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Curly Leaf
Pondweed (Potamogeton crispus
L.) Family: Potamogetonaceae (November 2004) Description and Variation: Curly-leaf
pondweeds grows entirely underwater except for the flower stalk which
rises above the water. Curly leaf pondweed has distinctly wavy-edged,
crispy olive-green to reddish-brown leaves. It usually grows early in
spring and dies back in summer. Similar plants include Flat-stem pondweed.
The leaves of flat-stem pondweed are long and narrow with smooth edges and
the sharp-edged stem is flat and about the same width as the leaves. Leaf: Alternate,
all submersed, no leaf stalks. Curly leaf: oblong, stiff,
translucent leaves (4-10 cm long, 5-10 mm wide) have distinctly wavy edges
with fine teeth and 3 main veins. Sheaths (stipules) up to 1 cm long are
free of the leaf base and disintegrate with age. Flat-stem:
smooth-edged leaves (5-20 cm long, 2-5 mm wide) have many veins. Sheaths
(stipules) 2-6 cm long are free of the leaf base and become fibrous with
age. Stem:
Curly leaf: branched, up to 90 cm long, somewhat flattened. Flat-stem:
generally few branched, up to 2 m long, 0.7-4 mm wide, flattened, with
sharp edges. Flower:
Tiny, with 4 petal-like lobes. Curly leaf: in spikes 1-3 cm long on
stalks up to 7 cm long. Flat-stem: in spikes up to 3 cm long on
stalks up to 10 cm long. Fruit: Seed-like
achene. Curly leaf: 4-6 m Economic Importance: Detrimental: Curly leaf pondweed (Potamogeton
crispus) is an invasive plant that forms surface mats that interfere
with aquatic recreation. Dense colonies of curly pondweed
can restrict access to docks and sport fishing areas during spring and
early summer months. Curly-leaf pondweed has been noted as
one of the most severe nuisance aquatic plants in the Midwest only out
ranked Eurasian Watermillfoil. Because populations of curly pondweed
usually decline during the summer months, it does not directly compete
with many of the native submersed species. Cost for control and can range
in the Millions per lake. Beneficial: none
known Habitat:
Curly leaf: shallow to deep still or flowing water, tolerant of
disturbance. Flat-stem: ponds, lakes, 1-2.5 m deep. Curly
leaf: nearly worldwide. Flat-stem: widespread in temperate
North America; found throughout Washington.
Geographic Distribution:
Native
to Eurasia, Africa, and Australia, this species has been found in most of
the United States since 1950 Washington
Distribution: Found in History:
Curly
pondweed, Potamogeton crispus L., is native to Eurasia and
apparently was introduced into the United States in the mid 1800’s
(Stuckey 1979). Prior to 1900, the distribution of P. crispus was the
northeastern United States. By 1930 curly pondweed had spread westward to
several states of the Great Lakes region. The species has since spread
across much of the United States, presumably by migratingwaterfowl,
intentional planting for waterfowl and wildlife habitat, and possibly even
as acontaminant in water used to transport fishes and fish eggs to
hatcheries (Stuckey 1979). Growth
and Development:
Curly
pondweed perennial,
rooted, submersed aquatic vascular plant
that produces seed, but the importance of
seed in the spread and maintenance of populations is unknown (Stuckey
1979) and is assumed to be less important than turions (Sastroutomo 1981).
In most portions of its range, Potamogeton crispus typically
reaches peak biomass in the late spring or early summer months, forms
turions, then declines and "survives" the warmer months in a
dormant state (i.e., as a turion) (Cypert 1967, Stuckey 1979, Sastroutomo
1981, Tobiessen and Snow 1984, Nichols and Shaw 1986). As water
temperatures cool during the late summer or fall months, the turions
germinate, grow through the winter months with the plants reaching peak
biomass in the spring before most other submersed macrophytes begin their
growth cycle. Once established, the plants regrow and form colonies from
rhizomes. Curly
leaf pondweed has a unique life cycle which gives it competitive
advantages over many native aquatic plants. Unlike most native plants,
curly leaf pondweed may be in a photosynthetically active state even under
thick ice and snow cover (Wehrmeister and Stuckey, 1978). Therefore, it is
often the first plant to appear after ice out. By late spring it can form
dense mats which may interfere with recreation and limit the growth of
native aquatic plants (Catling and Dobson, 1985). Curly leaf plants
usually die back in early summer in response to increasing water
temperatures, but they first form vegetative propagules called turions
(hardened stem tips). New plants sprout from turions in the fall (Catling
and Dobson, 1985). Control: Chemical - active ingredients that have
been successful in treating curly-leaf pondweed include diquat (G), copper with diquat (G),
endothall (E), and fluridone (E).
