Brazilian Water Milfoil

Myriophyllum aquaticum (Vell. Conc.) Verdc.

Synonyms - Enydria aquatica, Myriophyllum brasiliense, Myriophyllum proserpinacoides.
Family: Haloragaceae. 
Names:

Myriophyllum is from the Greek myrios meaning many and phyllon meaning leaf and refers to the many leaf segments on this plant.
Aquaticum is Latin for living in the water.
Brazilian refers to the country of origin and Milfoil is Latin meaning a thousand leaves.

Other names:

Parrots Feather refers to the feather like structure of the leaves.
Thread of Life.

Summary:

A long-tangle-stemmed, mat forming, perennial, fresh water plant with many feather like leaves in rings of 4-6 with larger leaves below the water line and smaller ones above.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Bright green or with a waxy bloom. Leaves are finely divided and feather like both above and below the water surface. Arranged in rings of 4-6 around the stem. Rings very close together near the top but separated near the base. Submerged leaves tend to rot leaving bare underwater stems.
Stipules -
Petiole -
Blade - Parallel sided, egg shaped or oval in outline.
Submerged leaves 35-40 mm long, obtuse tipped, deeply cut into 25-30 thread like segments up to 7 mm long.
Emergent leaves have a waxy bloom, 15-35 mm long with 18-36 linear or awl shaped segments, 4.5-5.5 mm long.

Stems:

Mats of tangled stems, yellow green, slender, 2000-5000 mm long. Hairless and smooth. Root at the nodes near the base. Stems are erect where they emerge from the water and are trailing underwater. Brittle and break off easily. Hairless.

Flower head:

Single flowers on a short stalk between 2 small bracts in the leaf axil.

Flowers:

Male and female flowers on separate plants usually.
In Australia all flowers are female.
Bracts - 2 small, white, awl shaped bracts, 1.2-1.5 mm long with one or two teeth or 3 lobes near the base.
Female flowers.
Have a short stalk.
Ovary - Prominent, pear shaped, 4 celled. White style and stigma with many fine translucent hairs.
Sepals - 4. White. Translucent. 0.4-1.5 mm long. Triangular.
Petals - None.
Male flowers.
May have a short stalk.
Sepals - Egg to triangular shaped, 0.7-0.8 mm long.
Petals - Yellow, weakly hooded and keeled, 3 mm long.
Stamens - 8
Anthers - Narrowly oblong.

Fruit:

None recorded in Australia.
Cylindric to egg shaped, 1.7 mm long with cylindric mericarps.

Seeds:

Doesn't produce seed in Australia.

Roots:

Fibrous. Threadlike. Arise from stem nodes. Attach to the stream bed.

Key Characters:

Robust perennial plants with stems 100-5000 mm long. Leaves all whorled and pectinate. Emergent leaves with 18-36 pinnae.

Biology:

Life cycle:

Perennial. Stem fragments produce roots to anchor the plant, then new stems emerge from buds. Grows mainly in summer and is semi-dormant in winter. Grows until it forms a dense mat on the water surface and waterlogged banks. Rarely grows in water more than 1.5 m deep. Flowers recorded in September, November and May.

Physiology:

Tolerates a wide range of temperatures including freezing. Grows best at high temperatures.
Uptake of nutrients and herbicides appears to be passive rather than active.
Increasing N, P, K, Ca, Mg and S increased growth 569.
Carbohydrate levels are probably lowest in autumn 570.
A bicarbonate medium was better than the standard Gerloff medium for growing Myriophyllum 571.

Reproduction:

Vegetative reproduction only in Australia.

Flowering times:

November to April in Perth.
Spring to autumn in WA.

Seed Biology and Germination:

No seed formed in Australia.
Seeds from M. spicatum loose some viability when dried but will tolerate at least 36 weeks of drying with 53% survival 572.

Vegetative Propagules:

Stem fragments break from the parent plant to form new plants.

Hybrids:

Other species of Myriophyllum hybridise and the hybrids can be more invasive than the parents 573

Allelopathy:

Not much allelopathy 574.

Population Dynamics and Dispersal:

Local spread is by stem fragments moving with the water flow. Wave action, boats and mechanical harvesting fragment stems.
Long distance spread is by dumping of discarded aquarium plants into water ways.
Prefers slow moving or stagnant water.
It has high growth rates 575.
Growth and development of Myriophyllum spicatum. Studies in a controlled environment have shown two distinct seasonal growth forms. In summer (150C-260C) a fine hair-like root system develops accompanied by rapid top growth; in winter (140C-60C) root growth is coarse and fibrous and the slow top growth is deep red; at the higher winter temperature, adventitious roots develop and the branches then abscise, producing the material for future infestations. Control may be possible mechanically or chemically in autumn and early winter to kill existing plants 576

Origin and History:

South America.
First recorded as naturalised in Centennial Park in Sydney in 1908.

