Contact herbicides are most effective against specific types of weeds. In general, contact herbicides work best on annual weeds. These are weeds that complete their life cycle in one growing season and do not regrow from the roots once they are killed.
On the other hand, perennial weeds regrow from their roots each year, making them more challenging to control with contact herbicides alone. Biennial weeds have a two-year life cycle, forming rosettes in the first year and flowering in the second year. While contact herbicides can affect biennial weeds during their initial growth stages, they may not provide long-term control due to the plants' regrowth ability.
Therefore, contact herbicides are most effective against annual weeds because they target the foliage of the plant, killing it without affecting the roots. This makes them a suitable choice for controlling weeds that complete their life cycle within a single growing season.
