Attracting Scelionidae egg parasitoids to enhance stink bug egg parasitisation in soybean crops using methyl salicylate and (E,E)-α-farnesene.

BACKGROUND: Plant volatile organic compounds (VOCs) play a crucial role in mediating interactions between plants, herbivores and natural enemies. Among these VOCs, methyl salicylate and (E,E)-α-farnesene are emitted as herbivore-induced plant volatiles (HIPVs) by soybean plants in response to feeding by the brown stink bug Eushistus heros. These HIPVs function as synomones, influencing the foraging behaviour of the egg parasitoid, Telenomus podisi, the main natural enemy of E. heros, one of the major soybean pests in Brazil. RESULTS: Laboratory experiments showed that two soybean cultivars, BRS 7580 and BRS 7880, produced similar qualitative blends of HIPVs, with methyl salicylate, (E,E)-α-farnesene and (Z)-3-hexenyl acetate being produced by both cultivars. Soybean cultivar BRS 7580 produced a significant lower amount of HIPVs compared to BRS 7880 but this difference did not affect the attractiveness of the egg parasitoid Telenomus podisi. Field experiments using these two cultivars and synthetic applications of methyl salicylate and (E,E)-α-farnesene showed a substantial increase in egg parasitism in all treated areas. Parasitism rates ranged from 50% to 80% in areas where these HIPVs were deployed, compared to only 10% in untreated control areas. CONCLUSIONS: The egg parasitoid Telenomus podisi demonstrated an adept ability in recognising between HIPVs in soybean blends, even in the presence of significant quantitative differences. The results from the field experiment showed the potential of HIPVs in attracting natural enemies to specific target areas within fields. (E,E)-α-Farnesene showed an improved action during the later stages of soybean growth, notably at R6. In addition, this volatile attracted other families of natural enemies. © 2024 Society of Chemical Industry.

Companion and Smart Plants: Scientific Background to Promote Conservation Biological Control.

To attain sustainable agricultural crop protection, tools such as host plant resistance, enhanced ecosystem services (i.e. conserving natural enemies) and the deployment of companion plants should be promoted in pest management programmes. These agro system manipulations could be based on chemical ecology studies considering the interactions with natural enemies and pests, regarding specifically plant defence signalling. Further, new crop protection strategies might rise from widening the knowledge regarding how herbivore-induced plant volatiles can govern a multifaceted defence response including natural enemy recruitment, pest repellence or induced defence in neighbouring plants. It is crucial to use a multitrophic approach to understand better the interactions involving companion plants, herbivores and natural enemies in the field, increasing the knowledge to build more efficient and sustainable pest management strategies. In this review, we explore the perspectives of companion plants and their semiochemicals to promote conservation biological control according to the 'smart plants' concept. Further, we discuss the advantages and disadvantages of using companion plants and explore the application of companion plants in different agroecosystems using several case studies.

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine.

The 9-azabicyclo[3.3.1]nonane ring system is present in several insect- and plant-derived alkaloids. (-)-Adaline (1) and (+)-euphococcinine (2), found in secretions of Coccinelid beetles, and (+)-N-methyleuphococcinine (3), isolated from the Colorado blue spruce Picea pungens, are members of this alkaloid family. Their unique bicyclic system with a quaternary stereocenter, and the potent biological activity exerted by these homotropane alkaloids, make them attractive synthetic targets. This work aims briefly to review the chemical ecology of Adalia bipunctata and the recent methodologies to obtain adaline (1), euphococcinine (2), and N-methyleuphococcinine (3).

Identification of a non-host semiochemical from miniature pinscher, Canis lupus familiaris, that repels Rhipicephalus sanguineus sensu lato (Acari: Ixodidae).

