H., L.J. Mehrhoff, M.A. Cleland, and J.D. Gable. 1997. J. Aquat.

Plant Manage. 35:10-14

Northern Latitudes for Hydrilla

Balciunas, J.K. and P.P. Chen. 1993. J. Aquat. Plant Manage. 31:105-109.

Hydrilla Distribution

Rybicki. 2013. J. Aquat. Plant Manage. In Review.

Temperature Comparison

Balciunas, J.K. and P.P. Chen. 1993. J. Aquat. Plant Manage. 31:105-109.

Tuber Weight • The longevity of a

tuber is hypothesized to be linked to its weight

• Differences found in weights between dioecious and monoecious

• Every published study on monoecious tuber weights was conducted in a mesocosm

Biotype Tuber weight (mg) Situation Citation Dioecious 63-91 Mesocosm Sutton et al. (1992)

160-386 Mesocosm Spencer et al. (1987) 42-44 Mesocosm Van (1989)

188-290 Field, lake Miller et al. (1976)

Monoecious 42-53 Mesocosm Sutton et al. (1992) 117-202 Mesocosm Spencer et al. (1987)

33-34 Mesocosm Van (1989) 30-320 Field, lake NCSU

*Avg max=186.6mg *Avg min=70mg

Tuber Weight

Tuber Density

• Very little field

research performed on

monoecious

• Large discrepancy

between mesocosm

and field densities

• Tracking densities can

aid in management

decisions

Tuber Density Results

Biotype Tuber density Situation Citation

Dioecious 2,153 Mesocosm, 12 mo. Steward and Van (1987)

2,293 Mesocosm, 7 mo. Steward (1980)

257 Field, ponds Haller and Sutton (1975)

293-605 Field, lake Miller et al. (1976)

62-900 Field, ponds Steward (1980)

Monoecious 2,099-9,053 Mesocosm, 16-28 mo Steward and Van (1987)

910-2,985 Mesocosm, 2 mo Poovey and Kay (1998)

189-1,312 Field, 3 lakes Harlan et al. (1985)

101-1,705* Field, 2 lakes Nawrocki (2011)

* 3077 T/m2 10/28/2008

Hydrilla Spread

Madsen and Owens 2000

This is an 80% rate of increase per year in monoecious hydrilla

How many

shoots?

Monoecious:

Various

planting

depths

pH Trial

• pH

– Conducted in SEPEL on the campus of NCSU

– Full sunlight and constant tempurature of

25⁰C

– Clear glass jars filled with 300 ml of solution

and 10 tubers

– 7 treatments , replicated 5 times

– Allowed to sprout for 2 weeks

– Data collected 1 WAT and 2 WAT

• Number germinated in each jar

6.5

6.0 5.5

8.0

7.5

7.0

8.5

Hydrilla Growth: Light vs Dark

Tuber Growth and

Development in Darkness Results Cont.

Absence of light and

constant light after 2 wk

Absence of light and

constant light after 56

days

Short Term Salinity Exposure

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

2 4 6 8 10

Mean

Sp

rou

ted

Tu

bers

Ou

t o

f 10

Weeks

12 ppt

2 Week Exposure

4 Week Exposure

6 Week Exposure

8 Week Exposure

0

2

4

6

8

10

12

2 4 6 8 10

Mean

Sp

rou

ted

Tu

bers

Ou

t o

f 10

Weeks

18 ppt

2 Week Exposure

4 Week Exposure

6 Week Exposure

8 Week Exposure

• Carter et al. 1987 found salinities

of 5-9 ppt resulted in 4-20% of

tubers sprouting and >9 ppt none

sprouted in monoecious hydrilla

• Steward and Van 1987 found

growth was severely suppressed

growth above 13 ppt for both

dioecious and monoecious

hydrilla

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

Avian Vacuolar Myelinopathy

Stigonematales sp. culture

100X Light

Stigonematales sp. culture 100X

Epifluorescence, Rhodamine filter --Prime Suspect-- 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.

Natural

Site Hydrilla

Stigonematales

on hydrilla

Invasion

Toxin

Production

Diseased

primary feeders

(coots)

Diseased

secondary

feeders (eagles)

Bioaccumulation

Timeframe for Management

Water Drawdown

• Will sediment get dry enough to kill tubers?

– No: 1987-88, Lake Gaston, NC/VA; 4 mos.

