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Research Direction generate 
Branch de la recherche 

Technical Bulletin 1989-6F 

aguculture CANADA 

GOT 89/03/31 NO. 



Aquatic vegetation on the 
Canadian prairies: physiology, 
ecology, and management 

630 . 72 
C «<?- c 



Canada 1 

Digitized by the Internet Archive 
in 2013 

Aquatic vegetation on the 
Canadian prairies: physiology, 
ecology, and management 

Research Station 
Lethbridge, Alberta 

Technical Bulletin 1989-6E 

Lethbridge Research Station Contribution No. 14 

Research Branch 
Agriculture Canada 

t opies >>t (luv publication are available from 

Di | K Ulan 

soil Science Section 

Research Station 

Research Branch, Agriculture Canada 

P.O Box 5000, Main 

1 ethbridge, Mberta 

1 IJ 4B1 

Produced l>\ Research Program Service 

C Ministei ol Suppl) and Services Canada 1989 
Cat No \~>»-s I989-6E 
lsB\ 0-662-16807-0 

Cover illustration 

The dots on the map represent 
Agriculture Canada research 







Environment (abiotic or non-living component) 6 

Biological community (biotic or living component) 8 


Algae 10 

Aquatic macrophytes 11 



Short-term management techniques 15 

Long-term preventive management 16 


Non-chemical techniques 19 

Habitat manipulation 19 

Biological control 21 

Chemical (herbicide) control 23 

Algae 24 

Submergent macrophytes 25 

Floating-leaved macrophytes 26 

Free-floating macrophytes 26 

Emergent macrophytes 27 

Marginal or ditchbank weeds 27 




This publication describes the aquatic ecosystem and discusses the 
interrelationships between the nonliving environment and the living 
biotic communities. Emphasis is on the understanding of the life cycles 
of aquatic plants and how their growth should be limited before it 
becomes excessive. 

Aquatic vegetation management techniques are discussed and control 
procedures are given for specific aquatic vegetation problems in 
different aquatic environments. This information should assist farmers, 
irrigators, irrigation managers, water users and environmentalists in 
understanding and planning integrated aquatic vegetation management 
programs to preserve the Prairies' freshwater resources. 


Cette publication deer it l'ecosysteme aquatique. II y est egalement 
question des relations reciproques entre le milieu abiotique et les 
collectivites biotiques vivantes. On insiste surtout sur la comprehension 
des cycles biologiques des plantes aquatiques et sur les moyens de 
restreindre la croissance de ces plantes avant qu'elle ne devienne 

De plus, on traite des techniques de gestion de la vegetation aquatique 
et on propose certaines mesures de controle a adopter pour regler des 
problemes precis a ce chapitre dans divers milieux aquatiques. Grace 
a ces renseignements, les agriculteurs, les irrigateurs, les exploitants 
d'entreprises d' irrigation, les utilisateurs des ressources en eau et 
les environnementalistes seront en mesure de mieux comprendre et de 
planifier des programmes de gestion integree de la vegetation aquatique 
en vue de preserver les ressources en eau douce des Prairies. 


The industrial and agricultural development along the East Slope of the 
Rocky Mountains has created enormous demands for freshwater supplies and 
these demands will increase in the years to come. Nearly one-half of 
Canada's total irrigated land is in Alberta's 13 irrigation districts. 
With new dams, improved on-stream storage, and more efficient delivery 
systems, Alberta could double its 578,000 ha of land presently under 
irrigation. However, aquatic vegetation can seriously impede the 
movement of water through irrigation conveyance systems, reducing the 
canal flow rates by as much as 91% of design carrying capacity. At 
present, over 12,000 km of canals and drains in Alberta are plugged with 
excessive aquatic weed growths. Some canals require as many as four 
aquatic herbicide treatments per year to permit the irrigation districts 
to meet peak water demands. Weed control costs in older main delivery 
canals can reach $2,500/km per season. 

This manual will outline the theories and goals of vegetation management 
and the techniques available to control excessive aquatic vegetation in 
agriculturally associated freshwater ecosystems. Information on the 
composition of aquatic ecosystems is presented here to enable managers 
to keep their system healthy, i.e., to maintain excellent water quality 
while preventing excessive weed growth. A healthy freshwater ecosystem 
permits the development of a management program that will generate 
revenue from the system through aquaculture, the growth and harvesting 
of aquatic organisms that can be marketed as food or food byproducts. 

- 2 - 


Water has always added to the aesthetic value and recreational potential 
of land. The farm pond or dugout was originally built to supply water 
for livestock and to irrigate the family garden. Later it was found it 
could be used for domestic purposes excluding cooking and drinking. 
Recently, the farm pond has begun to supply potable water after 
filtration and water treatment. It also has a potential for boating, 
fishing and swimming as well as being an attractor of wildfowl and wild 
animals. When trees and shrubs were planted and a picnic table was 
added for family outdoor meals, the pond became a place for relaxation 
for the entire family as well as a source of water. 

As leisure time increased, the public made greater demands for 
water-based recreation. Urban parks have been developed along the 
shores and banks of lakes and rivers. Abandoned gravel pits have been 
converted into parks with biking and walking paths and man-made ponds 
have been constructed to supply shallow ponds for leisure activities. 
Golf course designers construct ponds to act as water hazards to 
complement the sand traps and greens, which provide challenge as well as 
aesthetic beauty for golfers and club members. 

Urban land developers construct small lakes, 10 to 15 ha in size, as 
focal points for new urban communities. The purpose of these man-made 
lakes is to collect surface runoff to provide irrigation water for the 
adjacent park areas and for the enjoyment and relaxation of the people 
of the community. 

As urban development continues, city planners are faced with increased 
surface runoff problems from city streets and parking lots. This runoff 
overloads the sewage treatment facilities. Storm water can not be 
dumped directly into the river systems because it contains contaminates 
such as silt and organic material washed in from the streets. The water 
must be stored in storm-water retention or storage ponds to allow the 
silt and other material to settle and then it can be released slowly 
into natural drainage systems. While these ponds do not contain water 
of top quality, they can be used as focal points in city parks and green 
strips . 

Even agricultural irrigation reservoirs, on-stream storage ponds, 
irrigation canals and drainage canals developed for the production of 
food are subjected to public pressure for further development into 
recreational areas. Canal banks and shorelines are excellent habitats 
for waterfowl and wildlife and large reservoirs offer recreational as 
well as commercial fishing possibilities. 

The vast diversity of these aquatic environments is evident; a great 
variety of physical, chemical and biological characteristics exist in 
each system. However, they all have one thing in common: they are all 
highly eutrophic, meaning that they are nutrient-rich. 

- 3 - 

Eutrophic bodies of water are characterized by a shallow to intermediate 
depth, variable surface area, and oxygen levels that decrease sharply in 
the summer. They are subjected to nutrient enrichment from surface 
runoff and water temperature that rises rapidly in the summer, and they 
contain an abundance of dissolved nutrients and sediments that wash in 
from the surrounding land. These factors contribute to an overabundance 
of aquatic vegetation. 

The seasonal growth and decay of this vegetation has a compounding 
effect on the aquatic ecosystem. The excessive growth of rooted aquatic 
macrophytes causes stagnation of the water column. This stagnant water 
generally has a higher temperature than that of flowing water. 
Increased water temperatures stimulate the growth of algae, both 
filamentous and planktonic, which in turn increases the organic content 
of the ecosystem. This creates a greater demand for dissolved oxygen. 
With the continued demand, the levels of dissolved oxygen drop and fish 
and related organisms are killed, which adds more organic matter and 
stagnation to the ecosystem. Bacteria begin to work on the decaying 
organic matter, odors are released into the water, the aquatic 
environment deteriorates further, and the aesthetic quality is 

For maximum fish growth and reproduction there must be at least 50% open 
water (research data from the United States suggest as high as 60% open, 
weed-free water for maximum sunf ish and perch production) . This allows 
for a normal size gradient from fry up to mature adult fish. The open 
water is the area for the adults while the fry seek refuge in aquatic 
vegetation in the shallower areas. 

Trout require a minimum dissolved oxygen content of 3.0 ppm; serious 
die-off occurs at levels below 2.0 ppm. Widely fluctuating oxygen 
levels tend to shift the fish population from game fish to the coarse 
fish. As the water column warms in the summer, the ability of the water 
to retain oxygen decreases and the heavy phytoplankton blooms appear. 
When these blooms die, the biological oxygen demand increases and as the 
oxygen levels in the water decrease, even the coarse fish die off. 

As the water body deteriorates, the nutrients and organic matter 
continue to increase and the aquatic vegetation becomes even more 
abundant. When the vegetation reaches the surface of the water, it 
forms mats which raise the surface water temperature. This increases 
water loss through increased evapotranspiration from the water's 
surface. Once this aquatic vegetation starts its prolific growth, it 
continues to increase in density, causing further deterioration in water 
quality and a subsequent large buildup of organic matter, which drops to 
the lake bed and contributes nutrients for further weed growth. 

In a very short time, usually three to five years, a water body can lose 
its aesthetic value, the fishery can be destroyed, the water quality 

- 4 - 

deteriorates, odors develop from the rotting vegetation, and where the 
water is used for irrigation the aquatic vegetation and debris begin to 
plug intake screens and pumps. Dense vegetative growth will also block 
turn-outs, thus preventing the movement of water from the water body. 

The goal in aquatic vegetation management must be to prevent the buildup 
of excessive vegetation. Corrective steps after the buildup occurs are 
very expensive and, in the case of aquatic herbicides, the treatments 
must be applied year after year. To develop a successful aquatic 
vegetation management program we must first understand the aquatic 
ecosystem: what makes up the total ecosystem; where the water and 
nutrients come from; how the different components interact with each 
other, and, finally, how a semblance of balance can be maintained to 
keep the aquatic ecosystem healthy, viable, and functional. 

- 5 - 


Aquatic ecosystems are dynamic systems which are in a state of slow but 
continual change both physically and biologically. Like most biological 
organisms, they undergo a constant aging process. Natural freshwater 
lakes can be viewed as small worlds composed of environmental factors 
and living organisms organized and bound together by interdependences of 
food and interrelationships of energy. These lakes may be influenced by 
surface runoff from the surrounding land and by the people who use and 
manage this land. Human activities may accelerate the natural aging 
process through increased and enriched surface runoff and the lake thus 
may become highly eutrophic over a shortened period of time. Young 
aquatic ecosystems begin nutrient-poor, with a low organic matter 
content that restricts the biological component of plants and fish. 
This is called an oligotrophic water body. As the water body matures, 
it receives more nutrients and silt from surface runoff, the organic 
content of the water increases and the aquatic vegetation becomes more 
abundant. This vegetation offers food and shelter to numerous aquatic 
organisms. This in turn begins to support a small game fish 
population. The body of water is now called mesotrophic. 

