Dispensers for pheromonal pest control

Discovery of novel skeletons of aphid repellents based on the key fragment of nepetalactone and plant volatiles

BACKGROUND

Aphids are significant agricultural pests, causing extensive crop damage and transmitting plant viruses. Conventional insecticide-based pest control faces challenges such as human and environmental toxicity and resistance. As alternative solutions, pheromone-based repellents have emerged as a promising approach. However, the instability of key compounds like (E)-β-Farnesene (EBF) has limited their effectiveness in field applications. To address these limitations, this study focuses on developing novel aphid repellent compounds based on plant volatiles and nepetalactone key fragments.

RESULTS

In this study, a series of derivatives were designed and synthesized from the lead compound (±)I by incorporating plant volatiles, leading to the discovery of two novel compounds with new skeletons, IV-13 and IV-4. Through further modifications of the ring size and the alkyl substitutions, two optimized structures, compounds IV-30 and IV-36, were identified, demonstrating promising aphid repellent activities. Bioassays indicated that IV-30 (RV = 85.2%) and IV-36 (RV = 70.3%) exhibited significantly enhanced repellent properties compared to their precursor compounds. Molecular docking studies revealed strong binding interactions of these compounds with aphid odorant-binding protein 3(OBP3), providing further evidence of their improved biological efficacy.

CONCLUSION

The introduction of novel structures such as compounds IV-30 and IV-36 based on nepetalactone and plant volatile fragments resulted in the discovery of novel promising para-pheromones for aphid control. These compounds exhibit stable and effective repellent activities, providing a solid foundation for further development of synthetic aphid repellents in integrated pest management strategies. © 2025 Society of Chemical Industry.

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.

Evaluation of Lure and Dispenser Combinations for Halyomorpha halys (Hemiptera: Pentatomidae) Trapping

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is a polyphagous pest native to East Asia and invasive in many countries. Various approaches have been used to control its spread, including IPM strategies. Monitoring pest populations is the starting point for developing an appropriate control strategy. The most common attractant for H. halys is based on its two-component aggregation pheromone ((3S,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol and (3R,6S,7R,10S)-10,11-epoxy-1-bisabolen-3-ol), in combination with the synergist methyl (2E,4E,6Z)-2,4,6-decatrienoate. The aim of this research was to evaluate the most effective combination of the pheromone and the synergist for different types of adjuvants and dispensers, i.e., Blister Pack, Wax Tablet, and Polymers (Non-Biodegradable and Biodegradable Polymers). Field trials were carried out in Northern Italy, during summer and autumn 2023 and 2024. The effectiveness of the different combinations was evaluated on the basis of the number of H. halys individuals caught in sticky traps baited with the different treatments, separated by 50 m each. Individuals actively collected in the surrounding vegetation were also monitored. During the first year, the Non-Biodegradable Polymer performed better than the others. In the second year, H. halys captures were quite similar among the tested dispensers, and all were higher than the control. Captures of non-target stink bugs and other bugs of the Coreidae family were evaluated but, in most cases, were negligible. Under laboratory conditions, the release rate of the chemical compounds differed depending on the type of dispenser. Our results confirm the specificity of the semiochemical lure combination tested towards H. halys and its persistence in the field for at least 12 weeks. The results could be useful for improving the effectiveness of H. halys trapping, as well as for attract-and-kill or push-pull strategies of the pest.

Trypanosoma cruzi infection enhances olfactory response in Triatoma pallidipennis Stål (Hemiptera: Triatominae) to compounds potentially useful for insect control

In Mexico, Triatoma pallidipennis is a major vector of Trypanosoma cruzi, the causative agent of Chagas disease. Current efforts are focused on developing attractants to control these vectors, using volatile substances derived from vertebrate hosts or compounds known to attract hematophagous insects. However, the efficacy of these compounds in attracting parasite-infected triatomines remains to be evaluated. In this study, we assessed the attractant activity of octenol (1-octen-3-ol), nonanal and a mixture of odorants consisting of ammonium hydroxide, lactic acid and hexanoic acid (in a ratio of 1:0.2:0.4 respectively), at concentrations of 1, 10 and 100 ng on the N3, N4 and N5 nymphal stages of T. pallidipennis, both infected and non-infected with T. cruzi. We also evaluated the synergistic effect of the most effective compounds and doses. All experiments were performed in a laboratory using a Y-type glass olfactometer. We found that both infected and non-infected N3 and N4 nymphs were attracted to low doses of octenol, nonanal and the odorant mixture. Particularly noteworthy was the synergistic effect observed between the odorant mixture and nonanal, which significantly increased attraction of T. cruzi-infected individuals. These findings contribute to the development of baited traps utilising these compounds for monitoring triatomines in epidemiological studies or for mass trapping to control these vectors.

