Sprays to kill adult mosquitoes are a source of insecticide exposure to beneficial insects, including pollinators,but the risks to pollinators are not well quantified. In this study, silicone bands were deployed to capture drift from hired home mosquito sprays and from mosquito control district (MCD) sprays. We found an average insecticide load of 1563.6 ng/g per band in hired spray yards, 28.6 ng/g in neighboring yards, and 7.3 ng/g in yards exposed to MCD sprays. We calculated honey bee “risk quotients” (an RQ of 1 = the LD50 for honey bees), and found concerning potential for risk to pollinators, with an average pyrethroid insecticide RQ of 6.6, 0.12, and 0.03 for yards with hired sprays, neighbor drift, and MCD sprays, respectively. Even though the latter two categories had lower risk quotients, there was considerable variation and some individual yards showed elevated levels with the potential to harm pollinators. We also calculated risk quotients for specific pyrethroids and three species of butterflies, and found levels of risk tied to moderate to high levels of risk in many yards. Our results suggest that, on a site by site basis, residential mosquito sprays, in particular barrier sprays performed by private companies, likely pose a significant risk to pollinators.

Human-managed green spaces in urban landscapes have become important focal points for insect conservation, partly because of the desirable insect diversity that these areas support, and also because exposure to nature is important for human health and wellbeing. An important issue in insect conservation is the extent to which nonpest insects are impacted by pesticide applications, but this has been relatively less examined outside of agricultural landscapes. Here, we investigated green spaces, including parks and private yards, in two urban areas (Sacramento, California, and Albuquerque, New Mexico, United States), asking if larval host plants for butterflies in the two regions contained herbicides, insecticides, and fungicides. We assayed 336 individual plants in 19 genera, including woody and herbaceous plants. Pesticide presence was ubiquitous: only 22 samples had no detectable levels of pesticides; the median number of compounds detected in the other 314 individual plants was three; and the maximum detected in any one plant was 18. Within Sacramento, azoxystrobin was detected in 84% of all samples, whereas atrazine was detected in 70% of samples within Albuquerque. Two compounds (azoxystrobin and chlorantraniliprole) were found to exceed concentrations that are known to cause lethal and sublethal effects in 71 out of 336 plants. Our results suggest that the effects of pesticides on nontarget species should be further explored in urban areas, and that nontarget effects on desirable insects are possible in these areas without thoughtful management and elimination of nonessential pesticide applications.

The decline of monarch butterflies in both the eastern and western United States has garnered widespread public interest. Planting milkweed, the larval host plants, has been promoted as one action that individuals can take, but little is known with respect to potential pesticide 27 contamination of store-bought milkweeds during the process of production and transport to 28 market. In this study, we collected 235 milkweed leaf samples from 33 retail nurseries across the 29 US to screen for pesticides. Across all samples, we detected 61 different pesticides with an 30 average of 12.2 compounds per leaf. While only 9 of these compounds have been experimentally 31 tested on monarch caterpillars, 89 samples contained a pesticide above a concentration shown to 32 have a sub-lethal effect for a monarch. We detected only a modest predictive ability of retailer 33 size and milkweed species; and plants with labels advertising their value for wildlife were not 34 more likely to have fewer pesticides at concentrations known to have a negative effect on 35 monarchs. These results demonstrate the extensiveness of pesticide exposure within nursery milkweeds and the potential impacts on monarchs and other insects consuming store-bought 37 plants.

The decline of monarch butterflies in both the eastern and western United States has garnered widespread public interest. Planting milkweeds, their larval host plants, has been promoted as one action individuals can take, but little is known with respect to potential pesticide contamination of store-bought milkweeds. In this study, we collected leaf samples from 235 milkweed plants purchased at 33 retail nurseries across the US to screen for pesticides. Across all samples, we detected 61 different pesticides with an average of 12.2 (±5.0) compounds per plant. While only 9 of these compounds have been experimentally tested on monarch caterpillars, 38% of samples contained a pesticide above a concentration shown to have a sub-lethal effect for monarchs. We detected only a modest predictive ability of retailer size and milkweed species; and plants with labels advertising their value for wildlife did not have fewer pesticides at concentrations known to have a negative effect on monarchs. These results demonstrate the extensiveness of pesticide exposure within nursery milkweeds and the potential impacts on monarchs and other insects exposed to store-bought plants. Highlights Milkweeds were collected from stores in the United States and screened for pesticides. We detected multiple pesticides in every milkweed plant sampled. Over one third of samples contained a pesticide at a known harmful concentration for monarchs. Plants labeled as wildlife-friendly did not have fewer potentially harmful compounds.

