Non-Target Insects and Beneficial Species
Impact of Pesticides on Non-Target Insects and Beneficial Species
Non-target and beneficial species can be impacted by pesticides through direct or indirect routes, such as water contamination and runoff, pesticide residues, and by consuming food that has been sprayed.
- A 2014 study published in Chemosphere examined the effects of different pesticides on a common insect predator.
- Researchers found that exposure to some pesticides were lethal, while exposure to others led to a decrease in plant feeding time and reduced predation rates.
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A study on non-target molluscan herbivores and their insect predators found that neonicotinoid seed-treated soy beans can unintentionally impact predatory, beneficial insects through a previously unexplored pathway.
Chlaenius tricolor, beneficial beetle - Soy beans were treated with the neonicotinoid thiamethoxam.
- The seed treatments had zero effect on pest slugs, and instead were bioaccumulated and then transferred through the slugs into their insect predators, impairing or killing >60%.
- This resulted in a loss of crop due to a decline in beneficial insect predators and an increase in pest slug population.
[See More Scientific Studies Below]
Economic Cost
The European Academies' Science Advisory Council (EASAC) estimates global natural pest control to be worth $100 billion annually. Natural pest control is where insects consume pests so that chemicals are not necessary. It focuses on encouraging predatory insects to consume pests, which is a least-toxic approach that is undermined through chemical usage by destroying the balance that exists within a predator-prey relationship.
Non-target insects also act as a food source for animals that bring in a substantial amount of revenue. US citizens spend over $60 billion annually on hunting, fishing and observing wildlife, much of which is dependent on insects as a food source. Researchers have found that there is a steady decline in these insects due to pesticide exposure and an overall decline in biodiversity. It could be concluded then that, as beneficial insect populations decline, their ability to provide ecosystem services will also decline, impacting the available wildlife for hunting, fishing, and observing. The demand for these recreational activities will stay constant while the supply (availability) will decline, causing an increase in dollars spent by US citizens for each year.
Litigation & Lawsuits
See our Pollinators and Soil Biota pages.
What Can You Do?
- Learn about the Hazards and Alternatives to using lawn pesticides.
- Go Organic – Visit our Eating with a Conscience page to learn why eating organic foods is the right choice.
- Visit our Tools for Change page to learn how to organize your community against pesticide use.
- Sign up for Beyond Pesticides’ Action Alerts to stay up-to-date on the latest petitions and news.
Scientific Studies:
As agricultural production increases, the use of chemical fertilisers, herbicides, and other synthetic pesticides has equally increased over the years. Inadequate pesticide application description and monitoring has generated a heated debate among governmental organisations, agricultural industries, and conservation organisations about pesticide effects on insect species richness and abundance. This review is therefore aimed at summarizing the decline in insects’ species and individual numbers as a result of extensive pesticide utilisation and recommends possible management strategies for its mitigation. This review revealed an average pesticide application of 1.58 kg per ha per year, 0.37 kg per person per year, and 0.79 kg per USD 1000 per year. Insects have experienced a greater species abundance decline than birds, plants, and other organisms, which could pose a significant challenge to global ecosystem management. Although other factors such as urbanisation, deforestation, monoculture, and industrialisation may have contributed to the decline in insect species, the extensive application of agro-chemicals appears to cause the most serious threat. Therefore, the development of sustainable and environmentally friendly management strategies is critical for mitigating insect species’ decline.
[Quandahor, P. et al. (2024) Effects of agricultural pesticides on decline in insect species and individual numbers, Environments. Available at: https://www.mdpi.com/2076-3298/11/8/182.]
Mounting evidence shows overall insect abundances are in decline globally. Habitat loss, climate change, and pesticides have all been implicated, but their relative effects have never been evaluated in a comprehensive large-scale study. We harmonized 17 years of land use, climate, multiple classes of pesticides, and butterfly survey data across 81 counties in five states in the US Midwest. We find community-wide declines in total butterfly abundance and species richness to be most strongly associated with insecticides in general, and for butterfly species richness the use of neonicotinoid-treated seeds in particular. This included the abundance of the migratory monarch (Danaus plexippus), whose decline is the focus of intensive debate and public concern. Insect declines cannot be understood without comprehensive data on all putative drivers, and the 2015 cessation of neonicotinoid data releases in the US will impede future research.
[Deynze, B.V. et al. (2024) Insecticides, more than herbicides, land use, and climate, are associated with declines in butterfly species richness and abundance in the American Midwest, PLoS ONE. Available at: https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0304319. ]
Despite the major role that insect pollinators play in crop production, agricultural intensification drives them into decline. Various conservation measures have been developed to mitigate the negative effects of agriculture on insect pollinators.
