Field attraction of Eurydema ornata (Hemiptera: Pentatomidae) to allyl isothiocyanate.

Several Eurydema species (Hemiptera: Pentatomidae) are considered as pests, however, reports on their chemical ecology are scarce. In the current study we focused on Eurydema ornata (Linnaeus) a pentatomid pest of several brassicaceous crops. Since the species is known to feed preferably on generative parts of plants, a series of floral and green leaf volatiles were tested by electroantennography and compounds eliciting remarkable responses were also tested in the field. Three compounds elicited the most outstanding responses from antennae of E. ornata: allyl isothiocyanate, phenylacetaldehyde and ± linalool. Field experiments were conducted in Hungary between 2017 and 2021 to test the potential attractive effects of the compounds. Three Eurydema species were caught in the experiments E. ornata, E. oleracea (Linnaeus) and E. ventralis Kolenati. In the experiments combinations containing allyl isothiocyanate attracted both males and females of E. ornata. The compound was also attractive on its own, in a positive, dose-dependent manner. When presented alone, neither phenylacetaldehyde nor ± linalool was attractive to the species, furthermore, addition of these compounds to allyl isothiocyanate did not affect attraction considerably. To our knowledge this is the first demonstration of field attration of an Eurydema species to a semiochemical and one of the few reports on trapping of a pentatomid species with a synthetic plant volatile in the field. Perspectives regarding research and potential practical applications are discussed in the paper.

Cacopsyllapruni (Hemiptera, Psyllidae) in an apricot orchard is more attracted to white sticky traps dependent on host phenology.

The colour preference of the plum psyllid, Cacopsyllapruni (Hemiptera, Psyllidae), is yet poorly studied. This species is the only known vector of the 'Candidatus Phytoplasma prunorum', the agent of European stone fruit yellows (ESFY), a devastating disease of several cultivated Prunus species in Europe. As ESFY is still uncurable, vector control, thus vector monitoring, is pivotal to protect these trees. Cacopsyllapruni is a univoltine, host-shelter-alternating species; overwintered adults migrate from conifer to wild or cultivated Prunus species (family Rosaceae) in late winter-early spring. To select the most effective colour indicating the arrivals of the immigrants, yellow, fluorescent yellow, white, red and transparent sticky traps were deployed in an apricot orchard in Hungary. The two most abundant species in sticky traps were C.pruni and C.melanoneura. Catches of white traps were significantly biased towards C.pruni as compared to C.melanoneura specimens. Moreover, white sticky traps were better at catching plum psyllids than the other colours. Attraction to white was strongest when immigrants from shelter plants kept arriving in the orchard, coinciding with the blooming principal phenophase of apricot trees. When the host flowering growth stage was over, catches of C.pruni in white traps declined sharply to the level of yellow traps that was highest during this post-blooming period. We recommended white sticky traps for promptly monitoring C.pruni in apricot orchards because it is more potent and more selective than yellow ones during the critically important early flowering interval.

Responses of green lacewings to semiochemicals: species- and sex-specificity (Neuroptera: Chrysopidae)

ABSTRACT Green lacewings (Chrysopidae) are important predators in agroecosystems. Frequently there are studies which treat these beneficial insects at family level as a whole. This approach, despite its practical advantages, may, however, include many species with markedly different life history traits. As green lacewings are also rather diverse in their chemical ecology, treating several different species within one unit may lead to confusion and confounding effects of natural phenomena in research. Besides interspecific differences, sex-specificity is another important factor to consider in respect of insect chemical ecology. This is especially important for green lacewings, in particular the attraction of females, since oviposition is crucial in their application as biological control agents. The aim of our paper is to provide a brief insight into the diversity of the chemical ecology of green lacewings with a special emphasis on the species- and sex-specific differences in their responses to semiochemicals.

Sex Pheromone of the Alfalfa Plant Bug, Adelphocoris lineolatus: Pheromone Composition and Antagonistic Effect of 1-Hexanol (Hemiptera: Miridae).

The sex pheromone composition of alfalfa plant bugs, Adelphocoris lineolatus (Goeze), from Central Europe was investigated to test the hypothesis that insect species across a wide geographical area can vary in pheromone composition. Potential interactions between the pheromone and a known attractant, (E)-cinnamaldehyde, were also assessed. Coupled gas chromatography-electroantennography (GC-EAG) using male antennae and volatile extracts collected from females, previously shown to attract males in field experiments, revealed the presence of three physiologically active compounds. These were identified by coupled GC/mass spectrometry (GC/MS) and peak enhancement as hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal. A ternary blend of these compounds in a 5.4:9.0:1.0 ratio attracted male A. lineolatus in field trials in Hungary. Omission of either (E)-2-hexenyl-butyrate or (E)-4-oxo-2-hexenal from the ternary blend or substitution of (E)-4-oxo-2-hexenal by (E)-2-hexenal resulted in loss of activity. These results indicate that this Central European population is similar in pheromone composition to that previously reported for an East Asian population. Interestingly, another EAG-active compound, 1-hexanol, was also present in female extract. When 1-hexanol was tested in combination with the ternary pheromone blend, male catches were reduced. This compound showed a dose-response effect with small doses showing a strong behavioral effect, suggesting that 1-hexanol may act as a sex pheromone antagonist in A. lineolatus. Furthermore, when (E)-cinnamaldehyde was field tested in combination with the sex pheromone, there was no increase in male catch, but the combination attracted both males and females. Prospects for practical application are discussed.