When the water body reaches middle age it has received years of fertile 
runoff and is very nutrient-rich with a high organic matter content in 
the water column as well as the sediments. The aquatic vegetation is 
overabundant and there is very little open water. This overproduction 
of organic matter causes the oxygen levels to fluctuate widely and the 
fishery to shift to a few coarse fish. If organic matter production is 
allowed to continue, the water body will in time fill in with organic 
matter and become a marsh and then a swamp or muskeg. This is the 
natural aging process for a freshwater ecosystem. 

Agriculturally associated freshwater ecosystems are usually aquatic 
systems that are made or at least modified by man. They may be small 
lakes, reservoirs, ponds, or dugouts that contain standing water; they 
are lentic environments. If the water is moving, such as in rivers, 
streams, creeks, irrigation delivery canals, farmer supply canals and 
drainage canals, the water system is referred to as a lotic 
environment. This distinction is important since we will see later 
that the type of aquatic vegetation and the preventive and corrective 
vegetation management techniques applied will depend on the type of 
aquatic environment involved. 

These aquatic environments are only a small part of the total farm or 
irrigation district. They are composed of the physical environment, 
namely the water, the sediment of the pond bed, shorelines or banks, and 
the living organisms or biological community. The surrounding or 
adjacent land that supplies the surface runoff is the watershed and 
development on this watershed comprises the urban or rural land use 
pattern. The water may come from the local watershed or it may 

- 6 - 

originate from an outside source such as irrigation water. It may stay 
on the site or pass through the site. The quality of the water is 
dependent on the quality of the input as well as the quality of the 
water that is discharged. The critical point to remember is that the 
better the water quality the fewer the aquatic vegetation problems/ and 
hence less erosion and flooding, lower maintenance costs, fewer problems 
with irrigation equipment, fewer water taste and odor problems and 
greater aesthetic benefits to the landowner and the general public. 

Large natural lakes with their large volume of water are essentially 
self-sustaining and require only radiant energy, the non-living or 
abiotic environment, and the communities of living or biotic organisms 
to function. These organisms act in the roles of producers, consumers, 
and decomposers to make the ecosystem function. Generally, the large 
system is very stable and essentially self-sustaining, being maintained 
more or less independently of the influence of other outside 
communities. The smaller agriculturally associated ecosystems, however, 
are much less stable and require outside help to maintain their 
equilibrium. Because change will manifest itself very rapidly, the 
system must be monitored closely. This should be viewed as a positive 
point since it means that we can manipulate the agricultural ecosystems 
to prevent excesses or correct deficiences. It only requires that the 
manager spend as much time on the aquatic ecosystem as on the rest of 
the agricultural holdings. 

Environment (abiotic or non-living component) 

The environment or non-living component of the aquatic ecosystem is 
composed of the sediments and soil of the banks and shores of the water 
body, and the water. The water is the most visible and important of the 
three. Of the many extraordinary properties of freshwater that 
contribute to its ability to maintain life in aquatic ecosystems, none 
is more important than the capacity of water to hold substances in 
solution and its ability to enter into numerous chemical reactions. 
Many of the naturally occurring elements of the earth's crust can be 
found in inland fresh water. Some of these substances occur in minute 
concentrations but in most cases they are only needed in minute 
quantities to support aquatic life. 

Of all the chemical substances in fresh water, oxygen is one of the most 
significant both as a regulator of metabolic activity in the communities 
and the individual organisms and as an indicator of the health of the 
aquatic ecosystems. This oxygen exists as a dissolved gas in the water 
and may be derived from atmospheric oxygen or from the photosynthetic 
activity of green plants. The oxygen moves through the water column and 
may enter the sediments where it takes part in the oxidation of various 
compounds. The extent to which a compound may undergo oxidation- 
reduction processes is dependent on the concentration of other oxidizing- 
reducing systems and their products in the sediments and water column. 

- 7 - 

This oxidation-reduction potential or redox potential is important to 
the cycling of the nutrients such as phosphates from the sediments and 
their subsequent availability for the excessive growth of aquatic 

The other major dissolved gas in the aquatic ecosystem is carbon 
dioxide. This gas contributes three essential factors to the water. 
First, it acts as a buffer in the water to protect against rapid shifts 
in the acidity-alkalinity state. Through its reaction with water, 
carbon dioxide may form a weak acid, neutral salts, or a weak base in 
the water column. The maintenance of the near-neutral conditions in 
mineralized fresh water is due to the carbon dioxide-bicarbonate- 
carbonate complex. The second contribution is the role of carbon 
dioxide in regulating biological processes such as seed germination and 
plant growth as well as being involved in animal respiration and oxygen 
transport in blood. The third and most important contribution is that 
carbon dioxide is a source of carbon, one of the most versatile of all 
the elements in the aquatic ecosystem. Carbon dioxide and water supply 
the major components of carbon, oxygen, and hydrogen necessary for all 
living organisms. 

The most conspicuous dissolved compounds found in varying concentrations 
in fresh water are the major anionic compounds such as carbonates, 
sulfates, phosphates, and nitrates and the minor anionic compounds of 
chlorides, sulfites, silicates, and nitrites. These compounds occur in 
combination with the major cationic elements of calcium, sodium, 
potassium, magnesium, and iron to form ionizable salts. Occurring at 
much lower concentrations are the minor or trace cationic elements of 
cobalt, zinc, copper, manganese, molybdenum, and boron. Generally, both 
the qualitative and quantitative composition of the fresh water are 
influenced by the geochemistry of the watershed surrounding the basin 
through which the surface runoff flows to reach the water body. 

The inorganic composition of the water body is further modified by 
precipitation and concentration of salts due to evaporation. The total 
concentration of dissolved compounds or minerals is a useful parameter 
for describing the suitability of the water for irrigation, livestock or 
domestic use. This measure, total dissolved solids, is the dried 
residue of the water containing both inorganic and organic materials. 
The quality and quantity of the dissolved solids in large part determine 
the type and abundance of aquatic vegetation found in the ecosystem. 

The sediments of aquatic ecosystems differ from terrestrial soils in a 
number of fundamental ways, thus providing a unique environment in which 
the aquatic plants take root and derive much of their nutrients. 
Sediments are typically anaerobic except for a few centimeters at the 
interface of the water column with the sediment bed. The inorganic 
compounds are primarily in the reduced state. At the interface with the 
water column the inorganic and organic compounds may undergo oxidation 
and diffuse up into the water column. Generally, there is a rich 

- 8 - 

organic layer of particulate matter of decaying vegetation from 25-30 cm 
thick that floats over the sediment. Numerous adaptations are required 
by the submerged rooted aquatic macrophytes and their root systems to 
exist on this unique substrate and function under these physiological 
stresses. The aquatic plants exert a pronounced effect on the physical 
and chemical properties of the bottom sediments. Once submerged plants 
are established, their vegetative tops stimulate the settling of 
additional sediments by decreasing the water flow velocity and creating 
underwater currents. 

Although extensive literature is available on the role of the 
rhizosphere of agronomically important terrestrial plants, little is 
known about aquatic plants. It is safe to suggest that the microfloral 
rhizosphere of aquatic plants probably plays a critical role in the 
nutrient uptake and subsequent vegetative growth of aquatic plants. 
More research into the interactions between the aquatic plant root 
systems, the sediments, the availability and uptake of nutrients, and 
the microfloral rhizosphere will give us a better understanding of the 
nutritional physiology of aquatic plants. This will lead to the 
development of innovative, ecologically safe vegetation management 
techniques to prevent excessive plant infestations and to even encourage 
beneficial aquatic vegetation. 

Biological community (biotic or living component) 

All agriculturally associated aquatic ecosystems are composed of 
biological communities of plants, animals, bacteria, and fungi. The 
maintenance of these communities is dependent to a great extent upon 
food relationships and energy flows that involve interactions between 
the non-living environment and the biological communities. In a small 
system these relationships are so closely connected that a change in one 
nutrient can cause a serious disruption in the entire ecosystem. The 
basic operation of the community's metabolism rests on the roles that 
the different organisms perform at various nutritional levels in 
maintaining the transfer of energy in the form of food through the 
various individuals of the aquatic ecosystem. 

The aquatic vegetation makes up the group referred to as the primary 
producers. These organisms use nutrients from the water and sediments, 
dissolved carbon dioxide from the water, and solar energy to produce 
energy-containing organic substances through photosynthesis with the 
oxygen released back into the water. The organic substances are used by 
the plants to grow and reproduce. The consumers, mainly animals, are 
incapable of synthesis of matter from the sun's energy and hence depend 
directly on the producers. Within this group we recognize the 
herbivores, which feed on aquatic vegetation, and the carnivores, which 
feed upon herbivores or other carnivores. Both subgroups use the 
dissolved oxygen given off by the green plants to grow and develop while 
returning carbon dioxide and energy from respiration to the water 

- 9 - 

column. The decomposers are composed of heterotrophic bacteria and 
fungi which in turn break down the organic substances from both the 
producers and consumers and return the inorganic and organic nutrients 
to the water column to be recycled by the producers. 

The various links in the food chain represent different levels of food 
synthesis/ feeding and being fed upon, and nutrient release by decay. 
The aquatic ecosystem is thus a pyramid with the dissolved nutrients at 
the base. The algae and aquatic macrophytes or producers occupy the 
next level. Located on and in the sediments of the water body are the 
bacteria and fungi of the decomposer group that break down the organic 
matter. The next level is composed of the grazing herbivores followed 
by the small carnivores such as trout fry. Last are the medium and 
large carnivores such as the perch, trout, and finally the pike of the 
consumer group. 

While our major concern is the management of aquatic vegetation of the 
agriculturally associated aquatic ecosystem, it can readily be seen that 
the entire ecosystem is interrelated and what we do to one small segment 
may have a pronounced effect on the entire system. 