In a novel comparison of the efficacy of three conservation measures on honeybee colony growth, we monitored experimental honeybee colonies in 16 landscapes that comprised orthogonal gradients of organic agriculture, annual flower strips and perennial semi-natural habitats. Using structural equation modelling, we assessed the effects of conservation measures on the prevalence of 11 parasites, Varroa destructor loads and their collective impact on colony growth.
Increasing area coverage of perennial semi-natural habitat related to higher V. destructor load and indirectly to lower colony growth.
Increasing area of annual flower strips was associated with lower V. destructor load and indirectly with higher colony growth.
Increasing area of organic farming related to lower parasite richness and also directly to improved colony growth.
Synthesis and applications: Landscape features can affect pollinators directly through the provision of food resources and indirectly through modulation of parasite prevalence. To promote honeybee colony health in agro-ecosystems, our results suggest that organic agriculture and annual flower strips should be prioritized conservation measures. Landscape management should consider the merits and demerits of different measures to sustain healthy populations of pollinators in agro-ecosystems.
[Pluta, P. et al. (2024) Organic farming and annual flower strips reduce parasite prevalence in honeybees and boost colony growth in agricultural landscapes, Journal of Applied Ecology. Available at: https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.14723. ]
Ecological risk assessments (ERAs) are crucial when developing national strategies to manage adverse effects from pesticide exposure to natural populations. Yet, estimating risk with surrogate species in controlled laboratory studies jeopardizes the ERA process because natural populations exhibit intraspecific variation within and across species. Here, we investigate the extent to which the ERA process underestimates the risk from pesticides on different species by conducting a meta-analysis of all records in the ECOTOX Knowledgebase for honey bees and wild bees exposed to neonicotinoids. We found the knowledgebase is largely populated by acute lethality data on the Western honey bee and exhibits within and across species variation in LD50 up to 6 orders of magnitude from neonicotinoid exposure. We challenge the reliability of surrogate species as predictors when extrapolating pesticide toxicity data to wild pollinators and recommend solutions to address the (a)biotic interactions occurring in nature that make such extrapolations unreliable in the ERA process.
[Shahmohamadloo, R., Guzman, L. and Tissier, M. (2024) Risk assessments underestimate threat of pesticides to wild bees, Conservation Letters. Available at: https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/conl.13022. ]
Bees carry out vital ecosystem services by pollinating both wild and economically important crop plants. However, while performing this function, bee pollinators may encounter potentially harmful xenobiotics in the environment such as pesticides (fungicides, herbicides and insecticides). Understanding the key factors that influence the toxicological outcomes of bee exposure to these chemicals, in isolation or combination, is essential to safeguard their health and the ecosystem services they provide. In this regard, recent work using toxicogenomic and phylogenetic approaches has begun to identify, at the molecular level, key determinants of pesticide sensitivity in bee pollinators. These include detoxification systems that convert pesticides to less toxic forms and key residues in insecticide target-sites that underlie species-specific insecticide selectivity. Here we review this emerging body of research and summarise the state of knowledge of the molecular determinants of pesticide sensitivity in bee pollinators. We identify gaps in our knowledge for future research and examine how an understanding of the genetic basis of bee sensitivity to pesticides can be leveraged to, a) predict and avoid negative bee-pesticide interactions and facilitate the future development of pest-selective bee-safe insecticides, and b) inform traditional effect assessment approaches in bee pesticide risk assessment and address issues of ecotoxicological concern.
[Bass, C. et al (2024) The molecular determinants of pesticide sensitivity in bee pollinators, Science of The Total Environment. Available at: https://www.sciencedirect.com/science/article/pii/S0048969724003097.]
Biodiversity plays a fundamental role in enhancing agricultural resilience and sustaining food production by supporting critical ecosystem services. A diverse array of species within agroecosystems, from crops and livestock to soil organisms and pollinators, contributes to the stability, productivity, and adaptability of farming systems. This biodiversity-driven resilience is essential for mitigating the impacts of climate change, pests, diseases, and resource scarcity, which pose significant threats to global food security. Agricultural systems rich in biodiversity benefit from improved soil fertility, enhanced pollination, natural pest control, and water regulation, all of which reduce dependence on external inputs such as chemical fertilizers and pesticides. Moreover, maintaining genetic diversity within crops and livestock strengthens resilience against environmental stressors and promotes long-term sustainability. However, modern intensive agricultural practices, including monocropping and the overuse of agrochemicals, have resulted in significant biodiversity loss, compromising ecosystem health. This article explores the role of biodiversity in agricultural resilience, examines the threats posed by conventional farming practices, and discusses strategies for integrating biodiversity into agricultural systems to protect ecosystem services. By fostering biodiversity, farmers and policymakers can enhance the sustainability and resilience of agricultural landscapes, contributing to global food security in a changing climate.
