Organic farmers give first priority to the prevention of the introduction and multiplication of weeds. Management practices aim at keeping the weed population at a level that does not result in economic loss of the crop cultivation or harms its quality. The goal is not to completely eradicate all weeds, as they also have a role to play on the farm. For example, weeds provide cover that reduces soil erosion. In addition, most of the biological diversity in our crop fields comes from the presence of weeds. They provide habitat for both beneficial biocontrol insects and mycorrhiza fungi. Because weeds offer pollen and nectar, they allow biocontrol insects to maintain their populations and, therefore, serve as a valuable instrument in controlling pests.