Farmers, regulators, and researchers rely on pesticide use data to assess the effects of pesticides on crop yield, farm economics, off-target organisms, and human health. The publicly available pesticide use data in the United States do not currently account for pesticides applied as seed treatments. We find that seed treatment use has increased in major field crops over the last several decades but that there is a high degree of uncertainty about the extent of acreage planted with treated seeds, the amount of regional variability, and the use of certain active ingredients. One reason for this uncertainty is that farmers are less likely to know what pesticides are on their seed than they are about what pesticides are applied conventionally to their crops. This lack of information affects the quality and availability of seed treatment data and also farmers' ability to tailor pesticide use to production and environmental goals.

Monarch butterflies ( Danaus plexippus ) are in decline in the western United States and are encountering a range of anthropogenic stressors. Pesticides are among the factors that likely contribute to this decline, though the concentrations of these chemicals in non-crop plants is not well documented, especially in complex landscapes with a diversity of crop types and land uses. In this study, we collected 227 milkweed ( Asclepias spp.) leaf samples from 19 sites representing different land use types across the Central Valley of California. We also sampled plants purchased from two stores that sell to home gardeners. We found 64 pesticides (25 insecticides, 27 fungicides, and 11 herbicides, as well as 1 adjuvant) out of a possible 262 in our screen. Pesticides were detected in every sample, even at sites with little or no pesticide use based on information from landowners. On average, approximately 9 compounds were detected per plant across all sites, with a range of 1 to 25 compounds in any one sample. For the vast majority of pesticides detected, we do not know the biological effects on monarch caterpillars that consume these plants, however we did detect a few compounds for which effects on monarchs have been experimentally investigated. Chlorantraniliprole in particular was identified in 91% of our samples and found to exceed a tested LD 50 for monarchs in 58 out of 227 samples. Our primary conclusion is the ubiquity of pesticide presence in milkweeds in an early-summer window of time that monarch larvae are likely to be present in the area. Thus, these results are consistent with the hypothesis that pesticide exposure could be a contributing factor to monarch declines in the western United States. This both highlights the need for a greater understanding of the lethal and sublethal effects of these compounds (individually, additively, and synergistically) and suggests the urgent need for strategies that reduce pesticide use and movement on the landscape. Contribution to the Field Insects are facing multifaceted stressors in the Anthropocene and are in decline in many parts of the world. The widespread use of pesticides is believed to be an important part of the problem. In particular, the monarch butterfly is in sharp decline in the western United States. Here we show that milkweeds in the Central Valley of California, a large urban and agricultural landscape that is part of the monarch breeding and migration route, are contaminated with a diverse array of pesticides. We found a few in high concentrations and many in trace amounts. We do not know how these compounds act together and with other large-scale stressors to cause declines, but it is clear that monarchs and other non-target insects are encountering these pesticides. These results provide critical insight into the growing literature on the impact of pesticides on butterflies specifically and non-target insects more broadly. We hope these field realistic concentrations will aid in the design of further experiments in the field and the lab.

The relationship between pesticides and pollinators, while attracting no shortage of attention from scientists, regulators, and the public, has proven resistant to scientific synthesis and fractious in matters of policy and public opinion. This is in part because the issue has been approached in a compartmentalized and intradisciplinary way, such that evaluations of organismal pesticide effects remain largely disjoint from their upstream drivers and downstream consequences. Here, we present a socioecological framework designed to synthesize the pesticide-pollinator system and inform future scholarship and action. Our framework consists of three interlocking domains-pesticide use, pesticide exposure, and pesticide effects-each consisting of causally linked patterns, processes, and states. We elaborate each of these domains and their linkages, reviewing relevant literature and providing empirical case studies. We then propose guidelines for future pesticide-pollinator scholarship and action agenda aimed at strengthening knowledge in neglected domains and integrating knowledge across domains to provide decision support for stakeholders and policymakers. Specifically, we emphasize (1) stakeholder engagement, (2) mechanistic study of pesticide exposure, (3) understanding the propagation of pesticide effects across levels of organization, and (4) full-cost accounting of the externalities of pesticide use and regulation. Addressing these items will require transdisciplinary collaborations within and beyond the scientific community, including the expertise of farmers, agrochemical developers, and policymakers in an extended peer community.