[Christianah, D. and Folarin, I. (2024) The Role of Biodiversity in Agricultural Resilience: Protecting Ecosystem Services for Sustainable Food Production, International Journal of Research Publication and Reviews. Available at: https://www.researchgate.net/publication/384848907_The_Role_of_Biodiversity_in_Agricultural_Resilience_Pr]
In North America, approximately 21 % (739 species) of the total wild bee diversity is known to be associated with crops, with bee species varying in the extent of this association. While current evaluations of pesticide effects on bees primarily focus on a limited subset of species, a new focus is needed to ensure comprehensive protection of all wild bees in agricultural contexts. This study introduces a novel approach to characterize and compare the relative potential pesticide risk for wild bee species of their association with crops. Using intrinsic bee vulnerability traits and extrinsic factors like crop toxic loads and association strength, we calculated Bee-Crop Risk Scores for 594 wild bee species, identifying those experiencing the highest potential risk from pesticide exposure in North American agroecosystems. We discuss the influence of intrinsic and extrinsic factors on the relative potential risk calculated and outline avenues for refining our approach. As most species facing the highest potential risk from pesticide exposure across North America are ground-nesters, our study suggests that species (e.g., Osmia spp., Megachile spp.) commonly proposed as models for pesticide risk assessments may not accurately represent risk for those bee species facing the highest potential risk in agricultural contexts.
[Chan, D. and Rondeau, S. (2024) Understanding and comparing relative pesticide risk among North American wild bees from their association with agriculture, Science of The Total Environment. Available at: https://www.sciencedirect.com/science/article/pii/S0048969724055281.]
Declining bee populations diminish pollination services, damaging plant and agricultural biodiversity. One of the causes of this decline is the use of pesticides. Pesticides with glyphosate as the main active ingredient are among the most used pesticides worldwide, being the most used in Brazil. This study determined the 24 and 48 h LD50 (median lethal dose) of the herbicide’s glyphosate-based formulation by ingestion, identified sublethal doses, and investigated its effects on the locomotion and behavior of Tetragonisca angustula workers. The LD50 found indicates that a glyphosate-based formulation is highly toxic to T. angustula. The doses applied, including concentrations found in nature, caused death, motor changes (decreased speed and tremors), excessive self-cleaning, and disorientation (return to light and stop). Although we did not test for pollination effects, we can infer from our results that this formulation can negatively affect the pollination activity of T. angustula. Evaluation of the toxicity and sublethal effects of pesticides on bees contributes to a better understanding of their harmful effects on hives and allows for the development of strategies to reduce these impacts.
[Prado, I.S., da Rocha, A.A., Silva, L.A. and Gonzalez, V.C., 2023. Ecotoxicology, 32(4), pp.513-524.]
Even though honey bees in the field are routinely exposed to a complex mixture of many different agrochemicals, few studies have surveyed toxic effects of pesticide mixtures on bees. To elucidate the interactive actions of pesticides on crop pollinators, we determined the individual and joint toxicities of thiamethoxam (THI) and other seven pesticides [dimethoate (DIM), methomyl (MET), zeta-cypermethrin (ZCY), cyfluthrin (CYF), permethrin (PER), esfenvalerate (ESF) and tetraconazole (TET)] to honey bees (Aplis mellifera) with feeding toxicity test. Results from the 7-days toxicity test implied that THI elicited the highest toxicity with a LC50 data of 0.25 (0.20–0.29) μg mL−1, followed by MET and DIM with LC50 data of 4.19 (3.58–4.88) and 5.30 (4.65–6.03) μg mL−1, respectively. By comparison, pyrethroids and TET possessed relatively low toxicities with their LC50 data from the range of 33.78 (29.12–38.39) to 1125 (922.4–1,442) μg mL−1. Among 98 evaluated THI-containing binary to octonary mixtures, 29.59% of combinations exhibited synergistic effects. In contrast, 18.37% of combinations exhibited antagonistic effects on A. mellifera. Moreover, 54.8% pesticide combinations incorporating THI and TET displayed synergistic toxicities to the insects. Our findings emphasized that the coexistence of several pesticides might induce enhanced toxicity to honey bees. Overall, our results afforded worthful toxicological information on the combined actions of neonicotinoids and current-use pesticides on honey bees, which could accelerate farther comprehend on the possible detriments of other pesticide mixtures in agro-environment.
