Cyperus difformis L.

France - Camargue: Cyperus difformis flowers from June to September. This species can carry two growing cycles during the growing season. His delayed emergence allows it to escape the post-emergence, treatments but it is very sensitive to competition.
Mayotte: C. difformis flowers and fruits all year round.

Cyperus difformis usually grows in flooded or very humid soils. It is a weed which is mainly found in flooded rice fields or paddies. It is often found in small ponds, along rivers, canals and streams, in open and humid zones and marshy meadows. It grows best in rich, fertile soils but can also be satisfied with poor sands of uncultivated land or rice fields in fallow. This species occurs preferably where the water blade is thin.

Comoros: very common plant in the three islands. It is very abundant in flooded areas in Anjouan and Moheli, forming clumps with very strong stems. In Grande Comore where there is no swamp, it is present in humid and muddy places. It grows in marshy areas of Anjouan in rice farming and vegetable cultivations.
French Guiana: A species already widely naturalised in Suriname and recently observed in French Guiana in a barely disturbed lowland savannah situation.
Madagascar: Aquatic cyperaceae of warm regions, very prolific, it infests the swamps, the rivers edge and canals and especially irrigated rice fields. It infests preferably quite fertile rice fields with clay soils.
Mauritius: Species very rare on the island.
Mayotte: C. difformis is a frequent species around and in wetlands, including brackish meadows and marshes of alluvial plains. It is sometimes maintained in ditches and secondarized environments.
Reunion: Rare species in Reunion, limited to coastal freshwater ponds.
Seychelles: absent.

Global control
 
Cultural control: Precaution: Avoid fine-textured seedbed and shallow water. Maintain a high density of rice plants. Avoid excessive nitrogen fertilizers.
Mechanical control: The manual or mechanical weeding in the rice fields planted in line can be effective against Cyperus difformis.
Chemical control: In rice cultivation, bentazon, butachlor, 2,4-D, MCPA, pretilachlor, propanil and thiobencarb are known to be effective. Devoid of underground storage organ, C. difformis is easier to manage than species such as C. rotundus and C. esculentus. Post-emergence herbicides can be used in transplanted rice (for example, application of 2,4-D after lifting to 5090 g / ha). Pre-emergence products are also available on rice as butachlor and oxidiazon.
Note: In many parts of the world, C. difformis has developed a form of resistance to many herbicides inhibiting acetolactate synthase (ALS-resistant). Do not use Londax on resistant biotypes.
For weed control tips for annual Cyperaceae irrigated rice and lowland in Africa, visit: http://portal.wiktrop.org/document/show/27
 
Local control

Madagascar: The shallow tillage tends to favor their multiplication. Pulling or even manual weeding are very demanding work and difficult to drive at times.These cyperaceae are generally not susceptible to alachlor, atrazine, diuron or pendimethalin, but sensitive enough to oxadiazon at preemergence. At postemergence, they are fairly well controlled by bentazon, 2,4-D or glyphosate.
A vegetation cover usually delays them enough.

Herbarium pictures ReCOLNAT: https://explore.recolnat.org/search/botanique/simplequery=Cyperus%2520difformis