''Crotalaria retusa'' is a species of flowering plant in the

legume family The Fabaceae or Leguminosae,International Code of Nomenc ...

known by various common names including devil-bean, rattleweed, shack shack, and wedge-leaf rattlepod. It is poisonous to livestock, and contaminates human food. Its original native range is unclear, probably including tropical Asia, Africa and Australia. It has been introduced as a crop plant in many tropical areas and has escaped from cultivation to become a troublesome weed; it is listed as a

noxious weed A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is injurious to agricultural or horticultural crops, natural habitats or ecosystems, or humans or liv ...

in several US states,

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

, the

Virgin Islands The Virgin Islands ( es, Islas Vírgenes) are an archipelago in the Caribbean Sea. They are geologically and biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Rico Trench and St. Croix ...

, and is listed as an

invasive weed An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

in India,

Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...

, and

Cocos Island Cocos Island ( es, Isla del Coco) is an island in the Pacific Ocean administered by Costa Rica, approximately southwest of the Costa Rican mainland. It constitutes the 11th of the 13 districts of Puntarenas Canton of the Province of Puntarenas ...

. Unlike some other species of ''Crotalaria'', it is an

annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical ...

Description

It is an annual herb, about high, with erect, angular, green branches. The soft leaves (dark green on the upper surface, lighter underneath) are alternate, and narrowly oblong or wedge-shaped. The yellow flowers grow widely spaced in racemes at the end of the stem. The pods are thin walled, and widely spaced along the stems, and when ripe are purple to black, containing about 18-20 small brown seeds.

Habitat/ecology

In Australia, where it is considered a native, it grows in the

Kimberley Kimberly or Kimberley may refer to: Places and historical events Australia * Kimberley (Western Australia) ** Roman Catholic Diocese of Kimberley * Kimberley Warm Springs, Tasmania * Kimberley, Tasmania a small town * County of Kimberley, a ...

on sand, clay, sandstone, and rocky basaltic soils, and is found along creeks and rivers, and on the floodplains.

Uses

''Crotalaria retusa'' is grown as a

fibre crop Fiber crops are field crops grown for their fibers, which are traditionally used to make paper, cloth, or rope. Fiber crops are characterized by having a large concentration of cellulose, which is what gives them their strength. The fibers may b ...

and as

green manure In agriculture, a green manure is a crop specifically produced to be incorporated into the soil while still green. Typically, the green manure's biomass is incorporated with a plow or disk, as is often done with (brown) manure. The primary goal ...

. It is also used as a

forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used m ...

plant, but is poisonous to livestock.

Toxins

The primary source of toxicity for many species of ''Crotalaria'' is the presence of

pyrrolizidine alkaloid Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Pyrrolizidine alkaloids are produced by plants as a defense mechanism against insect he ...

s, which are poisonous to birds and large mammals. ''Crotalaria retusa'' seeds are some of the most toxic of ''Crotalaria'' species. Pyrrolizidine alkaloids in

honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primar ...

are a threat to human health.

Animals affected

In Australia, in the field, only horses are known to die from eating this plant, with most cases occurring during the

wet season The wet season (sometimes called the Rainy season) is the time of year when most of a region's average annual rainfall occurs. It is the time of year where the majority of a country's or region's annual precipitation occurs. Generally, the sea ...

. Grazing on the fresh plant over a period of 3 or 4 weeks typically leads to death in about three months, from "Kimberley Horse Disease" (or "walkabout" disease). Death in chronic cases can take two or more years. First signs of poisoning are loss of weight, followed by sleepiness and depression. The horses then become irritable and start walking aimlessly until they die. In the U.S.A. the seeds have been found to be poisonous to chickens.

References

retusa {{faboideae-stub