[Li, W. et al. (2023) Mixture effects of thiamethoxam and seven pesticides with different modes of action on honey bees (Aplis mellifera), Scientific Reports. Available at: https://www.nature.com/articles/s41598-023-29837-w#ref-CR30. ]
Piperonyl butoxide (PBO) is a popular insecticide synergist present in thousands of commercial, agricultural, and household products. PBO inhibits cytochrome P450 activity, impairing the ability of insects to detoxify insecticides. PBO was recently discovered to also inhibit Sonic hedgehog signaling, a pathway required for embryonic development, and rodent studies have demonstrated the potential for in utero PBO exposure to cause structural malformations of the brain, face, and limbs, or more subtle neurodevelopmental abnormalities. The current understanding of the pharmacokinetics of PBO in mice is limited, particularly with respect to dosing paradigms associated with developmental toxicity. To establish a pharmacokinetic (PK) model for oral exposure, PBO was administered to female C57BL/6J mice acutely by oral gavage (22–1800 mg/kg) or via diet (0.09 % PBO in chow). Serum and adipose samples were collected, and PBO concentrations were determined by HPLC-MS/MS. The serum concentrations of PBO were best fit by a linear one-compartment model. PBO concentrations in visceral adipose tissue greatly exceeded those in serum. PBO concentrations in both serum and adipose tissue decreased quickly after cessation of dietary exposure. The elimination half-life of PBO in the mouse after gavage dosing was 6.5 h (90 % CI 4.7–9.5 h), and systemic oral clearance was 83.3 ± 20.5 mL/h. The bioavailability of PBO in chow was 41 % that of PBO delivered in olive oil by gavage. Establishment of this PK model provides a foundation for relating PBO concentrations that cause developmental toxicity in the rodent models to Sonic hedgehog signaling pathway inhibition.
[Jenkins, A. et al. (2023) Pharmacokinetic analysis of acute and dietary exposure to piperonyl butoxide in the mouse, Toxicology Reports. Available at: https://www.sciencedirect.com/science/article/pii/S2214750023001099. ]
The widespread use of glyphosate-based formulations to eliminate unwanted vegetation has increased concerns regarding their effects on non-target organisms, such as honey bees and their gut microbial communities. These effects have been associated with both glyphosate and co-formulants, but it is still unknown whether they translate to other bee species. In this study, we tested whether glyphosate, pure or in herbicide formulation, can affect the gut microbiota and survival rates of the eastern bumble bee, Bombus impatiens. We performed mark-recapture experiments with bumble bee workers from four different commercial colonies, which were exposed to field relevant concentrations of glyphosate or a glyphosate-based formulation (0.01 mM to 1 mM). After a 5-day period of exposure, we returned the bees to their original colonies, and they were sampled at days 0, 3 and 7 post-exposure to investigate changes in microbial community and microbiota resilience by 16S rRNA amplicon sequencing and quantitative PCR. We found that exposure to glyphosate, pure or in herbicide formulation, reduced the relative abundance of a beneficial bee gut bacterium, Snodgrassella, in bees from two of four colonies when compared to control bees at day 0 post-exposure, but this reduction became non-significant at days 3 and 7 post-exposure, suggesting microbiota resilience. We did not find significant changes in total bacteria between control and exposed bees. Moreover, we observed an overall trend in decreased survival rates in bumble bees exposed to 1 mM herbicide formulation during the 7-day post-exposure period, suggesting a potential negative effect of this formulation on bumble bees.
[Motta, E.V. and Moran, N.A., 2023. Science of The Total Environment, 872, p.162102.]
Several previous studies have investigated changes in insect biodiversity, with some highlighting declines and others showing turnover in species composition without net declines. Although research has shown that biodiversity changes are driven primarily by land-use change and increasingly by climate change, the potential for interaction between these drivers and insect biodiversity on the global scale remains unclear. Here we show that the interaction between indices of historical climate warming and intensive agricultural land use is associated with reductions of almost 50% in the abundance and 27% in the number of species within insect assemblages relative to those in less-disturbed habitats with lower rates of historical climate warming. These patterns are particularly evident in the tropical realm, whereas some positive responses of biodiversity to climate change occur in non-tropical regions in natural habitats. A high availability of nearby natural habitat often mitigates reductions in insect abundance and richness associated with agricultural land use and substantial climate warming but only in low-intensity agricultural systems. In such systems, in which high levels (75% cover) of natural habitat are available, abundance and richness were reduced by 7% and 5%, respectively, compared with reductions of 63% and 61% in places where less natural habitat is present (25% cover). Our results show that insect biodiversity will probably benefit from mitigating climate change, preserving natural habitat within landscapes and reducing the intensity of agriculture.
[Outhwaite, C.L., McCann, P. and Newbold, T., Nature, pp.1-6.]
