Insecticide and Fungicide Residues Following a Foliar Application in Cotton and Soybean

Authors: LAWSON, A - University Of Tennessee; STECKEL, S - University Of Tennessee; WILLIAMS, M - University Of Tennessee; Adamczyk, John; STEWART, S.D. - University Of Tennessee

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2020
Publication Date: 1/6/2021
Citation: Lawson, A., Steckel, S., Williams, M., Adamczyk Jr, J.J., Stewart, S. 2021. Insecticide and Fungicide Residues Following a Foliar Application in Cotton and Soybean. Journal of Cotton Science. 24:159-167.

Interpretive Summary: The residual control of target pests and impacts on pollinators is affected by the persistence of pesticides on plants following an application. An experiment was done in Tennessee to investigate the levels of pesticide residues on cotton and soybean following an insecticide application made when the plants were flowering. The pesticides residues (i.e. small amounts that remain) of four types of insecticides and three types of fungicides were assessed at different times after they were applied. Initial pesticide residues on cotton leaves were many times higher than those on cotton flower parts or soybean flowers. With the exception of a specific fungicide on cotton leaves, fungicide residues tended to persist longer than insecticides. Also, pesticide residues on soybean flowers degraded more slowly than those on cotton leaves or anthers. For cotton leaves, insecticide residues decreased sharply within 24 h after application, again with the exception of a specific fungicide. All pesticide residues on cotton anthers were dramatically lower by 24 h after application, indicating little systemic movement to pollen. By 216 h after application, and considerably sooner in most scenarios, pesticide residues on cotton and soybean had diminished by 90% or more. The implications of these results on pest management and pollinator safety are discussed.

Technical Abstract: The residual control of target pests and impacts on non-target arthropods, including pollinators, is affected by the persistence of pesticides on plants following an application. To that end, a study was done in Tennessee to investigate the levels of pesticide residues on cotton, Gossypium hirsutum L., and soybean, Glycine max (L.), following a foliar application made during early flowering. The residues of four classes of insecticides and three classes of fungicides were assessed at 1, 24, 72, 144, and 216 hours (h) after application on cotton leaves, the anthers of cotton flowers, and on soybean flowers. Specific active ingredient included acephate, imidacloprid, lambda-cyhalothrin, chlorantraniliprole, fluxapyroxad, pyraclostrobin, and propiconazole. Initial pesticide residues on cotton leaves were many times higher than those on cotton anthers or soybean flowers. With the exception of chlorantraniliprole on cotton leaves, fungicide residues tended to persist longer than insecticides. Also, pesticide residues on soybean flowers degraded more slowly than those on cotton leaves or anthers. For cotton leaves, insecticide residues decreased sharply within 24 h after application, again with the exception of chlorantraniliprole. All pesticide residues on cotton anthers were dramatically lower by 24 h after application, indicating little systemic movement to pollen. By 216 h after application, and considerably sooner in most scenarios, pesticide residues on cotton and soybean had diminished by 90% or more. The implications of these results on pest management and pollinator safety are discussed.