How Adsorption of Pheromones on Aerosols Controls Their Transport

How to Control the Release Behavior of Insect Sex Pheromones Using Nanomicro Fiber: Insights from Experiment and Molecular Dynamics Simulation

Polymer-based electrospun fibers can effectively sustain pheromone release for pest control, yet their regulatory mechanisms remain unclear. In this study, fibers from various polymers were loaded with multicomponent sex pheromones of Grapholitha molesta and characterized. Release tests showed that poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (PHB) fibers released 90% of pheromones in 81.93 days, compared to 14.01 days for polycaprolactone fibers. Molecular dynamics (MD) simulations revealed that pheromones diffused through the polymer network via vibrations, cavity formation, and jumping. PHB fibers exhibited the lowest diffusion coefficient (0.0064 × 10-9 m2 s-1) and highest activation energy (24.56 kJ mol-1). Additionally, PHB exhibited good crystallinity and crystal arrangement, thereby enhancing the restriction on pheromone molecules. By combining MD simulations with experimental studies, molecular structure, intermolecular forces, and crystallinity were identified as the main factors regulating the release behavior of these polymer fibers. Finally, trapping experiments confirmed their effectiveness, indicating that release studies can guide field applications.

Mating disruption of Chilo suppressalis (Lepidoptera: Crambidae) with novel aerosol dispensers in rice field

BACKGROUND

Chilo suppressalis is an important rice pest. Its control has relied heavily on synthetic insecticides. To reduce the application of insecticides, integrated pest management strategies such as incorporating mating disruption (MD) with insect pheromones are critically needed.

RESULTS

A novel aerosol dispenser was evaluated for MD efficacy against C. suppressalis. Laboratory tests revealed that pheromone adsorption on rice plants increased with exposure time (2-10 h) at 0.05 m from the dispenser, but no significant differences were observed at 2 m. Field trials demonstrated a 31% reduction in female pheromone titers of Z11-16:Ald under MD. While mating rates remained unaffected at low adult densities (1 or 5 pairs of adults in a cage), they decreased by 31% at high density (20 pairs in a cage), with the total numbers of eggs laid decreased by 45.5%. MD suppressed the adult populations by 89-100% in the overwintering generation and by 67-100% in the first generation. MD reduced the larval densities by 80-90%, and the number of damaged rice plant by 64-89%, compared to controls.

CONCLUSION

The novel dispenser effectively diffused and retained sex pheromones in rice fields, reducing C. suppressalis female sex pheromone secretion, and mating success. Consequently, the amount of eggs laid by C. suppressalis females in the field was strikingly reduced, leading to decreased number of larvae and reduced damage in rice plants. The findings highlight MD as a sustainable alternative to insecticides for managing C. suppressalis population. © 2025 Society of Chemical Industry.

Olfactory performance explains duality of antennal architectural designs in Lepidoptera

Male attraction by females through sex pheromones is widespread among Lepidoptera, and antennae are key olfactory organs during male orientation. Broadly speaking, two designs of antennae coexist in Lepidoptera: complex (pectinate) or stick-like (filiform) ones. Pectinate antennae have attracted attention because of their multiscale geometry, assumed to outperform filiform. Yet, the filiform design is by far more common. We compare the olfactory performance of the two designs using modelling, particle image velocimetry on three-dimensional-printed scaled-up models and computational simulations. In terms of absolute odour capture, pectinate antennae perform better at nearly all flying speeds. However, when considering drag, filiform designs are more energy efficient than pectinate ones at low-flight speeds, while the reverse holds at high speeds. This is owing to the differential scaling of drag and molecule capture with flight speed. According to our results, small and slow moths would bear filiform antennae whereas big and fast moths would have pectinate ones, which is the general trend observed in nature. We discuss exceptions to this general pattern and how species could evolve from one design to the other by investigating the influence of the antennal structural elements.

Recalibrating Olfactory Neuroscience to the Range of Naturally Occurring Odor Concentrations

Sensory systems enable organisms to detect and respond to environmental signals relevant for their survival and reproduction. A crucial aspect of any sensory signal is its intensity; understanding how sensory signals guide behavior requires probing sensory system function across the range of stimulus intensities naturally experienced by an organism. In olfaction, defining the range of natural odorant concentrations is difficult. Odors are complex mixtures of airborne chemicals emitting from a source in an irregular pattern that varies across time and space, necessitating specialized methods to obtain an accurate measurement of concentration. Perhaps as a result, experimentalists often choose stimulus concentrations based on empirical considerations rather than with respect to ecological or behavioral context. Here, we attempt to determine naturally relevant concentration ranges for olfactory stimuli by reviewing and integrating data from diverse disciplines. We compare odorant concentrations used in experimental studies in rodents and insects with those reported in different settings including ambient natural environments, the headspace of natural sources, and within the sources themselves. We also compare these values to psychophysical measurements of odorant detection threshold in rodents, where thresholds have been extensively measured. Odorant concentrations in natural regimes rarely exceed a few parts per billion, while most experimental studies investigating olfactory coding and behavior exceed these concentrations by several orders of magnitude. We discuss the implications of this mismatch and the importance of testing odorants in their natural concentration range for understanding neural mechanisms underlying olfactory sensation and odor-guided behaviors.

