Water Quality Impairments Due to Aquatic Life Pesticide Toxicity: Prevention and Mitigation in California, USA

Developing agricultural pest management strategies with reduced-risks to surface water: An economic case study of California's Central Coast region

Pesticides are critical for protecting agricultural crops, but the off-site transport of these materials via spray drift and runoff poses risks to surface waters and aquatic life. California's Central Coast region is a major agricultural hub in the United States characterized by year-round production and intensive use of pesticides and other chemical inputs. As a result, the quality of many waterbodies in the region has been degraded. A recent regulatory program enacted by the Central Coast Regional Water Quality Control Board set new pesticide limits for waterways and imposed enhanced enforcement mechanisms to help ensure that water quality targets are met by specific dates. This regulatory program, however, does not mandate specific changes to pest management programs. In this study, we evaluate the economic, environmental, and pest management impacts of adopting two alternative pest management programs with reduced risks to surface water: 1) replacing currently used insecticide active ingredients (AIs) that pose the greatest risk to surface water with lower-risk alternatives and 2) converting conventional arthropod pest management programs to organic ones. We utilize pesticide use and toxicity data from California's Department of Pesticide Regulation to develop our baseline and two alternative scenarios. We focus on three crop groups (cole crops, lettuce and strawberry) due to their economic importance to the Central Coast and use of high-risk AIs. For Scenario 1, we estimate that implementing the alternative program in the years 2017-2019 would have reduced annual net returns on average by $90.26 - $190.54/ha, depending on the crop. Increased material costs accounted for the greatest share of this effect (71.9%-95.6%). In contrast, Scenario 2 would have reduced annual net returns on average by $5,628.12 - $18,708.28/ha during the study period, with yield loss accounting for the greatest share (92.8-97.9%). Both alternative programs would have reduced the associated toxic units by at least 98.1% compared to the baseline scenario. Our analysis provides important guidance for policymakers and agricultural producers looking to achieve environmental protection goals while minimizing economic impacts.

New-generation pesticides are prevalent in California's Central Coast streams

Pesticides are widely recognized as important biological stressors in streams, especially in heavily developed urban and agricultural areas like the Central California Coast region. We assessed occurrence and potential toxicity of pesticides in small streams in the region using two analytical methods: a broad-spectrum (223 compounds) method in use since 2012 and a newly developed method for 30 additional new-generation fungicides and insecticides. At least one pesticide compound was identified in 83 of the 85 streams sampled. About one-half (48%) of the 253 pesticides measured were detected at least once and 27 were detected in 10% or more of samples. Three of the top 4, and 6 of the top 10 most frequently detected compounds (chlorantraniliprole, dinotefuran, boscalid, thiamethoxam, clothianidin and the fluopicolide degradate 2,6-dichlorobenzamide) were analyzed by the new method. Pesticide mixtures were common, with two or more pesticide compounds detected in 81% of samples and 10 or more in 32% of samples. The pesticide count at a site was relatively consistent over the 6-week study. Four sites with mixed land-use in the lower basin (<5 km from the sampling site) tended to have the highest pesticide counts and the highest concentrations. Potential toxicity (assessed by comparison to benchmarks) to invertebrates was much more common than potential toxicity to fish or plants and was associated with a wide array of insecticides. The common occurrence of new-generation pesticides highlights the need to continuously update analytical methods to keep pace with changing pesticide use for a fuller assessment of pesticide occurrence and effects on the environment.

Clothianidin loaded TA/Fe (III) controlled-release granules: improve pesticide bioavailability and alleviate oxidative stress

Neonicotinoid insecticides have been widely used due to their excellent systemic activity and high insecticidal activity, but the problems of low utilization rate and environmental risk have attracted widespread attention. Controlled-release technology is an approach to realize the efficient utilization of pesticides and reduce environmental pressure. In this study, clothianidin (CLO) controlled-release granules (CLO@GR- TA (tannic acid)/Fe (III)) were prepared with TA/Fe (III) coordination chelate as the coating material. These granules exhibited the core-shell structure with 500-1200 µm of particle size, and had obvious release performance and hydrolysis behavior of coating materials. Pot experiments by root application showed that the CLO@GR-TA/Fe (III) showed balanced and lasting control efficacy to broad bean aphids. The plants have a stronger capacity for absorption and enrichment and a higher utilization rate of CLO for CLO@GR-TA/Fe (III), than those for 10% suspension concentrate (SC). One of the hydrolysates of coating materials, TA, a polyphenolic antioxidant, could improve the bioaccumulation amount and alleviating the oxidative stress response of CLO in plants. Our study illustrates that the controlled-release granules base on TA have efficient controlled-release properties and free radical scavenging performance that may eventually be used as pesticide carriers and antioxidants in the field of plant protection.