- 10 - 


The aquatic vegetation, or primary producers, is composed of two major 
groups of plants: the microphytes or algae and the macrophytes or 
vascular plants. Before any vegetation management program can be 
developed for our agriculturally associated aquatic ecosystems, the 
water bodies must be surveyed and the specific problem areas examined. 
After surveying, the nuisance aquatic vegetation must be properly 


Algae are plants of simple structure and organization and lack true 
leaves or flowers. They reproduce asexually by continuous vegetative 
growth and from specialized cells or minute spores. Generally 
free-floating, a few specialized species may become attached to 
submerged rocks, grow on damp soil, or even grow on the ice face of 
glaciers. Algae vary in size from microscopic forms to giant seaweeds 
that extend several hundred feet in the oceans. They are found in 
oceans, lakes, ponds, swamps, rivers, creeks, and canals where they can 
grow down to the depth of light penetration. Algae are considered 
primitive because the individual plant cell is capable of carrying out 
all the critical life processes without the assistance of specialized 
cells or tissues found in higher plants. 

The algae found in our agricultural water systems are subdivided into 
three subgroups: 

1. phytoplanktonic algae 

2. filamentous algae 

3. branching algae 

The phytoplanktonic algae are microscopic, free-floating, only 
slightly mobile and exist at or near neutral buoyancy, usually existing 
in the upper 1 to 2 meters of the water column where they are subjected 
to the surface movements of water currents and wind. Phytoplankton 
production is influenced by sunlight, water temperature, dissolved 
inorganic and organic nutrient content of the surface water, the size, 
shape, slope and type of pond bed, and water currents. Phytoplankton 
are best known for the production of summer water blooms which cause 
colored water because of the rapid proliferation of algal colonies. In 
agricultural water systems the green water usually comes from species of 
Anacystis , Microcystis , and Anabaena ; blue to blue-green water from 
Aphanizomenon ; and reddish-brown water from Oscillatoria , Melosira , 
Fraqilaria , and Navicula . Generally, phytoplankton do not interfere 
with irrigation systems but may cause serious problems in ponds and 
dugouts where toxic algae can kill hogs, sheep, and cattle. These 
plants decrease the aesthetic quality of the water, may cause 
objectionable odors and tastes, and in isolated incidences may cause 

- 11 - 

summer fish kills because the collapse of the massive blooms causes 
serious oxygen deficiencies or releases toxins into the water column. 
During the collapse and death of individual phytoplankton blooms, 
bacterial populations may build up because of the breakdown of the algal 
cells and the release of organic matter into the water. This can cause 
additional nutrient enrichment, odors, and objectionable taste problems. 

The filamentous algae are colonial types that consist of long, 
stringy, hair-like strands of cells. They may be attached to the pond 
bottom, draped over rooted macrophytes, or form floating mats or 'scums' 
on the surface of the water. The filaments may be bright green to 
yellow-green in color and appear as cotton-like masses on the surface of 
the water ( Cladophora ) ; be dark green in color and feel like coarse 
horse-hair ( Pithophora ) ; or appear as loose, slimy strands, bright green 
and rising from the pond bottom ( Spirogyra ) . The filaments may form 
large mats that can clog screens, intakes, pumps, and sprinkler heads of 
irrigation systems. During hot, sunny weather the algae may trap air 
bubbles in the filaments and float up to the surface where it forms 
extensive mats that interfere with water-based recreation. These 
surface mats also increase the adsorption of radiant energy from the 
sun, causing the water temperature to rise. This in turn increases the 
evapotranspiration of water. During periods of drought this water loss 
can be critical to farmers and ranchers. 

Branching algae are the most advanced algae possessing stems and 
branches. They grow attached to the pond bottom but lack true roots. 
They are usually found in hard water and have a gritty feeling when 
crushed because of the high calcium deposits in their vegetative parts. 
They are low-growing and generally cause very little trouble to the 
farmer or rancher. The low-growing, creeping habit makes it an 
excellent plant to stabilize and hold down the silt of pond or dugout 
bottoms. Branching algae are excellent cover for small aquatic 
organisms such as freshwater shrimp, which serve as food for fish. 
Chara and Nitella are the only representatives found in Canada and may 
be mistaken on first glance for coontail or water milfoil. The key 
difference is that the algae lack true roots and do not have true flower 
heads. When crushed, Chara will give off a strong musky, fish smell. 

Aquatic macrophytes 

The aquatic macrophytes or vascular hydrophytes are classified very 
simply according to their habit of vegetative growth: 

1. submergent macrophytes 

2. floating-leaved macrophytes 

3. free-floating macrophytes 

4. emergent macrophytes 

5. marginal or ditchbank macrophytes 

- 12 - 

Subroergent macrophytes grow completely submerged at water depths from 
0.5 to 5 meters and are rooted in the hydrosoil. Although the plants 
are totally submerged, the flower heads may extend to the surface of the 
water and above for wind or insect pollination. The leaves may be 
thread-like, ribbon-like, broad or finely dissected. Four distinct 
types of leaf attachment occur in the submerged macrophytes. Whorled 
leaf arrangements have more than two leaves attached at the same point 
on the main stem ( Ceratophyllum demersum , Myriophyllum spp., and Elodea 
canadensis ) . Opposite leaves are those with just two leaves attached at 
one point on the main stem but the leaves are attached opposite each 
other ( Zannichellia pulustris and Najas f lexilis ) . The alternate leaf 
attachment is where a single leaf is attached to each point along the 
main stem ( Potomageton crispus , P. praelongus , P. richardsonii , P. 
gramineus , P. f iliformis , P. pectinatus , P. vaginatus , P. zosterformis , 
P. pusullus , P. f riesii , P. berchtoldii , P. foilose , and Ru ppia 
occidentalis ) . 

The floating-leaved macrophytes grow on submerged soils at water 
depths of 0.25 to 3.5 meters. In crowded habitats, the large leaves 
float to the waters surface on long flexible petioles. This subgroup is 
represented by the waterlilies ( Nymphaeo and Nuphar spp.) as well as a 
few dimorphic pondweeds ( Potomageton natans , P. gramineus and P. 
vaseyi ) . 

Free-floating macrophytes are typically unattached plants that float 
freely on or just below the surface of the water. Some species may have 
extensive root systems extending down into the water column. In Canada, 
they range from the subsurface floaters with no roots ( Utricularia spp. 
and Lemna trisulcata ) to the surface floaters with very simple roots 
( Lemna and Spirodela spp.). 

Emergent macrophytes are rooted in waterlogged soils, soils covered by 
up to 0.5 meters of water, or on exposed mud flats above the waterline 
but where the water table is within 0.25 meters of the soil surface. 
The plants are mainly perennials growing from creeping rhizomes or 
rootstocks. The mature leaves and stems as well as the flower parts are 
aerial. This subgroup is represented by T ypha , Scirpus , Juncus , and 
Carex spp., Phragmites maximus , Zizamia aquatica , and Flumen festuccea . 

The marginal or ditchbank plants are really terrestrial plants 
commonly found along waterways, ditchbanks, and in moist, seepage waste 
areas. These include many of the grasses ( Gramineae spp.) such as manna 
grass, wild millet, cut-grass, blue joint grass, and reed canary 
( Glyceria spp., Echinochloa spp., Leersia oryzoides , Calamagrostis spp., 
and Phalaris arundinacea ) . Also in this subgroup are the woody 
herbaceous shrubs and trees of Cottonwood, willows, wild rose, and water 
hemlock ( Populus spp., Salix spp., Rosa acicularis and Cicuta spp.). 

- 13 


After identification of the aquatic weeds, the complete life cycle of 
each group of aquatic macrophytes must be determined, from the breaking 
of dormancy of the seed or tuber to the early development of the 
seedling to the initiation of flowering and the subsequent development 
of the seed, overwintering turion or winter bud. The rate of vegetative 
growth is important since chemical control measures are usually most 
effective and economical during a brief time of early plant growth or 
just after the initiation of flowering. Late in the season the mature 
plants are usually more resistant to the herbicide because of a heavy 
layer of marl (calcium carbonate) encasing the leaves, which prevents 
the absorption of the herbicide. Also, the total plant biomass may be 
so great that the dosage necessary to build up a toxic level of 
herbicide in the aquatic plant tissue makes the application of the 
herbicide uneconomical, environmentally impractical, and perhaps even 
unsafe. It is imperative that the mode of reproduction in the different 
aquatic plant species be fully understood. 

The aquatic macrophytes in western Canada increase and become serious 
weed problems through prolific asexual or vegetative reproduction. 
After the first introduction, over 90% of the subsequent reproduction is 
by vegetative means. A cut or broken stem tip, 2.5-5.0 cm long and 
containing two whorls of leaves, can produce roots in 3-5 days, become 
attached to the substrate in 5-7 days, and will produce a water milfoil 
plant in 4 weeks. Canada waterweed and coontail can also reproduce by 
this fragmentation method and spread quickly throughout the aquatic 
ecosystem in two growing seasons. 

Where overwintering buds, dormant apices, and specialized overwintering 
turions are formed at the ends of the vegetative shoots, the use of 
mechanical harvesters actually spreads the aquatic plant infestations 
and increases the density of the plant populations. The cutting of some 
rooted submerged aquatic plants by mechanical means tends to make the 
plants bushier and, as the plant matures, there are many more vegetative 
stem tips which give rise to overwintering structures. These drop to 
the mud of the pond or canal bottom and remain dormant until the 
following spring when they begin to grow as the water warms up. The 
tuber-producing pondweeds can also be stimulated to produce large 
numbers of axillary tubers and stoloniferous runners when subjected to 

The pondweeds, particularly P. pectinatus , are known for their prolific 
production of tubers when given sufficient nutrients and space, with 
ideal physical and chemical conditions of the substrate. One tuber of 
P. pectinatus planted in a child's wading pool in April and given ample 
light, nutrients, warm water, and a rich organic mud for a substrate can 
produce up to 36,000 subterranean tubers, 6,000 seeds, and 1,000 
axillary tubers in a single growing season. 

- 14 - 

Once established in a reservoir or canal, the plant begins a prolific 
vegetative reproduction by runners, dormant apices, tubers, turions or 
seeds and rapidly develops a dense stand which slows up the flow of 
water and causes a further deposition of silt and organic matter, which 
further stimulates aguatic plant growth. 

Geotextiles and geomembranes (such as polyethylene, polyvinyl and butyl 
rubbers) used to line ponds and canals are often held in place and 
protected from the sun by a 5-25 cm layer of soil on top of the liner. 
The soil provides a good seedbed for shallow-rooted pondweeds such as P. 
pusillus to become established and to spread by runners and small 
vegetative dormant apices. A layer of soil, 2.5-5.0 cm thick, above the 
herbicide-treated canal bottom is enough to permit the shallow-rooted 
aquatic weeds to become established. However, the herbicide in treated 
soil below this deposition is still effective for the control of 
deep-rooted aquatic species. 

