An arvense, commonly called weed, weed or undesirable plant grows predominantly in situations altered by humans (in agricultural crops or gardens) and is undesirable for crops at a given time or place.
▶ Therefore, any species of the plant kingdom can be a weed. Of the approximately 270,000 species of plants that exist, 8,000 are considered as weeds, since the species considered as weeds in a given area are different from those in another, so that the number of undesirable plants in a given place is around 200.
Specifically, plant species that compete with cultivated species, in conventional agriculture controls are applied to eradicate them, for example; generally in crops three weed controls are applied at the beginning, development, and before flowering, since after planting optimum yields are achieved.
It is assumed that growers who do not apply controls on their crops have lower yields, and in those cases where controls are applied, the crop yields twice as much with controls.
Weed controls in some crops may start later than in other crops with less impact on yield, as the critical period also varies among species.
Aggressive perennial weeds such as Cyperus rotundus L. or Convolvulus arvensis L. will need more frequent weed controls than annual species because perennials resprout several times from food reserves in underground stored organs. On the other hand, fields with very little weed pressure do not require as intensive and time-consuming control practices as those with abundant weed pressure.
