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BACKGROUND: Populations of red palm weevil (RPW), a severe pest of palms in Mediterranean countries, might be limited by semiochemical-based behaviour-disrupting methods. We evaluated the effects of electroantennogram (EAG)-active plant volatiles on the behaviour of RPWs from Italy and Israel. In field experiments, α-pinene, citronellol, geraniol, citral and 1-octen-3-ol were tested for their ability to disrupt attraction to pheromone-kairomone and molasses baited traps. Those that were found to be disruptive in the field were evaluated in a laboratory choice bioassay in individual cages for their effect on RPW female feeding and oviposition. RESULTS: Field experiments showed reduced captures in traps loaded with geraniol (-57%), 1-octen-3-ol (-50%) or α-pinene (-45% to -60%); captures in citronellol- or citral-loaded traps did not differ from control. In laboratory experiments, 1-octen-3-ol was the most potent behaviour-modifying compound, eliciting a significant/marginally significant reduction in both feeding and oviposition at the lowest dose tested in both populations. Geraniol generally caused a strong reduction in feeding and oviposition at each dose tested (Israel), or at the highest dose (Italy). α-Pinene caused some reduction in feeding activity at the highest dose tested (Italy), but no consistent repellency (Israel). CONCLUSION: Field and laboratory data suggest the potential for the use of 1-octen-3-ol, geraniol and α-pinene for RPW population management.

Aims: Larvae of the red palm weevil (RPW) Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) feed inside palm stem tissues, making galleries and producing a wet fermenting frass. We characterized the culturable micro-organisms associated with frass produced by tunnelling larvae inside the Canary island date palms and investigated the role of frass and gut bacteria in plant polymers breakdown. Methods and Results: A culture-dependent method was used to isolate bacteria from frass and noninfested palm tissues. Bacterial isolates were grouped into operational taxonomic units based on polymorphisms in the ITS-PCR profiles, and representative isolates were identified by partial sequencing of the 16S rRNA gene. Frass bacteria were dominated by 2,3-butanediol fermenter Enterobacteriaceae. None of the bacterial isolates was able to degrade cellulose; however, cellulolytic and hemicellulolytic bacteria were isolated from the larval gut enrichment cultures. Conclusions: Frass bacteria are specifically associated with the RPW larvae and might play beneficial roles for RPW, other than nutritional, that deserve further investigations. Breakdown of plant polymers probably occurs inside the larvae digestive system. Significance and Impact of the Study: Frass and gut micro-organisms of R. ferrugineus should be included in studies of the interactions between RPW, its plant hosts, and its enemies.

Chemical residues deposited by walking adults of the southern green stink bug (SGSB), Nezara viridula (L.) (Heteroptera: Pentatomidae), which play a role as contact kairomones inducing arrestment behavior in the egg parasitoid Trissolcus basalis (Wollaston), were investigated in laboratory experiments. Female wasps encountering an area contaminated by chemical residues from adult hosts showed an arrestment response characterized by prolonged periods of walking and turning, resulting in systematic return to the stimulus after encountering the treatment borders. When SGSB adults were dissected into separate body parts, extracts from legs and the dorsal laminar pronota of adult females elicited equal responses, whereas extracts of legs and dorsal laminar pronota of adult males elicited lower responses. These results corroborate previous results showing the wasp’s preference for chemical residues from female hosts, and they suggest that contact kairomones are not confined to the legs, but are distributed over the adult cuticula. Hexane extracts of laminar pronotua and legs of SGSB adults induced stronger responses than methanol extracts. Silica gel chromatography of SGSB cuticular extracts indicated that the activity was associated with the fraction containing saturated and unsaturated hydrocarbons. The potential significance of these results to the host location behavior of T. basalis in the field is discussed.

Several studies showed that egg parasitoids are able to detect host sex pheromones produced by adult hosts as a host cue. In this way female wasps are directed toward an area where host mating is in progress and where an oviposition has probably taken place or is soon to occur. Telenomus busseolae Gahan (Hymenoptera: Scelionidae) is a solitary egg parasitoid of various noctuids (Lepidoptera, Noctuidae) belonging to the genera Sesamia. In field observations, it has been demonstrated that T. busseolae reacts to the pheromone emitted by females of the corn stalk borer, Sesamia nonagrioides (Lefebvre) and the pink stem borer, Sesamia calamistis (Hampson). It is known that the sex pheromone produced by calling lepidopteran females are usually a mixture of compounds. In laboratory experiments, it was shown that three components of the synthetic sex pheromone of the Mediterranean stem borer, e.g. (Z)-11–16:Ac (the main component), (Z)-11–16:Ald and 12:Ac, attract wasp females, while a fourth compound, (Z)-11–16:OH, did not. Interestingly, these active compounds are also present in the sex pheromone blends of other host Sesamia species, and in the sex pheromone blends of other non-host noctuid species. To evaluate the role played by some components of noctuid sex pheromone in the host specificity of T. busseolae, we carried a series of laboratory experiments with a Y-tube olfactometer coupled a video tracking and motion analysis system. In particular we analyzed the behavioural response of T. busseolae females to the main compounds of the synthetic sex pheromones of the corn earworm, Helicoverpa armigera (Hübner). Bioassays were carried out with the whole corn earworm sex pheromone blend [(Z)-9–16:Ald : (Z)-11–16:Ald at ratio of 3 : 97], and the following single compounds: (Z)-9–16:Ald present only in the corn earworm sex pheromone, (Z)-11–16:Ac the main component of the Mediterranean stem borer sex pheromone, and (Z)-11–16:Ald common to both noctuids. All the treatments were bioassayed at two different doses (0.1 mg and 1.0 mg). The results showed that T. busseolae females were 1) attracted by (Z)-11–16:Ac at 0.1 mg and by (Z)-11–16:Ald at 1.0 mg; 2) not attracted by the whole sex pheromone of the corn earn borer at both concentrations; and 3) slightly deterred by (Z)-9–16:Ald at both concentrations. These results suggest that (Z)-9–16:Ald is a key compound which prevents T. busseolae females responding to the corn earworm sex pheromone

