Nectar yeasts enhance the interaction between Clematis akebioides and its bumblebee pollinator

• It has been hypothesised that intense metabolism of nectar‐inhabiting yeasts (NIY) may change nectar chemistry, including volatile profile, which may affect pollinator foraging behaviours and consequently plant fitness. However, empirical evidence for the plant–microbe–pollinator interactions remains little known.
• To test this hypothesis, we use a bumblebee‐pollinated vine Clematis akebioides endemic to southwest China as an experimental model plant. To quantify the incidence and density of Metschnikowia reukaufii, a cosmopolitan NIY in floral nectar, a combination of yeast cultivation and microscopic cell‐counting method was used. To examine the effects of NIY on plant–pollinator interactions, we used real flowers filled with artificial nectar with or without yeast cells. Then the volatile metabolites produced in the yeast‐inoculated nectar were analysed with coupled gas chromatography and mass spectrometry (GC‐MS).
• On average 79.3% of the C. akebioides flowers harboured M. reukaufii, and cell density of NIY was high to 7.4 × 10⁴ cells mm^?3. In the field population, the presence of NIY in flowers of C. akebioides increased bumblebee (Bombus friseanus) pollinator visitation rate and consequently seed set per flower. A variety of fatty acid derivatives produced by M. reukaufii may be responsible for the above beneficial interactions.
• The volatiles produced by the metabolism of M. reukaufii may serve as an honest signal to attract bumblebee pollinators and indirectly promote the female reproductive fitness of C. akebioides, forming a potentially tripartite plant–microbe–pollinator mutualism.

     

Genetic interactions reveal the antagonistic roles of FT/TSF and TFL1 in the determination of inflorescence meristem identity in Arabidopsis

During the transition to the reproductive phase, the shoot apical meristem switches from the developmental program that generates vegetative organs to instead produce flowers. In this study, we examined the genetic interactions of FLOWERING LOCUS T (FT)/TWIN SISTER OF FT (TSF) and TERMINAL FLOWER 1 (TFL1) in the determination of inflorescence meristem identity in Arabidopsis thaliana. The ft‐10 tsf‐1 mutants produced a compact inflorescence surrounded by serrated leaves (hyper‐vegetative shoot) at the early bolting stage, as did plants overexpressing TFL1. Plants overexpressing FT or TSF (or both FT and TFL1) generated a terminal flower, as did tfl1‐20 mutants. The terminal flower formed in tfl1‐20 mutants converted to a hyper‐vegetative shoot in ft‐10 tsf‐1 mutants. Grafting ft‐10 tsf‐1 or ft‐10 tsf‐1 tfl1‐20 mutant scions to 35S::FT rootstock plants produced a normal inflorescence and a terminal flower in the scion plants, respectively, although both scions showed similar early flowering. Misexpression of FT in the vasculature and in the shoot apex in wild‐type plants generated a normal inflorescence and a terminal flower, respectively. By contrast, in ft‐10 tsf‐1 mutants the vasculature‐specific misexpression of FT converted the hyper‐vegetative shoot to a normal inflorescence, and in the ft‐10 tsf‐1 tfl1‐20 mutants converted the shoot to a terminal flower. TFL1 levels did not affect the inflorescence morphology caused by FT/TSF overexpression at the early bolting stage. Taking these results together, we proposed that FT/TSF and TFL1 play antagonistic roles in the determination of inflorescence meristem identity, and that FT/TSF are more important than TFL1 in this process.     

Trade‐off between attraction to aggregation pheromones and repellent effects of spike lavender essential oil and its main constituent linalool in the flour beetle Tribolium confusum

Essential oils of aromatic plants and their individual volatile components have been tested in pest management strategies for their toxic and often repellent effects on target insects. When evaluating their possible effects on crucial behaviours of the pest insects, the olfactory environment including intraspecific communication cues has to be considered. We used the flour beetle Tribolium confusum du Val (Coleoptera: Tenebrionidae), a common stored‐product pest, to investigate the influence of oil of spike lavender, Lavandula spica Medik. (Labiaceae), and its main component, linalool, at various doses on olfactory‐guided behaviour. Using four‐way olfactometers, a dose‐dependent repellent effect of L. spica oil and linalool alone was revealed. On the other hand, we confirmed that T. confusum is attracted by conspecifics, by means of an aggregation pheromone and by 10 ng of one of its components, 1‐tetradecene. Twenty‐four hour pre‐exposure to 10 μl of L. spica oil abolished subsequent attraction to 1‐tetradecene and reduced attraction to five conspecifics. Simultaneous exposure to L. spica oil or linalool and five conspecifics reduced the repellent effect of the volatiles in a dose‐dependent manner, whereas simultaneous exposure to 1‐tetradecene at 10 ng abolished the repellent effect of L. spica oil only at a dose of 0.01 mg. These results indicate a dose‐dependent trade‐off between attractive and plant‐derived repellent volatiles, which may influence the effectiveness of such volatiles in their potential use in alternative pest management strategies.     