Identification and field verification of the aggregation pheromone components produced by male Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae)

BACKGROUND

The chafer beetle, Holotrichia parallela, causes damage to numerous economically significant crops worldwide. Adult beetles exhibit aggregation behavior likely mediated by a male-produced pheromone. Advancements in biological research technology have facilitated the identification of insect aggregation pheromones and promoted their applications as bait for trapping and monitoring pests. Currently, only a few active components of aggregation pheromones from Holotrichia species have been identified. However, the specific components of aggregation pheromones produced by H. parallela remain unknown.

RESULT

In this study, we initially observed from Y-tube olfactometer assays that both male and female H. parallela were significantly attracted to volatiles emitted by males, but not to those from females. We then collected hindgut crude extracts of male adults and carried out gas chromatography-mass spectrometry analysis to identify potential aggregation pheromone components. Pentadecyl acetate, cis-13-docosenol, and behenic acid were identified as male-specific compounds in comparison to female extracts, serving as components of the aggregation pheromone in H. parallela. We further evaluated their attractiveness to H. parallea in both laboratory and field experiments. In laboratory settings, pentadecyl acetate, cis-13-docosenol, and behenic acid evoked significant responses to both males and females at specific concentrations, as evidenced by both electroantennography tests and behavioral bioassays. Under field conditions, traps baited with these three compounds captured significantly more H. parallela adults compared to control traps.

CONCLUSION

In this study, we found that pentadecyl acetate, cis-13-docosenol, and behenic acid are specifically present in male H. parallela, serving as aggregation pheromones. Both laboratory and field-trapping experiments suggest their potential as monitoring and controlling tools against H. parallela adults. © 2024 Society of Chemical Industry.

The Dynamics of Pheromone Release in Two Passive Dispensers Commonly Used for Mating Disruption in the Control of Lobesia botrana and Eupoecilia ambiguella in Vineyards

BACKGROUND

Mating disruption (MD) is a worthwhile technique for the control of Lobesia botrana and Eupoecilia ambiguella in central Europe and Mediterranean areas. MD efficacy is affected by the pheromone release (PR), which in turn is influenced by environmental conditions.

METHODS

The effect of weather conditions on PR was evaluated under four different fields in northern Italy. The PR of two commercial types of MD passive dispensers was correlated with different variables.

RESULTS

For both dispensers, the temperature and vapor pressure deficit explained PR in vineyards with diverse weather conditions better than time. The effect of temperature was not linear, and any temperature increase at high temperatures accelerated the PRR more than proportionally. One dispenser type showed a non-linear release trend of the pheromone emission in field conditions with respect to the considered variables; further, the stepwise regression pointed out the importance of the dichotomous variable associated with the vineyard for increasing the goodness-of-fit.

CONCLUSIONS

The equations developed in this work are dispenser-dependent and can provide information on the PR during the season for each dispenser type, as influenced by weather conditions. These equations could serve as an input for a pheromone concentration model to predict concentrations based on meteorological conditions.

Murine vaginal secretory responses to a male volatile chemical messenger

Many species use chemical messengers to communicate a remarkable range of information. Mice appear to make particular use of chemical messengers, including effects on estrous cycling and initiation, pregnancy, aggression, stress and of course attraction. Behavioral studies have helped identify several candidate messengers, or pheromones, that mediate attraction in mice. One question is whether attractive chemical messengers induced a physical vaginal secretory response. The preparation hypothesis posits that increased vaginal secretion would lubricate and protect the vagina in response to the prospect of imminent coitus, but this has been difficult to assess experimentally, particularly in mice. We developed a rapid, sensitive, minimally invasive method of quantifying vaginal moisture in mice and used this model to test vaginal secretory responses to male bedding. We report that female mice experience an increase in vaginal moisture after exposure to male, but not female, bedding. This response is induced by either physical or airborne exposure to male urine, to preputial gland extract, and to the preputial gland-derived pheromone alpha/beta farnesenes. This vaginal response is diurnally regulated, seen only during their active phase. The response is sensitive to the estrous phase, with a clear response during estrus but not during metestrus. We conclude that mice may serve as a model for aspects of vaginal function and that this assay will be readily applicable to other small animals. The identification of a pheromone-mediated vaginal secretory response offers a window into the regulation of the vaginal environment and the neurobiology of sexual responses in mice.

