A guide to

Invasim

imCa

■!i.

.^i^M^

Robert S. Capers, G„„„-^

The Connecticut Ai

RO. Box 1106
New Haven, Connecticut 06504

Bulletin No. 99'
January 2005

© 2005 The Connecticut Agricultural Experiment Station
Bulletin No. 997

Cover photo: Eurasian water-milfoil, Myriophyllum spicatum, by Alison Fox,
University of Florida

as

Introd: ction to aquatic plants *

Aquatic plants are essential components of healthy ecosystems in o a

freshwater lakes and ponds, producing oxygen, reducing erosion and regulating
nutrient cycling (Hutchinson, 1975). They provide food for many birds as well
as habitat that supports rich communities of aquatic invertebrates and
vertebrates (Sculthorpe, 1967).

Invasive plants, however, are not native species, and they are often
destructive (Vitousek et al., 1996). Non-native plants and animals are
responsible for economic losses and control costs estimated in one analysis at
$137 billion per year in the United States alone (Pimentel et al. 2000). Invasive
aquatic plants are noted for their explosive growth potential (Barrett, 1989) and
their ability to grow from a few plants to cover hundreds of acres in a few years
(Groth et al., 1996). Invasive aquatic plants have caused declines in native plant
populations throughout New England (Sheldon, 1994). In some water bodies,
invasive plants have become so abundant that they have displaced native
species (Langeland, 1996). Many biologists feel invasive species are second
only to habitat destruction as the most serious threat to endangered species
globally (Wilcove et al., 1998). ^

Because of their great growth potential, invasive aquatic plants can block
navigation channels, irrigation ditches and water intake pipes, and they can
reduce aesthetic and recreational value of water bodies, affecting tourism and .
real estate values (Catling and Dobson, 1985). In some cases, the plants have
been found to increase breeding habitat for mosquitoes (Eiswerth et al., 2000).
An estimated 76% of the invasive aquatic plants in southern New England were
introduced as cultivated plants and later escaped (Les and Mehrhoff, 1999). It is
thought that much of the subsequent spread of invasive plants from one lake to
another is from recreational boating (Couch and Nelson, 1985).

Attempts to eradicate invasive aquatic plants once they become established
often have failed (Anonymous, 1993; Groth et al., 1996; Simberloff, 1997), and
management is expensive (Langeland, 1997; Center et al., 1997). Early
identification of invasive plant populations, thus, is critically important
(Simberloff, 1997; Wittenberg & Cook, 2001).

The Connecticut Agricultural Experiment Station (CAES) has begun a
surveillance and monitoring program to establish the geographical distribution
of invasive aquatic plants in state lakes and ponds. The program will establish
where invasive plants occur and track their spread in the future. In many cases,
quantitative vegetation surveys have not previously been done, and the absence
of historic information makes it difficult to determine what changes resulted
from plant invasions and what resulted from management activities (Sheldon,
1994). The CAES surveillance program will provide baseline information so the
extent and nature of ecological change resulting from any future plant invasions
can be determined. The surveys build on aquatic plant and bathymetric work
done through the state Department of Environmental Protection's Geologic and
Natural History Surveys as well as many decades of collecting by professional
and amateur botanists in the state.

This guide contains information on the history, ecology and identification
of nine invasive aquatic plants. Distribution maps for each species, based on
herbarium records and surveys done by many biologists, are also shown.
However, all of the state's lakes have not been surveyed, so the maps likely
represent incompete distributions of the plants. The nine plants discussed here
are not all of the species that threaten Connecticut lakes and ponds, but they are
among those with the greatest potential to cause environmental and economic
damage. This guide is intended to help non-scientists identify the plants in the
interest of retarding their spread in the state and, where possible, preventing
their introduction.

EURASIAN WATER-MILFOIL

Myriophyllum spicatum

Eurasian water-milfoil is one of
the most serious threats among
invasive aquatic plants in the United
States (Bartodziej and Ludlow, 1998).
A native of Europe and Asia, the first
reliable collections of Eurasian water-milfoil

Figure 1 . Distribution of Myriophyllum
spicatum in Connecticut.

in the United States date from the 1940s, when it was reported from
Washington, D.C., Arizona, California and other states, apparently as the result
of independent escapes from cultivation (Les and Mehrhoff, 1999). The species
was first collected in Connecticut in 1979, and it has spread quickly since then,
occurring primarily in the alkaline waters of the western part of the state.
Herbarium records and surveys indicate that it occurs in more than 40 ponds
and lakes in Connecticut as well as in many areas on the Connecticut River
(Figure 1).