E = excellent, G = good Reward is a liquid diquat formulation
that has been effective on curly-leaf pondweed and is more effective if
mixed with a copper compound. It
is a contact herbicide. Contact
herbicides act quickly and kill all plants cells that they contact. Cutrine Plus, K-Tea,
Captain, Algae Pro, Clearigate are
all chelated or compound copper herbicides and can be used in a mixture
with Reward or Aquathol K. Other
chelated or compound copper formulations are available but are not linked
to this web site.
Aquathol, Aquathol K, and Aquathol
Super K are dipotassium salts of endothall and comes in both liquid
and granular formulations. These
endothall products have been effective on curly-leaf pondweed and can be
mixed with copper compounds for additional effectiveness.
Contact herbicides act quickly and kill all plants cells that they
contact. This herbicide has been found to be an effective and ideal
method. If applied in early spring, Aquathol K will not harm the native
plants since curly‑leaf is the first plant to grow in the spring. It
dissipates quickly leaving no residue and does not bio‑accumulate in
fish or hydro‑soil. This treatment should kill curly‑leaf,
reduce or eliminate seed and turion production in the treated areas, and
have less negative impact on native plants than treatments done later in
summer. Hydrothol 191 is an
alkylamine salt of endothall and comes in both liquid and granular
formulations. It is a contact
herbicide and has been effective on curly-leaf pondweed.
Contact herbicides act quickly and kill all plants cells that they
contact. Hydrothol can be
toxic to fish.
Sonar and Avast are
fluridone compounds, come in both liquid and granular formulations, and
have been effective on curly-leaf pondweed.
These are broad spectrum, systemic herbicides. Systemic herbicides are absorbed and move within the plant to
the site of action. Systemic
herbicides tend to act more slowly than contact herbicides.
One danger with any chemical control method is the chance of an oxygen
depletion after the treatment caused by the decomposition of the dead
plant material. Oxygen
depletions can kill fish in the pond.
If the pond is heavily infested with weeds it may be possible
(depending on the herbicide chosen) to treat the pond in sections and let
each section decompose for about two weeks before treating another
section. Aeration,
particularly at night, for several days after treatment may help control
the oxygen depletion.
One common problem in using aquatic herbicides is determining area and/or
volume of the pond or area to be treated The
mechanical and physical control methods have been used with minimal
success for the management of curly leaf pondweed. These methods include:
Benthic Barrier, Drawdown, Dredging/Sediment Removal, Hand Removal,
Harvesting Rotovation, Shading/Light Attenuation Aquashade
is a non-toxic dye or colorant. It
prevents or reduces aquatic plant growth by limiting sunlight penetration,
similar to fertilization. However,
Aquashade does not enhance the natural food chain and may suppress the
natural food chain of the pond. Biological - Grass carp will seldom
control aquatic vegetation the first year they are stocked.
They will consume curly-leaf pondweed.
Grass carp stocking rates to control curly-leaf pondweed are
usually in the range of 7 to 15 per surface acre. References:
Cypert,
E. 1967. The curly-leaved pondweed problem at Reelfoot Lake. Journal of
the Tennessee Academy of Science 42:10-11. Nichols,
S. A. and B. H. Shaw. 1986. Ecological life histories of the three aquatic
nuisance plants, Myriophyllum spicatum, Potamogeton crispus,
and Elodea canadensis. Hydrobiologia 131: 3-21. Sastroutomo,
S. S. 1981. Turion formation, dormancy and germination of curly pondweed, Potamogeton
crispus L. Aquatic Botany 10: 161-173. Stuckey,
R. L. 1979. Distributional history of Potamogeton crispus (curly
pondweed) in North America. Bartonia 46: 22-42. Tobiessen,
P. and P. D. Snow. 1984. Temperature and light effects on the growth of Potamogeton
crispus in Collins Lake, New York State. Canadian Journal of Botany
62: 2822-2826. Rationale
for Listing: Dense colonies of curly pondweed can
restrict access to docks and sport fishing areas during spring and early
summer months.
This page was last updated 03/31/07 |
