A comparative study on pesticide formulations for application in running waters

Area of Science:

• Environmental Chemistry
• Aquatic Toxicology
• Polymer Science

Background:

• Aquatic weeds pose challenges in running waters, necessitating effective control methods.
• Pesticide formulation significantly impacts the release kinetics and duration of active ingredients (AI).

Purpose of the Study:

• To investigate the release rates of monolinuron, desmetryne, and carbofuran from different formulations into water.
• To evaluate the long-term herbicidal efficacy of ethylene-vinyl acetate copolymeric matrix (EVA) formulations for aquatic weed management.

Main Methods:

• Studied AI release rates from wettable powder, EVA, and calcium alginate bead formulations.
• Measured diffusion coefficients of pesticides in polymeric matrices.
• Assessed herbicidal effectiveness using a laboratory-scale simulated flow system with duckweed (Lemna minor).

Main Results:

• Wettable powder formulations released AI within 1 day.
• EVA formulations exhibited significantly slower AI release due to low diffusion coefficients (10⁻⁸–10⁻¹² cm²/s), enabling herbicidal action for potentially years.
• Calcium alginate beads released AI over 2 weeks.
• Approximately 20 ppb terbutryne in EVA formulation achieved duckweed growth inhibition in a steady state.

Conclusions:

• EVA-based formulations provide a promising approach for sustained aquatic weed control in running waters.
• Formulation design is critical for managing pesticide release duration and environmental impact.
• Controlled release technologies can significantly extend the effective period of herbicides.