It should be evident that control and management techniques must be 
matched to the problem plant species and their mode of vegetative growth 
and reproduction. From the general life cycles of the four different 
groups of aquatic plants one can determine the most susceptible times 
within the life cycle of the plant and select control procedures that 
are most effective to control the problem infestation with the least 
impact on water quality and the environment. 

- 15 - 


Short-term management techniques 

Until a long-term management program can be developed to manage the 
varied aquatic ecosystems, temporary or cosmetic corrective measures of 
integrated mechanical and chemical techniques will have to be used. 
Although critics may complain of the pollution and destruction of our 
environment through the use of aquatic herbicides, it is just as 
criminal to sit back and do nothing. Aquatic plants have a tremendous 
capacity to reproduce and to spread once introduced into an aquatic 
environment, and to eventually destroy the aquatic ecosystem through 
stagnation of the water, the subsequent deposition of mineral sediments, 
and the production of large amounts of organic matter from the decaying 
plant matter. This organic matter decomposition depletes the water 
column of oxygen and causes deficiencies, particularly during the winter 
months when the water is ice-covered. Odor and taste problems may 
develop as well as destruction of the fish population from lack of 
oxygen. Stagnation also causes reduced circulation of the water and 
subsequent stratification of the water column. The aquatic ecosystem is 
in a constant state of change. Today's technology helps maintain and in 
some cases improve the water quality of our freshwater ecosystems when 
they become stressed through overuse and abuse. Many management 
techniques can, in reality, restore the ecosystem to its normal sequence 
and rate of change. 

Many different aquatic plant harvesting machines have been developed 
since the mid 1940s. Basically, the harvesters have been designed as 1) 
underwater cutters which cut the weeds and an inclined porous conveyor 
which collects the cut material and loads it into a holding compartment; 
2) a transporter system to move the cut material from the cutter holding 
compartment to the shore; and 3) an unloading facility on shore to move 
the material from the transporter to trucks for delivery to a disposal 
site. Recent modifications have included equipment to dewater, shred 
and compact the bulky plant material to make transportation and disposal 
more economical. The big advantage of cutting and harvesting the 
aquatic plant material is the removal of the plant nutrients and organic 
matter from the water column and the aquatic environment. 

The main disadvantages are the fact that the plants start regrowth 
immediately after cutting and develop a bushier habit of growth and 
stimulate greater development of asexual reproductive structures. Dense 
aquatic weed populations slow the forward cutting speed of the 
harvester, because of the resistance of the matted cut material on the 
pick-up conveyor belt. Speeds exceeding 1 km/hr cause a large 
displacement of water in front of the cutter/conveyor and the cut plant 
material tends to move around the pick-up system. Any plant material 
that escapes the pick-up system acts as a source of new aquatic plant 
infestations. The increased bulk of plant material, which is about 85% 

- 16 - 

water, increases the problems of transportation and disposal since the 
material must be drained of water and then dried down for final 
disposal. Mechanical cutting tends to be very capital- and 
labor-intensive and is a slow, tedious process. One must weigh the cost 
and slowness of the cutting operation along with the potential for 
developing bushier aquatic plants and spreading of aquatic plant 
infestations throughout the ecosystem against the advantage of removing 
the organic matter from the ecosystem, the removal of some of the 
nutrients bound up in the plant material, and the fact that no new 
foreign substances are added to the freshwater ecosystem. The 
environmentally acceptable mechanical cutting method may, in fact, cause 
the spread of the problem and do more harm than the spot treatment with 
a small amount of aquatic herbicide. 

Aquatic herbicides are easy to apply and require a minimal amount of 
capital expense and labor. Since they are so easy to apply, a 
misconception may be that if there is nothing else to do, then go out in 
the boat and "treat the weeds". However, aquatic herbicides are just 
like medicine; you must prescribe the correct herbicide at the 
prescribed dosage for the specific problem aquatic plant at its most 
susceptible growth stage. Applied too late in the season or at too low 
a dosage, the herbicide may just chemically prune the target aquatic 
plants. If a herbicide is applied too often, the plant may develop a 
resistance to it or, worse still, the herbicide may select out resistant 
aquatic plant species that can take over the ecosystem. Treating an 
aquatic plant biomass that is too extensive will create serious problems 
when the plant material drops to the pond bottom and causes an organic 
matter buildup. A problem of real concern is the use of aquatic 
herbicides to treat only the visible result of a deeper, more basic 
problem, causing the excessive growth of specific plant species in the 
freshwater ecosystem. Once started, the aquatic herbicide program must 
be planned as a yearly maintenance procedure to selectively control 
excess vegetation, to minimize interference with water use, and to apply 
the herbicide at the correct time to attain maximium effectiveness. 

In old, mature ecosystems the best program would be an integrated 
program using mechanical and chemical management techniques. Here the 
overabundance of aquatic vegetation is cut to remove it from the lake or 
pond. This removes some of the nutrients and a fair amount of the 
organic matter. Then herbicides could be applied at a reduced dosage to 
kill the remaining plants and to prevent regrowth and reinfestation due 
to fragmentation and clippings. 

Long-term preventive management 

Most bodies of freshwater will become infested with aquatic vegetation 
in time. Aquatic plants are necessary for the stabilization of the 
sediments, the oxygenation of the water column, and the shelter and 
protection of aquatic organisms. Seeds and tubers of aquatic 

- 17 - 

macrophytes are important sources of food for waterfowl and wildlife. 
Aquatic ecosystems should be designed and managed to control excessive 
aquatic plant growth through the manipulation of the water body and the 
surrounding watershed. Aquatic plants do not grow well on rocky, 
gravelly or clay pond or canal beds. They prefer an organic-rich 
substrate with a steady supply of nitrogen and phosphorus. They grow 
very slowly at water temperatures below 15°C and cannot tolerate 
shading. With this knowledge, guidelines can be set for the design of 
ponds, reservoirs and irrigation conveyance systems to minimize 
potential aquatic weed problems. 

The bottoms of ponds and canals should be excavated down to clay to 
prevent seepage and to provide a harsh environment for the introduction 
and development of aquatic seedlings. If the pond or canal site 
contains a high percentage of coarse-grained soils, then the bottom 
should be lined by 'blanketing' with a 30-cm layer of packed clay. If 
clay is not available at the site then the pond or canal should be lined 
with geotextiles. Slopes and canal banks should be lined with rocks and 
gravel to prevent erosion. If geomembranes or geotextiles are used for 
lining the pond or canal, then the covering material should be coarse 
and nutrient-poor. Once a harsh environment is established in the pond 
or canal it is imperative that the silt content of the introduced water 
be controlled through the use of silt traps and sediment catch basins. 
Little is accomplished if the rocky bed is allowed to silt in, because 
just 2.5-5.0 cm of sediment is enough for shallow-rooted aquatics to 
become established. This is particularly important during 
rehabilitation work because all the improvements are for nothing if part 
of the system can still release sediments and nutrients into the newly 
renovated pond or canal. Canals in southern Alberta can deposit enough 
sediment at bends in the canal in one season to permit the deposition of 
sediment-rich substrates for colonization by P. pusillus . After the 
pondweeds become established, the sediment deposition extends further 
upstream and increases in depth. Soon the deeper-rooted pondweeds such 
as P. pectinatus and P. richardsonii begin to appear in the center of 
the siltbar. Once established, the pondweeds extend into the harsher 
areas between the rocks and coarse gravel and continue to spread. 
Within five years the rehabilitated canal can be so infested that the 
delivery capacities are seriously reduced because of restricted flow. 
The weed bed can now serve as a source of plant inoculum for the rest of 
the canal system downstream. 

The surrounding area must be landscaped and managed to prevent the 
introduction of nutrients from soil and organic matter carried into the 
pond by surface runoff and wind erosion. In the western Prairies the 
wind can be a problem and every effort should be made to establish 
windbreaks and shelter belts to prevent soil drifting into the ponds, 
dugouts, and canals and to retain snow for spring runoff. Shelter belts 
must be placed far enough away from the pond, reservoir, and canal bank 
to allow for a grass vegetative filter area to intercept sediment in the 
spring runoff. This will prevent the direct introduction of organic 

- 18 - 

matter into the water. The area must be fenced to keep livestock away 
from the water's edge, thus preventing the destruction of the banks and 
the introduction of nutrients from manure. Particular attention should 
be paid to runoff gulleys and field drainage areas to prevent flash 
flooding and soil erosion. 

Lastly, "dilution is never the solution"! Waste water must be treated 
to prevent the introduction of nutrients and organic matter into a water 
body. Through the use of biological vegetative filters, most of the 
sediment and oxygen-demanding organic matter can be removed before the 
runoff reaches the water body. Livestock runoff should never be allowed 
to drain directly into a water body without first passing through a 
vegetative filter. 

The water user must remember that the better the water guality, the 
cheaper its cost and the fewer the problems that will arise. The poorer 
the water quality the more algae and hence the greater the problems with 
irrigation intakes, pumps, delivery systems and sprinkler nozzles. Poor 
water quality also means more expense in setting up and maintaining a 
farm and ranch domestic water treatment facility. Poor water quality 
also means greater aquatic plant problems which contribute to increased 
water loss through evapotranspiration and increased water temperature. 
With increased water temperatures there is increased algal and bacterial 
growth which creates odor and taste problems as well as potential toxic 
water problems. 

19 - 


Non-chemical techniques 

The mechanical methods of aquatic plant removal developed over the years 
all seem to neglect the fact that aquatic plants have the capacity to 
reproduce vegetatively from stem fragments, specialized stem apices, 
tubers, stoloniferous rhizomes, axcillary tubers and runners. Cutting, 
chaining, dredging or drag-lining, and pulling all tend to leave the 
root system, the crown at the substrate, and usually part of the 
vegetative plant intact. Regrowth begins immediately and with the 
healthy root system the plant grows even faster. In the case of 
cutting, the underwater plant becomes more bushy, increasing the 
potential for more turions and overwintering apices. Timing the cutting 
to remove the vegetative top growth before the tubers have developed and 
hence before there is a reserve food supply in the plant can be very 
effective in controlling some rooted submerged macrophytes. Combining 
the removal of the excessive vegetative top-growth or 'standing crop' of 
the aquatic plant population with timely injection of herbicides 
underwater, just above the new regrowth, will kill the plant back to the 
substrate and in some cases may even destroy the crown and root system. 

