Diesel exhaust and ozone adversely affect pollinators and parasitoids within flying insect communities

The effects of air pollution on human and animal health, and on the functioning of terrestrial ecosystems, are wide-ranging. This potentially includes the disruption of valuable services provided by flying insects (e.g. pollination and biological control). However, quantifying the extent of this disruption requires a clearer understanding of insect community responses at field-scale. By elevating diesel exhaust and ozone (O3) pollutants, individually and in combination, over two summers, we investigated the field-scale effects of air pollution on the abundance and diversity of flying insects from pan traps. We quantified which groups of insects were more at risk of air pollution-mediated decline and whether responses to air pollution were influenced by the presence of flowering plants. In addition, a common pest of Brassicaceae, the large cabbage white butterfly (Pieris brassicae L.) was used to investigate the effects on oviposition success of the two interacting air pollutants. Air pollution had the most detrimental effects on pollinators and parasitoids, compared with other insect groups, lowering their abundance by up to 48 % and 32 %, respectively. The adverse effects of O3 and diesel exhaust on pollinators occurred only when flowers were available, indicating the relative importance of floral odors compared with visual cues. Air pollutants resulted in either increased insect herbivore abundance or had no effect, potentially increasing the threat air pollution poses to food security. However, both pollutants resulted in decreased oviposition by cabbage white butterflies, which, if demonstrated to be a more ubiquitous phenomenon, may result in reduced larval pest damage. Quantifying the relative changes in composition and abundance among feeding guilds is valuable for predicting the effects of air pollution on insect communities. Of the groups identified, pollinators are likely to be at the greatest risk of air pollution-mediated decline due to their use of floral odour cues for foraging.

Conventional agriculture affects sex communication and impacts local population size in a wild bee

Man-made agricultural stressors have been identified to compromise the reproductive dynamics of bee populations within agricultural environments. With the aid of bee hotels, we explored the influence of conventional and organic farming systems on local population size and body traits of the mason bee, Osmia bicornis, in southern Germany. We further used a chemical ecology approach and bioassays to test whether farming management influence male pre-copulatory behaviors. We observed a positive relationship between the extent of organic agriculture in the landscape and both overall brood cell production and nesting frequency. Moreover, farming systems were found to influence body traits, with bees from organic sites being smaller in size and having a different cuticular hydrocarbon composition compared with those at conventional sites. Bioassays revealed that males were more sexually attracted to freeze-killed females from conventional sites compared with those from organic sites. Intriguingly, treating females from organic fields with synthetic semiochemicals enhanced their sexual attraction to levels comparable with females from conventional sites. Our findings shed light on the intricate interplay between farming practices and the reproductive behaviors of wild mason bees, emphasizing the need for a comprehensive understanding of these dynamics for effective conservation and management strategies.

Adverse effects of the Bordeaux mixture copper-based fungicide on the non-target vineyard pest Lobesia botrana

BACKGROUND

Bordeaux mixture is a copper-based fungicide commonly used in vineyards to prevent fungal and bacterial infections in grapevines. However, this fungicide may adversely affect the entomological component, including insect pests. Understanding the impacts of Bordeaux mixture on the vineyard pest Lobesia botrana is an increasing concern in the viticultural production.

RESULTS

Bordeaux mixture had detrimental effects on the development and reproductive performance of L. botrana. Several physiological traits were adversely affected by copper-based fungicide exposure, including a decrease in larval survival and a delayed larval development to moth emergence, as well as a reduced reproductive performance through a decrease in female fecundity and fertility and male sperm quality. However, we did not detect any effect of Bordeaux mixture on the measured reproductive behaviors (mating success, pre-mating latency and mating duration).

CONCLUSION

Ingestion by larvae of food contaminated with Bordeaux mixture had a negative effect on the reproductive performance of the pest L. botrana, which could affect its population dynamics in vineyards. Although this study highlighted collateral damage of Bordeaux mixture on L. botrana, the potential impact of copper-based fungicides on vineyard diversity, including natural predators is discussed and needs to be taken in consideration in integrated pest management. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Exploring behavioural and physiological adaptations in mountain pine beetle in response to elevated ozone concentrations

Elevated ozone (eO3) concentrations pose a threat to insect populations by potentially altering their behaviour and physiology. This study investigates the effects of eO3 concentrations on the mountain pine beetle which is a major tree-killing species of conifers in northwestern North America. We are particularly interested in understanding the effects of eO3 concentrations on beetle behaviour and physiology and possible transgenerational impacts on bark beetle broods. We conducted O3-enrichment experiments in a controlled laboratory setting using different O3 concentrations (100-200 ppb; projected for 2050-2100) and assessed various beetle responses, including CO2 respiration, mating behaviour, survival probability, locomotion, and attraction behaviour. Transgenerational impacts on the first and second generations were also analyzed by studying brood morphology, mating behaviour, survival, and pheromone production. We found that beetles exposed to eO3 concentrations had shorter oviposition galleries and reduced brood production. Beetle pheromones were also degraded by eO3 exposure. However, exposure to eO3 also prompted various adaptive responses in beetles. Despite reduced respiration, eO3 improved locomotor activity and the olfactory response of beetles. Surprisingly, beetle survival probability was also improved both in the parents and their broods. We also observed transgenerational plasticity in the broods of eO3-exposed parents, suggesting potential stress resistance mechanisms. This was evident by similar mating success, oviposition gallery length, and brood numbers produced in both control and eO3 concentration treatments. This study demonstrates the sensitivity of mountain pine beetles to increased O3 concentrations, contributing crucial insights into the ecological implications of eO3 concentrations on their populations. Overall, the outcome of this study contributes to informed climate change mitigation strategies and adaptive management practices for the development of resilient forests in response to emerging forest insect pests worldwide.

