If we use weedicides, why are useful crops not affected?

Weedicides, which are also known as herbicides, are chemicals which are harmful to plants. Herbicides can be selective (only kill certain types of plants) or non-selective (kill all types of plants).

Selective herbicides have different mechanisms of action. Different plants will have varying degrees of susceptibility to different mechanisms of action due to differences in absorption of the chemical and the physiology or morphology of the plant. Thus, care is taken to select the appropriate...

Weedicides, which are also known as herbicides, are chemicals which are harmful to plants. Herbicides can be selective (only kill certain types of plants) or non-selective (kill all types of plants).

Selective herbicides have different mechanisms of action. Different plants will have varying degrees of susceptibility to different mechanisms of action due to differences in absorption of the chemical and the physiology or morphology of the plant. Thus, care is taken to select the appropriate herbicide to eliminate the specific type of weed present.

With respect to non-selective herbicides, it is generally the manner in which these herbicides are applied which limits the effects on useful crops. Non-selective herbicides are generally dispensed as a liquid spray which is applied directly onto the weeds. Care is taken to prevent applying the herbicides to the useful crop plants. Alternatively, these types of herbicides may be applied to entire fields before the useful crop is planted.