Dredging or drag-lining is used extensively in the irrigation conveyance 
systems of southern Alberta but this has a tendency to spread the plant 
tubers. Mud and water that escape in the dredging operation spread a 
thin layer of nutrient-rich substrate and numerous tubers and rhizomes 
along the canal. These catch in crevices and give rise to new 

Recently, new machines such as rotovators and hydro-jets mounted on 
barges have been designed and prototypes tested to dislodge the tubers, 
rhizomes, root systems and crowns from the muddy sediments. These 
research machines are in the experimental stage but may offer some 
long-term control once the design has been perfected. The important 
aspect of this engineering is that we are recognizing the significance 
of destroying the root systems. For control of aquatic weeds the plant 
must be dislodged from the substrate and then collected and removed from 
the water. 

Habitat manipulation 

Aquatic vegetation is only the visible symptom of a deeper underlying 
problem or cause. Aquatic plants can be harvested from now until the 
end of time but they will always grow back. They can never be 
eradicated because of their fantastic vegetative reproductive ability. 
A single plant can colonize a pond, reservoir or canal system in three 
to five years. Once established in a freshwater environment, the 
aquatic plants not only spread through that system vegetatively but form 

- 20 - 

seeds that can then be spread to other systems by migrating duck and 

We must learn to manage the growth of aguatic vegetation and control the 
spread of aguatic weeds in our freshwater systems. By designing our 
freshwater ecosystems to limit the sunlight, manage the water 
temperatures to maintain cool water, restrict the inflow of necessary 
plant nutrient and prevent the accumulation of rich organic sediments 
necessary for the rooting of aguatic macrophytes, we can do much to slow 
up the establishment of overabundant aguatic weeds. A healthy aguatic 
environment actually reguires some vegetation to support the aguatic 
invertebrate populations and a viable sport or commercial fishery. 

Water level manipulation has long been one of the most often practised 
but least understood technigues. Certainly the lowering of the water 
level in the winter will achieve a degree of control through the 
freezing of the exposed crowns. Recent studies have shown that there is 
a minimum freezing period of 60 days and a minimum temperature of -10°C 
to kill tubers of P. pectinatus . It is probably safe to assume that 
each aguatic plant species has its own specific temperature 
reguirements . Dormant apices and turions of a number of species appear 
to be much more resistant to low temperatures but less tolerant of 
desiccation. Preliminary studies suggest that the combination of 
freezing and desiccation proves much more effective for aguatic plant 
species with specialized overwintering vegetative structures that lie 
within the top 5.0-7.5 cm of the sediment surface. 

A drawdown treatment in the summer for periods as short as 10 days 
appears to achieve good control through the desiccation of the aguatic 
plant tops, crowns and shallow root systems. This has been seen in 
irrigation canals and along pond banks during the last few drought years 
on the Prairies. Generally, the peak demand is for summer water but 
alternate storage sources could be designed to permit occasional summer 
drawdowns. Success is only achieved if the sediments are dried out. An 
elevated water table or saturated sediments prevent the aguatic plants 
from being killed. 

Related to this is the increasing of the pond or dugout water level to 
flood out or drown aguatic plants at the beginning of the flowering 
stage of the life cycle. Studies have shown that pondweeds such as P. 
richardsonii , P. illinoisis , P. pectinatus and P. zosteriformis can be 
killed by raising the water level 5.0-8.0 cm above the plant tops after 
the plants begin to initiate flowering but before the flower buds open. 
This is attributed to the disruption of the final stages of the life 
cycle with the initiation of flowering and the approaching senescence 
stage. The increased water depth does not permit the plants to complete 
the flowering and seed development stages and the vegetative stage is 
completed. However, since tuber formation has already taken place, this 
technigue will do nothing towards alleviating the following years' 
problems . 

- 21 - 

The introduction of cool water can slow the growth of rooted submerged 
aquatic macrophytes. Another technique is to circulate the water 
throughout the water body by moving colder water from deep in the pond 
or lake up to the surface by aeration. Stagnant water tends to be 
warmer because of summer heating and in shallow water bodies this 
stimulates vegetative macrophyte and algal growth. If colder water can 
be circulated through the entire pond and moved from deeper water to the 
shallower areas, the cooling effect will inhibit aquatic vegetative 
growth. Oxygenation through aeration is also beneficial with the 
cooler, more oxygenated water restricting the growth of some 
phytoplankton species. 

Although research is lacking on the effect of oxygen levels in the water 
column on the growth of macrophytes, it is known that low oxygen levels 
stimulate algae production. Blue-green phytoplanktonic algae prefer 
warmer water temperatures (above 22°C) and oxygen levels below 2.0 ppm, 
whereas filamentous algae prefer oxygen levels above 5.0 ppm. Thus the 
use of aerators to mix, cool, and oxygenate the water all assist in the 
reduction of some nuisance aquatic vegetation. In western Canada the 
use of wind power has proven effective in running air compressors which 
supply air to air stones located on the bottom of dugouts, ponds and 
small irrigation reservoirs which aid in the cooling, circulation, and 
aeration of farm and ranch freshwater ecosystems. All these habitat 
improvement techniques make the aquatic ecosystem that much better for 
the growth and development of aquatic organisms including fish species. 

Biological control 

Aquaculture has been practised in many countries of the Old World and in 
Asia to supply food to the local inhabitants. The principles are based 
on maintaining a healthy and balanced aquatic ecosystem. The prime 
function of aquaculture in Israel is to grow sufficient fish to meet the 
demand for 20-25 kg per person per year. Through the careful selection 
of specific fish species it is possible to establish a polyculture 
which will utilize the entire water column from surface to substrate. 
It is even possible to select species that will feed in the mud of the 
pond bottom. The incorporation of other aquatic organism such as eels, 
shrimp and mussels permits the further purification of the water. 
Research in Israel and Germany has shown that aquatic vegetation and 
aquatic organisms can be used to purify water after domestic use. 

In North America we grow enough food on the land so our freshwater 
resources have been used primarily for recreation, but the increased 
population growth has still put intense pressure on the aquatic 
ecosystems and the surrounding watersheds. This is seen in the nutrient 
enrichment of our waterways and the subsequent proliferation of aquatic 
vegetation and the deterioration of much of our surface water quality. 
In Canada aquaculture can be used to restore and maintain a healthy and 
balanced aquatic ecosystem and provide the added advantage of supplying 

- 22 - 

fish protein. We cannot expect to maintain our freshwater resources in 
the pure primitive state while using our land intensely to support our 
present population. We must look at every available technology to 
improve and maintain our freshwater resources. In Canada there seems to 
be a real potential for biological control of aguatic vegetation. 

Since the mid-1960s extensive research has been conducted around the 
world on the use of herbivorous organisms to harvest and control aguatic 
vegetation. Most of the research has been directed towards the 
determination of the efficiency of the white amur fish ( C tenopharyngodon 
idella ) as a biological control agent for controlling noxious aguatic 
weed growth. Emphasis has been on the evaluation of the effects of 
space and plant nutrients resulting from the destruction of excessive 
weed growth in the aguatic ecosystem. 

The Netherlands has about 150,000 ha of surface water, much of it in 
canals and drainage ditches. Filamentous algae create the major 
problems, but these waterways also contain extensive populations of 
higher plants. The Dutch started to investigate the potential for the 
use of the white amur or grass carp in 1966 with the importation of fish 
from Hungary and Taiwan. The impact studies in the Netherlands showed 
that the fish caused less ecological damage than herbicides and that 
dramatic changes in water guality did not occur. Czechoslovakia has 
been importing the white amur from Russia for the control of rooted 
aguatic macrophytes since the mid-1960s. 

Austria has used the white amur since the early 1970s and has stocked 
most of its lakes and ponds with the fish. It has been in major 
Austrian river systems for the last 16 years without reproducing 
naturally. In West Germany the stocking of white amur has proven not 
only economical and cheaper than herbicides but environmental impact 
studies on the effect the grass carp has on native fish species have 
shown that the survival and growth of native species have not been 
adversely affected. 

In North America the U.S. Army Engineers Waterways Experiment Station 
has been planning and conducting large-scale operations and management 
tests using grass carp to control aguatic plants such as hydrilla 
( Hydrilla verticillata ) in the state of Florida. Their original 
research was concerned with the efficiency of the diploid fish as well 
as the long-term effect of the fish on the water guality. In 1980, the 
Bureau of Reclamation, Division of Research entered into a cooperative 
agreement with the U.S. Fish and Wildlife Service, The California 
Coachella Valley Water Users Organization, the Imperial Irrigation 
District of California and three State of California agencies to conduct 
research into the evaluation of the sterile triploid white amur for 
controlling aguatic weeds in the irrigation canals in southern 

- 23 - 

The favorable results from these studies prompted the Province of 
Alberta to establish a research committee on the potential use of 
biological organisms such as sterile grass carp to control aquatic 
vegetation in southern Alberta irrigation canals. The Committee is 
composed of representatives from the Alberta Fish and Wildlife Division, 
the Vegreville Environmental Research Centre, and the Pollution Control 
Branch of the Alberta Department of Environment; the Alberta Department 
of Agriculture, Irrigation Planning Division; Agriculture Canada, 
Lethbridge Research Station; and the Irrigation Projects Managers 
Association of southern Alberta. The research project is investigating 
certified imported stocks of grass carp fry under quarantine for 
potential diseases and parasites and studying their growth and 
development under laboratory conditions. The field studies will 
determine the seasonal water quality and vegetative biomass of selected 
southern Alberta irrigation canals before and after the introduction of 
sterile grass carp. Investigations will include the growth and survival 
of these fish under Alberta climatic conditions. 

If these studies prove successful then further research into the 
potential for the use of other herbivorous organisms such as other fish, 
snails, and crayfish should be conducted. Studies on the harvesting and 
marketing of the grass carp as a source of fish protein for human food 
and as food supplements should be conducted. 

Chemical (herbicide) control 

Excessive aquatic weed infestations can be killed, controlled, or 
maintained at acceptable plant population densities through the use of 
aquatic herbicides and plant growth inhibitors. They offer an effective 
way to restore the flow rate of water through irrigation conveyance 
systems. Generally, the management of nuisance aquatic plant biomass is 
easiest and most economical through the use of aquatic herbicides. 
However, chemical management techniques are usually short-term, lack 
target plant specificity, may have undesirable side effects on other 
aquatic organisms, and be toxic to specific aquatic animals. The 
aquatic herbicide program is only a treatment and not a cure. Hence, 
once the herbicide program is started, it must be continued on a yearly 

Before any aquatic herbicides are applied to water the applicator must 
become familiar with the federal, provincial and local regulations. 
Only federally licensed herbicides may be used and the label 
restrictions must be followed. Standard safety precautions must be 
followed and particular care must be taken to avoid herbicide spillage 
where children and pets may come in contact with the herbicide. In 
public waters a provincial permit is required and the applicator must be 
licensed by the province. 

