Female adult puncture-induced plant volatiles promote mating success of the pea leafminer via enhancing vibrational signals

Volatile Organic Compounds Mediate Host Selection of Wheat Midge, Sitodiplosis Mosellana (Géhin) (Diptera: Cecidomyiidae) between Preanthesis and Postanthesis Stages of Wheat

The orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), is a significant wheat pest in the Prairie Provinces of Canada and northern regions of the USA. Wheat phenology plays a critical role in wheat midge oviposition. We hypothesized that S. mosellana oviposition behaviour is influenced by volatile organic compounds (VOCs) emitted by wheat at two adjacent wheat growth stages: preanthesis and postanthesis. A higher number of S. mosellana eggs laid on preanthesis than postanthesis spikes in an oviposition choice experiment using the susceptible spring wheat cultivar 'Roblin'. In preanthesis, wheat emitted higher amounts of Z-3-hexenyl acetate (Z3-06:OAc) than at the postanthesis stage. Higher amounts of methyl ketones such as 2-tridecanone, 2-pentadecanone, and 2-undecanone were emitted by wheat in the postanthesis stage and these VOCs were sensitive to S. mosellana antennae used in the Gas Chromatography-Electroantennographic Detection. Females were attracted to synthetic Z3-06:OAc but were deterred by 2-tridecanone relative to the solvent control in the vertical Y-tube olfactometer. 2-Undecanone and 2-pentadecanone did not show any attractiveness or deterrence. In a no-choice oviposition experiment, fewer eggs were laid in preanthesis wheat exposed to a synthetic VOC blend of Z3-06:OAc, 2-undecanone, 2-tridecanone, and 2-pentadecanone at the concentrations released by postanthesis spikes. This study shows that the reduction of Z3-06:OAc, in the VOC mix, and possibly the increase in 2-tridecanone, are likely responsible for the reduction in oviposition on postanthesis wheat. These results elucidate for the first time the role of specific VOCs mediating S. mosellana oviposition in preanthesis and postanthesis wheat.

The pyrexia channel remodels egg-laying of Liriomyza huidobrensis in response to temperature change

BACKGROUND

The pea leafminer, Liriomyza huidobrensis, is one of the most important insect pests on vegetables and ornamentals. The survival and egg-laying behavior of leafminers are markedly affected by the environment temperature. However, the mechanisms underlying the relationship between egg-laying and temperature are still largely unknown.

RESULTS

Here, we find that leafminers have evolved an adaptive strategy to overcome the stress from high or low temperature by regulating oviposition-punching plasticity. We further show that this oviposition-punching plasticity is mediated by the expression of pyx in the ovipositor when subjected to disadvantageous temperature. Specifically, down-regulation of pyx expression in leafminers under low temperature stress led to a significant decrease in the swing numbers of ovipositor and puncture area of the egg spot, and consequently the lower amount of egg-laying compared to leafminers at ambient temperature. Conversely, activation of pyx expression under high temperature stress increased the swing numbers and puncture area, still resulting in a reduction of egg-laying amount.

CONCLUSION

Thereby, leafminers are able to coordinate pyx channel expression level and accordingly depress the oviposition. Our study uncovers a molecular mechanism underlying the adaptive strategy in insects that can avoid disadvantageous temperature for reproducing offspring. © 2024 Society of Chemical Industry.

Prolonged Exposure to Plant Volatiles does not Significantly Affect Pban Expression and Mating Behavior in Diamondback Moth [Plutella Xylostella (Lepidoptera: Plutellidae)]

Herbivorous insects use plant volatiles to locate hosts, find food, and identify oviposition sites to aid survival and reproduction. Plant volatiles not only regulate the synthesis and release of sex pheromones in insects, but also help them in the search and orientation of sources of sex pheromones. However, after prolonged exposure to plant volatiles, the changes mediating the mating behavior of diamondback moth (DBM) [Plutella xylostella (L.) (Lepidoptera: Plutellidae)] are unclear. DBMs treated with allyl isothiocyanate, a volatile from cruciferous vegetables, did not show improved rates of mating with a limited effect on mating rhythm. This treatment inhibited mating behaviors in 3-day-old DBMs and decreased mating duration in 5-day-old DBMs. After prolonged exposure to allyl isothiocyanate, the total mating duration of DBM was not significantly different from that after prolonged exposure to n-hexane (control). The longest mating duration after emergence in DBM after prolonged exposure to allyl isothiocyanate was delayed by 1 day compared with exposure to n-hexane. Prolonged exposure to plant volatiles intensified the response behavior of DBM to sex pheromones. However, the amount of Z11-16: Ald, a major component of the sex pheromone blend exhibited no change in female pheromone glands. Pheromone biosynthesis activating neuropeptide gene (PBAN) was down-regulated in DBMs after prolonged exposure to plant volatiles. These findings suggest that prolonged exposure (6 h) to plant-derived volatiles have little effect on the mating behavior of DBM. This study provides practical guidance for applying phytochemicals in pest control by regulating insect behavior.

