New World
In California, the Capraria biflora, one plants accidentally introduced in the New World in the second half of century XIX, in 1940 more than already had dominated 120,000 hectares of pastures, being finally controlled for parasitic insects (FARB, 1982). However, in the case of some vegetal species, the control by means of insects can arrive late excessively, when native plants already will have been extinct or the invaders caused great economic damages, of a form or another one. Still insects had not been found capable to control the aquatic jacinths that obstruct navigable canals in the Luisiana, in Africa Occidental person and Sudan. One is about a showy plant, that produces similar flowers to the orqudeas. The same one was taken of Venezuela for the Exposition of Cotton of New Orleans, in 1884. Some visitors, magic with the beauty of the plant, they had gotten changes of same for its lakes and streams.
The plant currently grows in Americas, Asia, in Africa and Australia, obstructing canals and hindering the navigation, as well as the irrigation and the installations hydroelectric plants. In the United States the control is tried by means of drags, but the same it does not follow the rhythm of growth of the plant. An exit then is the attempt of control by means of chemical products, but this could cause pollution of waters (FARB, 1982). In case that seemed it occurs in the south of Brazil, where the forrageiro turnip (Raphanus sativus) and the nabia (Raphanus raphanistrum) had become invading of difficult control, occurring as harmful in farmings, over all in typical cultures of winter, as the wheat. Initially the vegetable was planted in lands incultas to serve as alternative form of green fertilization in the periods of winter (RASP et al, 2007). The two species, beyond revealing of difficult control and eradication, dispute space and nutrients with proper planted culture e, in the specific case of the wheat, affect the harvest process.