Crotalaria retusa L.

Mayotte: Crotalaria retusa flowers and fruits all year round.

A common weed of cultivated crops, bush regrowth, waste areas and roadsides.

Northern Cameroon: Crotalaria retusa is a common ruderal species along roadsides and in vacant lots, particularly in areas of humid lowland. Also it is a weed of crops in plots of heavy and humid soils, but it is infrequent and is never abundant.
Comoros: C. retusa is a ruderal species occurring especially in wetlands in low-lying areas of the three islands.
Madagascar: This species is found in crops or fallow on fairly rich, deep soils (alluvial plains, depressions or terraces around the lowlands) throughout the island.
Mauritius: ruderal species present in coastal areas and in the interior of the island.
Mayotte: C. retusa is a very common cryptogenic species in a wide range of disturbed environments, from the xerophilic coastline (as in the dry thickets of the islets and points) to the crops and villages of the humid area.
New Caledonia: This is a common ruderal species along roadsides and in wastelands, especially in low-lying wetlands.
Reunion: C. retusa is a common ruderal species along roadsides and in vacant lots, particularly in the humid lowland areas.
Seychelles: Species occurring in clearings and abandoned places. It is rarely abundant.
West Indies: Crotalaria retusa is an exotic species. It grows in many ecological situations. In agricultural areas, it often occupies the edges of poorly tended fields, fallow land and wasteland.

Toxicity: Crotalaria retusa is a highly toxic plant for humans and animals because it contains pyrrolizidine alkaloids, mainly monocrotaline, but also retronecin N-oxide, retusine, and retusamine.

Local harmfulness
 
Benin: rare and scarce.
Burkina Faso: rare and scarce.
Chad: rare and scarce.
Comoros: Crotalaria retusa is a weed of vegetable crops and cassava fields.
Madagascar: Species infrequent and rarely abundant in crops.
Mali: rare and scarce.
Mauritius: This species is not present in crops.
New Caledonia: Like other Crotalaria species, Crotalaria retusa is a secondary weed in the pastures. Significant infestations are rarely observed, but this may be the case after tillage for pasture planting.
Uganda: common and scarce.
Reunion: A weed present in less than 10% of cultivated land, mainly vegetables.
Senegal: rare and scarce.
Seychelles: A weed low harmfulness.
West Indies: Crotalaria retusa is present in all crops except established banana plantations and is considered a minor weed.
weed.

Medicinal: Seeds of Crotalaria retusa contain basic alkaloid with N-oxides in their leaves and are used in ethno-medicine for the treatment of fever, as vermifuge and as an antispasmodic (uterus & intestine) agent. Also seeds powdered & boiled with milk are used for enhancing body strength, life span and also for curing skin diseases, leprosy, flatulence and fever. The leaves are the excellent remedy for Ptyalism, Diarrhoea, Scabies and Impetigo (Devendra et al., 2011).

Agronomical: Crotalaria retusa is used as a cover crop; see the following document:
Datasheets cover plants. Crotalaria retusa. Data sheets and training materials SCV. Inspired Practical Handbook of direct seeding in Madagascar, adapted by the team of the Soil Conservation Project (PCS / ESA II) in northern Cameroon. Abba Abu Abdoulaye Oumarou Balarabe Mahamat Alifa, Dourwe Gaston Daoudou, Toumba, Mana Justin, Adoum Yaouba. 2013 (download)

Rituals: In Mayotte, the toxic seeds of Crotalaria retusa are used in certain magic-religious rites.

Global control

For weeding Advice for broadleaf annual weeds of irrigated rice and lowland in Africa, visit:
http://portal.wiktrop.org/document/show/19

Local control

New Caledonia: Chemical treatment against Crotalaria retusa can be considered in early-stage cover crops. Picloram products are preferred (see table for products and doses). On pastures in place, isolated individuals must be manually destroyed. In case of more extensive infestation, a chemical treatment with picloram on regrowths will be applied after a rotary grinding carried out during the active growth period and before fruiting.

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