Attraction of Chrysotropia ciliata (Neuroptera, Chrysopidae) Males to P-Anisaldehyde, a Compound with Presumed Pheromone Function.

In a field-trapping experiment with plant volatiles, we observed notably high attraction of green lacewing (Chrysotropia ciliata) males to the compound p-anisaldehyde. Based on this finding, we initiated the present study to elucidate this phenomenon and to investigate the chemical ecology of C. ciliata. Scanning electron microscopy revealed elliptical glands abundantly distributed on the 2nd to 6th abdominal sternites of C. ciliata males, whereas females of the species completely lacked such glands. No p-anisaldehyde was found in extractions of body parts of C. ciliata. Methyl p-anisate and p-methoxybenzoic acid were identified exclusively in the extract from abdominal segments 2-8 of males. Field-trapping experiments revealed no attraction of C. ciliata to either methyl p-anisate or p-methoxybenzoic acid. In contrast, males showed marked attraction to p-anisaldehyde in the field and antennae showed strong responses to this compound. Headspace collections in the field from living insects in their natural environment and during their main daily activity period indicated that p-anisaldehyde was emitted exclusively by C. ciliata males. Our overall results suggest that p-anisaldehyde might serve as a male-produced pheromone that attracts conspecific C. ciliata males. Here, we discuss hypotheses regarding possible mechanisms involved in regulation of p-anisaldehyde production, including involvement of the compounds methyl p-anisate and p-methoxybenzoic acid, and the potential ecological function of p-anisaldehyde in C. ciliata.

Development of a Female-Targeted Lure for the Box Tree Moth Cydalima perspectalis (Lepidoptera: Crambidae): a Preliminary Report.

The box tree moth, Cydalima perspectalis, is an invasive pest in Europe causing damage on Buxus species. In this study, we aimed to develop a "bisexual" lure to attract both female and male moths. Based on a previous screening bioassay we tested methyl salicylate, phenylacetaldehyde and eugenol as potential attractants in different combinations. The trapping results showed that both binary and ternary blends attracted male and female moths. Catches with these blends were comparable to catches with the synthetic pheromone. Subsequently we carried out single sensillum recordings, which proved the peripheral detection of the above-mentioned compounds on male and female antennae. To identify synergistic flower volatiles, which can be also attractive and can increase the trap capture, we collected flower headspace volatiles from 12 different flowering plant species. Several components of the floral scents evoked good responses from antennae of both females and males in gas chromatography-electroantennographic detection. The most active components were tentatively identified by gas chromatography coupled mass spectrometry as benzaldehyde, cis-ß-ocimene, (±)-linalool and phenethyl alcohol. These selected compounds in combination did not increase significantly the trap capture compared to the methyl salicylate- phenyacetaldehyde blend. Based on these results we discovered the first attractive blend, which was able to attract both adult male and female C. perspectalis in field conditions. These results will yield a good basis for the optimization and development of a practically usable bisexual lure against this invasive pest.

New perspectives for simultaneous attraction of Chrysoperla and Chrysopa lacewing species for enhanced biological control (Neuroptera: Chrysopidae).

Green lacewings (Chrysopidae) are important predators of many soft-bodied pest insects, for instance aphids. Previous studies reported attraction of Chrysoperla carnea species-complex to a ternary floral bait. The larvae of these lacewings are important generalist predators in agroecosystems, however adults are non-predatory, they feed on pollen, nectar or honeydew. Squalene, a plant originated compound was previously reported to be attractive to the nearctic Chrysopa nigricornis. In the current study squalene was tested alone and in combination with the ternary bait in field experiments in Hungary. In our experiments, traps baited with squalene attracted predatory males of Chrysopa formosa. Traps baited with squalene and the ternary floral bait attracted adults of both C. formosa and C. carnea complex lacewings. To our knowledge this is the first report of a bait combination attractive to both Chrysoperla and Chrysopa species. This finding is of special interest considering the remarkably different feeding habits of the adults of these lacewings. Potential perspectives in biological control are discussed.

Benzaldehyde: an alfalfa-related compound for the spring attraction of the pest weevil Sitona humeralis (Coleoptera: Curculionidae).