The risk of honey bee (Apis mellifera L.) exposure to pesticide residues while foraging for nectar and pollen is commonly explored in the context of agroecosystems. However, pesticides are also used in urban and suburban areas for vegetation management, vector control, and the management of ornamental plants in public and private landscapes. The extent to which pesticides pose a health risk to honey bees in these settings remains unclear. We addressed this at a landscape scale by conducting pesticide residue screening analyses on 768 nectar and 862 pollen samples collected monthly over 2 years from honey bee colonies located in urban and suburban areas in eight medium to large cities in California, Florida, Michigan, and Texas (USA). A risk assessment was performed using the US Environmental Protection Agency's BeeREX model whenever an oral toxicity value was available for a compound. Chemical analyses detected 17 pesticides in nectar and 60 in pollen samples during the survey. Approximately 73% of all samples contained no detectable pesticide residues. Although the number of detections varied among the sampled regions, fewer pesticides were detected in nectar than in pollen. Per BeeREX, four insecticides showed a potential acute risk to honey bees: imidacloprid, chlorpyrifos, and esfenvalerate in nectar, and deltamethrin in nectar and pollen. In general, exposure of honey bees to pesticides via nectar and pollen collection was low in urban and suburban areas across the United States, and no seasonal or spatial trends were evident. Our data suggest that honey bees are exposed to fewer pesticides in developed areas than in agricultural ones.
[Démares, F.J. et al. (2022) Honey Bee (Apis mellifera) Exposure to Pesticide Residues in Nectar and Pollen in Urban and Suburban Environments from Four Regions of the United States, Environmental Toxicology and Chemistry. Available at: https://setac.onlinelibrary.wiley.com/doi/10.1002/etc.5298. ]
Deltamethrin and piperonyl butoxide two synthetic pyrethroids, when used in a combination it produces synergistic effect. This two insecticide has found to be widely used in the management of mosquito, housefly and other insects to control the various vector born diseases. In this review we assessed the toxic effect of deltamethrin and piperonyl butoxide on beneficial organisms commonly available in the ecosystem. It was found to be toxic to fish, honey bees the prime pollinators of crop plant; earthworm is also susceptible at a lethal concentration for a particular exposure. As far the birds are concerned, they have a less toxic risk in lower concentration of exposure. The alterations obtained in the hematological, biochemical and histopathological studies, further conclude that it can cause environment hazards and toxic to the non-targeted organisms. This investigation gives an insight into the combined toxicological profile of deltamethrin and PBO for better risk assessment and safe use of pyrethroids and their synergist in non-targeted organisms.
[Basak, Mrinmoy and Choudhury, Rejwan Ahmed and Goswami, Priyanka and Dey, Biplab Kumar and Laskar, Moksood Ahmed (2021) A Review on Non-target Toxicity of Deltamethrin and Piperonyl Butoxide: Synergist. Journal of Pharmaceutical Research International, http://scholar.researcherseuropeans.com/id/eprint/323/]
Major declines in insect biomass and diversity, reviewed here, have become obvious and well documented since the end of World War II. Here, we conclude that the spread and intensification of agriculture during the past half century is directly related to these losses. In addition, many areas, including tropical mountains, are suffering serious losses because of climate change as well. Crops currently occupy about 11% of the world’s land surface, with active grazing taking place over an additional 30%. The industrialization of agriculture during the second half of the 20th century involved farming on greatly expanded scales, monoculturing, the application of increasing amounts of pesticides and fertilizers, and the elimination of interspersed hedgerows and other wildlife habitat fragments, all practices that are destructive to insect and other biodiversity in and near the fields. Some of the insects that we are destroying, including pollinators and predators of crop pests, are directly beneficial to the crops. In the tropics generally, natural vegetation is being destroyed rapidly and often replaced with export crops such as oil palm and soybeans. To mitigate the effects of the Sixth Mass Extinction event that we have caused and are experiencing now, the following will be necessary: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice that empowers the less wealthy people and nations of the world, where the vast majority of us live, will be necessary.
[Raven, P. and Wagner, D. (2021) Agricultural intensification and climate change are rapidly decreasing insect biodiversity, PNAS. Available at: https://www.pnas.org/doi/abs/10.1073/pnas.2304663120. ]
Critical gaps in understanding how species respond to environmental change limit our capacity to address conservation risks in a timely way. Here, we examine the direct and interactive effects of key global change drivers, including climate change, land use change, and pesticide use, on persistence of 104 odonate species between two time periods (1980–2002 and 2008–2018) within 100 × 100 km quadrats across the USA using phylogenetic mixed models. Non-target effects of pesticides interacted with higher maximum temperatures to contribute to odonate declines. Closely related species responded similarly to global change drivers, indicating a potential role of inherited traits in species’ persistence or decline. Species shifting their range to higher latitudes were more robust to negative impacts of global change drivers generally. Inherited traits related to dispersal abilities and establishment in new places may govern both species’ acclimation to global change and their abilities to expand their range limits, respectively. This work is among the first to assess effects of climate change, land use change, and land use intensification together on Odonata, a significant step that improves understanding of multispecies effects of global change on invertebrates, and further identifies conditions contributing to global insect loss.