Eurasian water-milfoil is one of several milfoils that occur in Connecticut
ponds and lakes, including several native species, so identification can be
difficult. Leaves occur in whorls around the stem, usually four leaves together
(Aiken et al., 1979), as shown in Figures 2 and 3. Eurasian water- milfoil leaves

have a very fine, feathery
appearance. Each leaf is composed
^ of threadlike leaflets, and Eurasian
water-milfoil leaves usually have
more than 14 pairs of leaflets on
each leaf (Moody and Les, 2002).
Other milfoil species usually have
fewer than 14 pairs of leaflets.
Eurasian water-milfoil can be

Figure 2. Eurasian water-milfoil, Myriophyllum distinguished from variable-leaf

spicatum

'■■ r,

milfoil, another invasive species,
by the distance between the leaves
on the stem. On Eurasian water-
milfoil, leaves are more spread out
on the stem and are generally more
than an inch apart except at the
very top of the stem, whereas
variable-leaf milfoil has whorls of
leaves less than an inch apart all up and down the stem (Hellquist and Straub,
2002).

Plants begin to grow early in the year, producing long stems that can reach
the surface in 12 feet of water or more (Reed, 1997). When it reaches the surface
(Figure 4), the stems spread out and can form a thick mat of vegetation (Aiken et
al., 1979). The species can produce very thick stands of large plants (Reed,
1977), interfering with boating, swimming and other recreational activities (Reed,

Photo by Vic Ramey University of Borida

Figure 3. Eurasian water-milfoil,
Myriophyllum spicatum

Figure 4. Eurasian water-milfoil, Myriophyllum spicatum

1977; Bates et al., 1985), displacing native plants (Madsen et al., 1991), altering
the abundance offish populations (Keast, 1984) and depressing real estate
values (Bates et al., 1985).

Stems of Eurasian water-milfoil break easily, producing fragments that then
can grow into new plants. In fact, the plants reproduce primarily in this way,
although they also produce seed and spread over short distances with horizontal
stems in the sediment (Madsen et al., 1988; Madsen et al., 1991). Propellers on
boat motors are effective at producing fragments that then act as propagules,
dispersing the plant to new locations (Liddle and Scorgie, 1980).

Once established, Eurasian water-milfoil spreads aggressively, and
managing it is difficult and expensive (Pimentel et al., 2000; Eiswerth et. al.
2000). As a result, preventing the species from arriving is important. Once it is
introduced into a region, the species can spread by boaters who carry fragments
of plants on their propellers or trailers (Johnstone et al., 1985; Howard-
Williams, 1993), although the species likely spreads in other ways as well (Les
and Mehrhoff, 1999). Any fragment can act as a propagule that could establish a
new population of the species in a lake where it does not already occur.

VARIABLE-LEAF WATER-MILFOIL

Myriophyllum heterophyllum

This species is native to the
southern United States and has become
a nuisance in many Connecticut lakes
since arriving in 1936, especially in the

southeast part of the state (Les and ^^^-^ ^''^""'^ ^- Distribution of Myriophyllum

heterophyllum in Connecticut.

Mehrhoff, 1999). It is known to occur in at least 30 ponds and lakes in
Connecticut (Figure 5) and appears to prefer water with lower pH and alkalinity
than Eurasian water-milfoil.

Variable-leaf milfoil produces long stems that rise to the surface of the
water, where they spread out, producing mats of vegetation (Figure 6) that can

Figure 6. Variable-leave water-milfoil. Myriophylliiin heterophyllum

interfere with boating and other activities. Stems of the plant are thickly covered
by fine, feathery leaves that are close together (Hellquist and Straub 2002) and
collapse onto the stems when they are removed from the water. The stems have
a coarse, ropy appearance in the water.
Leaves are arranged in whorls on the thick often-
red stems (Godfrey and Wooten, 1981), usually
4 to 6 leaves in each whorl. Like other milfoils,
each leaf has paired, thread-like elements
arranged along a central axis. On variable-leaf
milfoil, there usually are 10 or fewer pairs of
these threadlike pinnae on each leaf (Figure 7),
which distinguishes them from Eurasian water-
milfoil, which has 14 or more pairs of pinnae on
each leaf (Aiken et al., 1979). Variable-leaf

milfoil plants produce flowering spikes that can be several inches long and
emerge above the surface of the water. Identification of the species can be
difficult because it closely resembles a hybrid of M. heterophyllum and a
Southern milfoil species, and the two can be reliably distinguished from each
other only with molecular analysis (Moody and Les, 2002).

