15
Apr
Indiscriminate Poisoning of Neonicotinoid Insecticides Contributes to Insect Apocalypse, Study Finds
(Beyond Pesticides, April 15, 2025) A study in Communications Earth & Environment, through field, greenhouse, and laboratory experiments involving three plant bug species, finds both species-specific and sex-specific sensitivity responses to neonicotinoid insecticide exposure—highlighting the threats to grassland insect communities that are disregarded in risk assessments. By assessing the effects of Mospilan®SG, with the active ingredient acetamiprid, the researchers determine that nontarget plant bug species are highly sensitive to neonicotinoids and face community-level harm with exposure. As systemic insecticides, neonicotinoids move through the vascular system of plants, expressing the poison through pollen, nectar, and guttation droplets. As persistent pesticides, these chemicals indiscriminately poison insects and organisms in the soil.
“Although pesticides have been proposed as one of the main causes of insect decline, there are still few studies assessing their effects on non-target species under field conditions,†the authors state. They continue: “In this study, we address the existing research gap on insecticide exposure of non-target herbivorous insects, focusing on two main aspects: (1) realistic exposure scenarios, (2) community-level effects, i.e., differential sensitivity between closely related species and between sexes of the same species. We chose plant bugs (Heteroptera: Miridae) as a model group because they are one of the 20 most diverse insect families and a common component of non-target insect communities in agroecosystems.â€
The environmental threats from pesticide exposure are becoming increasingly apparent. As the researchers point out, “We are facing an unprecedented decline in biodiversity, which has been particularly evident for insects in recent years, with many studies showing global declines in insect biomass, abundance, and richness.†The scientific literature shows pesticides as a major driver of these declines from both agricultural and nonagricultural exposure.
As previously reported by Beyond Pesticides, insects provide many important services, such as maintaining healthy soil, recycling nutrients, pollinating flowers and crops, and controlling pests. These nontarget and beneficial species are at risk through pesticide exposure, both directly and indirectly, which then affects these essential functions. The pesticide residues that contaminate plants and insects that provide a food source for other organisms can lead to population effects throughout multiple trophic levels. Since the active ingredients in pesticides can affect a wide range of taxonomic groups, they cause harm to numerous species rather than just the target species.Â
As Dave Goulson, PhD—a speaker at Beyond Pesticides’ 40th National Forum Series—says, an insect apocalypse is occurring that threatens all ecosystems. In an essay in Current Biology, he states, “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… we may have failed to appreciate the full scale and pace of environmental degradation caused by human activities in the Anthropocene.â€
Plant bugs, with high diversity and abundance, represent an important group that supports the function of ecosystems but is understudied in existing scientific literature and “are not considered in the risk assessment procedure for plant protection products,†the authors note. They continue: “We argue that plant bugs are an ecologically relevant group to study. They are most certainly an important food source for birds and a wide range of predatory invertebrates. In addition, species within plant bug communities are often similar in many traits (e.g., morphology, habitat, diet, and phenology) and therefore offer the opportunity to study physiological differences in insecticide sensitivity at the species level due to the high diversity of this family.â€
The study includes field, greenhouse, and laboratory experiments in southern Germany conducted with the neonicotinoid acetamiprid, which is both a contact and a systemic insecticide that can be absorbed by plants and distributed throughout their tissues. This active ingredient was chosen due to its worldwide use and because it is the only neonicotinoid still registered for open-field use in the European Union (EU).
The plant bugs in the experiments include the three most abundant species: Stenotus binotatus, Leptopterna dolabrata, and Megaloceroea recticornis, which can be considered representative nontarget herbivorous insects. Through direct and indirect exposure to acetamiprid, these species show high sensitivity and impacted survival rates. In summarizing the results, the authors say: “In a controlled field study, the abundance of three focal species was reduced by up to 92% two days after field exposure at concentrations expected at field margins, with mortality varying among species. Follow-up feeding assays with insecticide-treated host plants in the greenhouse and controlled dose-response laboratory assays confirmed the strong negative effects on non-target species.â€
In comparing the three species, there are pronounced species-specific differences, with S. binotatus being significantly more sensitive to acetamiprid than the other two species. Additionally, of note is that males of L. dolabrata and M. recticornis are 20 times more sensitive than females and the LD50 (lethal dose of half the test population) levels calculated for the plant bug species show that acetamiprid is over 11,000 times more toxic to plant bugs than to honey bees. Â
Honey bees are used as a model species in EU risk assessments, as well as those incorporated in U.S. Environmental Protection Agency (EPA) protocol, but do not adequately reflect the nontarget insect community. “As a result, the disruption to these communities caused by pesticide exposure is not considered,†the researchers point out. They continue: “In addition, risk assessment is currently only done at the species level, and sex-specific sensitivity is not considered. However, the up to 22-fold difference in LD50 values between sexes that we found could scale to detrimental long-term effects on plant bug community composition.â€
This study, which focuses on EU risk assessments, applies even more so to current EPA regulatory protocol, as they allow many pesticides, particularly neonicotinoids, to be used that are banned in other countries. As shared in a previous Daily News article, EPA’s reliance on honey bee data from lab studies focused on LD50 does not accurately capture the threats that pesticides pose in the real world to all insects, including thousands of other bee species, with diverse life histories, genetic compositions, and sensitivities to pesticides. (See more on the deficiencies of pollinator risk assessments here and EPA failures here.)
Available ecotoxicological studies also have a narrow scope, in which the authors say, “Herbivorous insects, which account for about 50% of all insect species globally, have been largely neglected.†Studies that are representative of all species and their varied sensitivity need to be performed in order to make proper assessments. The researchers say their study results stress the need for the urgent adoption of risk assessments that adequately address the environmental harm of pesticide contamination to all species within ecosystems that are threatened by exposure.
The authors close by stating that continuous exposure to neonicotinoids, such as acetamiprid, “may reduce plant bug populations and promote insecticide-tolerant species, altering community composition. We suggest that sex-specific sensitivity be considered in risk assessment and conclude that the true risk to non-target insects is currently greatly underestimated.†The varied species susceptibility, which is not included during regulatory assessments, could cause entire community structures to be altered. This, in turn, can cascade throughout multiple trophic levels and the entire ecosystem, especially when insect herbivores are involved, as they play a central role in terrestrial food webs.
With large numbers of insects at risk, the reliance on pesticides in agriculture and land management threatens biodiversity, which is a key driver of ecosystem services. (See more on the importance of biodiversity here and here.) Within this context, organic agriculture and land management provide a holistic solution for enhancing and protecting biodiversity. Ultimately, the only way to ensure the safety of the world’s agricultural systems, as well as natural ecosystems, is to end the use of toxic petrochemical pesticides, including neonicotinoid insecticides.
Beyond Pesticides advocates for the widespread adoption of organic management practices as key to protecting insects, including pollinators, and the environment and has long sought a broad-scale marketplace transition to organic practices that legally prohibits the use of toxic synthetic pesticides and encourages a systems-based approach. Support Beyond Pesticides’ mission by becoming a member today and sign up to receive Action of the Week and Weekly News Updates to stay informed and engaged.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Sedlmeier, J.E. et al. (2025) Neonicotinoid insecticides can pose a severe threat to grassland plant bug communities, Communications Earth & Environment. Available at: https://www.nature.com/articles/s43247-025-02065-y.