[Sirois-Delisle, C. and Kerr, J.T., 2021. ]
Survey data show a large-scale decline in insects. This global decline is often linked to human actions in intensive agricultural areas. To investigate whether this decline has a causal relationship with neonicotinoid insecticides, we performed an outdoor experiment with representative surface water concentrations of the neonicotinoid thiacloprid. We exposed naturally formed aquatic communities to increasing neonicotinoid concentrations and monitored insect emergence during a 3-mo period. We show that increasing neonicotinoid concentrations strongly decreased the abundance and biomass of five major insect orders that together comprised >99% of the 55,574 collected insects as well as the diversity of the most species-rich freshwater family, thus showing a causal relation between insect decline and neonicotinoids.
[Barmentlo, S.H., Schrama, M., De Snoo, G.R., Van Bodegom, P.M., van Nieuwenhuijzen, A. and Vijver, M.G. Proceedings of the National Academy of Sciences, 118(44).]
Semi-natural field borders are frequently used in midwestern U.S. sustainable agriculture. These habitats are meant to help diversify otherwise monocultural landscapes and provision them with ecosystem services, including biological control. Predatory and parasitic arthropods (i.e., potential natural enemies) often flourish in these habitats and may move into crops to help control pests. However, detailed information on the capacity of semi-natural field borders for providing overwintering refuge for these arthropods is poorly understood. In this study, we used soil emergence tents to characterize potential natural enemy communities (i.e., predacious beetles, wasps, spiders, and other arthropods) overwintering in cultivated organic crop fields and adjacent field borders. We found a greater abundance, species richness, and unique community composition of predatory and parasitic arthropods in field borders compared to arable crop fields, which were generally poorly suited as overwintering habitat. Furthermore, potential natural enemies tended to be positively associated with forb cover and negatively associated with grass cover, suggesting that grassy field borders with less forb cover are less well-suited as winter refugia. These results demonstrate that semi-natural habitats like field borders may act as a source for many natural enemies on a year-to-year basis and are important for conserving arthropod diversity in agricultural landscapes.
[Clem, C.S. and Harmon-Threatt, A.N. Journal of Insect Science, 21(3), p.2.]
Seed coating (‘seed treatment’) is the leading delivery method of neonicotinoid insecticides in major crops such as soybean, wheat, cotton and maize. However, this prophylactic use of neonicotinoids is widely discussed from the standpoint of environmental costs. Growing soybean plants from neonicotinoid-coated seeds in field, we demonstrate that soybean aphids (Aphis glycines) survived the treatment, and excreted honeydew containing neonicotinoids. Biochemical analyses demonstrated that honeydew excreted by the soybean aphid contained substantial concentrations of neonicotinoids even one month after sowing of the crop. Consuming this honeydew reduced the longevity of two biological control agents of the soybean aphid, the predatory midge Aphidoletes aphidimyza and the parasitic wasp Aphelinus certus. These results have important environmental and economic implications because honeydew is the main carbohydrate source for many beneficial insects in agricultural landscapes.
[Calvo-Agudo, M., Dregni, J., González-Cabrera, J., Dicke, M., Heimpel, G.E. and Tena, A. Environmental Pollution, 289, p.117813.]
Insecticides are widely used in the Midwestern USA to combat soybean aphids (Aphis glycines), a globally important crop pest. Broad-spectrum foliar insecticides such as chlorpyrifos, lambda-cyhalothrin, and bifenthrin (hereafter, “target insecticides”) are toxic to wildlife in laboratory settings; however, little information exists regarding drift and deposition of these insecticides in fragmented tallgrass prairie grasslands such as those in Minnesota, USA. To address this information gap, target insecticide spray drift and deposition were measured on passive samplers and arthropods in grasslands adjacent to crop fields in Minnesota. Samples were collected at focal soybean field sites immediately following target insecticide application and at reference corn field sites without target insecticide application. Target insecticides were detected 400 m into grasslands at both focal and reference sites. Residues of chlorpyrifos, an insecticide especially toxic to pollinators and birds, were measured above the contact lethal dose (LD50) for honey bees (Apis mellifera) up to 25 m from field edges in adjacent grasslands. Chlorpyrifos residues on arthropods were below the acute oral LD50 for several common farmland bird species but were above the level shown to impair migratory orientation in white-crowed sparrows (Zonotrichia leucophrys). Deposition of target insecticides on passive samplers was inversely associated with distance from field edge and percent canopy cover of grassland vegetation, and positively associated with samplers placed at mid-canopy compared to ground level. Target insecticide deposition on arthropods had an inverse relationship with vertical vegetation density and was positively associated with maximum height of vegetation. Tallgrass prairie with cover ≥25 m from row crop edges may provide wildlife habitat with lower exposure to foliar application insecticides. Prairie management regimes that increase percent canopy cover and density of vegetation may also reduce exposure of wildlife to these insecticides.