BACKGROUND: Sitona weevils (Coleoptera: Curculionidae) are a species complex comprising pests of many leguminous crops worldwide, causing damage to young plants as adults and to rootlets as larvae, resulting in significant yield losses. Timely detection of migrating adult weevils is needed to determine when deployment of control measures becomes necessary. With the aim of developing plant volatile-based lures for Sitona spp. detection, we investigated the responses of S. humeralis to host plant-related aromatic compounds. RESULTS: In olfactometer studies, both male and female S. humeralis responded positively to the odour of alfalfa flowers, a source of aromatic volatiles. In single sensillum recordings, basiconic sensilla located on the third and fourth terminal segments of the antennal club of both sexes were found to respond to benzaldehyde at doses of 10-5 and 10-4  g, suggesting that the weevil is able to detect this compound at the peripheral sensory level. In field studies, S. humeralis was attracted to benzaldehyde in the spring, but not in the autumn. CONCLUSION: Benzaldehyde, as described in this study, may be a suitable candidate for the development of monitoring tools for S. humeralis. © 2019 Society of Chemical Industry.

Conspecific and Heterogeneric Lacewings Respond to (Z)-4-Tridecene Identified from Chrysopa formosa (Neuroptera: Chrysopidae).

Green lacewings (Chrysopidae) are predators of soft-bodied pest insects and are among the most important biological control agents in crop protection. Chrysopa spp. are of special importance since, unlike most green lacewing species, adults are also predatory. The current study was undertaken in search of Chrysopa formosa compounds with semiochemical activity. Using coupled gas chromatography-electroantennography (GC-EAG), head and thorax extracts of C. formosa elicited EAG responses to a compound subsequently identified by coupled GC/mass spectrometry, microchemistry, chemical synthesis and GC peak enhancement as (Z)-4-tridecene. In field experiments, this compound decreased attraction of adult C. formosa to (1R,4aS,7S,7aR)-nepetalactol and that of Chrysoperla carnea species-complex to a ternary floral lure, with the inhibitory effect found to be dose-dependent. Our results suggest that (Z)-4-tridecene may serve as a general warning signal among multiple green lacewing species. Perspectives for potential practical applications are discussed.

Aphid Sex Pheromone Compounds Interfere with Attraction of Common Green Lacewings to Floral Bait.

Common green lacewings (Chrysoperla carnea complex) form a group of generalist predators important for biological control. Several reports show attraction of these insects to plant volatiles, and a highly attractive ternary compound floral bait has been developed. With aphids being a preferred prey of larvae, one might expect these lacewings to be attracted to aphid semiochemicals, for instance, to aphid sex pheromones, as found for several other green lacewing species. However, in a previous study, we found that traps containing aphid sex pheromone compounds (1R,4aS,7S,7aR)-nepetalactol (NEPOH), (4aS,7S,7aR)-nepetalactone (NEPONE), and a ternary floral bait attracted fewer individuals than those containing the ternary floral bait alone. In the present study, possible causes for this effect of NEPOH and NEPONE on trap capture were studied. We established that C. carnea complex catches in traps with a ternary floral lure were not influenced by the presence of Chrysopa formosa individuals in traps (attracted by NEPOH and NEPONE) or by synthetic skatole (a characteristic component of Chrysopa defense secretion). A direct negative effect of NEPOH and NEPONE on attraction of C. carnea complex was found, suggesting active avoidance of these aphid sex pheromone components. This finding is surprising as the larvae of these lacewings prey preferentially on aphids. Possible mechanisms underlying this phenomenon are discussed.

Attraction of Chrysoperla carnea complex and Chrysopa spp. lacewings (Neuroptera: Chrysopidae) to aphid sex pheromone components and a synthetic blend of floral compounds in Hungary.

BACKGROUND: The deployment of synthetic attractants for the manipulation of lacewing populations as aphid predators is currently used in integrated pest management. This study investigates a synthetic bait comprising floral compounds previously found to attract the Chrysoperla carnea complex, and, for the first time, the aphid sex pheromone components (1R,4aS,7S,7aR)-nepetalactol and (4aS,7S,7aR)-nepetalactone, in field experiments in Hungary, for their ability to manipulate lacewing populations. RESULTS: The synthetic floral bait attracted both sexes of the Chrysoperla carnea complex, and Chrysopa formosa Brauer showed minimal attraction. The aphid sex pheromone compounds alone attracted males of C. formosa and C. pallens (Rambur). When the two baits were combined, Chrysopa catches were similar to those with aphid sex pheromone baits alone, but carnea complex catches decreased significantly (by 85-88%). CONCLUSION: As the floral bait alone attracted both sexes of the carnea complex, it showed potential to manipulate the location of larval density via altering the site of oviposition. Aphid sex pheromone compounds alone attracted predatory males of Chrysopa spp. and can potentially be used to enhance biological control of aphids. For the carnea complex, however, a combination of both baits is not advantageous because of the decrease in adults attracted. Assumptions of intraguild avoidance underlying this phenomenon are discussed.