– No: 1996-2001, Lake Raleigh, NC; 5 years

– No: 2007, Tar River Reservoir, NC; 6 mos.

– No: 1993-94, Lake Ray Roberts, TX; 12 mos.

• Doyle and Smart (2001) Weed Sci. 49:135-140.

• Winter drawdown unlikely to effect monoecious, unless sediment freezes; does not disrupt life cycle

• Summer drawdown would disrupt life cycle

– Target around July 4 in North Carolina

– Not a politically achievable management solution

Let’s Clip the Sprouts and…

Watch Them Sprout…

Shoot

Removed From

Tuber

Biological - Insects

• No success to date in establishing insects

for control of monoecious hydrilla

• Reasons:

– No hydrilla biomass January – April

– Hydrilla only topped out July – Dec.

– Colder climate limits overwintering and reproduction

• Insects that require hydrilla biomass to

overwinter should not be expected to control

monoecious

Biotype Phenology

Modified from Harlan et al. (1985. J. Aquat. Plant Manage. 23:68-71).

Triploid Grass

Carp • Some NC lakes stocked with grass carp have had

non-detectable hydrilla for several years

• On Lake Gaston (Stitch and Murphy, VA Tech):

– 16 year old fish still present

– Mortality rate only 20% per year

– Little movement after stocking

– Fish congregate in areas, not uniform distribution

• Cannot be used in all lakes due to feeding on native vegetation and resulting environmental impacts

• More research on grass carp behavior/feeding

Filizadeh et al. http://iirc.narod.ru/4conference/Fullpaper/50031.pdf

Table 1. A few common Florida aquatic plants eaten by grass carp

in the approximate order of preference. Order of

preference Common name Scientific name

1 Hydrilla Hydrilla verticillata [L.f] Royle

2 Musk-grass Chara spp.

3 Southern naiad Najas guadalupensis (Spreng,) Magnus

4 Brazilian elodea Egeria densa Planch.

5 Water-meal Wolffia spp.

6 Duckweeds Lemna spp. and Spirodela spp.

7 Azolla or water-fern Azolla caroliniana WilId.

8 Pondweeds Potamogetan spp.

9 Coontail Ceratophyllum demersum L.

10 Torpedograss Panicum repens L.

11 Cat-tail Typha spp.

12 Water-aloe Stratiotes aloides L.

13 Watercress Nasturtium officinale R. Br.

14 Eurasian watermilfoil Myriophyllum spicatum L.

15 Tapegrass or eel-grass Vallisneria americana Michx.

16 Parrott-feather Myriophyllum aquaticum (Vell.) Verdc.

17 Water hyacinth Eichhornia crassipes (Mart.) Solms

18 Water-lettuce Pistia stratiotes L.

19 Water-lillies Nymphaea spp.

20 Spatterdock Nuphar luteum (L.) Sibth. & Sm.

Sutton and VanDiver http://edis.ifas.ufl.edu/fa043

Effect of grass carp on plant coverage in four hydrilla infested

and four Southern naiad infested lakes in Florida. (Derived from

Hanlon et al. 2000)

Stocking

rate Initial

vegetation Vegetation

decline Years

carp/veg A % coverage % points #

Hydrilla 10.5 ± 0.6 26.5 ± 6.6 3.5 ± 13.2 6.0 ± 0.4

Southen

naiad 9.5 ± 0.7 76.5 ± 20.6 42.5 ± 26.8 3.5 ± 0.3

Herbicides

• Coppers: Frequent use in NC/VA

• Diquat: Similar responses from dioecious &

monoecious (Steward and Van 1987)

• Endothall: Similar responses from dioecious &

monoecious (Steward and Van 1987)

• Fluridone: Frequent use in NC/VA

• Imazamox: Use pattern in development

• Penoxsulam: Use pattern in development

Treatment Comparison

One Year Off = 0.7-2 Lost Years

• Lyons Creek was treated 3 consecutive yrs.

– After 3rd yr density was 7% of the original

– 1 yr of non-treatment density rebounded to roughly 70% of the original

• Two cycles of alternate yr treatments faired slightly better at roughly 60% of the original

Monoecious Tuber Declines

Year 1

77% decline

Year 2

55% decline Year 3

48% decline

Tuber numbers

Michel et al. (2004)

Questions?

Sunrise over a 4,100A Cooling Pond for a 900MW Nuclear Reactor