[Goebel, K. et al. (2021) Tallgrass prairie wildlife exposure to spray drift from commonly used soybean insecticides in Midwestern USA, Science of The Total Environment. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0048969721068212. ]
The widespread prophylactic usage of neonicotinoid insecticides has a clear impact on non-target organisms. However, the possible effects of long-term exposure on soil-dwelling organisms are still poorly understood especially for social insects with long-living queens. Here, we show that effects of chronic exposure to the neonicotinoid thiamethoxam on black garden ant colonies, Lasius niger, become visible before the second overwintering. Queens and workers differed in the residue-ratio of thiamethoxam to its metabolite clothianidin, suggesting that queens may have a superior detoxification system. Even though thiamethoxam did not affect queen mortality, neonicotinoid-exposed colonies showed a reduced number of workers and larvae indicating a trade-off between detoxification and fertility. Since colony size is a key for fitness, our data suggest long-term impacts of neonicotinoids on these organisms. This should be accounted for in future environmental and ecological risk assessments of neonicotinoid applications to prevent irreparable damages to ecosystems.
[Schläppi, D., Kettler, N., Straub, L., Glauser, G. and Neumann, P., 2020. Communications biology, 3(1), pp.1-9.]
Declining insect population sizes are provoking grave concern around the world as insects play essential roles in food production and ecosystems. Environmental contamination by intense insecticide usage is consistently proposed as a significant contributor, among other threats. Many studies have demonstrated impacts of low doses of insecticides on insect behavior, but have not elucidated links to insecticidal activity at the molecular and cellular levels. Here, the histological, physiological, and behavioral impacts of imidacloprid are investigated in Drosophila melanogaster, an experimental organism exposed to insecticides in the field. We show that oxidative stress is a key factor in the mode of action of this insecticide at low doses. Imidacloprid produces an enduring flux of Ca2+ into neurons and a rapid increase in levels of reactive oxygen species (ROS) in the larval brain. It affects mitochondrial function, energy levels, the lipid environment, and transcriptomic profiles. Use of RNAi to induce ROS production in the brain recapitulates insecticide-induced phenotypes in the metabolic tissues, indicating that a signal from neurons is responsible. Chronic low level exposures in adults lead to mitochondrial dysfunction, severe damage to glial cells, and impaired vision. The potent antioxidant, N-acetylcysteine amide (NACA), reduces the severity of a number of the imidacloprid-induced phenotypes, indicating a causal role for oxidative stress. Given that other insecticides are known to generate oxidative stress, this research has wider implications. The systemic impairment of several key biological functions, including vision, reported here would reduce the resilience of insects facing other environmental challenges.
[Martelli, F., Zhongyuan, Z., Wang, J., Wong, C.O., Karagas, N.E., Roessner, U., Rupasinghe, T., Venkatachalam, K., Perry, T., Bellen, H.J. and Batterham, P., 2020. Proceedings of the National Academy of Sciences, 117(41), pp.25840-25850.]
Recent studies have reported alarming declines in insect populations, but questions persist about the breadth and pattern of such declines. van Klink et al. compiled data from 166 long-term surveys across 1676 globally distributed sites and confirmed declines in terrestrial insects, albeit at lower rates than some other studies have reported (see the Perspective by Dornelas and Daskalova). However, they found that freshwater insect populations have increased overall, perhaps owing to clean water efforts and climate change. Patterns of variation suggest that local-scale drivers are likely responsible for many changes in population trends, providing hope for directed conservation actions.
[van Klink, R. et al. (2020) Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances, Science. Available at: https://www.science.org/doi/10.1126/science.aax9931. ]
The global increase in the proportion of land cultivated with pollinator-dependent crops implies increased reliance on pollination services. Yet agricultural practices themselves can profoundly affect pollinator supply and pollination. Extensive monocultures are associated with a limited pollinator supply and reduced pollination, whereas agricultural diversification can enhance both. Therefore, areas where agricultural diversity has increased, or at least been maintained, may better sustain high and more stable productivity of pollinator-dependent crops. Given that >80% of all crops depend, to varying extents, on insect pollination, a global increase in agricultural pollinator dependence over recent decades might have led to a concomitant increase in agricultural diversification. We evaluated whether an increase in the area of pollinator-dependent crops has indeed been associated with an increase in agricultural diversity, measured here as crop diversity, at the global, regional, and country scales for the period 1961–2016. Globally, results show a relatively weak and decelerating rise in agricultural diversity over time that was largely decoupled from the strong and continually increasing trend in agricultural dependency on pollinators. At regional and country levels, there was no consistent relationship between temporal changes in pollinator dependence and crop diversification. Instead, our results show heterogeneous responses in which increasing pollinator dependence for some countries and regions has been associated with either an increase or a decrease in agricultural diversity. Particularly worrisome is a rapid expansion of pollinator-dependent oilseed crops in several countries of the Americas and Asia that has resulted in a decrease in agricultural diversity. In these regions, reliance on pollinators is increasing, yet agricultural practices that undermine pollination services are expanding. Our analysis has thereby identified world regions of particular concern where environmentally damaging practices associated with large-scale, industrial agriculture threaten key ecosystem services that underlie productivity, in addition to other benefits provided by biodiversity.