It is already known that the beagle breed of domestic dogs produces semiochemicals capable of repelling the brown dog tick, Rhipicephalus sanguineus sensu lato (s.l.). With a view to discovering new non-host semiochemicals as tick repellents, we compared the semiochemicals produced by a putative tick-resistant breed of dog, miniature pinscher, with known tick-resistant (beagle) and tick-susceptible (English cocker spaniel) breeds. Two non-host compounds produced by beagles, i.e. 2-hexanone and benzaldehyde, were shown to be present in samples collected from all three breeds. Furthermore, two compounds, 6-methyl-5-hepten-2-one and 1,2,4-trimethylbenzene, were found in higher amounts in samples collected from miniature pinscher dogs. The mean amounts of benzaldehyde, 2-hexanone and 1,2,4-trimethylbenzene were similar for beagles and miniature pinschers (P > 0.05) and higher than the means observed for cocker spaniels (P < 0.05), whereas the mean amount of 6-methyl-5-hepten-2-one produced by miniature pinschers was significantly higher (P < 0.05) than for the other breeds of dogs. In Petri-dish assays with adult R. sanguineus s.l., 6-methyl-5-hepten-2-one was repellent for all observation periods evaluated for the two highest concentrations (0.100 and 0.200 mg.cm-2, P < 0.01). The obtained results support our hypothesis that miniature pinschers are a tick-resistant dog breed and agree with previous observations of miniature pinschers being the breed least parasitized by ticks. Furthermore, the non-host semiochemical 6-methyl-5-hepten-2-one has potential to be developed for use as a repellent for the protection of susceptible dogs from R. sanguineus s.l. ticks.

Transcriptional profile of genes involved in the production of terpenes and glyceollins in response to biotic stresses in soybean.

Terpenes produced by plants comprise a diverse range of secondary metabolites, including volatile organic compounds (VOCs). Terpene VOC production may be altered after damage or by biological stimuli such as bacterial, fungal and insects, and subsequent triggering of plant defense responses. These VOCs originate in plants from two independent pathways: the mevalonate and the methylerythritol phosphate pathways, which utilize dimethylallyl and isopentenyl diphosphates to form the terpenoidal precursors. Phakopsora pachyrhizi fungi causes Asian soybean rust, limiting soybean production and resulting in losses of up to 80% if no control strategies are applied. By using a transcriptome datasets, we investigated the regulation of genes of the mevalonate pathway under different biotic stresses. We studied the impact of P. pachyrhizi infection in vivo expression profile of genes involved in terpenoid and glyceollin biosynthesis in genotypes harboring different resistance genes (Rpp), and across the infection cycle. In addition, we used UPLC and UPGC analysis to evaluate glyceollin and VOC production, respectively, to identify metabolites associated with soybean responses to pathogen infection. The regulation of soybean genes involved in terpene production was influenced by genotypes, depending on the Rpp gene, while glyceollin was induced in all genotypes. Furthermore, a sesquiterpene was identified as a potential marker associated with rust symptoms on soybean.

Inefficient weapon-the role of plant secondary metabolites in cotton defence against the boll weevil.

MAIN CONCLUSION: Cotton genotypes displayed similar volatile organic compound (VOC) profiles, but major differences in terpenoid aldehyde (TA) content. The differences in VOC production were minor among genotypes, but these differences are crucial for boll weevil attraction. Weevils did not display any preference in feeding behaviour towards cotton genotypes, suggesting physiological adaptation to cope with cotton chemical defence mechanisms. Plant cultivar selection for resistance to herbivore pests is an effective, environmentally safe and inexpensive method to implement in integrated pest management programmes. In this study, we evaluated seven cotton genotypes with respect to the production of volatile organic compounds (VOCs) and non-volatile compounds [terpenoid aldehydes (TAs)], and the attraction and feeding preference of adult boll weevils. Chemical analyses of VOCs from BRS-293, BRS-Rubi, CNPA TB-15, CNPA TB-85, CNPA TB-90, Delta Opal, and Empire Glandless showed that there were few qualitative and quantitative differences across the range of genotypes. In contrast, major differences in TA content were observed, with CNPA TB-15 and CNPA TB-85 producing higher levels of TAs compared to the other genotypes. Our results showed that boll weevil attraction to cotton genotypes varied, suggesting that the ratios and quantities of emitted cotton VOCs are important for host location. However, boll weevil feeding behaviour was neither positively nor negatively influenced by the terpenoid content (non-volatile compounds) of cotton genotypes. The results in this study suggest that boll weevils have adapted physiologically to cope with cotton chemical defence mechanisms.