Dynamic trajectories of volatile and non‐volatile specialised metabolites in ‘overnight’ fragrant flowers of Murraya paniculata

• Ephemeral flowers, especially nocturnal ones, usually emit characteristic scent profiles within their post‐anthesis lifespans of a few hours. Whether these flowers exhibit temporal variability in the composition and profile of volatile and non‐volatile specialised metabolites has received little attention.
• Flowers of Murraya paniculata bloom in the evenings during the summer and monsoon, and their sweet, intense fragrance enhances the plant's value as an ornamental. We aimed to investigate profiles of both volatile and non‐volatile endogenous specialised metabolites (ESM) in nocturnal ephemeral flowers of M. paniculata to examine whether any biochemically diverse groups of ESM follow distinct patterns of accumulation while maintaining synchrony with defensive physiological functions.
• Targeted ESM contents of M. paniculata flowers were profiled at ten time points at 2‐h intervals, starting from late bud stage (afternoon) up to the start of petal senescence (mid‐morning). Emitted volatiles were monitored continuously within the whole 20‐h period using headspace sampling. The ESM contents were mapped by time point to obtain a highly dynamic and biochemically diverse profile. Relative temporal patterns of ESM accumulation indicated that the active fragrance‐emitting period might be divided into ‘early bloom’, ‘mid‐bloom’ and ‘late bloom’ phases. Early and late bloom phases were characterised by high free radical generation, with immediate enhancement of antioxidant enzymes and phenolic compounds. The mid‐bloom phase was relatively stable and dedicated to maximum fragrance emission, with provision for strong terpenoid‐mediated defence against herbivores. The late bloom phase merged into senescence with the start of daylight; however, even the senescent petals continued to emit fragrance to attract diurnal pollinators.
• Our study suggests that dynamic relations between the different ESM groups regulate the short‐term requirements of floral advertisement and phytochemical defence in this ephemeral flower. This study also provided fundamental information on the temporal occurrence of emitted volatiles and internal pools of specialised metabolites in M. paniculata flowers, which could serve as an important model for pollination biology of Rutaceae, which includes many important fruit crops.

     

Chemical Composition,Antioxidant Properties, α‐Glucosidase Inhibitory,and Antimicrobial Activity of Essential Oils from Acacia mollissima and Acacia cyclops Cultivated in Tunisia

The genus Acacia is quite large and can be found in the warm subarid and arid parts, but little is known about its chemistry, especially the volatile parts. The volatile oils from fresh flowers of A. mollissima and A. cyclops (growing in Tunisia) obtained by hydrodistillation were analyzed by GC then GC/MS. Eighteen (94.7% of the total oil composition) and 23 (97.4%) compounds were identified in these oils, respectively. (E,E)‐α‐Farnesene (51.5%) and (E)‐cinnamyl alcohol (10.7%) constituted the major compounds of the flower oil of A. mollissima, while nonadecane (29.6%) and caryophyllene oxide (15.9%) were the main constituents of the essential oil of A. cyclops. Antioxidant activity of the isolated oils was studied by varied assays, i.e., 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and 2,2‐azinobis 3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS); the isolated oils showed lowest IC₅₀ (4 – 39 μg/ml) indicating their high antioxidant activity. The α‐glucosidase inhibitor activity was also evaluated and Acacia oils were found to be able to strongly inhibit this enzyme with IC₅₀ values (81 – 89 μg/ml) very close to that of acarbose which was used as positive control. Furthermore, they were tested against five Gram‐positive and Gram‐negative bacteria and one Candida species. Essential oil of A. mollissima was found to be more active than that of A. cyclops, especially against Pseudomonas aeruginosa (MIC = 0.31 mg/ml and MBC = 0.62 mg/ml).     