Variable-leaf milfoil can reproduce by fragmentation, by spreading along
horizontal shoots in the sediment and possibly by seed (Les and Mehrhoff,

tjl'(' habiixi/2

Figure 7. Variable-leaf water-milfoil,
Myriophyllum heterophyllum.

1999). Control of the species can be difficult, and CAES scientists are
continuing research on the effectiveness of spot herbicide treatments at Bashan
Lake (Bugbeeetal. ^003).

PARROT-FEATHER

Myriophyllum aquaticum

Parrot-feather is an ornamental
milfoil species that is native to the
Amazon (Sytsma and Anderson,
1993). It is commonly sold for use
in aquariums and water gardens
(Aiken, 1981; Les and Mehrhoff,
1999) because of its distinctive, blue-green leaves, which, unlike other milfoil
species, rise above the surface of the water (Crow and Hellquist 2000a), making
this species relatively easy to recognize (Figure 8, 9). The emergent leaves, which
occur in whorls of 4-6 leaves, are twice as long as they are wide (Aiken, 1981).

Figure 8. Parrot-feather, Myriophyllum aquaticum.

.^^Jj.

Figure 9. Parrot-feather, Myriophyllum aquaticum.

Parrot-feather has been collected in
few Connecticut locations (Figure 10), but
the species overwinters in the Northeast
(Hellquist and Straub, 2002) and may
represent a serious threat to the state's
water bodies (Les and Mehrhoff , 1999). It
reproduces in the United States only by
fragmentation (Aiken, 1981) and can be
dispersed on boat trailers (Les and
Mehrhoff, 1999).

EGERIA, BRAZILIAN ELODEA

Egeria densa

Egeria densa is originally from South
America and until recently was sold as
"Brazilian elodea" or "South American
waterweed" in aquarium supply stores. Egeria is
related to Elodea species native to Connecticut,
and it looks much like them (Figures 11, 12) but
has leaves in whorls of four around the stem,
whereas leaves occur in whorls of three on
Elodea plants. Leaves on Egeria also are longer
and wider than those on Elodea, generally 1-3
cm long and up to 5 mm wide (Crow and
Hellquist, 2000b).

The species was introduced in the United
States in 1893, and the first Connecticut
specimen dates from 1992 (Les and Mehrhoff,
1999). The plant is popular with aquarium
hobbyists and water gardeners, and it has spread
through the United States as a result of

Figure 10. Distribution of Myriophyllum
aquaticum in Connecticut.

(Photo courtesy of Washington Department of

Ecology)

Figure 11. Egeria densa on the right,
shown with the much smaller native
species, Elodea canadensis, on the left.

(Li\'cAquaria.com photo)

Figure 12. Egeria densa.

introductions and escapes from cultivation (Crow and Hellquist, 2000b).

Like many aquatic plants,
Egeria spreads via fragments . Any
piece of a stem with leaves on it
can establish a new plant or
population in a new lake. Once
established, the species can
produce thick mats of plants,
growing from the bottom to the pig^^e 13. Distribution of Egeria densa in Connecticut.

surface in shallow water, then spreading out, shading out native plants (Hofstra
et al., 1999). Egeria densa has been reported in at least five ponds in
Connecticut, although it may have been eradicated in two of them (Figure 13).
It remains a threat because of its popularity, its aggressive growth, its ability to
tolerate northern winters, and the difficulty with which it is controlled (Les and
Mehrhoff, 1999). It often is misidentified as Elodea and commonly is shipped
as an unordered contaminant with other aquarium plants (Maki and
Galatowitsch, 2004).

