''Damasonium minus'' is a species of flowering plant in the water-plantain family known by the common names starfruit and star-fruit (not to be confused with the cultivated

starfruit Carambola, also known as star fruit, is the fruit of ''Averrhoa carambola'', a species of tree native to tropical Southeast Asia. The edible fruit has distinctive ridges running down its sides (usually 5–6). When cut in cross-section, it res ...

). It is native to

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, where it occurs everywhere except the

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

.''Damasonium minus''.
Threatened Flora of Tasmania. It is perhaps best known as an agricultural weed. It is a major weed of Australian rice crops. This species is an emergent

aquatic plant Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...

. It is an annual or short-lived perennial herb growing up to a meter tall. The floating or emergent leaves have blades up to 10 centimeters long by 4 wide and lance-shaped to heart-shaped. They are borne on petioles up to 30 centimeters long. The branching

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

has whorls of flowers. Each flower has tiny green

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s and white or pink petals a few millimeters long. The star-shaped

aggregate fruit A raspberry_beetle.html" ;"title="raspberry fruit (shown with a raspberry beetle">raspberry fruit (shown with a raspberry beetle larva) is an aggregate fruit, an aggregate of drupelets. image:Aquilegia vulgaris 004.JPG, The fruit of an ''Aquilegi ...

is made up of follicles containing seeds.''Damasonium minus''.
New South Wales Flora Online. National Herbarium, Royal Botanic Garden, Sydney. This plant grows in habitat with slow-moving and still water, such as

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

s. In agriculture, this plant has been called "the most important broadleaf weed in the Australian rice crop." Most rice is grown in

Victoria Victoria most commonly refers to: * Queen Victoria (1819–1901), Queen of the United Kingdom and Empress of India * Victoria (state), a state of Australia * Victoria, British Columbia, Canada, a provincial capital * Victoria, Seychelles, the capi ...

and

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

. This weed has been controlled with the

herbicide Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

bensulfuron-methyl, but it has become less effective as herbicide-resistant strains have evolved. A

pathogenic In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ...

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

, '' Rhynchosporium alismatis'', was discovered on the plant, and it has become an option for

biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...

as a

mycoherbicide A mycoherbicide is a herbicide based on a fungus. As a biological agent, these "mycoherbicides... work by producing toxic compounds that dissolve the cell walls of targeted plants". Unlike traditional herbicides, mycoherbicides can reproduce themse ...

. The fungus causes

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

and

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who i ...

of the leaves on the mature plant and stunting of immature individuals. If immature weeds in a paddy are stunted, the rice plants may have a competitive advantage. The fungus can kill seedlings, and if it infects the inflorescence of the weed it can reduce seed weight and viability.Cother, E. J., et al. "Development of the mycoherbistat fungus ''Rhynchosporium alismatis'' for control of Alismataceae weeds in rice." In: Hill, J. E. and B. Hardy, Eds. ''Proceedings of the Second Temperate Rice Conference''. June 13–17, 1999. Sacramento, California. pg. 509. The fungus can also help control another rice weed, ''

Alisma lanceolatum ''Alisma lanceolatum'' is a species of aquatic plant in the water plantain family known by the common names lanceleaf water plantain and narrow-leaved water plantain. It is widespread across Europe, North Africa and temperate Asia. It is natural ...

''.

References

{{Taxonbar, from=Q15296272 Alismataceae Agricultural pests Freshwater plants