[Aizen, M. et al. (2019) Global agricultural productivity is threatened by increasing pollinator dependence without a parallel increase in crop diversification, Global Change Biology. Available at: https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14736. ]
The majority of conservation efforts and public attention are focused on large, charismatic mammals and birds such as tigers, pandas and penguins, yet the bulk of animal life, whether measured by biomass, numerical abundance or numbers of species, consists of invertebrates such as insects. Arguably, these innumerable little creatures are far more important for the functioning of ecosystems than their furry or feathered brethren, but until recently we had few long-term data on their population trends. Recent studies from Germany and Puerto Rico suggest that insects may be in a state of catastrophic population collapse: the German data describe a 76% decline in biomass over 26 years, while the Puerto Rican study estimates a decline of between 75% and 98% over 35 years. Corroborative evidence, for example from butterflies in Europe and California (which both show slightly less dramatic reductions in abundance), suggest that these declines are not isolated. The causes are much debated, but almost certainly include habitat loss, chronic exposure to pesticides, and climate change. The consequences are clear; insects are integral to every terrestrial food web, being food for numerous birds, bats, reptiles, amphibians and fish, and performing vital roles such as pollination, pest control and nutrient recycling. Terrestrial and freshwater ecosystems will collapse without insects. These studies are a warning that we may have failed to appreciate the full scale and pace of environmental degradation caused by human activities in the Anthropocene.
[Goulson, D. (2019) The insect apocalypse, and why it matters, Current Biology. Available at: https://www.sciencedirect.com/science/article/pii/S0960982219307961. ]
Neonicotinoid insecticides are commonly-used as seed treatments on flowering crops such as oilseed rape. Their persistence and solubility in water increase the chances of environmental contamination via surface-runoff or drainage into areas adjacent to the crops. However, their uptake and fate into non-target vegetation remains poorly understood. In this study, we analysed samples of foliage collected from neonicotinoid seed-treated oilseed rape plants and also compared the levels of neonicotinoid residues in foliage (range: 1.4–11 ng/g) with the levels found in pollen collected from the same plants (range: 1.4–22 ng/g). We then analysed residue levels in foliage from non-target plants growing in the crop field margins (range: ≤ 0.02–106 ng/g). Finally, in order to assess the possible risk posed by the peak levels of neonicotinoids that we detected in foliage for farmland phytophagous and predatory insects, we compared the maximum concentrations found against the LC50 values reported in the literature for a set of relevant insect species. Our results suggest that neonicotinoid seed-dressings lead to widespread contamination of the foliage of field margin plants with mixtures of neonicotinoid residues, where levels are very variable and discontinuous, but sometimes overlap with lethal concentrations reported for some insect species. Understanding the distribution of pesticides in the environment and their potential effects on biological communities is crucial to properly assess current agricultural management and schemes with biodiversity conservation aims in farmland.
[Botías, C. et al. (2016) Contamination of wild plants near neonicotinoid seed-treated crops, and implications for non-target insects, Science of The Total Environment. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0048969716309950. ]
Wild bee declines have been ascribed in part to neonicotinoid insecticides. While short-term laboratory studies on commercially bred species (principally honeybees and bumblebees) have identified sub-lethal effects, there is no strong evidence linking these insecticides to losses of the majority of wild bee species. We relate 18 years of UK national wild bee distribution data for 62 species to amounts of neonicotinoid use in oilseed rape. Using a multi-species dynamic Bayesian occupancy analysis, we find evidence of increased population extinction rates in response to neonicotinoid seed treatment use on oilseed rape. Species foraging on oilseed rape benefit from the cover of this crop, but were on average three times more negatively affected by exposure to neonicotinoids than non-crop foragers. Our results suggest that sub-lethal effects of neonicotinoids could scale up to cause losses of bee biodiversity. Restrictions on neonicotinoid use may reduce population declines.
[Woodcock, B.A. et al. (2016) Impacts of neonicotinoid use on long-term population changes in wild bees in England, Nature Communications. Available at: https://www.nature.com/articles/ncomms12459. ]
Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture. However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns. It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees. Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals. Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.
[Goulson, D. (2013) An overview of the environmental risks posed by neonicotinoid insecticides, Journal of Applied Ecology. Available at: https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.12111. ]