Development of pull and push-pull systems for management of lesser mealworm, Alphitobius diaperinus, in poultry houses using alarm and aggregation pheromones.

BACKGROUND: The lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae), is the most important insect pest affecting poultry production around the world, with all life stages being susceptible to infection by bacteria, viruses and fungi. Control of A. diaperinus in poultry houses using intensive insecticide application is not effective due to the cryptic behaviour of this pest. Here, we evaluated the potential of recently identified A. diaperinus alarm (1,4-benzoquinone, 2-methyl-1,4-benzoquinone and 2-ethyl-1,4-benzoquinone) and aggregation [(R)-limonene, 2-nonanone, (E)-ocimene, (S)-linalool, (R)-daucene and (E,E)-α-farnesene] pheromones as tools for the management of this pest in poultry houses in Brazil. RESULTS: Laboratory arena assays with synthetic alarm pheromone confirmed A. diaperinus repellency. In an initial field assay, traps baited with synthetic aggregation pheromone captured significantly more insects than control traps. In further field assays that compared a pull (aggregation pheromone) and a push-pull (simultaneous alarm/aggregation pheromone deployment) system, a higher number of A. diaperinus were captured in aggregation pheromone-baited traps in the push-pull system. CONCLUSION: Our results suggest that alarm and aggregation pheromones can be deployed in poultry houses to trap significant numbers of adult A. diaperinus. Studies are underway to determine the potential for using these components as part of an integrated A. diaperinus management strategy. © 2018 Society of Chemical Industry.

Persistence and efficacy of a new formulation based on dog allomonal repellents against Rhipicephalus sanguineus sensu lato tick / Persistência e eficácia de uma nova formulação baseada em repelentes alomônios de cães contra o carrapato Rhipicephalus sanguineus sensu lato

Beagles are less susceptible to Rhipicephalus sanguineus sensu lato tick due to the production of the allomones benzaldehyde and 2-hexanone. Our previous published work showed that these compounds can reduce tick burden on susceptible dogs. Here we tested the hypothesis that an increase in repellent dose and release rate could increase repellent efficacy and persistence. Slow-release formulations of these compounds, with higher doses and release rates, were tested on artificially-infested dogs. Ten dogs were randomly assigned to two groups with five dogs each. The treated group received collars with slow-release formulations of the compounds attached, while the control group received collars with clean formulations attached. Five environmental infestations were performed, with the number of ticks (at all stages) on the dogs being counted once a day for 40 days. No significant increase in repellent efficacy was observed with the higher doses and release rates, whereas a greater persistence in repellent activity was observed. Treatment with the formulations resulted in a two-to-three-fold reduction in the number of immature stage ticks for up to three weeks. However, the number of adults was similar in both groups. Loss of repellent activity after the third week of testing coincided with a marked change in the relative release rates for the two compounds. It is hypothesized that relative amounts, rather than absolute amounts, of repellent release from slow-release formulations are important for repellent activity. We also hypothesize that the avoidance of less-preferred hosts by ticks relies on olfactory-mediated perception of specific blends of volatile cues from less preferred hosts.(AU)

Beagles são menos suscetíveis ao carrapato Rhipicephalus sanguineus sensu lato devido à produção de benzaldeído e 2-hexanona. Nosso trabalho anterior já publicado mostrou que esses compostos podem reduzir a carga de carrapatos em cães suscetíveis. Aqui testamos a hipótese de que um aumento na dose destes repelentes e na taxa de liberação poderia aumentar a eficácia e a persistência do efeito repelente. As formulações de liberação lenta destes compostos, com doses e taxas de liberação mais elevadas foram testadas em cães infestados artificialmente. Dez cães foram distribuídos aleatoriamente em dois grupos com cinco cães cada. O grupo tratado recebeu colares contendo formulações de liberação lenta dos compostos, enquanto o grupo controle recebeu colares com formulações limpas. Cinco infestações ambientais foram realizadas, com o número de carrapatos (em todas as fases) nos cães sendo contados, uma vez ao dia, por 40 dias. Não se observou aumento significativo na eficácia do repelente com doses e taxas de liberação mais elevadas e, enquanto observou-se maior persistência na atividade repelente. O tratamento com as formulações resultou em uma redução de duas a três vezes no número de carrapatos dos estágios imaturos, por até três semanas. No entanto, o número de adultos foi semelhante em ambos os grupos. A perda de atividade repelente após a terceira semana de teste coincidiu com uma mudança nas taxas de liberação relativa para os dois compostos. A hipótese é que as quantidades relativas, ao invés das quantidades absolutas de liberação lenta, são importantes para a atividade repelente. Então, a hipótese é de que a repelência apresentada por hospedeiros menos susceptíveis aos carrapatos depende da percepção pelos carrapatos de misturas específicas de voláteis liberados por estes hospedeiros.(AU)