Olive fruit fly Bactrocera oleae (Rossi) (Diptera: Tephritidae) is a major olive pest in the Mediterranean basin where increasing insecticide resistance has enhanced damage and necessitates more reliance on other control strategies, such as biological control. Provision of floral resources has been reported to improve the effectiveness of natural enemies. Here, we tested the effect of six plant nectars and two honeydew sources on the survival of Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae), a parasitoid wasp used in the biological control of olive fruit fly. Our results showed a positive effect on survival associated with nectars of Anchusa azurea Mill., Rosmarinus officinalis L., Lavatera cretica L. and Calamintha nepeta (L.) Savi, while honeydew proved to be a valuable alternative food source. When offering flowers directly to insects, Anchusa azurea, Lavatera cretica, and Foeniculum vulgare L. were found to be the most beneficial species, indicating also that P. concolor feeds predominantly on shallow corollas.

The venom gland is a ubiquitous organ in Hymenoptera. In insect parasitoids, the venom gland has been shown to have multiple functions including regulation of host immune response, host paralysis, host castration and developmental alteration. However, the role played by the venom gland has been mainly studied in parasitoids developing in larval or pupal hosts while little is known for parasitoids developing in insect eggs. We conducted the first extensive characterization of the venom of the endoparasitoid Ooencyrtus telenomicida (Vassiliev), a species that develops in eggs of the stink bug Nezara viridula (L.). In particular we investigated the structure of the venom apparatus, its functional role and conducted a transcriptomic analysis of the venom gland. We found that injection of O. telenomicida venom induces: 1) a melanized-like process in N. viridula host eggs (host-parasitoid interaction), 2) impairment of the larval development of the competitor Trissolcus basalis (Wollaston) (parasitoid-parasitoid interaction). The O. telenomicida venom gland transcriptome reveals a majority of digestive enzymes (peptidases and glycosylases) and oxidoreductases (laccases) among the most expressed genes. The former enzymes are likely to be involved in degradation of the host resources for the specific benefit of the O. telenomicida offspring. In turn, alteration of host resources caused by these enzymes may negatively affect the larval development of the competitor T. basalis. We hypothesize that the melanization process induced by venom injection could be related to the presence of laccases, which are multicopper oxidases that belong to the phenoloxidases group. This work contributed to a better understanding of the venom in insect parasitoids and allowed to identify candidate genes whose functional role can be investigated in future studies.

Bagrada hilaris Burmeister, is a stink bug native to Asia and Africa and invasive in the United States, Mexico, and more recently, South America. This species can cause serious damage to various vegetable crops in the genus Brassica, with seedlings being particularly susceptible to B. hilaris feeding activity. In this study, the role of volatile organic compounds (VOCs) emitted by seedlings of three Brassica species on the host preference of B. hilaris was evaluated. In dual choice arena and olfactometer bioassays, adult painted bugs preferred B. oleracea var. botrytis and B. napus over B. carinata. Volatiles from B. oleracea seedlings were collected and bioassayed with B. hilaris adults and late stage nymphs, using electroantennographic (EAG) and behavioral (olfactometer) techniques. When crude extracts of the VOCs from B. oleracea var. botrytis seedlings and liquid chromatography fractions thereof were bioassayed, B. hilaris adults and nymphs were attracted to the crude extract, and to a non-polar fraction containing hydrocarbons, whereas there were no responses to the more polar fractions. GC-MS analysis indicated that the main constituents of the non-polar fraction was an as yet unidentified diterpene hydrocarbon, with trace amounts of several other diterpene hydrocarbons. The major diterpene occurred in VOCs from both of the preferred host plants B. oleracea and B. napus, but not in VOCs of B. carinata. Our results suggest that this diterpene, alone or in combination with one or more of the minor compounds, is a key mediator in this insect-plant interaction, and could be a good candidate for use in lures for monitoring B. hilaris in the field.