- 24 - 

The small 13.5-22.5 liter garden pressure-type sprayers available from 
most hardwares, garden supply stores, and farm supply centres are more 
than adequate for treating small ponds, dugouts, and irrigation 
conveyance systems. For ponds and lakes greater than 5-10 ha the use of 
larger commercial or farm field-type sprayers is recommended. In many 
cases the sprayer with its tank and pressure system can be loaded onto a 
flat-bottom boat or pontoon boat with a small outboard motor and be used 
for lakes up to 50 ha in size. It must be remembered that a large body 
of water cannot be treated at one time. Generally, no more than 10 to 
20 per cent of the surface area should be treated at one time with 
successive treatments every third day. This is to prevent a massive 
oxygen depletion from the decaying aquatic vegetative biomass that is 
knocked down by the herbicide. Thus, large sprayers and large boats are 
of little value in aquatic herbicide spraying. 

Granules can be spread by hand-operated, crank-type seed or fertilizer 
spreaders for spot treatment of areas around boat launching sites, 
docks, and swimming areas. Large commercial versions are available for 
tractor power takeoff or battery operation but again the goal should not 
be to see how much can be done in one day but to treat a small area very 
uniformly with no skips or excess material applied at any point. 
Helicopters have been used in the United States for liquids and granules 
but it is impossible to see any such application in Canada because of 
the diversity of our aquatic environments, the diversity of our 
irrigated crops, and the multiuse concept of our aquatic ecosystems. 

Aquatic herbicide applications should start near the shore and move out 
into deeper water so that fish and other aquatic organisms are driven 
out of the treatment area. Particular attention must be paid to inflow 
areas since the herbicide must have sufficient contact time with the 
aquatic vegetation to permit absorption. Inlets and spillways must be 
closed and the treated water generally ponded for a minimum of three 
days before it is allowed to flow out of the area. 

Where possible, the aquatic herbicide treatments should be made in the 
late spring or early summer when the aquatic plants are young and 
actively growing. In the case of emergent vegetation, applications must 
be made at the early inflorescence stage before the plants begin to 
flower. Treatments must be made on calm days to avoid the possibility 
of spray drift. It has been found that late evening applications allow 
the herbicide to mix through the water column and be absorbed more 
readily by the aquatic vegetation during darkness. This also applies to 
the application of herbicides to emergent, floating-leaved and ditchbank 
vegetation where the herbicide is absorbed by the plant tissue and 
translocated down the stem and into the rootstocks during darkness. 


The most common algae problems are from filamentous algae in dugouts and 
irrigation reservoirs where they cause stagnation and plug intake 

- 25 

screens, pumping systems and nozzle heads in irrigation delivery 
systems. Phytoplanktonic algae are usually associated with domestic 
water supply reservoirs and small farm and ranch systems. Here the key 
to success is the early application of herbicides before the algal 
population becomes dense since early application will have a better 
chance of getting the entire infestation and will enable the water 
manager to use less herbicide and hence be more economical. The water 
manager must check the pond or irrigation reservoir daily since an algal 
bloom may appear overnight. Algae exist in the water column all year 
round but under cool water temperatures they exist near the bottom of 
the water body. As the water temperature warms and the sunlight begins 
to penetrate beneath the surface of the water, the algae begin to grow. 
As the water temperature approaches the 22 °C point, growth is greatly 
accelerated and the scums and dense floating mats begin to appear at the 
surface of the water. In the spring, daily checks should be made of the 
water bodies and daily microscopic examination of surface and subsurface 
water samples is an excellent practice for domestic reservoir water 
managers. Although every water body is different, water managers can 
generally become acquainted with their own systems. Through experience 
they will learn to anticipate when the critical first treatment in the 
spring is necessary and then read the seasonal signs for possible 

The herbicide used and the dosage required will depend on the type of 
algae involved, the degree of infestation, the water chemistry of the 
pond or reservoir, and the use to which the water is put. Appendix I 
lists the herbicides registered for algae control and the restrictions 
placed on each chemical. On the Prairies, the surface water is 
generally hard with a pH in the high 7 to mid 8 range and will require 
lower dosages applied in split treatments three to four times per 
season. For a split treatment, the recommended dosage is divided in 
thirds and applied as a surface spray every second day over a one-week 
period. This split treatment is also a good idea where trout are in the 
pond since trout are very sensitive to copper sulfate at levels above 1 
ppm. Early treatment before a dense algae population occurs will ensure 
that when the algae are killed there is no serious oxygen depletion. 
The destruction of the algal population and the subsequent decay of the 
algal organic matter can cause a serious drop in the dissolved oxygen 
content of the water column. If this starts to occur it may be 
necessary to provide supplementary oxygen by aeration. Aeration cools, 
circulates, and oxygenates, making a healthier aquatic ecosystem. 


The submergent aquatic plants spend their entire life cycle beneath the 
surface of the water, except during flowering and pollination. The key 
to successful herbicide control of these plants is to apply the 
herbicide when the plants are actively growing and before the vegetative 
biomass becomes too great. This means applying the herbicide beneath 

- 26 - 

the surface of the water just above the growing tip. With granules this 
is a simple matter but with liquid herbicides this requires the 
injection of the material underwater. A pressure-type application 
system and an extension system to permit delivery of the herbicide 
1.0-1.5 meters underwater must be used. The herbicide should be diluted 
with 5-10 parts of clean water to permit uniform application of the 
material to the test area. Remember that beneath the surface of the 
water there is very little water movement so the application should be 
made in a criss-cross manner, north to south first and then east to 
west. It has been found at the Lethbridge Research Station that evening 
applications permit the herbicide to diffuse through the water column 
and to be more uniformly absorbed by the submergent aquatic plants. 
Evening applications also permit a reduction in the herbicide dosage by 
up to 25 per cent. 

For large water bodies, spot treatment or channel cutting is a very 
effective way to reduce the aquatic nuisance population and at the same 
time not create serious oxygen depletions from massive weed kills. 
Remember, if it has taken many years to build up a serious aquatic weed 
infestation, it cannot be corrected with one massive herbicide 
treatment. Plan the control program to remove the aquatic infestation 
for 3-5 years and the management program for another 2-4 years. 


Floating-leaved aquatic plants such as water lilies and water smartweeds 
are valued by fishermen and outdoor enthusiasts but may cause serious 
problems when they take over a pond or boating area. Herbicides must be 
applied to the actively growing leaves by surface spraying. It is best 
to add a wetting agent to the herbicide mixture to ensure uniform 
coverage and hence maximum absorption of the herbicide. Spray to the 
point of runoff. Evening spraying has proven effective since the 
herbicide is absorbed and translocated down the stems to the underwater 
tubers before the plants are exposed to sunlight again. 


The free-floating aquatic plants such as the bladderworts, coontail, 
some buttercups and the duckweeds must be surface-sprayed but without 
the addition of wetting agents. The plants exist in the upper 12 cm of 
the water column and will absorb the herbicide from the water. Evening 
spraying has proven very effective on the Prairies. The lowest 
recommended dosage should be used since the plants appear very sensitive 
to all registered aquatic herbicides. 

- 27 - 


Emergent aquatic plants grow in moist, water-saturated, swampy shoreline 
areas and extend out into the water to a depth of 30 cm from the shore. 
Most emergent plants are greatly valued by wildlife for food and 
shelter. They also stabilize the shoreline and banks to prevent water 
erosion. Before any control program is started, the long-term impact of 
vegetation removal must be examined. Foliar herbicide sprays should be 
applied in the early summer at the time of emergence of the flowers or 
inflorescences. At this time there is a narrow one-month period when 
the translocation of photosynthates in the plant is down from the leaves 
into the tubers and this is the most effective time for herbicide 
application to achieve total plant kill. Depending on the season, this 
is usually from the 15th of June to the 15th of July with effective 
control dropping off during August to almost no control in September. 
During this 'window' period it is necessary to have maximum absorption 
of the herbicide and so additional wetting agent must be added to the 
spray mixture. The spray must be applied to the point of runoff and 
every leaf must be thoroughly covered. Cattail control has been 
improved by evening applications so the herbicide is absorbed overnight 
and translocated in the carbohydrate stream down into the tubers. This 
is particularly true when using the herbicide Gramoxone. 


Many of the marginal and ditchbank plants are valuable plants for 
waterfowl and wildlife as shelter for nests and cover for the young. 
They also prevent bank erosion and act as vegetative biological filters 
to prevent the introduction of sediments and nutrients from surface 
runoff. At times it may be desirable to remove the vegetation from the 
bottom of the canal bed but leave the grass species on the upper inner 
banks and over the tops of the banks. Here the foliar application of a 
herbicide should be made in large volumes of water and sprayed to the 
point of runoff. The addition of a wetting agent will assist in 
ensuring uniform coverage and maximum herbicide absorption. 

For the control of terrestrial weeds the manager should use the 
recommendation for the control of weed species used by farmers but must 
exercise care to avoid the contamination of irrigation water by 
overspray and spray drift. 

The use of the wick applicator is excellent since the weeds are wiped 
with the herbicide-saturated wick and there is no chance of herbicides 
getting into the irrigation water. The wick applicator also permits the 
treatment of tall weeds while leaving the low-growing grasses 
untouched. This retains the grasses for ditchbank stabilization and 
surface runoff filtration. 

- 28 - 


Water quality is just begining to be recognized as important not only to 
the development of aquatic vegetation but also to the effectiveness of 
aquatic herbicides. Much more research is necessary before the full 
role of the nutrients in the water column and the sediments is 
understood. Knowledge of the effect that seasonal variations in 
nutrient content have on the growth and development of algae and aquatic 
macrophytes is just beginning to enable us to establish guidelines for 
freshwater lakes, reservoirs, dugouts and irrigation conveyance 
systems. It is wise for all water users and water managers to start 
accumulating a database on their aquatic systems now. At least one 
sampling should be made every spring, midsummer, early fall and once 
through the ice in midwinter. These measurements will enable the 
manager to compare the water quality from year to year and should 
provide advanced warning of potential problems. Summer measurements 
will assist in the better utilization of aquatic herbicides under 
varying levels of pH, electrical conductivity, water hardness, soluble 
salts concentrations, and total solid and total dissolved solid 
concentrations. This information is also useful when designing and 
installing domestic water filtration and purification systems. 