Substrate-borne vibrational signals and stridulatory organs for sexual communication in leafminer, Liriomyza sativae (Diptera: Agromyzidae)

The vegetable leafminer (Liriomyza sativae [Burgess]) is a highly polyphagous pest that threatens vegetables and horticultural plants. Although sexual communication is a key component of the animal behavioral repertoire, the mechanism underlying sexual communication in L. sativae remains to be elucidated. Here, we used laser vibrometry to characterize the vibrational signals emitted by L. sativae during pair formation. By emitting trains of vibrational pulses (male calling) the male initiated communication on the host plant. The female then became immobile and responded to the male calling by emitting replies (female replies), which in turn triggered male replies consisting of a rapid series of chirps and trills. If the female replied, a continuous exchange of male and female replies ensued, representing a duet. In playback trials, a playback signal caused responses from the opposite sex. Moreover, scanning electron microscopy revealed vibration-producing stridulatory organs in both male and female individuals. The files in males were more developed than those in females, and older male specimens had more signs of abrasion. The results provide new insight into the mating biology of L. sativae.

Functional Diversity of Vibrational Signaling Systems in Insects

Communication by substrate-borne mechanical waves is widespread in insects. The specifics of vibrational communication are related to heterogeneous natural substrates that strongly influence signal transmission. Insects generate vibrational signals primarily by tremulation, drumming, stridulation, and tymbalation, most commonly during sexual behavior but also in agonistic, social, and mutualistic as well as defense interactions and as part of foraging strategies. Vibrational signals are often part of multimodal communication. Sensilla and organs detecting substrate vibration show great diversity and primarily occur in insect legs to optimize sensitivity and directionality. In the natural environment, signals from heterospecifics, as well as social and enemy interactions within vibrational communication networks, influence signaling and behavioral strategies. The exploitation of substrate-borne vibrational signaling offers a promising application for behavioral manipulation in pest control.

Components and composition of active volatiles attract on Diorhabda tarsalis (Coleoptera: Chrysomelidae) from Glycyrrhiza uralensis (Rosales: Leguminoseae)

Introduction

Perennial Chinese licorice, Glycyrrhiza uralensis, is an important medicinal plant. Diorhabda tarsalis, a leaf beetle, is a serious insect pest on the plant and cause serious yield losses every year and is attracted to healthy and pest-damaged licorice by plant volatiles.

Aim

The biologically active components of the volatiles released from G. uralensis have not been reported; the components of the volatiles that attract D. tarsalis need to be identified. Such compounds could potentially be used for monitoring and mass-trapping pests.

Methods

GC-EAD, GC-MS, EAG, Y-shaped olfactometer behavioral bioassays, and field trials were performed to identify the components and composition of active volatiles.

Results

Male and virgin female adults were generally attracted to volatiles from licorice, and volatiles from pest-infested plants were more attractive. Four compounds from licorice elicited a significant electrophysiological response (EAD) and were confirmed by EAG, including hexanal, (Z)-3-hexenal, (Z)-3-hexen-1-ol, and (E)-2-hexenal. With the exception of the (E)-2-hexenal, these molecules significantly attracted adults in individual behavioral bioassays, and a proportional mixture corresponding to beetle-damaged licorice of hexanal, (Z)-3-hexenal, (Z)-3-hexen-1-ol, and (E)-2-hexenal (8.78:15.26:57.24:18.72) was most effective for attracting D. tarsalis in the field, attracted a mean of 26 ± 7.19 beetles per trap.

Discussion

D. tarsalis was attracted to volatiles from healthy and herbivore-induced G. uralensis under both laboratory and field conditions. The aforementioned compounds show considerable potential for commercial application to monitor and control D. tarsalis populations.

The molecular identification, odor binding characterization, and immunolocalization of odorant-binding proteins in Liriomyza trifolii

The Liriomyza trifolii is a highly invasive polyphagia pest. Understanding the physiological functions of odorant binding proteins (OBPs) in the chemical communication of L. trifolii can lead to effective pest management strategies. Seven full-length OBPs were identified by transcriptome screening of L. trifolii adults. Bioinformatics analyses classified the seven OBPs into two subfamilies (six classic OBPs, one minus-C OBP). The analysis of their expression in different development stages revealed that LtriOBP5 was highly expressed in the larval stage, LtriOBP4 in the pupa stage, and LtriOBP1, 2, 3, 6, 7 in the adult stage; the expression levels were higher in male adults than in females. The analysis of different tissues showed high expression of LtriOBP1, 3, 6, 7 in the antennae, which were selected for in vitro purification. To explore the ligand compounds of OBPs, fluorescence competitive binding experiments were performed. Immunofluorescence localization revealed that LtriOBP1, 3, 6, 7 showed strong binding abilities to plant volatiles and were located in the antennae, implying that LtriOBP1, 3, 6, 7 may play key roles in olfaction, such as host location. LtriOBP6 and LtriOBP7 had strong binding abilities to specific herbivore-induced plant volatiles, suggesting LtriOBP6 and LtriOBP7 may also play critical roles in chemoreception. This study provides preliminary exploration of the olfactory perception mechanism of L. trifolii, which can be used as a basis to design insect behavior regulators and develop highly effective insecticides using mixture of ligands and known pesticides.

