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.

Development of bespoke hardware and software to enable testing of a novel method of managing the charge and discharge of series-connected battery packs.

The novel feature of the method of battery management under development and testing is that routine balancing of the cells is eliminated throughout the service life of the battery pack. This requires preparation of the battery cells and configuration of the rigs in such a way as to ensure that the cells are accurately balanced on assembly and that thereafter there is no cell-to-cell variation in charge current or load at any time, measured to a low microamp level. In addition, the method requires a special charge control algorithm which was devised in order to accommodate cell-to-cell variations in capacity and dynamic response. Comprehensive experimental testing of this method, which is fully described in the associated paper (Hardy et al., 2023), required the development of hardware and software which would combine the necessary functions of a battery test rig and a battery management system capable of carrying out the special method of charge control described below. These included:•The automated control of contactors, loads and chargers to perform multiple charge/discharge cycles to predetermined patterns of current and maximum and minimum cell voltages.•Monitoring of cell voltages, current and temperature and the provision of test and diagnostic data.•Performing the safety functions of a Battery Management System to ensure that no cell was permitted to exceed limitations of current, voltage or temperature. The hardware and software were developed through three phases of testing with the operational principles (but not all the hardware and software elements) carrying over from one phase to the next.

Balancing Bees and Pest Management: Projected Costs of Proposed Bee-Protective Neonicotinoid Regulation in California.

Neonicotinoid insecticides are widely used in agriculture, including in many California specialty crops. With mounting evidence that these insecticides are harmful to bees, state and national governments have increasingly regulated their use. The European Union, Canada, and United States have imposed use restrictions on several neonicotinoids, such as on the timing of applications. In 2020, California proposed a draft regulation to mitigate harm to managed pollinators from four nitroguanidine-substituted neonicotinoids (NGNs): clothianidin, dinotefuran, imidacloprid, and thiamethoxam. We use data on California pesticide use from 2015 to 2017 to analyze the economic and pest management implications of the 2020 draft proposed regulation for seven crops: almond, cherry, citrus, cotton, grape, strawberry, and tomato. From 2015 to 2017, these crops accounted for approximately 85% of total hectares treated with NGNs and 87% of NGN use by kilograms of active ingredient applied in treatments that would have been affected by the proposed regulation. These insecticides often primarily target Hemipteran insect pests. In most cases there are alternatives; however, these are often more expensive per hectare and do not have the same residual effectiveness as the NGNs, which are systemic insecticides. Overall, we estimate that pest management costs for these crops would have increased an estimated $13.6 million in 2015, $12.8 million in 2016, and $11.1 million in 2017 if the 2020 draft proposed regulation had been in effect, representing a 61% to 72% increase in the cost of managing the target pests.

Assessment of pyrethroid contamination and potential mitigation strategies in California Central Coast surface waters.

Increased use of pyrethroids in the Central Coast of California since 2011 has resulted in a dramatic increase in the number and proportion of surface water samples with detectable concentrations at levels of concern to the public and state regulators. The goals of this study were to investigate the relationships between pyrethroid usage and environmental contamination, quantify and assess the potential risks, and recommend mitigation strategies. This study compiled the available pyrethroid use and surface water sampling data for the region, and then applied GIS methods to dynamic simulation modeling and usage-restriction buffer analyses. The results showed that in Monterey County alone, the agricultural usages of bifenthrin and permethrin each increased by ~50%, and the positive detection frequencies of both also increased around 2011-2013. County-wide, bifenthrin positive detections in surface water samples increased precipitously from 8.2% (7/85) for 2008-2012 up to 36.4% (106/291) for 2013-2017, and detections above its crustacean LC50 concentration went from 7.1% (6/85) to 35.7% (104/291). Despite its higher usage by mass, comparable figures for permethrin were more modest for the same time-periods, with positive detections going from 10.6% (9/85) to 14.4% (64/444), and detections above its crustacean LC50 going from 3.5% (3/85) to 7.2% (32/444). The seasonal lag between high bifenthrin usage in spring/summer and high detections in fall/winter samples showed the best correlations with 128- to 182-day lag times. This timing suggests that fallow season rain is likely the main driver of pyrethroid off-site movement into surface waters. SWAT modeling indicated that significant reductions in surface water permethrin concentrations only occurred with buffer distances of 1.6-3.2 km, but not with narrower buffers. However, if those wider buffers were implemented, permethrin could no longer be used on the majority of land where it is currently applied. Specifically, a 1.6-km buffer reduced the instream concentration by 8% but impacted 50% of the cropland, and a 3.2-km buffer reduced the concentration by 50% while impacting 76% of cropland. This study suggested that more promising alternative management practices could include an overall reduction in pyrethroid usage back to 2011 levels or other active mitigation strategies, like planting cover crops during the fallow winter wet season, or installing either vegetated buffer strips and/or sediment check dams on small tributaries to minimize sediment runoff.

Classical Biological Control of Invasive Legacy Crop Pests: New Technologies Offer Opportunities to Revisit Old Pest Problems in Perennial Tree Crops.

Advances in scientific disciplines that support classical biological control have provided "new tools" that could have important applications for biocontrol programs for some long-established invasive arthropod pests. We suggest that these previously unavailable tools should be used in biological control programs targeting "legacy pests", even if they have been targets of previously unsuccessful biocontrol projects. Examples of "new tools" include molecular analyses to verify species identities and likely geographic area of origin, climate matching and ecological niche modeling, preservation of natural enemy genetic diversity in quarantine, the use of theory from invasion biology to maximize establishment likelihoods for natural enemies, and improved understanding of the interactions between natural enemy and target pest microbiomes. This review suggests that opportunities exist for revisiting old pest problems and funding research programs using "new tools" for developing biological control programs for "legacy pests" could provide permanent suppression of some seemingly intractable pest problems. As a case study, we use citricola scale, Coccus pseudomagnoliarum, an invasive legacy pest of California citrus, to demonstrate the potential of new tools to support a new classical biological control program targeting this insect.

Contrasting the Tolerance of Wild and Domesticated Tomatoes to Herbivory: Agroecological Implications.

Application of plant life-history theory to strategies for breeding crop plants for sustainable agriculture remains relatively unexplored. We determined the relative tolerance of wild and domesticated tomatoes to simulated herbivory and evaluated plant characteristics that may contribute to tolerance. Wild and domesticated tomatoes were subjected to different levels of defoliation ranging from 0 to 70%. Single defoliation events at lower levels (15-30%) did not significantly affect total fruit mass produced in either wild or domesticated tomatoes. Increased defoliation resulted in significant reductions in total fruit mass per plant and mean mass per fruit. Reduction in fruit output by the cultivar was °3 times greater than the wild tomato for the first 8 wk of fruit production, whereas the loss in seasonal fruit production by the cultivar was 1.7 times greater than the wild tomato. We concluded that domestication of tomatoes may have decreased their relative tolerance to herbivory. Possible mechanisms for decreased tolerance include differences in leaf area index, light capture curves, and the relative allocation pattern to vegetative growth vs. reproductive structures. Optimization of potential life-history trade-offs between tolerance to herbivory and maximum fruiting abilities are proposed for cultivars of sustainable agriculture.