- 29 - 


Allan, J. R. and Braglin-Marsh, J. A.. 1987. Chemical analysis of 
surface and irrigation water in relation to aquatic plant management. 
Technical Bulletin 1987-1-E. Research Branch, Agriculture Canada, 

Bardach, J. E., Ryther, J. H. and McLarney, W. 0. 1972. Aquaculture. 
The farming and husbandry of freshwater and marine organisms. 
Wiley-Interscience Publications, John Wiley and Sons, Toronto. 

Bennett, G. W. 1971. Management of lakes and ponds. Van Nostrand 
Reinhold, New York. 

Fasset, N. C. 1966. A manual of aquatic plants. The University of 
Wisconsin Press, Madison, Wisconsin. 

Gangstad, E. 0. 1986. Freshwater vegetation management. Thomas 
Publications, Fresno, California. 

Gunnison, D., Barko, J. W. 1988. The rhizosphere microbiology of 
rooted aquatic plants. Miscellaneous Paper A-88-4. U.S. Army Engineers 
Waterways Experiment Station, Vicksburg, Mississippi. 

Mackenthun, K. M. , Ingram, W. M. and Porges, R. 1964. Limnological 
aspects of recreational lakes. U.S. Department of Health, Education, 
and Welfare, Public Health Service Publication No. 1167. U.S. 
Government Printing Office, Washington, D.C. 

Mitchell, R. 1972. Water pollution microbiology. Wiley-Interscience 
Publications, John Wiley and Sons, Toronto. 

Moultonn, F. R. (ed. ) 1939. Problems of lake biology. Publication No. 
10/ American Association for the Advancement of Science. The Science 
Press, Lancaster, Pennsylvania. 

Reid, G. K. 1961. Ecology of inland waters and estuaries. Reinhold 
Publishing, New York. 

Rutter, F. 1953. Fundamentals of limnology. University of Toronto 
Press, Toronto. 

Sculthorpe, C. D. 1967. The biology of aquatic vascular plants. 
Edward Arnold (Publishers) Ltd., London. 

Soil Conservation Service. 1971. Ponds for water supply and 
recreation. Agric. Handbook No. 387, U.S. Department of Agriculture. 
U.S. Government Printing Office, Washington, D.C. 

Warren, C. E. 1971. Biology and water pollution control. W. B. 
Saunders Co., Toronto. 

- 30 - 

Welch, P. S. 1952. Limnology. McGraw-Hill Book Co., New York, 
Wetzel, R. G. 1975. Limnology. W. B. Saunders Co., Toronto. 

- 31 - 


The use of chemicals in aquatic ecosystems is subject to federal 
registration of the herbicide and then provincial regulations as to 
their use, mode of application, restrictions on using treated water and 
waiting periods before treated water can be used for irrigation, 
livestock watering or human consumption. Contact provincial authorities 
to obtain regulations and permits where necessary. The labels must be 
read carefully and followed. All necessary health regulations must be 
followed to protect the applicators and the general public. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 
Dosage rates: 

Time of application: 



Contact herbicide causing disruption of 

cell enzyme systems. 

Irrigation ditches - moving water 

Injected beneath the water at 0.6-11 L/cm 

(0.12-2.3 gal cfs) applied over 0.5-4.0 


Apply when plants are young and water 

temperature is over 20°C. 

Treated water must not be used for 

drinking water or released into sources of 

drinking water. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 
Dosage rate: 

Time of application: 

1H-1, 2,4-triazol-3-amine 


Inhibits photosynthesis and regrowth from 

buds; slow absorption but good 

translocation throughout plant. 

Drainage ditches and marsh areas 

Foliar spray to the point of runoff in 45 

L of water with additional wetting agent 

at 2.25-11.2 kg/ha. 

Early infloresence stage to appearance of 

mature flower head. 

Avoid contaminating drinking water 

supplies and spray drift onto other crops. 


This is a water-soluble dye that suppresses algal growth by reducing the 
penetration of sunlight into the water column. Its use is only 
practical in fountains and small ornamental water gardens. 

- 32 - 

Chemical name: 

Type of plants controlled: 
Mode of action: 

Type of aquatic environment: 
Dosage rates: 

Time of application! 


8% copper as copper ethylenediamine or 

copper triethanolamine complexes 

Filamentous and planktonic algae 

Acts as general cell toxicant. Copper 

chelate is absorbed from the water column. 

Farm ponds and dugouts - standing water 

0.2 5-1.0 ppm applied to the water column 

as a surface spray. Split treatments 

applying 1/3 of the dosage every second 

day may prove more effective and safer 

when fish are in the pond. 

Apply at FIRST sign of algae. Early 

application permits lower dosages to be 


Not for use in public or potable water 



Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment! 
Dosage rates: 

Time of application: 

2, 2-dichloropropanoic acid 


Absorbed by roots and foliage and 

translocated throughout the plant. 

Accumulates in young tissue and buds. 

Drainage ditches and marsh areas 

Foliar application at 11.2-22.4 kg/ha in 

450 L water with additional wetting agent 

sprayed to point of runoff. 

Early inflorescence to mature flower head. 

Do not spray in high winds; avoid spray 

drift. Formulations mildly corrosive so 

wash equipment throughly. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment; 
Dosage rate: 

3 , 6-dichloro-2-methoxybenzoic acid 

Emergent (cattails) 

Selective herbicide absorbed and 

translocated from both the leaves and 

roots with translocation to the apical 

meristems. Growth-hormone type of 

activity causes defoliation, swelling of 

stems, destruction of conductive tissue, 

death of growing points and necrosis of 

the plant. 

Marshes, swailles, swampy areas 

Cattails require 4-6 kg/ha dicamba plus 6 

kg/ha of dalapon. 

- 33 - 

Time of application: 


Apply at early growth stages up to the 
early inflorescence stage, wetting foliage 
to point of runoff. 

Avoid direct application to water bodies 
and do not use treated water for 
irrigation for 14 days or for livestock 
for 7 days. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aguatic environment; 
Dosage rate: 

Time of application: 


2, 6-dichlorobenzonitrile 

Submergent, floating-leaved and emergent 

Nonselective herbicide absorbed mainly by 

the roots but with some absorption by 

submerged stems and leaves. Disrupts 

plant cell division in the growing tips 

causing death. 

Ponds and ornamental water gardens 

Applied to dewatered pond beds at 5.5-17 

kg/ha or as granulars spread over the 

surface of the water which sink through 

the water column. 

Apply to dewatered pond, reservoirs and 

shorelines in early spring before aguatic 

plant growth begins. May be applied as a 

granular formulation spread over the 

water's surface from a boat. 

Treated water should not be 

irrigation, livestock watering, 

consumption. A 90-day waiting 

reguired prior to the use of 

treated waters. 

non-selective and may 


used for 

or human 

period is 

fish from 

Herbicide is 

kill shoreline 

Chemical name: 

Type of plants controlled; 

Mode of action: 

Type of aguatic environment; 

6,7-dihydrodipyrido[l,2-a:2 ' ,l'-c] 

pyrazinediium ion 

Submergent, free-floating, floating-leaved, 

emergent, and filamentous algae 

Contact type, non-selective, rapidly 

absorbed by foliage but very little 

transloction. Forms a free radical in the 

plant that is readily reoxidized releasing 

very active free radicals such as 

peroxides within the plant cells. 

Drainage and irrigation canal, farm ponds 

and dugouts, reservoirs and lakes 

- 34 - 

Dosage rates: 

Time of application: 


2.25-4.50 kg/ha in 45 L of water injected 
underwater for submergent vegetation 
or surface-sprayed for free-floating, 
floating-leaved or filamentous algae. 
Evening applications assist in mixing 
throughout the water column giving uniform 
coverage and better absorption by the 
plant material before herbicidal activity 
begins in daylight. 

Must be applied after the green plant 
material begins to show in the water but 
before the plants begin to flower and 
become encrusted with marl. Water 
temperature should be 20°C. 

Do not use treated water for irrigation 
for 5 days or until chemical analysis 
shows less than 0.01 mg/L Diquat ion. Do 
not apply to muddy water or to plants 
heavily encrusted with marl or mud. Do 
not apply in high winds and avoid spray 
drift to food forage or desirable 
vegetation. Applicators should exercise 
extreme caution in handling Diquat. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 

Dosage rate: 

Time of application: 

N' -(3,4-dichlorophenyl) -N,N-dimethylurea 
Ditchbank grasses and broadleaf deep- 
rooted weeds 

Herbicide is readily absorbed through the 
root system and translocated upward into 
the plant. Disrupts the Hill reaction in 
the plant cells. 

For general weed control in drainage and 
irrigation ditches where the ditch beds 
are intermittently filled and drained. 
For total annual weed control apply at 
4.48-12 kg/ha and for grasses and 
deep-rooted perennials at 12-35 kg/ha. 
Higher rates will give 3-5 years control. 
Apply in 450-900 L water to ensure uniform 
coverage of area to be treated. 
Apply to dry canal beds in the fall before 
freeze-up. Adsorption increases as clay 
content and organic matter content of soil 
increase. Leaching from treated soils in 
the spring flush is greatest from sandy 

- 35 - 


Be sure to flush the canal with irrigation 
water in the spring before using ANY water 
for irrigation. 

Chemical name: 

Type of plants controlled: 
Mode of action: 

Type of aquatic environment: 
Dosage rate: 

Time of application: 


7-oxabicyclo[2, 2, l]heptane-2 / 3-dicarboxylic 
acid as dipotassium salt 
Submergent vegetation 

Contact type herbicide that inhibits 
protein synthesis. Very limited trans- 
location throughout the plant. 
Lakes, farm ponds and dugouts 
72-119 L/ha as a liquid and 374-631 
kg/ha. Herbicide must remain in contact 
with the target plants for 2 hours. 
Apply to young, actively growing 
vegetation when water temperature is at 
least 18°C. 

Do not use treated water for irrigation 
for 7 days, do not use for livestock or 
domestic use for 7-14 days, do not swim in 
the water for 24 hours and do not eat fish 
from treated water for 3 days. Applicators 
should use due care and read all label 


Chemi c al name : 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 

Dosage rate: 

Time of application: 

N- ( phosphonome thy 1 ) glyc ine 

Emergent aquatic vegetation and green 

ditchbank vegetation 

The herbicide apparently disrupts the 

biosynthesis of phenylalanine and other 

aromatic compounds in the growing plant. 

Dry drainage and irrigation canals and 

shorelines for cattails and general weeds 

and brush 

Emergent vegetation at 7.0 L/ha hectare 

sprayed to the point of runoff. Ditchbank 

vegetation at 5.3-8.8 L/ha applied to 

green foliage. 