Distribution:

NSW, QLD, SA, TAS, VIC, WA.
Invasive alien species in Africa 577, Australia 578, Britain 577;579, Japan 580;581, South Africa 582, USA 583.

Courtesy Australia's Virtual Herbarium.

Habitats:

Banks to water several metres deep.
It is rarely a problem in water more than 1.5 m deep 584.
A similar species M. spicatum (Eurasian Milfoil) is more invasive in eutrophic lakes and water with high P concentrations 584.

Climate:

Warm temperate and sub-tropical regions.

Soil:

Water saturated mud and gravels close to slowly moving or static fresh water.

Plant Associations:

Significance:

Beneficial:

Ornamental used in aquaria and ponds.
Vegetable.
Used as stock feed overseas.
It is capable of quickly transforming trinitrotoluene (TNT) in contaminated water 585 and used for phytoremediation of munition sites 586.
A related species M. triphyllum helps break down 1080 quickly 587.
May be useful for absorbing cadmium from water 588.
Extracts of the related Myriophyllum spicatum reduce algal growth 589, reduce mosquito larvae 590;591 and reduces mosquito populations592.

Detrimental:

Forms dense mats that impede water flow. Sections of floating mats break off and block irrigation and hydro-electric equipment. Invades rice fields reducing yields. Mats of weed interfere with recreational use of waterways.
Competes with native water plants and provides ideal breeding grounds for mosquitoes.
Slows stream and drain flows, which may result in flooding.
Weed of freshwater streams, dams and drains.

Toxicity:

Not recorded as toxic.

Symptoms:

Treatment:

Legislation:

Noxious weed WA and Tas.

Management and Control:

