Question

By spraying weedicides, weeds are killed, but not the crop plants why?

Answer 1

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.