Attraction of the Biocontrol Agent, Galerucella placida Towards Volatile Blends of Two Polygonaceae Weeds, Rumex dentatus and Polygonum glabrum

The Polygonaceae weed, Rumex dentatus L. grows in association with wheat, mustard and potato, while Polygonum glabrum Willd. grows in association with rice in India. Both larvae and adults of Galerucella placida Baly (Coleoptera: Chrysomelidae) voraciously consume these weeds. Applications of synthetic herbicides to control weeds are harmful to the environment including beneficial organisms. We propose to find volatile organic compounds (VOCs) from both weeds causing attraction of the biocontrol agent, G. placida, in order to attempt to use the insect as a biological weed control. Behavioral responses of G. placida towards volatile blends characteristic of undamaged (UD), insect-damaged (ID), jasmonic acid-treated (JA) or mechanically-damaged (MD) plants were conducted by Y-tube olfactometer bioassays. Cuminaldehyde was predominant in VOCs of UD R. dentatus, ID P. glabrum, and both JA and MD R. dentatus and P. glabrum. Geraniol was predominant in VOCs of UD P. glabrum, while 1,3-diethylbenzene predominated in VOCs of ID R. dentatus. Females were more attracted towards volatile blends of ID plants compared to UD or JA plants. Females did not show attraction towards volatile blends of JA plants. We identified two bioactive synthetics blends, one comprised of seven compounds - 16.65 µg 1,3-diethylbenzene, 10.72 µg acetophenone, 6.52 µg 2,6-(E,Z)-nonadienal, 2.46 µg 1-nonanol, 4.19 µg decanal, 9.86 µg 4-ethylacetophenone and 3.34 µg 1-hexadecene dissolved in 25 µl CH₂Cl₂ and the other containing five compounds - 2.50 µg 2-octanol, 6.84 µg limonene, 0.64 µg dodecane, 6.63 µg 4-ethylacetophenone and 0.24 µg geranyl acetone dissolved in 25 µl CH₂Cl₂. These two blends of volatile compounds could be used to attract the biocontrol agent during early vegetative period of these two weeds, which could lead to eradication of weeds from crop fields.

Fruit Volatiles of Creeping Cucumber (Solena amplexicaulis) Attract a Generalist Insect Herbivore

Herbivorous insects employ host plant volatile blends as cue for host recognition. Adults of Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) feed on leaves, flowers, and fruits of Solena amplexicaulis (Lam.) Gandhi (syn: Melothria heterophylla) (Cucurbitaceae), commonly known as creeping cucumber. Currently, this pest is controlled by insecticides application. Hence, it is necessary to find out volatile components from fruits attracting the insect, which might be used for eco-friendly pest management program. behavioral responses of females were measured by Y-tube olfactometer bioassays towards volatile blends from undamaged (UD), insect-damaged (ID), and mechanically damaged (MD) fruits with the aim to identify the compounds responsible for host fruit location. Volatile organic compounds were identified and quantified by GC-MS and GC-FID analyses, respectively. Nonanal was predominant in volatile blends of UD, ID, and MD fruits. 1-Octen-3-ol, 3-octanone, 2-octanol, heptadienal (2E,4E), 1-pentadecanol, and 1-hexadecanol were present in volatile blends of ID and MD fruits, but females did not show response to these six compounds. 1-Octanol and 1-heptadecanol were unique in volatile blends of UD fruits after 4 hr of damage, but females did not show response to these compounds. Females were more attracted to volatile blends from UD fruits after 4 hr of damage in comparison to volatile blends released by UD fruits, due to increased emissions of (E,Z)-2,6-nonadienal and 2E-nonenal. A synthetic blend of 3.35 μg (E,Z)-2,6-nonadienal and 1.72 μg 2E-nonenal dissolved in 25 μl CH₂Cl₂ could be used for the development of baited traps to control this insect pest in integrated pest management strategies.

Overview: biotic signalling for smart pest management

Biotic signalling refers to species or phylogenetic-clade-specific signals that elicit adaptive and acceptable responses within and among organisms. It is not only the molecular basis of the ecological relationships among different species, such as parasitism, symbiosis and predation, but also serves as ideal targets that can be used to manipulate these ecological relationships. This concept was proposed by a group of scientists from the Chinese Academy of Sciences (CAS) and actively pursued in a five-year research project in 2014 funded by the CAS ($40 million), entitled 'Decoding biotic interactions and mechanism for target management of agricultural pests'. The multi-disciplinary project aimed at a systematic investigation of the intra-species and inter-species and interactions via biotic signalling, with the ultimate goal being the development of novel methods to manage the pest insects and diseases. We hereby propose a topic 'Biotic signalling sheds light on smart pest control' as a theme issue for the Philosophical Transactions of the Royal Society B. It contains a total of 18 reviews and research articles under the topic of signalling manipulation for pest management. Unravelling these complex interactions among plants, microbial pathogens and insects holds promise for developing novel strategies to protect crop plants without compromising agricultural productivity and environmental health. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.