Persistence and efficacy of a new formulation based on dog allomonal repellents against Rhipicephalus sanguineus sensu lato tick / Persistência e eficácia de uma nova formulação baseada em repelentes alomônios de cães contra o carrapato Rhipicephalus sanguineus sensu lato

Abstract Beagles are less susceptible to Rhipicephalus sanguineus sensu lato tick due to the production of the allomones benzaldehyde and 2-hexanone. Our previous published work showed that these compounds can reduce tick burden on susceptible dogs. Here we tested the hypothesis that an increase in repellent dose and release rate could increase repellent efficacy and persistence. Slow-release formulations of these compounds, with higher doses and release rates, were tested on artificially-infested dogs. Ten dogs were randomly assigned to two groups with five dogs each. The treated group received collars with slow-release formulations of the compounds attached, while the control group received collars with clean formulations attached. Five environmental infestations were performed, with the number of ticks (at all stages) on the dogs being counted once a day for 40 days. No significant increase in repellent efficacy was observed with the higher doses and release rates, whereas a greater persistence in repellent activity was observed. Treatment with the formulations resulted in a two-to-three-fold reduction in the number of immature stage ticks for up to three weeks. However, the number of adults was similar in both groups. Loss of repellent activity after the third week of testing coincided with a marked change in the relative release rates for the two compounds. It is hypothesized that relative amounts, rather than absolute amounts, of repellent release from slow-release formulations are important for repellent activity. We also hypothesize that the avoidance of less-preferred hosts by ticks relies on olfactory-mediated perception of specific blends of volatile cues from less preferred hosts.

Resumo Beagles são menos suscetíveis ao carrapato Rhipicephalus sanguineus sensu lato devido à produção de benzaldeído e 2-hexanona. Nosso trabalho anterior já publicado mostrou que esses compostos podem reduzir a carga de carrapatos em cães suscetíveis. Aqui testamos a hipótese de que um aumento na dose destes repelentes e na taxa de liberação poderia aumentar a eficácia e a persistência do efeito repelente. As formulações de liberação lenta destes compostos, com doses e taxas de liberação mais elevadas foram testadas em cães infestados artificialmente. Dez cães foram distribuídos aleatoriamente em dois grupos com cinco cães cada. O grupo tratado recebeu colares contendo formulações de liberação lenta dos compostos, enquanto o grupo controle recebeu colares com formulações limpas. Cinco infestações ambientais foram realizadas, com o número de carrapatos (em todas as fases) nos cães sendo contados, uma vez ao dia, por 40 dias. Não se observou aumento significativo na eficácia do repelente com doses e taxas de liberação mais elevadas e, enquanto observou-se maior persistência na atividade repelente. O tratamento com as formulações resultou em uma redução de duas a três vezes no número de carrapatos dos estágios imaturos, por até três semanas. No entanto, o número de adultos foi semelhante em ambos os grupos. A perda de atividade repelente após a terceira semana de teste coincidiu com uma mudança nas taxas de liberação relativa para os dois compostos. A hipótese é que as quantidades relativas, ao invés das quantidades absolutas de liberação lenta, são importantes para a atividade repelente. Então, a hipótese é de que a repelência apresentada por hospedeiros menos susceptíveis aos carrapatos depende da percepção pelos carrapatos de misturas específicas de voláteis liberados por estes hospedeiros.