Air pollution disproportionately impairs beneficial invertebrates: a meta-analysis

Air pollution has the potential to disrupt ecologically- and economically-beneficial services provided by invertebrates, including pollination and natural pest regulation. To effectively predict and mitigate this disruption requires an understanding of how the impacts of air pollution vary between invertebrate groups. Here we conduct a global meta-analysis of 120 publications comparing the performance of different invertebrate functional groups in unpolluted and polluted atmospheres. We focus on the pollutants ozone, nitrogen oxides, sulfur dioxide and particulate matter. We show that beneficial invertebrate performance is reduced by air pollution, whereas the performance of plant pest invertebrates is not significantly affected. Ozone pollution has the most detrimental impacts, and these occur at concentrations below national and international air quality standards. Changes in invertebrate performance are not dependent on air pollutant concentrations, indicating that even low levels of pollution are damaging. Predicted increases in tropospheric ozone could result in unintended consequences to global invertebrate populations and their valuable ecological services.

Elevated ozone disrupts mating boundaries in drosophilid flies

Animals employ different strategies to establish mating boundaries between closely related species, with sex pheromones often playing a crucial role in identifying conspecific mates. Many of these pheromones have carbon-carbon double bonds, making them vulnerable to oxidation by certain atmospheric oxidant pollutants, including ozone. Here, we investigate whether increased ozone compromises species boundaries in drosophilid flies. We show that short-term exposure to increased levels of ozone degrades pheromones of Drosophila melanogaster, D. simulans, D. mauritiana, as well as D. sechellia, and induces hybridization between some of these species. As many of the resulting hybrids are sterile, this could result in local population declines. However, hybridization between D. simulans and D. mauritiana as well as D. simulans and D. sechellia results in fertile hybrids, of which some female hybrids are even more attractive to the males of the parental species. Our experimental findings indicate that ozone pollution could potentially induce breakdown of species boundaries in insects.

Carbonyl products of ozone oxidation of volatile organic compounds can modulate olfactory choice behavior in insects

Insects are a diverse group of organisms that provide important ecosystem services like pollination, pest control, and decomposition and rely on olfaction to perform these services. In the Anthropocene, increasing concentrations of oxidant pollutants such as ozone have been shown to corrupt odor-driven behavior in insects by chemically degrading e.g. flower signals or insect pheromones. The degradation, however, does not only result in a loss of signals, but also in a potential enrichment of oxidation products, predominantly small carbonyls. Whether and how these oxidation products affect insect olfactory perception remains unclear. We examined the effects of ozone-generated small carbonyls on the olfactory behavior of the vinegar fly Drosophila melanogaster. We compiled a broad collection of neurophysiologically relevant odorants for the fly from databases and literature and predicted the formation of the types of stable small carbonyl products resulting from the odorant's oxidation by ozone. Based on these predictions, we evaluated the olfactory detection and behavioral impact of the ten most frequently predicted carbonyl products in the fly using single sensillum recordings (SSRs) and behavioral tests. Our results demonstrate that the fly's olfactory system can detect the oxidation products, which then elicit either attractive or neutral behavioral responses, rather than repulsion. However, certain products alter behavioral choices to an attractive odor source of balsamic vinegar. Our findings suggest that the enrichment of small carbonyl oxidation products due to increased ozone levels can affect olfactory guided insect behavior. Our study underscores the implications for odor-guided foraging in insects and the essential ecosystem services they offer under carbonyl enriched environments.

Temperature-dependent modulation of odor-dependent behavior in three drosophilid fly species of differing thermal preference

Rapid and ongoing climate change increases global temperature, impacts feeding, and reproduction in insects. The olfaction plays an important underlying role in these behaviors in most insect species. Here, we investigated how changing temperatures affect odor detection and ensuing behavior in three drosophilid flies: Drosophila novamexicana, D. virilis and D. ezoana, species adapted to life in desert, global, and subarctic climates, respectively. Using a series of thermal preference assays, we confirmed that the three species indeed exhibit distinct temperature preferences. Next, using single sensillum recording technique, we classified olfactory sensory neurons (OSNs) present in basiconic sensilla on the antenna of the three species and thereby identified ligands for each OSN type. In a series of trap assays we proceeded to establish the behavioral valence of the best ligands and chose guaiacol, methyl salicylate and isopropyl benzoate as representatives of a repellent, attractant and neutral odor. Next, we assessed the behavioral valence of these three odors in all three species across a thermal range (10-35 °C), with flies reared at 18 °C and 25 °C. We found that both developmental and experimental temperatures affected the behavioral performance of the flies. Our study thus reveals temperature-dependent changes in odor-guided behavior in drosophilid flies.