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). It is native to Australia, where it occurs everywhere except the Northern Territory.[1] It is perhaps best known as an agricultural weed. It is a major weed of Australian rice crops.[2] [3] [4]
This species is an emergent aquatic plant. 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 has whorls of flowers. Each flower has tiny green sepals and white or pink petals a few millimeters long. The star-shaped aggregate fruit is made up of follicles containing seeds.[1] [5]
This plant grows in habitat with slow-moving and still water, such as swamps.[1]
In agriculture, this plant has been called "the most important broadleaf weed in the Australian rice crop."[3] Most rice is grown in Victoria and New South Wales.[3] This weed has been controlled with the herbicide bensulfuron-methyl, but it has become less effective as herbicide-resistant strains have evolved.[3] A pathogenic fungus, Rhynchosporium alismatis, was discovered on the plant, and it has become an option for biological control as a mycoherbicide. The fungus causes chlorosis and necrosis 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.[2] The fungus can kill seedlings, and if it infects the inflorescence of the weed it can reduce seed weight and viability.[6] The fungus can also help control another rice weed, Alisma lanceolatum.[4]