Persistence and efficacy of a new formulation based on dog allomonal repellents against Rhipicephalus sanguineus sensu lato tick.

Beagles are less susceptible to Rhipicephalus sanguineus sensu lato tick due to the production of the allomones benzaldehyde and 2-hexanone. Our previous published work showed that these compounds can reduce tick burden on susceptible dogs. Here we tested the hypothesis that an increase in repellent dose and release rate could increase repellent efficacy and persistence. Slow-release formulations of these compounds, with higher doses and release rates, were tested on artificially-infested dogs. Ten dogs were randomly assigned to two groups with five dogs each. The treated group received collars with slow-release formulations of the compounds attached, while the control group received collars with clean formulations attached. Five environmental infestations were performed, with the number of ticks (at all stages) on the dogs being counted once a day for 40 days. No significant increase in repellent efficacy was observed with the higher doses and release rates, whereas a greater persistence in repellent activity was observed. Treatment with the formulations resulted in a two-to-three-fold reduction in the number of immature stage ticks for up to three weeks. However, the number of adults was similar in both groups. Loss of repellent activity after the third week of testing coincided with a marked change in the relative release rates for the two compounds. It is hypothesized that relative amounts, rather than absolute amounts, of repellent release from slow-release formulations are important for repellent activity. We also hypothesize that the avoidance of less-preferred hosts by ticks relies on olfactory-mediated perception of specific blends of volatile cues from less preferred hosts.

Attractiveness of Host Plant Volatile Extracts to the Asian Citrus Psyllid, Diaphorina citri, is Reduced by Terpenoids from the Non-Host Cashew.

Diaphorina citri is a vector of the bacterial causative agent of Huanglongbing (HLB = Citrus greening), a severe disease affecting citrus crops. As there is no known control for HLB, manipulating insect behaviour through deployment of semiochemicals offers a promising opportunity for protecting citrus crops. The behavioural responses of D. citri to plant volatiles, and the identity of these plant volatiles were investigated. Volatiles were collected from host plants Murraya paniculata, Citrus sinensis, C. reshni, C. limettioides, Poncirus trifoliata, and from non-host plants Psidium guajava, Mangifera indica, Anacardium occidentale. In behavioural assays, female D. citri spent more time in the arms containing volatiles from either M. paniculata or C. sinensis compared to the control arms. When D. citri was exposed to volatiles collected from A. occidentale, they preferred the control arm. Volatiles emitted from the other studied plants did not influence the foraging behaviour of D. citri. Chemical analyses of volatile extracts from C. sinensis, M. paniculata, and A. occidentale revealed the presence of the terpenoids (E)-4,8-dimethylnona-1,3,7-triene (DMNT) and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT) in higher amounts in A. occidentale. In further behavioural bioassays, female D. citri spent less time in arms containing a synthetic blend of DMNT and TMTT compared to the control arms. Female D. citri also spent less time in arms containing the synthetic blend in combination with volatile extracts from either M. paniculata or C. sinensis compared to the control arms. Results suggest that higher release of the two terpenoids by A. occidentale make this species unattractive to D. citri, and that the terpenoids could be used in reducing colonisation of citrus plants and therefore HLB infection.

The natural plant stress elicitor cis-jasmone causes cultivar-dependent reduction in growth of the stink bug, Euschistus heros and associated changes in flavonoid concentrations in soybean, Glycine max.

To test the hypothesis that the plant stress related elicitor cis-jasmone (cJ) provides protection in soybean pods against the seed-sucking stink bug pest, Euschistus heros, the growth of E. heros on cJ-treated pods was investigated using three soybean cultivars differing in insect susceptibility, i.e. BRS 134 (susceptible), IAC 100 (resistant) and Dowling (resistant). E. heros showed reduced weight gain when fed cJ-treated Dowling, whereas no effect on weight gain was observed when fed other treated cultivars. Using analysis of variance, a three factor (cultivar x treatment x time) interaction was observed with concentrations of the flavonoid glycosides daidzin and genistin, and their corresponding aglycones, daidzein and genistein. There were increases in genistein and genistin concentrations in cJ-treated Dowling at 144 and 120 h post treatment, respectively. Higher concentrations of malonyldaidzin and malonylgenistin in Dowling, compared to BRS 134 and IAC 100, were observed independently of time, the highest concentrations being observed in cJ-treated seeds. Levels of glycitin and malonylglycitin were higher in BRS 134 and IAC 100 compared to Dowling. Canonical variate analysis indicated daidzein (in the first two canonical variates) and genistein (in the first only) as important discriminatory variables. These results suggest that cJ treatment leads to an increase in the levels of potentially defensive isoflavonoids in immature soybean seeds, but the negative effect upon E. heros performance is cultivar-dependent.