approved: Catherine Neumann The purpose of this study was to apply the Combined Index (Con, a hazard screening tool, developed by Dr. Debra Forman of EPA Region III Office of Air Radiation and Toxics Division, to the 1994 and 1995 Oregon Toxic Chemical Release Inventory (TRI) for pollution prevention and facility targeting analysis. This tool adds a chemical-specific, quantitatively derived toxicity factor to the mass (pounds per year -lbs./yr) of each chemical released on-site by TRI facilities. The mass and Col rankings were compared within chemical, facility, and industrial sector sections. In 1994, an estimated 18,926,399lbs of chemicals were released onsite (air, water, and land) in Oregon by 229 TRI facilities. The top ranking chemical by total mass was methanol with 6,873,392 lbs released; in contrast, by Col, methanol ranked 12th. The top Col ranking chemical was certain glycol ethers (represented by 2methoxyethanol), it ranked 15th by mass with 233, 174lbs released on-site. There was an estimated 21, 194, 711 lbs of chemical released on-site in Oregon by 208 TRI facilities in 1995. Methanol was the chemical released by all facilities in Oregon in the highest quantity; its rank dropped to 13th with the application of the Col. The top ranking Col chemical was polychlorinated alkanes, not listed in 1994 releases. IN contrast, by total mass, polychlorinated alkanes ranked 43rd, with 7,345lbs released. In 1994, the facility that released the largest mass of chemicals (2,650,637 lbs) into the environment in Oregon was a Redacted for Privacy paper company. The chemical that contributed the most to this facility's rank (known as the mass trigger chemical) was methanol with 1, 7 48,200 lbs released. In contrast, following ranking using the Col, the top facility was an instruments manufacturer that reported a total mass release of 9,975 lbs of ethylene oxide. In 1995, the same paper facility ranked first by mass; its total estimated releases were 2,650,637lbs, 68.3% (1,810,900 lbs) of that release was methanol. The top ranking facility following Col ranking was a transportation equipment facility with a total mass of 95,880 lbs of chemicals released into the environment. The Col trigger chemical for this facility was polychlorinated alkanes with 7,345lbs released. There were 18 and 19 industrial sectors reporting to the 1994 and 1995 Oregon TRI respectively. The industrial sector that ranked highest by mass in 1994 was the paper industry (SIC 26xx) contributing 48% or 9,269,309 lbs of the total TRI chemical releases. The paper industry also ranked highest following Col ranking. In 1995, the paper industry again ranked highest by mass with 44% of the total reported releases (9,55,976lbs). In contrast, using the Col, the transportation equipment industry (SIC 37xx) ranked first with 1,157,412lbs released. The vast majority of TRI chemicals released in Oregon were into the air. In 1994, stack gas releases contributed 71% (13,515,276 lbs) to the total on-site releases in Oregon. Stack gases also ranked highest based on Col ranking for all media releases. Likewise, in 1995, 69% (6,931,057 lbs) of all chemical releases in Oregon were from stack gases. Stack gas emissions also placed first following Col ranking. Based on Col ranking, the TRI chemicals released in Oregon in 1994 and 1995 of highest concern include certain glycol ethers, polychlorinated alkanes, ethylene oxide and trichloroethylene. In contrast, relying on mass alone methanol, ammonia, toluene and formaldehyde were identified as top chemicals of concern. The transportation equipment and instruments sectors (SIC 38xx) were identified using Col as being the sectors of highest potential public health concern for their releases in Oregon. While the paper sector, ranked first based on totallbs released in Oregon, but was of diminished public health concern relative to the other two sectors. This trend was sll.own both by the overall industrial sector analysis as well as the industrial sector-specific media analyses. Use of the Combined Index, A Hazard Screening Tool, to Target for Pollution Prevention in the State of Oregon