Latin name

Sagittaria guayanensis Kunth

Family

Alismataceae

Common name(s)

Arrowheads

Synonym(s)

Lophotocarpus guayanensis (Kunth) Micheli ex J.G. Sm. (accepted), Lophiocarpus guayanensis (Kunth) Micheli (accepted), Alisma echinocarpa (Mart.) Seub., Echinodorus guianensis (Kunth) Griseb., Lophiocarpus seubertianus (Mart. ex Seub.) Micheli, Sagittaria seubertiana Mart. ex Seub.

Geographical distribution

South and Southeast Asia: Bangladesh, Cambodia, India, Indonesia, Lao PDR, Malaysia, Myanmar, Nepal, Pakistan, Sri Lanka, Thailand, and Vietnam.

Rest of the world: Costa Rica, Ecuador, Guatemala, Honduras, Mexico, Nicaragua, and Paraguay.

Morphology

An aquatic herb containing latex, without stolon, and 10—80—cm—tall.

Stem: no apparent stem.

Leaf: simple, clustered at base, ovate to rounded-ovate, without hair, 3—11—cm—long; petiole ribbed, with air ducts, 15—30—cm—long.

Inflorescence: floating raceme with 2—6 whorls of 2—3 flowers, 10—30—cm—long peduncle; perianth segments 6 in 2 rows, where the 3 inner ones are petal-like, white, and with a purple spot near the yellowish base.

Fruit: short stalk, flattened, 3—4—mm—long warty achene; reproduces by seeds; seed brown, 1.5—mm with blunt, brown incisions.

Biology and ecology

Commonly found in tanks, marshes, reservoirs, and ditches, and in lowland rice fields.

Seeds require saturated conditions in rice fields for germination although can germinate under slightly submerged conditions; seedlings grow rapidly in standing water.

Agricultural importance

A weed of lowland rice and wet areas in other irrigated crops.

Management

Cultural control: hand weeding can be effective.

Chemical control: postemergence application of 2,4-D can control this weed in rice.

Selected references

AICAF (Association for International Cooperation of Agriculture and Forestry). 1997. Weeds in the Tropics. Tokyo (Japan): Sanbi Printing Co., Ltd. 304 p.

Den Hartog C.1957. Alismataceae. Flora Malesiana Ser. 1 5:317-334.

Gupta OP. 1987. Aquatic weed mangement. New Delhi (India): Today and Tomorrow's Printers and Publishers. 247 p.

Moody K. 1989. Weeds reported in rice in South and Southeast Asia. Manila (Philippines): International Rice Research Institute. 442 p.

Pancho JV, Soerjani M. 1978. Aquatic weeds of Southeast Asia. College, Laguna (Philippines): University of the Philippines at Los Baños and Bogor (Indonesia): SEAMEO Regional Center for

Tropical Biology (BIOTROP). 130 p.

Soerjani M, Kostermans AJGH, Tjitrosoepomo G. 1987. Weeds of rice in Indonesia. Jakarta (Indonesia): Balai Pustaka. 716 p.

Waterhouse DF. 1993. The major arthropod pests and weeds of agriculture in Southeast Asia. ACIAR Monograph No. 21. 141 p.

W3TROPICOS at http://mobot.mobot.org/Pick/Search/pick.html.

Contributors

JLA Catindig, RT Lubigan, and DE Johnson