Addition of Selected Plant-Derived Semiochemicals to Yellow Sticky Traps Does Not Improve Citrus Psyllid Captures

Fast and effective monitoring and surveillance techniques are crucial for the swift implementation of control methods to prevent the spread of Huanglongbing, a devastating citrus disease, and its invasive psyllid vector, Asian citrus psyllid, Diaphorina citri, into South Africa, as well as to control the native vector, African citrus triozid, Trioza erytreae. Monitoring for citrus psyllid pests can be improved by using semiochemical odorants to augment already visually attractive yellow sticky traps. However, environmental variables such as temperature and humidity could influence odorant release rates. Five field cages were used to test the ability of a selection of odorants to improve yellow sticky trap efficacy in capturing citrus psyllids. Environmental effects on odorant loss from the dispensers were also investigated. The odorants that most improved yellow sticky trap captures in field cages were then tested under open field conditions alongside lower concentrations of those same lures. Gas chromatography-mass spectrometry was used to calculate odorant release rates as well as to determine if any contamination occurred under field conditions. None of the odorants under field cage or field conditions significantly improved psyllid capture on yellow sticky traps. Temperature influenced odorant loss, and release rate from polyethylene bulbs decreased over time. Based on these results, the use of unbaited yellow sticky traps seems to be the most effective method for monitoring of Huanglongbing vectors.

Controlling the Uptake and Release of Semiochemicals in Channel-Type Metal-Organic Frameworks Through Pore Expansion

Semiochemicals can be used to manipulate insect behaviour for sustainable pest management strategies, but their high volatility is a major issue for their practical implementation. Inclusion of these molecules within porous materials is a potential solution to this issue, as it can allow for a slower and more controlled release. In this work, we demonstrate that a series of Zr(IV) and Al(III) metal-organic frameworks (MOFs) with channel-type pores enable controlled release of three semiochemicals over 100 days by pore size design, with the uptake and rate of release highly dependent on the pore size. Insight from grand canonical Monte Carlo simulations indicates that this is due to weaker MOF-guest interactions per guest molecule as the pore size increases. These MOFs are all stable post-release and can be reloaded to show near-identical re-release profiles. These results provide valuable insight on the diffusion behaviour of volatile guests in MOFs, and for the further development of porous materials for sustainable agriculture applications.

Discovery and properties of novel analogues of the aphid pheromones nepetalactone and nepetalactol

BACKGROUND

Pheromones have unique advantages for pest control. Current aphid pheromone research focuses on alarm and sex pheromones. However, practical applications are limited so far, as (E)-β-farnesene has only been investigated to a small extent as an alarm pheromone and only male aphids are targeted by sex pheromones. Previous literature reports electrophysiological responses and repellent behavior of asexual aphids to nepetalactone (1B), therefore our objective was to modify nepetalactone's structure to identify key fragments responsible for repellent effects, as guidance for subsequent modifications and further investigation.

RESULTS

In this study, seven derivatives were designed and synthesized based on nepetalactol (1A) and nepetalactone (1B) as lead compounds. Free-choice tests, conducted using cowpea aphids (Aphis craccivora), revealed that the lactone moiety was crucial for the repellent activity, and the removal of the carbonyl group eliminated the repelling effect. Compound (±)1I, an analogue of nepetalactone (1B), demonstrated a significantly higher repellent value than nepetalactone (1B) at three different concentrations, and even at 0.1 mg/mL it maintained a considerable repellent effect (26.5%). Electrostatic potential and density functional theory calculations supported the importance of the carbonyl group for the repellent effects.

CONCLUSION

The newly discovered para-pheromone (±)1I shows improved repellent effects and potential for development as a novel biological control agent. Based on our innovative findings, analogues with improved efficacy and properties can be designed and prepared. Our research contributes to understanding the effects of structural modifications on pheromone activity and properties, which is crucial for exploring novel pheromone-based products for crop protection. © 2024 Society of Chemical Industry.

Host Volatiles Potentially Drive Two Evolutionarily Related Weevils to Select Different Grains

The Sitophilus zeamais (maize weevil) and Sitophilus oryzae (rice weevil) are two insect pests that have caused huge economic losses to stored grains worldwide. It is urgent to develop an environmentally friendly strategy for the control of these destructive pests. Here, the olfactory-mediated selection preference of the two weevil species to three stored grains was analyzed, which should help establish a pull-push system in managing them. Bioassays showed that maize weevil adults prefer to select maize, followed by paddy and wheat, while rice weevil adults mainly migrate towards wheat. Volatile analyses revealed that 2-ethylhexanol, piperitone, and (+)-Δ-cadiene are the major components in volatiles from both maize and wheat, but the abundance of these chemicals is much lower in maize than that in wheat. The volatile limonene was only detected in paddy. Y-tube bioassays suggest that 2-ethylhexanol, piperitone, and (+)-Δ-cadiene were all attractive to both weevils, whereas limonene was attractive only to rice weevils. Overall, maize weevil appeared more sensitive to the tested volatiles based on having much lower effective concentrations of these volatiles needed to attract them. The differences in volatile profiles among the grains and the sensitivity of the two species towards these volatiles may explain the behavioral differences between maize and rice weevils in selecting host grains. The differences in sensitivity of maize and rice weevils towards host volatile components with abundance differences are likely determinants driving the two insect species to migrate towards different host grains.