HYDRILLA

Hydrilla verticillata

A native of Asia, Hydrilla (Figure 14)
was first recorded in the United States in
1960, when it appeared in Florida (Les
and Mehrhoff, 1999). Populations had
spread through the southeast states by
1967, primarily by escaping from
cultivation (Les and Mehrhoff, 1999), and
the species became established in
California after plants were shipped there

Photo copyright by Vic Ramc} University of Florida

in a shipment of water lilies Figure 14. Hydrilla verticillata

(Maki and Galatowitsch 2004). The

ability of the plant to survive Northern

winters had been questioned, but its

range in Asia extends to within 9

degrees of the Arctic circle (Les et al.,

1997), and it has survived in

Connecticut at least since 1989. The

Figure 15. Distribution of Hydrilla verticillata

first verifiable specimen of Hydrilla in in Connecticut.

Connecticut was collected in 1989 but not identified until several years later (Les
et al., 1997), and the species was found in a second town in 1997 (Figure 15).
Among all the invasive aquatic plants, Hydrilla may represent the most
serious threat to Connecticut ponds and
lakes (Les and Mehrhoff, 1999). The species
is extremely aggressive and can outcompete

native species and even other invasive ^-' '

species (Hofstra et al., 1999). It is also
difficult to control (Center et al., 1997).
Hydrilla grows very quickly in shallow and
deep water (Godfrey and Wooten, 1979) and

Figure 16. A whorl of five leaves on
occurs in lakes, ponds, streams and marshes, the stem of a Hydrilla plant.

A few plants can grow to cover hundreds of acres in a few years, crowding out

other plants (De Kozlowski, 1991). The plant reproduces by fragmentation and

produces tubers that overwinter in the sediment (Les et al., 1997). Plants can

disperse between lakes either as tubers or as fragments (Les and Mehrhoff,

1999).

Hydrilla is in the same plant family as Egeria and native Elodea, and these

species can be hard to differentiate. Hydrilla leaves generally occur in whorls of

five (Figure 16; whorls of 4 - 8 leaves can be found, Crow and Hellquist 2000b),

whereas leaves on Egeria occur in whorls of four leaves, and those on Elodea

are in whorls of three (Figure 17). In addition, Hydrilla leaves are about 1.5 cm

long, whereas leaves on Egeria are
usually about 2.5 cm long and those on
Elodea average aboift 1.0 cm in length.
The edges of Hydrilla leaves also have
clearly visible teeth; on Elodea and
Egeria leaves, teeth either are lacking or
are so small that they can be seen only
under magnification. The tubers that
Hydrilla plants produce on stems in the
sediment are small (14-18 mm long) and
whitish, and these are found on neither
Elodea nor Egeria plants.

CURLYLEAFPONDWEED

Potamogeton crispus

Curly-leaf pondweed is one of the
most common invasive plants in
Connecticut. A native of Asia, Europe
and Africa, the species arrived in the
United States before 1860 and had
spread across the continent by the early
20th century (Stuckey, 1979), reaching
Connecticut by 1932 (Les and
Mehrhoff, 1999).

Hydrilla

Elodea

Egeria

(Image copyright Center for Aquatic and Invasive Plants,
University of Florida, IFAS)

Figure 17. Hydrilla is related to native Elo-
dea species and to the invasive Egeria densa,
and the species in these three genera can be
hard to tell apart. Hydrilla leaves usually
occur in whorls of five, whereas Elodea
leaves are in whorls of three and those on
Egeria in whorls of four.

Figure 18. Distribution of Potamogeton
crispus in Connecticut.

The species occurs in more than 40 Connecticut ponds and lakes as well as
in the Connecticut and Housatonic rivers (Figure 18). Although its original
introduction and early spread through the United States was likely related to
distribution of fisheries stocks, it also has been spread by deliberate plantings
(Les and Mehrhoff, 1999) and may have been distributed by birds (Tehon, 1929).
Curly leaf pondweed is sometimes transported on boat trailers (Johnstone et al..

(Photo by Vic Ramey, Copyright 2001 University of Florida)

Figure 19. Curly leaf pondweed, Potamogeton
chspus.

1985), is sold through aquarium and
horticultural suppliers and sometimes
is shipped as a contaminant in orders
of other aquatic plants (Maki and
Galatowitsch, 2004).

