What issue arises with contact-type herbicides when controlling grass in the seedling stage?

When using contact-type herbicides to address grass in the seedling stage, the primary concern is that the growing point of the plant is typically located just below the surface of the soil. Contact herbicides are designed to kill only the plant tissue that they directly come into contact with. Since the essential growing point of seedlings is not exposed and is instead protected underneath the soil, these herbicides may not effectively reach or damage the part of the plant that is crucial for its growth and development. Consequently, even if the herbicide is applied, it will not eliminate the plant because it cannot effectively access and destroy the growing point that is necessary for the plant's continued growth.

In contrast, other types of herbicides, such as systemic herbicides, are more effective against seedlings because they move throughout the plant and affect its internal processes, including the growing point. Understanding this interaction helps in selecting the appropriate herbicides for managing specific plant growth stages.