Cyperus difformis L.
Small flower umbrella plant
Cyperus lateriflorus Torr., C. difformis var. maximus C.B. Clarke, C. difformis var. breviglobossus Kük., C. difformis var. subdecompositus Kük.
Asia: China, Japan, and Korea.
South and Southeast Asia: Bangladesh, Cambodia, India, Indonesia, Lao PDR, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Thailand, Sri Lanka, and Vietnam.
Rest of the world: Australia, Cameroon, Ecuador, Egypt, Fiji, Ghana, Iran, Liberia, Madagascar, Mexico, Nicaragua, Nigeria, Portugal, Swaziland, Tanzania, Turkey, United States, West Africa and Zimbabwe.
The weed is annual, fibrous and reddish roots; up to 100 cm tall.
Stem: tufted, smooth and erect, triangular and 2−3 mm thick; slightly winged.
Leaf: three to 4 basal leaves; sheaths united at base, lower ones straw-colored to brown; blades flaccid and linear, 15−45 cm long.
Inflorescence: umbellate and subtended by two leaf-like bracts; rays 1−5 cm long, some with long peduncle, some without stalk; spikelets numerous, crowded in masses about 2−5 mm long, each spikelet composed of 10−30 flowers.
Fruit: brownish nut, elliptical to slightly obovate, about 0.6 mm long and lightly pitted.
Biology and ecology
The small flower umbrella plant grows well in flooded or moist fertile soils and common in lowland rice. Also found on poorer sandy or clay soils in fallow lands but cannot tolerate deep flooding. It has a short life span; propagates by seeds and produces seeds throughout the year.
It produces large quantities of seed and can complete life cycle in about 30 days. A dominant weed in direct-seeded rice when it occurs in high plant densities; forms dense mats of vegetation in the young crop and can cause rice yield losses of 12−50%.
It is an alternate host of Xanthomonas campestris.
Cultural control: hand and mechanical weeding in row-planted rice plants can provide effective control.
Chemical control: Bentazon, butachlor, 2,4-D, MCPA, pretilachlor, propanil, and thiobencarb reported to be effective.
JLA Catindig, RT Lubigan, and D Johnson