Curly-leaf pondweed is broadly
tolerant of ecological conditions,
occurring in oligotrophic and
eutrophic waters of ponds, lakes,
marshes, ditches, canals, streams
and rivers (Stuckey, 1979). It appears
to have an affinity for water with high
alkalinity. It can occur in water more
than 5m deep and forms dense stands, inhibiting growth of native plants and
interfering with recreational activities (Nichols and Shaw, 1986).

Curly leaf pondweed is unusual in that it dies back by mid-summer (Nichols
and Shaw, 1986). The species reproduces mostly by vegetative turions, which
are hard, highly compact shoot tips, and this makes managing the species
difficult. Production of turions is triggered by warming water in the early spring
(Hartley and Spence, 1986). The turions, which are about 2.5 cm long, remain
dormant until the water begins to cool in the fall, when they sprout, producing
plants that grow slowly through the winter and flower in the spring, although
studies have shown that few seeds germinate (Nichols and Shaw, 1986).

Potamogeton crispus is easy to recognize. It has flattened stems and
distinctive leaves with wavy edges (Figure 19). Leaves are 3-8 cm long and about
50 mm wide, with rounded ends and tiny teeth (Catling and Dobson, 1985)

FANWORT

Cabomba caroliniana

Fanwort is native to the southeast
United States and South America and has
occurred in Connecticut since 1937 (Les and
Mehrhoff, 1999), becoming a serious
problem in a number of lakes since then.
Until recently, the plant was sold in
aquarium stores because of its attractive,
bright green, fan-shaped leaves.

Submerged leaves of fanwort are
opposite and have petioles (short "stems")
and have finely divided blades about 3 cm (Photo by Amy smaguia)

, , _ . . .—. _^. Figure 20. Fanwort, Cabomba caroliniana.

long and up to 5 cm wide (Figure 20).

Plants also produce floating leaves on flower shoots, but they are small and
inconspicuous (Godfrey and Wooten, 1981). White or pinkish flowers, about 1.5
cm across, are raised above the surface of the water.

Like many other invasive plant species, fanwort can form dense stands that
shade out native plants and interfere with recreation (Riemer and Ilnicki, 1986).
It is believed to reproduce primarily by vegetative fragments (Riemer and Ilnicki,
1986). Fanwort is a popular species in water gardening and for aquariums and
has escaped from cultivation many times (Les and Mehrhoff, 1999). Fanwort
plants are readily cut by boat motors, and
production of these vegetative fragments
is known to have accelerated its dispersal
within lakes, while plants carried on boat
trailers have likely resulted in the species'
dispersal to new lakes (Les and

Mehrhoff, 1999). CflZ?om/?<3 has been "" Figure 21. Distribution of Cabomba

caroliniana in Connecticut.

collected from wetlands

along the Connecticut River and from more than 30 lakes and ponds, primarily in
the southern and eastern parts of the state (Les and Mehrhoff, 1999), but it
probably is much more widespread (Figure 21). Lake Quonnipaug in Guilford has
been the site of recent C AES research on control of Cabomba for several years,
primarily using various herbicide treatments (Bugbee et al. 2005).

WATER CHESTNUT

Trapa natans

Like many other invasive aquatic
plants, water chestnut has escaped
from cultivation (Les and Mehrhoff,
1999). A native of Asia, the species
has been widely distributed for

Figure 22. Distribution of Trapa natans in

horticultural use in the United States Connecticut.

since the 19th century (Les and Mehrhoff, 1999). Individual rosettes can be
moved by water currents and wind, and the species is thought to have been
introduced to some lakes on boat trailers (Les and Mehrhoff, 1999). The species
arrived in Connecticut in 1999 (Nancy Murray, personal communication) and
represents a serious threat to the state's lakes, ponds and rivers (Les and
Mehrhoff, 1999). Trapa produces floating rosettes of leaves and spreads
clonally, producing secondary and tertiary rosettes during the growing season
(Grothetal, 1996).

Like other invasive aquatic plants, the growth of Trapa often is described
as explosive (Groth et al., 1996). Plants spread quickly and can cover the
surface of a lake within a few years. Biomass can increase tenfold from one year
to the next. Plants form dense mats on the surface of the water, shading out
submerged plants (Figure 23).

