Christian H. Krupke

Multiple Routes of Pesticide Exposure for Honey Bees Living Near Agricultural Fields

Populations of honey bees and other pollinators have declined worldwide in recent years. A variety of stressors have been implicated as potential causes, including agricultural pesticides. Neonicotinoid insecticides, which are widely used and highly toxic to honey bees, have been found in previous analyses of honey bee pollen and comb material. However, the routes of exposure have remained largely undefined. We used LC/MS-MS to analyze samples of honey bees, pollen stored in the hive and several potential exposure routes associated with plantings of neonicotinoid treated maize. Our results demonstrate that bees are exposed to these compounds and several other agricultural pesticides in several ways throughout the foraging period. During spring, extremely high levels of clothianidin and thiamethoxam were found in planter exhaust material produced during the planting of treated maize seed. We also found neonicotinoids in the soil of each field we sampled, including unplanted fields. Plants visited by foraging bees (dandelions) growing near these fields were found to contain neonicotinoids as well. This indicates deposition of neonicotinoids on the flowers, uptake by the root system, or both. Dead bees collected near hive entrances during the spring sampling period were found to contain clothianidin as well, although whether exposure was oral (consuming pollen) or by contact (soil/planter dust) is unclear. We also detected the insecticide clothianidin in pollen collected by bees and stored in the hive. When maize plants in our field reached anthesis, maize pollen from treated seed was found to contain clothianidin and other pesticides; and honey bees in our study readily collected maize pollen. These findings clarify some of the mechanisms by which honey bees may be exposed to agricultural pesticides throughout the growing season. These results have implications for a wide range of large-scale annual cropping systems that utilize neonicotinoid seed treatments.

Effects of neonicotinoids and fipronil on non-target invertebrates

We assessed the state of knowledge regarding the effects of large-scale pollution with neonicotinoid insecticides and fipronil on non-target invertebrate species of terrestrial, freshwater and marine environments. A large section of the assessment is dedicated to the state of knowledge on sublethal effects on honeybees (Apis mellifera) because this important pollinator is the most studied non-target invertebrate species. Lepidoptera (butterflies and moths), Lumbricidae (earthworms), Apoidae sensu lato (bumblebees, solitary bees) and the section “other invertebrates” review available studies on the other terrestrial species. The sections on freshwater and marine species are rather short as little is known so far about the impact of neonicotinoid insecticides and fipronil on the diverse invertebrate fauna of these widely exposed habitats. For terrestrial and aquatic invertebrate species, the known effects of neonicotinoid pesticides and fipronil are described ranging from organismal toxicology and behavioural effects to population-level effects. For earthworms, freshwater and marine species, the relation of findings to regulatory risk assessment is described. Neonicotinoid insecticides exhibit very high toxicity to a wide range of invertebrates, particularly insects, and field-realistic exposure is likely to result in both lethal and a broad range of important sublethal impacts. There is a major knowledge gap regarding impacts on the grand majority of invertebrates, many of which perform essential roles enabling healthy ecosystem functioning. The data on the few non-target species on which field tests have been performed are limited by major flaws in the outdated test protocols. Despite large knowledge gaps and uncertainties, enough knowledge exists to conclude that existing levels of pollution with neonicotinoids and fipronil resulting from presently authorized uses frequently exceed the lowest observed adverse effect concentrations and are thus likely to have large-scale and wide ranging negative biological and ecological impacts on a wide range of non-target invertebrates in terrestrial, aquatic, marine and benthic habitats.

Seeds of Change: Corn Seed Mixtures for Resistance Management and Integrated Pest Management

ABSTRACT The use of mixtures of transgenic insecticidal seed and nontransgenic seed to provide an in-field refuge for susceptible insects in insect-resistance-management (IRM) plans has been considered for at least two decades. However, the U.S. Environmental Protection Agency has only recently authorized the practice. This commentary explores issues that regulators, industry, and other stakeholders should consider as the use of biotechnology increases and seed mixtures are implemented as a major tactic for IRM. We discuss how block refuges and seed mixtures in transgenic insecticidal corn, Zea mays L., production will influence integrated pest management (IPM) and the evolution of pest resistance. We conclude that seed mixtures will make pest monitoring more difficult and that seed mixtures may make IRM riskier because of larval behavior and greater adoption of insecticidal corn. Conversely, block refuges present a different suite of risks because of adult pest behavior and the lower compliance with IRM rules expected from farmers. It is likely that secondary pests not targeted by the insecticidal corn as well as natural enemies will respond differently to block refuges and seed mixtures.

Conclusions of the Worldwide Integrated Assessment on the risks of neonicotinoids and fipronil to biodiversity and ecosystem functioning

The side effects of the current global use of pesticides on wildlife, particularly at higher levels of biological organization: populations, communities and ecosystems, are poorly understood (Kohler and Triebskorn 2013). Here, we focus on one of the problematic groups of agrochemicals, the systemic insecticides fipronil and those of the neonicotinoid family. The increasing global reliance on the partly prophylactic use of these persistent and potent neurotoxic systemic insecticides has raised concerns about their impacts on biodiversity, ecosystem functioning and ecosystem services provided by a wide range of affected species and environments. The present scale of use, combined with the properties of these compounds, has resulted in widespread contamination of agricultural soils, freshwater resources, wetlands, non-target vegetation and estuarine and coastal marine systems, which means that many organisms inhabiting these habitats are being repeatedly and chronically expose...