Aerosol Alteration of Behavioral Response to Pheromone in Bombyx mori

Because of the complexity to study them, aerosols have been neglected in nearly all studies on olfaction, especially studies dealing with odor capture. However, aerosols are present in large quantities in the atmosphere and have the physico-chemical ability to interact with odor molecules, in particular the many pheromones with low volatility. We submitted male moths of Bombyx mori to bombykol puffs, the main fatty alcohol component of its sex pheromone, depending on whether the air is free of aerosols, charged with ambient concentration aerosols or supplemented with aqueous aerosols and recorded their arousal behavior. Aerosols and pheromone do interact consistently over all experiments and moths react better in low aerosol-concentration conditions. We propose four hypotheses for explaining this impediment, the two most likely resorting to competition between odor molecules and aerosols for the olfactory pores and postulate a reversal to a positive impact of aerosols on communication, depending on the particular physico-chemical properties of the multiphasic interaction. Studying the partitioning between gas and particulate phases in the transport and reception of odors is key for advancing the chemico-physical understanding of olfaction.

Individual adsorption of low volatility pheromones: Amphiphilic molecules on a clean water-air interface

Environmental conditions can alter olfactory scent and chemical communication among biological species. In particular, odorant molecules interact with aerosols. Thermodynamics variables governing the adsorption from air to water surface of bombykol, the most studied pheromone, and of three derivative molecules, bombykal, bombykoic acid, and bombykyle acetate, are computed by steered and un-biased molecular dynamics in order to compare the role of their polar head group on adsorption on aqueous aerosols. When adsorbed, the molecule center of mass stands at about 1.2 Å from the interface and oscillates on the same length scale, trapped in an energy well. Gibbs energy of adsorption and desorption time of bombykol are found to be 9.2 k_BT and 59 µs, respectively. The following ordering between the molecules is observed, reading from the more to the least adsorbed: bombykoic acid > bombykol > bombykoic acetate > bombykal. It originates from a complex interplay of entropy and enthalpy. The entropy and enthalpy of adsorption are discussed in the light of structural arrangement, H-bonding, and hydrophilic tail positioning of the molecules at the interface. Our results show that, when dispersed in the air, pheromones adsorb on aqueous aerosols. However, the individual residence time is quite short on pure water surfaces. Aerosols can, therefore, only have a decisive influence on chemical communication through collective effects or through their chemical composition that is generally more complex than that of a pure water surface.

Shining New Light on the Kinetics of Water Uptake by Organic Aerosol Particles

The uptake of water vapor by various organic aerosols is important in a number of applications ranging from medical delivery of pharmaceutical aerosols to cloud formation in the atmosphere. The coefficient that describes the probability that the impinging gas-phase molecule sticks to the surface of interest is called the mass accommodation coefficient, α_M. Despite the importance of this coefficient for the description of water uptake kinetics, accurate values are still lacking for many systems. In this Feature Article, we present various experimental techniques that have been evoked in the literature to study the interfacial transport of water and discuss the corresponding strengths and limitations. This includes our recently developed technique called photothermal single-particle spectroscopy (PSPS). The PSPS technique allows for a retrieval of α_M values from three independent, yet simultaneous measurements operating close to equilibrium, providing a robust assessment of interfacial mass transport. We review the currently available data for α_M for water on various organics and discuss the few studies that address the temperature and relative humidity dependence of α_M for water on organics. The knowledge of the latter, for example, is crucial to assess the water uptake kinetics of organic aerosols in the Earth's atmosphere. Finally, we argue that PSPS might also be a viable method to better restrict the α_M value for water on liquid water.

The fate of methyl salicylate in the environment and its role as signal in multitrophic interactions

Phytohormones emitted into the atmosphere perform many functions relating to the defence, pollination and competitiveness of plants. To be effective, their atmospheric lifetimes must be sufficient that these signals can be delivered to their numerous recipients. We investigate the atmospheric loss processes for methyl salicylate (MeSA), a widely emitted plant volatile. Simulation chambers were used to determine gas-phase reaction rates with OH, NO₃, Cl and O₃; photolysis rates; and deposition rates of gas-phase MeSA onto organic aerosols. Room temperature rate coefficients are determined (in units of cm³ molecule^-1 s^-1) to be (3.20 ± 0.46) × 10^-12, (4.19 ± 0.92) × 10^-15, (1.65 ± 0.44) × 10^-12 and (3.33 ± 2.01) × 10^-19 for the reactions with OH, NO₃, Cl and O₃ respectively. Photolysis is negligible in the actinic range, despite having a large reported near-UV chromophore. Conversely, aerosol uptake can be competitive with oxidation under humid conditions, suggesting that this compound has a high affinity for hydrated surfaces. A total lifetime of gas-phase MeSA of 1-4 days was estimated based on all these loss processes. The competing sinks of MeSA demonstrate the need to assess lifetimes of semiochemicals holistically, and we gain understanding of how atmospheric sinks influence natural communication channels within complex multitrophic interactions. This approach can be extended to other compounds that play vital roles in ecosystems, such as insect pheromones, which may be similarly affected during atmospheric transport.