Trapa is an annual plant and each year produces large quantities of large
seeds with sharp spines that can injure swimmers (Les and Mehrhoff, 1999). A
single seed can produce more than 10 plants, each of which then can produce as

(Photo copyright 2002 by Ann Bo\e, mset photo b> Vic Ramey, University of Florida)

Figure -23. Water chestnut, Trapa natans. Inset: Fruits of water chestnut are hard and spiny

many as 20 seeds of its own. Seeds can remain viable in the sediment for as long
as 12 years. Unlike other annual species, however, Trapa is able to outcompete

perennial aquatic plants (Groth et
al., 1996). Control in Connecticut
has been through hand removal.

Water chestnut is easy to
recognize. The leaves on floating
rosettes are roughly triangular and
have teeth on their front edges

(Photo by Leslie J. Mehrhoff, University of Connecticut)

Figure 24. Water chestnut, Trapa natans (Figure 24). Plants produce small

inconspicuous white flowers. Fruits are hard and have sharp spines (Figure 23, .
inset).

NAJ AS MINOR

A native of Europe, Najas minor was
introduced to the United States in 1934 and
spread quickly, reaching the Midwest and
Florida within 30 years (Merilainen, 1968).
The species arrived in Connecticut during
the 1980s, and it is spreading quickly (Les

Figure 25. Distribution of Najas
minor in Connecticut.

and Mehrhoff, 1999). It has been collected from more than 20 Connecticut ponds

and lakes (Figure 25) and was found in 3 1 % of 32 lakes surveyed by the CAES
in 2004. It is likely that the species occurs in many more lakes but has been
mistaken for one of the native Najas species.

Unlike some invasive species, this plant does not produce long stems that
grow to and spread on the surface of the water. However, it can grow very
densely on the bottom and can produce shoots up to 1 m long (Merilainen,
1968), shading out native plants and becoming dense enough to interfere with
recreational activities (Hellquist and Straub 2002).

Najas minor can be confused with native Najas species, including the
common Najas flexilis. Both have leaves that appear opposite each other on the
stem, and small teeth occur on the leaves of both species. However, the teeth on
A^. flexilis are much smaller than those on A^. minor. Generally, if the teeth on the
leaves of a plant can be seen without a magnifying glass, it is the invasive A^.
minor (Figure 26).

Najas minor is an annual species and reproduces through production of
abundant seeds (Merilainen, 1968). Although introduced to the United States by
escaping from cultivation, the species likely has been spread since then
primarily by waterfowl, which eat the abundant seeds of Najas species
(Merilainen, 1968; Les and Mehrhoff, 1999). Controlling the spread of this
species by boat trailers and boats will be particularly challenging, because the
seeds are inconspicuous and can be carried in bilges, trailer wheel wells and
other out-of-the-way places.

Connecticut Aquabc Ptant Survey Pro-am

Figure 26. Najas minor,
above, and the native
A^. flexilis. below.

Methods for controlling invasive aquatic plants

Preventing invasive aquatic plants from reaching Connecticut lakes and
ponds is the preferred method of control. People can move plants from one
body of water to another on boats and trailers. Through the Sea Grant program
and the boating safety office of the state Department of Environmental
Protection, signs have been posted at state boat ramps, detailing what the
aquatic invasive plants look like and explaining the importance of checking
boats and trailers to make sure they are not carrying pieces of the plants. Recent
legislation (Connecticut Public Act No. 03-136) imposes fines on individuals
found transporting invasive, non-native plants in this way. Plants liberated from
aquariums or water gardens are another way non-native aquatic plants are
introduced into freshwater ecosystems. Properly disposing of aquarium plants
and isolating water gardens will help reduce these risks. Public Act No. 04-203
restricts the sale of most invasive aquatic plants in Connecticut.

Unfortunately, the spread of invasive, non-native aquatic plants in
Connecticut is likely to continue because large numbers of lakes and ponds
already contain the plants, and natural movement by flowing water and aquatic
wildlife is largely uncontrollable. Eradication of new infestations is more likely
to be successful than elimination of large areas of established plants. Volunteer
monitoring programs can be initiated to routinely check water bodies for new
plants. The Connecticut Agricultural Experiment Station can offer assistance to
volunteers on how to survey and identify aquatic vegetation.