Global warming presents new challenges for maize pest management

It has been conjectured that global warming will increase the prevalence of insect pests in many agro-ecosystems. In this paper, we quantitatively assess four of the key pests of maize, one of the most important systems in North American grain production. Using empirically generated estimates of pest overwintering thresholds and degree-day requirements, along with climate change projections from a high-resolution climate model, we project potential future ranges for each of these pests in the United States. Our analysis suggests the possibility of increased winter survival and greater degree-day accumulations for each of the pests surveyed. We find that relaxed cold limitation could expand the range of all four pest taxa, including a substantial range expansion in the case of corn earworm (H. zea), a migratory, cold-intolerant pest. Because the corn earworm is a cosmopolitan pest that has shown resistance to insecticides, our results suggest that this expansion could also threaten other crops, including those in high-value areas of the western United States. Because managing significant additional pressure from this suite of established pests would require additional pest management inputs, the projected decreases in cold limitation and increases in heat accumulation have the potential to significantly alter the pest management landscape for North American maize production. Further, these range expansions could have substantial economic impacts through increased seed and insecticide costs, decreased yields, and the downstream effects of changes in crop yield variability.

Non-cultivated plants present a season-long route of pesticide exposure for honey bees

Recent efforts to evaluate the contribution of neonicotinoid insecticides to worldwide pollinator declines have focused on honey bees and the chronic levels of exposure experienced when foraging on crops grown from neonicotinoid-treated seeds. However, few studies address non-crop plants as a potential route of pollinator exposure to neonicotinoid and other insecticides. Here we show that pollen collected by honey bee foragers in maize- and soybean-dominated landscapes is contaminated throughout the growing season with multiple agricultural pesticides, including the neonicotinoids used as seed treatments. Notably, however, the highest levels of contamination in pollen are pyrethroid insecticides targeting mosquitoes and other nuisance pests. Furthermore, pollen from crop plants represents only a tiny fraction of the total diversity of pollen resources used by honey bees in these landscapes, with the principle sources of pollen originating from non-cultivated plants. These findings provide fundamental information about the foraging habits of honey bees in these landscapes.

Evaluating western corn rootworm (Coleoptera: Chrysomelidae) emergence and root damage in a seed mix refuge.

ABSTRACT Resistance management is essential for maintaining the efficacy and long-term durability of transgenic corn engineered to control western corn rootworm (Diabrotica virgifera virgifera Le Conte). Theoretically, a refuge can be provided by growing susceptible (refuge) plants in either a separate section of the field adjacent to resistant (transgenic) plants, or as a seed mixture. We examined the effects of varying the structure of a 10 and 20% refuge between currently approved structured refuges (block or strip plantings), as well as deploying the refuge within a seed mix, on adult emergence timing and magnitude, root damage and yield. Our 2-yr field study used naturally occurring western corn rootworm populations and included seven treatments: 10 and 20% block refuge, 10 and 20% strip refuge, 10 and 20% seed mix refuge, and 100% refuge. Beetles emerging from refuge corn emerged more synchronously with those emerging from transgenic (Bacillus thuringiensis [Berliner] Bt-RW) corn in seed mix refuges when compared with block refuges. The proportion of beetles emerging from refuge plants was significantly greater in a block and strip refuge structure than in a seed mix refuge. More beetles emerged from Bt-RW corn plants when they were grown as part of a seed mix. We discuss the potential benefits and drawbacks of a seed mix refuge structure in light of these findings.

Field Attraction of the Stink Bug Euschistus conspersus (Hemiptera: Pentatomidae) to Synthetic Pheromone-Baited Host Plants

Abstract The attraction of the stink bug Euschistus conspersus Uhler to sources of the synthetic pheromone component methyl (2E,4Z)-decadienoate was investigated in a series of field experiments in native vegetation surrounding commercial apple orchards in Washington. In experiments with pheromone lures placed inside two different tube-type traps, stink bugs were attracted to the immediate area around traps in large numbers, but very few were caught in the traps. Pheromone lures attached directly to the host plant mullein, Verbascum thapsus L., demonstrated that these “baited” plants attracted significantly more E. conspersus than unbaited plants. Spring (reproductive) and summer (reproductively diapausing) E. conspersus adults, both males and females, were attracted to pheromone-baited plants. There was no significant difference in the number of male or female E. conspersus attracted to pheromone-baited traps or plants in any of the experiments, further characterizing methyl (2E,4Z)-decadienoate as an aggregation, and not a sex pheromone. Stink bug aggregations formed within 24–48 h of lure placement on mullein plants and remained constant until the lure was removed after which aggregations declined over 3–4 d to the level of unbaited plants. The implications of these studies for E. conspersus monitoring and management are discussed.

Ecology and management of the western bean cutworm (Lepidoptera: Noctuidae) in corn and dry beans.

The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a native North American pest that feeds mainly on corn and dry beans. The historical geographic range of the western bean cutworm covered the western Great Plains states, including Colorado, Nebraska, and Wyoming. Since 1999, the geographic range of the western bean cutworm has rapidly expanded eastward across the United States Corn Belt, causing significant and economic damage to corn and dry beans in parts of this region. This expansion has led to a resurgence of interest in this pest, particularly in areas where it has most recently caused damage. We summarize the ecology and biology of western bean cutworm and discuss options for scouting and management, with an emphasis in the expanded geographical range.

Intersections between neonicotinoid seed treatments and honey bees

A growing understanding of the often subtle unintended impacts of neonicotinoid seed treatments on both non-target organisms and their environment have led to concerns about the suitability of current pest management approaches in large scale agriculture. Several neonicotinoid compounds are used in seed treatments of the most widely grown grain and oilseed crops worldwide. Most applications are made prophylactically and without prior knowledge of pest populations. A growing body of evidence suggests that these compounds become contaminants of soil, water, and plant products, including pollen and nectar. These unforeseen routes of exposure are documented to have negative impacts on honey bee health and also have potential to exert effects on a broader environmental scale.