Prevent movement of stem fragments, especially by dumping of aquarium refuse. Control of existing infestations is highly desirable because of the possibility of explosive spread if male forms of the plant establish in Australia. Mechanical removal provides useful temporary control. Covering small dams with black plastic is effective 593.
Reduce the quantity of nutrients (especially phosphorous) entering the water body.
Chlorsulfuron and 2,4-D provide better control than glyphosate.
The effect of boats and management plans on spread has been modelled 594 and management strategies 595.
It is unlikely to establish in streams or drains with more than 13 high-flow disturbances per year 596 or in areas shaded by trees 597.
Herbicide trials
2,4-D
50 kg /ha 2,4-D granules gave good control in US on M. heterophyllum and M. spicatum without exceeding irrigation threshold of 100 ppb 573.
2,4 D at 1340 and 670 g/ha provided 100% control 598.
Spring to autumn applications of 2,4-D butoxy ethyl ester (19%) at 227 kg/ha provided good control whereas 2,4-D Na salt at 114 kg/ha only provided control in shallow areas and poor control in deeper open areas on M. heterophyllum 599.
6.48 kg 2,4-D amine applied in summer and repeated 2 months later provided better control than diquat, glufosinate or glyphosate 600.
The effect on algae after treatment depended on the species of alga present 601.
Severe Eurasian water milfoil injury occurred when exposed to 0.5 mg for 72 h, 1.0 mg for 36 h and 2 mg for 24 h. The threshold levels for control of Eurasian water milfoil was established in the 1.0 mg for 48 h and 2.0 mg for 36 and 48 h exposures 602.
Controlled release formulations provide good extended control 603.
1.5 kg diquat + 1.5 kg 2,4-D ester lasted about 60 days 604.
The distribution of Myriophyllum spicatum in Washington, USA, and its control with an invert oil emulsion of 2,4-D 583.
2,4-D did not adversely affect the non-target components in the sampled ecosystem 605.
Bensulfuron
20-100 ug/L bensulfuron provided good control of M. spicatum over a 12 week period. The length of exposure was more important the concentration 606.
Bensulfuron methyl at 100-300 g/ha applied to dry irrigation channels controlled M. variifolium for 4-5 months after water was returned a week after application 607;608.
Carfentrazone
200 ug/L carfentrazone did not provide adequate control 609;610.
Chlorfenac
20 kg chlorfenac/ha seemed a promising chemical treatment but 3 ppm in the water was ineffective 593.
Chlorsulfuron
EC50 = 10-9 M 611.
18.75-37.5 g chlorsulfuron/ha containing 0.5% by vol. of a non- ionic surfactant provided effective control of Myriophyllum aquaticum. An infestation sprayed in Jan. 1983 with 40 g chlorsulfuron/ha in 500 L water plus surfactant through a fine jet spray pistol was controlled 100% with no regeneration >12 months after spraying. The herbicide was also effective against Zantedeschia aethiopica, Salvinia molesta, Eichhornia crassipes and Pistia stratiotes.
Cyanoacrylate herbicides
These have potential for Myriophyllum control 612.
Dicamba
Myriophyllum spicatum and Hydrocotyle umbellata were controlled with glyphosate at 3 kg/ha and Banvel 720 at 14 L/ha., respectively 613
Diquat
Diquat at 204 g a.i./ha gave good initial control but regrowth was occurring by 36 days after treatment 598;600.
3 ppm in the water was ineffective 593.
Control with 2.64 kg diquat and 1.5 kg diquat + 1.5 kg 2,4-D ester lasted about 60 days 604.
Diuron
0.9 kg hexazinone + 0.8 kg diuron controlled the weeds for >145 days 604.
Endothal
Severe M. spicatum injury (>85% biomass reduction) occurred after exposure to 0.5, 1.0, 3.0 and 5.0 mg/litre endothal for 48, 36, 18 and 12 h, respectively 614.
Within 96 hours endothal in sediments and water falls below detectable levels 615.
Localized applications of Aquathol® (endothal granules) used to control Myriophyllum spicatum infesting >550 acres of Pat Mayse Lake had no direct or indirect effects on non-target species or abiotic water quality, even though the weed was temporarily eradicated 616.
Fluridone
Not available in Australia but is giving selective control in US 617.
3 kg fluridone/ha lasted about 60 days 604.
Glufosinate
1.0-2.4 kg glufosinate ammonium gave good initial control but regrew by 4 months after treatment 600.
Glyphosate
Generally not very effective 598;600.
Myriophyllum spicatum were controlled with glyphosate at 3 kg/ha 613.
Hexazinone
0.9 kg hexazinone + 0.8 kg diuron controlled the weeds for >145 days 604.
Hydrogen peroxide
20 ppm gave control of algae but little effect on Milfoil 618.
Imazapyr
Generally not very effective 598.
Metsulfuron
EC50 = 10-6 M 611.
Paraquat
0.83 kg paraquat/ha controlled the weeds for >145 days 604.
Terbutryn
0.2 ppm gives control in static water with long exposures for Myriophyllum propinquum. Higher rates required in the field. Terbutryn residues in the water decreased with 1st order half-life of about 9-20 days 619.
Thifensulfuron
Thifensulfuron is less effective than chlorsulfuron or metsulfuron 611
Tribenuron
Tribenuron is less effective than chlorsulfuron an metsulfuron 611
Triclopyr
Triclopyr is more effective than glyphosate endothal, dichlobenil, fluridone or clopyralid in NZ 620.
About 2 mg/L triclopyr applied in autumn provided 99% control in the first year and took about 7 days to drop to potable levels. Biodiversity doubled, non target biomass increased 5-10 times and adequate control lasted 3 years 621.
Triclopyr at 0.25 mg/L for 84 h and at 2.5 mg/L for 18 h reduced weed biomass by 98% 622.
Triclopyr triethylamine salt formulation - excellent control (>85% biomass reduction) was achieved at concentration/exposure time combinations of 0.25 mg for 72 h, 0.5 mg for 48 h, 1.0 mg for 36 h, 1.5 mg for 24 h, and 2.0 and 2.5 mg for 18 h. Treatments of 2.5 mg for 2 h, 1.0 mg for 6 h, and 0.25 and 0.5 mg for 12 h were ineffective for M. spicatum 623.
Mechanical
Variable success with disturbance based weed control methods 624.
Hand harvesting and suction harvesting needs to be repeated every 3 years and milfoil invades within a year or two of removal of benthic barriers 625.
Mechanical harvesting reduced species diversity in 3 out of 4 sites 626.
Harvesting for 4 years didn't reduce P levels enough to reduce growth 627.
Rotary hoeing reduced stem densities by 25-70% in the year following treatment 628.
Hand removal gave about 25% decrease in biomass the following year 629.
Dredging or covering sediments (with sand, gravel and plastic) failed to provide long-term suppression of M. exalbescens 630.

Thresholds:

Eradication strategies:

Prevent the sale and dumping of aquarium material. If possible lower water levels then treat with herbicides and repeat as required.
Hazard models for control have been developed 631.

Herbicide resistance:

Biological Control:

One or two triploid grass carp can be used in Water Lily (Nymphaea) production ponds if they are removed when there is little weed left and they start eating the lilies 632.
A number of weevils and fish have some potential for biocontrol.
A leaf-feeding beetle, Lysathia (Chrysomelidae) has been introduced to South Africa for biological control 633.
Introducing water fowl gave initial control but after 2 years recolonization ensued 634.
Root and stem rot of parrot feather (Myriophyllum brasiliense) caused by Pythium carolinianum 635.

Related plants:

Coarse Water Milfoil (M. elatinoides)
Hooded Water Milfoil (M. muelleri)
Red Water Milfoil (M. verrucosum)
(M. variifolium)
There are 16 native species of Myriophyllum in WA.

Plants of similar appearance:

Other Milfoil species have serrated edges on the leaves above water, whereas Brazilian Water Milfoil has feathery leaves both above and below the water surface.

References:

APB Advisory leaflet No. 85. (1982)1

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P168. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #859.1.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P363.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P485-487. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.