Which statement best reflects the effect of sorption on fumigant performance?

• A. Sorption reduces the fumigant's effectiveness by removing molecules from the air
• B. Sorption increases the fumigant's overall potency
• C. Sorption has no impact on fumigants
• D. Sorption speeds dispersion of fumigants into the ground

Answer: (A)

Sorption reduces fumigant performance because it pulls fumigant molecules out of the air phase and binds them to soil particles and organic matter. Fumigants must be present as gas in the soil pores to diffuse and reach pests throughout the treated zone. When a portion of the molecules sticks to surfaces, there’s less gas available to move and contact targets, so the overall exposure of pests drops and effectiveness declines. The extent of this effect depends on soil factors (like organic matter and texture), moisture, temperature, and the chemical’s tendency to adhere to surfaces. While sorption can slow off-gassing and may prolong residual presence, the immediate efficacy is reduced because fewer molecules are circulating in the air to act on pests.