Which chemical strategy is primarily used for controlling annual grassy weeds?

Preemergence herbicides are the primary chemical strategy used for controlling annual grassy weeds because they target weed seeds before they can emerge from the soil. These herbicides work by creating a chemical barrier in the top layer of soil, effectively preventing the germination and growth of weed seeds. As annual grassy weeds typically complete their life cycle within a single growing season, applying a preemergence herbicide at the appropriate time—usually in early spring or late winter—can significantly reduce their presence in the turf.

In contrast, postemergence herbicides, while useful for controlling weeds that have already emerged, are not effective against seeds that have not yet germinated. Foliar treatments primarily refer to the application of chemicals directly onto the leaves, suitable for addressing established weeds rather than preventing their occurrence. Fumigants are typically used for soil sterilization and pest control before planting and do not specifically target grassy weeds. Thus, preemergence herbicides are essential in a proactive pest management strategy for annual grassy weeds.