Many techniques are available for controlling unwanted aquatic vegetation.
Regardless of the method, knowing the potential harmful effects on non-target
organisms is important. Mechanical control includes hand-pulling, machine
harvesting, hydroraking, benthic barriers and dredging. Typically, these methods
are used in localized areas. Machine harvesting, hydroraking and dredging
require permits from local, state and federal agencies. Water drawdown,
particularly during the winter when freezing temperatures can damage plants, is
a low-cost weed-control option. The Connecticut Department of Environmental

Protection must be notified before any drawdown. Chemical aquatic weed
control involves applying an herbicide to decrease the population of a plant.
Invasive plants are rarely eliminated, but the recreational value of a lake or
pond can be improved, and the spread of the invasive plant can be slowed.
Selecting the proper herbicide and the time of application requires accurate
information on the life cycle of the nuisance plant. A permit from the state DEP
is required before an aquatic herbicide can be used. Experts at the experiment
station and the DEP can answer questions on the use of aquatic herbicides.
Biological control agents, including beneficial insects and microbes, may
someday be viable aquatic weed control alternatives. To date, the only
biological control used successfully in Connecticut is a plant-eating fish, the
grass carp {Ctenopharyngodon idella). This fish is not native and must be
certified as sterile (triploid) to assure it will not reproduce in the environment.
The DEP monitors the release of this fish, and a permit is required before they
can be purchased. Typically, grass carp are used in small ponds. Containment of
grass carp to the body of water where they are introduced is required, and
special screens are needed at inflows and outflows.

Because plants need nutrients to proliferate, reducing the nutrients reaching
a water body may inhibit the growth of invasive aquatic plants. Proper design
and maintenance of septic systems, establishment of unfertilized shoreline
buffer zones and minimizing the misapplication of fertilizer to paved areas can
reduce the amount of nutrients that reaches lakes and ponds.

Anyone with aquatic plant specimens to identify or with questions
about aquatic plants may call the Aquatic Plant Survey Program at (203)
974-8500 or, toll-free, 877-855-3327. Specimens may be sent to the
Connecticut Agricultural Experiment Station, Aquatic Plant Survey
Program, PO. Box 1 106, New Haven CT 06504.

Additional information on aquatic plants and the survey program is
available at our web site, www.caes.state.ct.us/aquaticplants

Information on aquatic plant ecology and management is available
from the Army Corps of Engineers Aquatic Plant Information System:
http://el.erdc.usace.army.mil/aqua/apis/

Information on management also is available at:
http://plants.ifas.ufl.edu/guide/and from the Connecticut Department of
Environmental Protection:
http://www.dep.state.ct.us/wst/pesticides/aweeds.pdf

Advice on how to protect a lake is available from the Vermont
Department of Environmental Conservation site:
http://www.anr.state.vt.us/dec/waterq/lakes/htm/lp_lakesonlyyou.htm

Information on monitoring of invasive aquatic plants is available from
the Massachusetts Department of Conservation and Recreation site:
http://www.mass.gov/dcr/waterSupply/lakepond/lakepond.htm

Other sources of information on invasive aquatic plants are:

Center for Aquatic and Invasive Plants http://plants.ifas.ufl.edu/

State of Washington Department of Ecology Non-Native Freshwater
Plants http://www.ecy.wa.gov/programs/wq/plants/weeds/exotic.html

The Invasive Plant Atlas of New England
http://invasives.eeb.uconn.edu/ipane/

The National Invasive Species Council http://ww.invasivespecies.gov

USGS Center for Aquatic Resource Studies
http://nas.er.usgs.gov/plants/index.html

Connecticut Federation of Lakes
http://ctlakes.org/ct_lakes_version_ 1_00 1 .htm

Acknowledgements: The Connecticut Aquatic Plant Survey Program is
supported by the U.S. Department of Agriculture under Specific
Cooperative Agreement 58-6629-2-205 and the USD A Hatch
CONH00768. Much information on the geographic distribution of
invasive plants was generously shared by Nancy Murray of the
Connecticut Department of Environmental Protection's Geologic and
Natural History Survey. Additional distributional information was
provided by Harry Yamalis of the DEP and the Invasive Plant Atlas of
New England, which we gratefully acknowledge. Nancy Murray and
Chuck Lee of the DEP's lakes program also made important comments
that improved presentation of the information in this guide. Additional
information was obtained from the agencies whose web pages are cited
on the previous page.

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