Revisiting the Male-Produced Aggregation Pheromone of the Lesser Mealworm, Alphitobius diaperinus (Coleoptera, Tenebrionidae): Identification of a Six-Component Pheromone from a Brazilian Population.

The lesser mealworm, Alphitobius diaperinus Panzer 1797 (Coleoptera: Tenebrionidae), is a cosmopolitan insect pest affecting poultry production. Due to its cryptic behavior, insecticide control is usually not efficient. Thus, sustainable and effective methods would have an enormous and positive impact in poultry production. The aim of this study was to confirm the identity of the male-produced aggregation pheromone for a Brazilian population of A. diaperinus and to evaluate its biological activity in behavioral assays. Six male-specific compounds were identified: (R)-limonene (1), (E)-ocimene (2), 2-nonanone (3), (S)-linalool (4), (R)-daucene (5), all described before in an American population, and a sixth component, (E,E)-α-farnesene (6), which is apparently exclusive to a Brazilian population. Y-Tube bioassays confirmed the presence of a male-produced aggregation pheromone and showed that all components need to be present in a similar ratio and concentration as emitted by male A. diaperinus to produce a positive chemotactic response.

Horn fly larval survival in cattle dung is reduced by endophyte infection of tall fescue pasture.

BACKGROUND: The potential for using endophytic microorganisms in pest control has increased during the last 40 years. In this study, we investigated the impact of endophyte (Neotyphodium coenophialum) infection of cattle pasture upon the survival of the horn fly, Haematobia irritans, a major agricultural pest affecting livestock in many parts of the world. RESULTS: In laboratory assays, where cattle dung collected from endophyte-infected (E+) tall fescue cultivar K-31 was used as the oviposition substrate, larval development was significantly reduced compared with development on cattle dung from steers that grazed uninfected (E-) tall fescue. Furthermore, studies with cattle dung supplemented with the alkaloid fraction extracted from the endophytic fungi revealed significant larval mortality, and HPLC analysis identified two alkaloids, peramine and lolitrem B. The development of larvae was shown to be significantly reduced in field-collected cattle dung. These results suggest that part of the toxicity of alkaloids contained in endophytes is transferred to faecal matter, causing an increase in mortality of H. irritans. CONCLUSION: These data suggest that endophyte infection of cattle pasture, i.e. modified pasture management, can significantly affect horn fly development. © 2015 Society of Chemical Industry.

Differences in the fly-load of Haematobia irritans (Diptera: Muscidae) on cattle is modified by endophyte infection of pastures

Background: The horn fly, Haematobia irritans, is an obligate bloodsucking ectoparasite of pastured cattle and is a major pest of livestock production in North and South America and Europe. In this study, we investigated the potential to use cattle pastures, infected with non-toxic, "friendly" fungal-endophyte-infected (E+) tall fescue, Festuca arundinacea Schreb., as a strategy for reducing horn fly loads in cattle, and to evaluate the possible bioinsecticide effect on horn fly larvae. Results: When cattle grazed in E+ tall fescue, a decrease in fly-load was observed, compared with other pastures (endophyte-free (E-) pastures). The infestation of horn fly load decreased according to an increase in the percentage of endophyte present in the different pastures (0 to 100%). Moreover, two groups of animals with significant differences in the fly-load (high and low fly-load) in the same herd were observed (P < 0.05). Additionally, it was possible to determine a bioinsecticide effect of cattle dung, upon horn fly larvae (80%), from animals fed E+ tall fescue. Conclusions: These results constitute the first report on the potential for exploiting pasture management for controlling 1) horn fly-loads on cattle and 2) the normal development of horn fly larvae. In conclusion, this information provides preliminary understanding of the role of cattle pasture diet management for controlling horn fliesas part of an integrated pest management strategy for this major pest of farmed livestock.

