Latin name

Monochoria hastata (L.) Solms

Family

Pontederiaceae

Common name(s)

Monochoria and pickerel weed

Synonym(s)

Monochoria hastata (L.) (basionym); M. dilatata (Buch.-Ham.) Kunth, M. hastifolia Presl C., M. sagittata (Roxb.) Kunth, Pontederia dilatata Buch.-Ham.

Geographical distribution

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

Rest of the world: Fiji and United States (Hawaii).

Morphology

A robust, obliquely erect, rhizomatous, annual or perennial herb up to 125—cm—tall.

Stem: smooth and erect with well-developed branched rhizomes.

Leaf: broadly ovate, leathery, 10—30—cm—long with base prominently arrowhead-shaped; petiole long and stout with sheaths below, up to 60—cm—long.

Inflorescence: spike-like racemes composed of 15—60 flowers with 6 violet-blue petals.

Fruit: ellipsoid capsule, 1—cm—long.

Seed: oblong, brown, 1—mm—long, with approximately 10 longitudinal ribs.

Biology and ecology

Favors aquatic, wet conditions in canals, ponds, drains, swampy places, and occasionally in paddy fields. Propagated by seed and rhizomes.

Agricultural importance

A high density of M. hastata can reduce rice yield substantially (e.g., 5 plants per m2 reduced rice yield by 10%). Used in Malaysia as vegetable/medicinal plant and as cattle fodder in Bangladesh, yet also occurs as a weed of rice in these countries. It is an alternate host of rice grassy stunt virus, rice ragged stunt virus, and fungal diseases.

Management

Cultural control: usually controlled by land preparation of plowing and rotovation, and also by hand weeding.

Chemical control: reported to be controlled by butachlor, bensulfuron, bentazon, MCPA, and oxadiazon.

Selected references

Backer CA. 1951. Pontederiaceae. Flora Malesiana Ser. 1 4:255 - 261.

Holm L, Plucknett DL, Pancho JV, Herberger JP. 1977. The world's worst weed - distribution and biology. Hawaii (USA): University Press of Hawaii. 609 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: a systematic account of common Southeast Asian aquatic weeds. Bogor (Indonesia): SEAMEO Regional Center for Tropical Biology. 130 p.

Patwary MU, Haque MM, Zaman MA. 1989. Polyploidy in Monochoria hastata Solms and M. vaginalis Presl grown in Bangladesh. Cytologia 54(3):505-511.

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

Contributors

JLA Catindig, RT Lubigan, and DE Johnson