When vegetation is actively growing and 

with emergent aquatic vegetation, best 

results are obtained in the early 

inflorescence state until the beginning of 

the mature seed head. 

- 36 - 


Avoid spray drift and direct application 
to surface of water. Do not use 
contaminated water for irrigation or 
livestock use. Do not apply within 0.8 km 
upstream of domestic water intake. Do not 
exceed the 8.8 L/ha rate. Effects on 
target plants may not appear for up to 4 
weeks depending on the growth stage of the 
plants . 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 
Dosage rate: 

Time of application: 

(4-chloro-2-methylphenoxy) acetic acid 

Emergent aquatic vegetation and ditchbank 

weeds and brush 

Selective broadleaf foliage herbicide 

acting as a growth regulator absorbed 

through the foliage and readily 

translocated throughout the plant. 

Generally accumulates and is active in the 

meristematic tissue. 

Dry drainage and irrigation canals and 

along shorelines 

0.6-1.12 kg/ha applied as a low volume 

spray in 9-100 L water with additional 

wetting agent. 

Apply to actively growing plants where the 

herbicide is in contact with the plant for 

2-4 days. Herbicide is readily washed off 

by rain. 

Avoid spray drift and contamination of 

adjacent water bodies. 

Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment; 
Dosage rate: 

1,1' -dimethyl-4,4 ' -bipyridinium dichloride 


Submergent, free-floating, floating-leaved 

and emergent vegetation 

Contact type of herbicide absorbed by the 

foliage; may be translocated via the xylem 

under certain growing conditions. 

Emergent vegetation and as a 1:1 mixture 

with diquat for submerged vegetation 

General emergent control at 0.6-1.12 kg/ha 

with a compatible surfactant. For 

submerged vegetation injected underwater 

as a 1:1 mixture with diquat at 4.5-9.4 

L/ha mixed 10:1 with clean water. 

- 37 

Time of application: 


Apply in the late spring to early summer 
when the plants are actively growing. 
Treat before the biomass gets too great. 
For submerged vegetation inject underwater 
to the area just above the growing plants 
and criss-cross the plot to ensure uniform 
coverage. Evening application to emergent 
and submerged aquatic vegetation seems to 
improve herbicide uptake. 

For emergent vegetation avoid spray drift 
and contamination of standing water. Do 
not use treated water for irrigation for 5 
days or until chemical analysis shows less 
than 0.01 mg/L. Do not apply to muddy 
water or to plants heavily encrusted with 
marl or mud. Do not apply in high winds 
and avoid spray drift. 

Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 

Dosage rate: 

Time of application: 

6-chloro-N,N' -diethyl-1, 3, 5-triazine-2,4- 

Used as a selective herbicide for the 
control of broadleaf and grassy weeds in 
perennial grasses used for ditchbanks and 
as non-selective control of all vegetation 
in the canal bottoms of intermittently 
filled and drained irrigation canals in 
community pastures. 

Herbicide is absorbed through the roots 
with little foliar absorption. 
Translocated to the apical meristematic 
tissue where it inhibits photosynthesis. 
Dry drainage and intermittently filled 
irrigation canals. Beach area above the 
high water level. 

For selective control of broadleaf weeds 
in established grasses apply at 2.0-4.5 
kg/ha in 80-100 L of water to ensure 
uniform coverage. For total vegetation 
control apply in the fall to dewatered 
canal bottoms at 15-22 kg/ha in 150-200 L 
water to ensure complete coverage. Do not 
treat above the usual operating water 
level of the canal. 

Generally apply to bare soil as herbicide 
must be root-absorbed. For total 
vegetation control apply in the fall just 
before freeze-up. The winter moisture 
will wash the herbicide into the soil 
where it will be bound in the top 10 cm of 

- 38 - 


Simazine is strongly adsorbed on clay and 
muck soils with little leaching downward 
due to its low solubility in water. To be 
safe, the first irrigation water in the 
spring should be flushed out of the system 
and wasted. Carefully and correctly 
applied herbicide to the canal bottom will 
give 3-5 years control before retreatment 
is necessary. Subsequent treatments at 
5-10 kg/ha generally restore weed control 
for another 5 years. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 
Dosage rate: 

Time of application: 


2.4-D as dimethylamine salt (liquid) 
Emergent aquatic plants and broadleaved 
weeds and brush 

Selective as a systemic growth regulator 
with hormone-like activity. Readily 
absorbed from the roots and foliage and 
translocated throughout the plant. 
Inhibits or stimulates cell division in 
meristematic tissue causing necrosis in 
young tissue and death in mature tissues. 
Dry drainage and irrigation ditches 
Canal bank vegetation at 1-2 kg/ha; 
emergent vegetation at 2-4 kg (active 
equivalent ) /ha . 

Apply in early spring when vegetation is 
actively growing. Additional water and 
wetting agent applied to the point of 
runoff will assist in the uptake of the 

Liquid formulations are for use on 
emergent and ditchbank weeds and brush. 
Do not spray during high winds and prevent 
spray drift to nontarget vegetation. Do 
not use contaminated water for irrigation, 
livestock watering or domestic use for 3 
weeks OR until chemical assays contain 
less than 0.1 ppm (0.1 mg/L) of 2,4-D acid. 


Chemical name: 

Type of plants controlled: 

Mode of action: 

Type of aquatic environment: 

2,4-D as butoxyethanol ester (Granular) 

Submergent aquatic vegetation, especially 

the water milfoils 

Same as above 

Drainage ditches and farmponds and dugouts 

where water is not used for irrigation 

- 39 - 

Dosage rate: 

Time of application! 


9.5-38 kg/ha using the higher dosage for 
heavy infestations. 

Apply granulars through the water column 
in early spring while the submerged 
vegetation is actively growing. Use 
criss-cross application methods to ensure 
uniform coverage. Plots should be 
separated by a buffer, untreated plots of 
egual size. 

Do not use treated water for irrigation, 
livestock watering or domestic use until 
chemical assays of treated water contain 
less than 0.1 ppm of 2,4-D acid. Contact 
local fish and game authorities for 
specific restrictions on fishing and 

- 40 - 

Figure 1. Typical prairie aquatic ecosystems. A. Shallow irrigation 
reservoir located along the foothills of southern Alberta. B. Main 
delivery canal out of Travers Reservoir near Taber, Alberta. C. 
Henderson Lake at Lethbridge, Alberta, which serves as an on-stream 
irrigation storage reservoir and recreational lake in the center of the 
city. D. Typical farm dugout used for livestock watering and 
irrigation as well as domestic water after filtration and purification. 

- 41 - 

Figure 2. Life cycle of the submergent rooted aquatic macrophyte, 
Potamogeton richardsonii . A. Vegetative shoot of pondweed. B. Leaf 
structure showing the clasping characteristic of the leaf blade around 
the stem. C. Flower bud initiation in the axil of leaves underwater. 
D. Flower head extended to the surface of the water for wind 
pollination. E. Details of the flower head showing formation of a 
single seed at the tip of the flower head. F. Young shoots of pondweed 
at the sediment surface before water is turned into the reservoir. G. 
Young pondweed rhizome taken from 15-20 cm beneath the sediment surface 
in the spring. H. Same rhizome 7 days later showing the young plant 
vegetative shoot and the horizontal rhizome continuing its growth and 
the appearance of young roots at the site of the next vegetative shoot. 

- 42 - 

Figure 3. Life cycle of the submergent rooted aquatic macrophyte, 
Potamogeton pectinatus . A. Vegetative shoot of pondweed. B. 
Appearance of the plant in flowing water. C. Appearance of the plant 
in standing water growing with other rooted aquatic plant species. D. 
Overwintering tuber. E. Sprouting tuber showing root and shoot 
development. F. Vegetative shoot showing the runner and the start of a 
second plant from the parent tuber. G. Flower head showing the 
characteristic space or separation of the first and subsequent flower 
whorls. H. Details of the flower head showing flower structure. 

- 43 - 

Figure 4. Life cycle of the submergent rooted aquatic macrophyte, 
Myriophyllum verticil latum . A. Vegetative shoot of water milfoil. B. 
Mature plant of water milfoil showing the production of overwintering 
buds or turions at the tip of each vegetative branch. C. Appearance of 
the plant in flowing water. D. Appearance of the plant in standing 
water with other rooted aquatic plant species. E. Stem fragments 
showing root development at the base of the shoot. F. Leaf structure 
of overwintering turion. G. Typical leaf structure of water milfoil 
plant. H. Flower head at the surface of the water. I. Flower head 
extending into the air for wind pollination. J. Details of flower head 
showing characteristic flower bracts used to identify Myriophyllum spp. 
K. Details of Myriophyllum spp. turions. 

- 44 - 

Figure 5. Life cycle of the free-floating aguatic macrophyte, 
Utricularia vulgarius . A. Vegetative shoot completely lacking roots 
but possessing small black bladders that assist in the trapping of 
aquatic organisms for food. B. Overwintering turion of the common 
bladderwort. C. The expansion of the turion in the spring when water 
temperature reaches 15°C. D. Details of leaf structure showing the 
small bladders. E. The free-floating bladderwort along the shore of a 
stock-watering pond showing the showy flower. F. Details of the flower 
head. G. Typical habitat of the common bladderwort showing the 
numerous flower heads. 

- 45 - 

Figure 6. Life cycle of the floating-leaved aquatic macrophyte, 
Nymphyia odorata . A. The typical plant growing under greenhouse or 
ornamental water garden conditions. B. Aerial view of water lilies 
growing in lakes in northern Alberta. C. Crown of water lily plant 
showing vegetative shoots. D. Tuber of water lily plant showing 
extended leaf petiole. E. Water lily plant planted 
ornamental water garden. F. Detail of floating leaf 
plant. G. Water lily plant with fully open flower. H. 
opened water lily flower. 

in tub in an 

of water lily 

Detail of the 

- 46 - 

Figure 7. Life cycle of the emergent aguatic macrophyte, Typha 
latifolia . A. Colony of cattails growing at the edge of a pond. B. 
Underground rhizome system showing two vegetative shoots and the root 
system. C. Young cattail shoots in 10-20 cm of water. D. Mature 
plant showing leaf formation and structure. E. Crown of a mature plant 
with root system. F. Early infloresence stage or 'window' when plants 
are most susceptible to chemical control showing male flowers above the 
female flowers. G. Young flower head with developing female portion 
and the male portion above after the pollen is shed. H. Mature cattail 
head just begining to shed the wind-disseminated seeds. I. Exploded 
cattail seed head with winged seeds ready to be wind-blown to potential 
marsh sites. 



3 T073 aaat,so?5 b