Comparing imidacloprid, clothianidin, and azoxystrobin runoff from lettuce fields using a soil drench or treated seeds in the Salinas Valley, California

Emily E Woodward; Michelle L Hladik; Anson R Main; Michael Cahn; James L Orlando; Jennifer Teerlink

doi:10.1016/j.envpol.2022.120325

Comparing imidacloprid, clothianidin, and azoxystrobin runoff from lettuce fields using a soil drench or treated seeds in the Salinas Valley, California

Environ Pollut. 2022 Dec 15:315:120325. doi: 10.1016/j.envpol.2022.120325. Epub 2022 Oct 10.

Authors

Emily E Woodward¹, Michelle L Hladik², Anson R Main³, Michael Cahn⁴, James L Orlando², Jennifer Teerlink³

Affiliations

¹ U.S. Geological Survey, California Water Science Center, Sacramento, CA, 95819, USA. Electronic address: ewoodward@usgs.gov.
² U.S. Geological Survey, California Water Science Center, Sacramento, CA, 95819, USA.
³ California Department of Pesticide Regulation, Sacramento, CA, 95814, USA.
⁴ University of California, Cooperative Extension, Monterey County, Salinas, CA, 93901, USA.

PMID: 36228859
DOI: 10.1016/j.envpol.2022.120325

Abstract

Neonicotinoid insecticide use has increased over the last decade, including as agricultural seed treatments (application of chemical in a coating to the seed prior to planting). In California, multiple crops, including lettuce, can be grown using neonicotinoid treated seeds or receive a direct neonicotinoid soil application (drenching) at planting. Using research plots, this study compared pesticide runoff in four treatments: (1) imidacloprid seed treatment; (2) clothianidin seed treatment; (3) imidacloprid drench and an azoxystrobin seed treatment; and (4) a control with no pesticidal treatment. Neonicotinoid and azoxystrobin concentrations were measured in surface water runoff during six irrigations events in the 2020 growing seasons. Results showed runoff concentrations up to 1308 (±1200) ng L^-1 for imidacloprid drench treatment, 431 (±100) ng L^-1 for clothianidin seed treatment, 135 (±60) ng L^-1 for imidacloprid seed treatment, and 13 (±10) ng L^-1 for azoxystrobin seed treatment (treatments averaged). The percent of applied mass in runoff over the entire sampling period varied by compound; the imidacloprid seed treatment and drench were similar (0.015 and 0.019%, respectively) to the clothianidin seed treatment (0.036%) while the azoxystrobin seed treatment was much higher (15%). Although the proportion of imidacloprid in runoff was similar for imidacloprid treatments, the mass applied during soil drench was > 4x the amount applied from the imidacloprid seed treatment. Surface soils were collected before planting and at the end of the trial. The neonicotinoids were detected in soil throughout the study and average maximum concentrations were 9-13 ng g^-1; azoxystrobin was detected in only two soils at concentrations up to 0.57 ng g^-1. These results elucidate the comparative mass runoff resulting from planting treated seed and soil drench applications and highlight the value of additional work to characterize off-site transport from the many commodities that may be utilizing treated seeds.

Keywords: Azoxystrobin; Irrigation runoff; Neonicotinoids; Seed coatings; Seed treatment; Transport.

MeSH terms

Animals
Arthropods*
Insecticides* / analysis
Lactuca
Neonicotinoids / analysis
Nitro Compounds / analysis
Seeds / chemistry
Soil / chemistry

Substances

imidacloprid
clothianidin
Soil
azoxystrobin
Neonicotinoids
Nitro Compounds
Insecticides