Why are systemic herbicides typically ineffective against aquatic weeds?

Systemic herbicides are designed to move throughout a plant to disrupt its physiological processes. However, in aquatic environments, the effectiveness of these herbicides can be limited due to the nature of how many aquatic plants reproduce and survive.

Aquatic weeds often have structures such as tubers and rhizomes that allow them to grow and spread independently of the parts of the plant that may be directly exposed to the herbicide. When systemic herbicides are applied, they may not adequately affect these underground structures, allowing the plants to continue thriving despite treatment. Thus, the inability of systemic herbicides to effectively impact tubers, rhizomes, and seeds is a significant reason for their ineffectiveness against aquatic weeds.

While options suggesting that aquatic weeds reproduce solely via seeds or that herbicides work too slowly may be valid points in some contexts, they do not address the primary reason systemic herbicides fall short: their failure to reach and affect all parts of the plant's life cycle, especially the resilient structures like tubers and rhizomes. The idea that herbicides might be too weak to penetrate the water doesn't consider that many systemic herbicides are designed to be effective in water. Understanding these dynamics is crucial for effective aquatic weed management.