Herbivory by a Phloem-feeding insect inhibits floral volatile production.

There is extensive knowledge on the effects of insect herbivory on volatile emission from vegetative tissue, but little is known about its impact on floral volatiles. We show that herbivory by phloem-feeding aphids inhibits floral volatile emission in white mustard Sinapis alba measured by gas chromatographic analysis of headspace volatiles. The effect of the Brassica specialist aphid Lipaphis erysimi was stronger than the generalist aphid Myzus persicae and feeding by chewing larvae of the moth Plutella xylostella caused no reduction in floral volatile emission. Field observations showed no effect of L. erysimi-mediated floral volatile emission on the total number of flower visits by pollinators. Olfactory bioassays suggested that although two aphid natural enemies could detect aphid inhibition of floral volatiles, their olfactory orientation to infested plants was not disrupted. This is the first demonstration that phloem-feeding herbivory can affect floral volatile emission, and that the outcome of interaction between herbivory and floral chemistry may differ depending on the herbivore's feeding mode and degree of specialisation. The findings provide new insights into interactions between insect herbivores and plant chemistry.

cis-Jasmone induces accumulation of defence compounds in wheat, Triticum aestivum.

Liquid phase extraction (LPE) and vapor phase extraction (VPE) methodologies were used to evaluate the impact of the plant activator, cis-jasmone, on the secondary metabolism of wheat, Triticum aestivum, var. Solstice. LPE allowed the measurement of benzoxazinoids, i.e. 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA), 2-hydroxy-7-methoxy-1,4-benzoxazin-3-one (HMBOA) and 6-methoxy-benzoxazolin-2-one (MBOA), and phenolic acids such as trans-p-coumaric acid, syringic acid, p-hydroxybenzoic acid, vanillic acid and cis- and trans-ferulic acid. Using LPE, a significantly higher level of DIMBOA was found in aerial parts and roots of T. aestivum following treatment with cis-jasmone, when compared with untreated plants. Similar results were obtained for phenolic acids, such as trans-ferulic acid and vanillic acid in roots. Using VPE, it was possible to measure levels of 2-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (HBOA), benzoxazolin-2(3H)-one (BOA), ferulic acid, syringic acid and coumaric acid. The levels of HBOA in aerial parts and roots were significantly greater in cis-jasmone treated plants compared to untreated plants. cis-Jasmone is known to be a plant activator in terms of production of defence-related volatile semiochemicals that repel aphids and increase the foraging activity of aphid parasitoids. These results show, for the first time, that cis-jasmone also induces selective production of secondary metabolites that are capable of directly reducing development of pests, diseases and weeds.

Sex attractant pheromone from the rice stalk stink bug, Tibraca limbativentris Stal.

The male-produced sex pheromone from the Brazilian rice stalk stink bug Tibraca limbativentris is reported. Olfactometer bioassays with sexually mature males and females showed that males attracted females, which suggests that males release a sex pheromone. Males were not attracted to either sex, nor were females attractive to conspecific females. Attraction of the females to males was highest at night. The headspace volatiles collected from male and female bugs were analyzed by gas chromatography (GC) and GC-mass spectrometry. Two male-specific compounds were identified as isomers of 1'S-zingiberenol, whereas a series of defensive compounds were identified in extracts from both sexes. Zingiberenol has three chiral centers, and the nonselective syntheses used produced two groups of isomers, zingiberenol I containing four isomers, namely (1RS,4RS,1'R)-4-(1',5'-dimethylhex-4'-enyl)-1-methylcyclohex-2-en-1-ol, and zingiberenol II containing the other four isomers, namely (1RS,4RS,1'S)-4-(1',5'-dimethylhex-4'-enyl)-1-methylcyclohex-2-en-1-ol. Both groups of stereoisomers were more attractive than hexane controls. The absolute configuration of the insect-produced pheromonal components remains to be elucidated, but the 1'S stereochemistry was established for at least one of the isomers.