Bulb and Root Rot in Lily (Lilium longiflorum) and Onion (Allium cepa) in Israel

In the past 10 years, there has been a substantial increase in reports, from growers and extension personnel, on bulb and root rots in lily (Lilium longiflorum) in Israel. Rot in these plants, when grown as cut flowers, caused serious economic damage expressed in reduction in yield and quality. In lily, the fungal pathogens involved in the rot were characterized as binucleate Rhizoctonia AG‐A, Rhizoctonia solani, Pythium oligandrum, Fusarium proliferatum (white and purple isolates) and F. oxysporum, using morphological and molecular criteria. These fungi were the prevalent pathogens in diseased plants collected from commercial greenhouses. Pathogenicity trials were conducted on lily bulbs and onion seedlings under controlled conditions in a greenhouse to complete Koch's postulates. Disease symptoms on lily were most severe in treatments inoculated with binucleate Rhizoctonia AG‐A, P. oligandrum and F. proliferatum. Plant height was lower in the above treatments compared with the control plants. The least aggressive fungus was R. solani. In artificial inoculations of onion, seedling survival was significantly affected by all fungi. The most pathogenic fungus was F. proliferatum w and the least were isolates of F. oxysporum (II and III). All fungi were successfully re‐isolated from the inoculated plants.     

Chemical Composition,Antimicrobial and Insecticidal Activities of Flowers Essential Oils of Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm. from Martinique Island

Alpinia species, used as ornamental plants and flavoring agents, are renowned for their therapeutic properties and their subsequent use in traditional medicines throughout the world. Alpinia zerumbet (Pers .) B.L.Burtt & R.M.Sm . is the most common Alpinia species encountered in Martinique. Several essential oils (EOs) obtained by hydrodistillation of A. zerumbet flowers collected in various locations on the island at different seasons were analysed to evaluate the influence of the collection period and area on the EOs’ chemical compositions and to assess their bioactivity. A combination of GC‐FID and GC/MS techniques was used to examine the volatile constituents, leading to the identification of a total of 71 components accounting for 97.8 – 99.3% of the respective total GC‐FID areas: among them, nineteen compounds were characterized for the first time in A. zerumbet EOs. The antimicrobial activity of these EOs was assessed against eight bacterial, yeast and fungal strains and two multi‐resistant strains: some significant bacteriostatic and fungistatic activities of A. zerumbet flower oils were evidenced. Finally, an interesting insecticidal activity of the flower EO was highlighted for the first time against Aedes aegypti.     

Size‐structured vulnerability of the colonial cyanobacterium,Microcystis aeruginosa,to grazing by zebra mussels (Dreissena polymorpha)

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Volatiles released from foliar extract of host plant enhance landing rates of gravid Polygonia c‐album females,but do not stimulate oviposition

The role of olfactory cues for host search is much less investigated in day‐active butterflies than in their relatives, the nocturnal moths. The goal of this study was to investigate whether host‐plant volatiles from foliar extracts of hop, Humulus lupulus L. (Cannabaceae), evoke electroantennographic (EAG) responses, increase landing rates, and stimulate egg‐laying behavior of gravid Polygonia c‐album L. (Lepidoptera: Nymphalidae) females. Eighty‐nine volatile compounds were detected in a non‐concentrated methanol extract of hop by gas chromatography–mass spectrometry, 11 of which elicited an EAG response. Concentration of the crude extract significantly reduced landing rates on artificial leaves treated with the sample due to loss of volatile compounds, but after landing the oviposition response of gravid females was not affected. A mixture of eight commercially available EAG‐active volatiles increased the landing rate of gravid females to their source but did not act as oviposition stimulants. Dividing the volatile compounds into two groups – consisting of (1) hexanal, (E)‐2‐hexenal, octanal, nonanal, and decanal, and (2) sulcatone, humulene, and benzyl alcohol – obliterated effectiveness, revealing synergism between compounds. Although volatiles did not stimulate oviposition, they significantly contributed to the distribution of eggs by increasing the landing rates on treated artificial leaves.     

Host plant volatiles responsible for the invasion of Stenotus rubrovittatus (Heteroptera: Miridae) into paddy fields

We investigated the attractiveness of synthetic volatile blends or individual volatiles of flowering rice panicles or flowering Scirpus juncoides spikelets to the sorghum plant bug Stenotus rubrovittatus (Matsumura). None of the individual chemicals tested attracted either sex of the bug. Synthetic volatile blends of flowering rice panicles composed of geranyl acetone, β‐caryophyllene, n‐decanal, methyl salicylate, β‐elemene and n‐tridecene attracted females. The synthetic blend of volatiles was just as attractive as natural flowering rice panicles to females. Other synthetic blends did not attract the bug. We sampled headspace volatiles from flowering S. juncoides spikelets with solid‐phase microextraction and analysed them using gas chromatography–mass spectrometry. The main volatile emitted from S. juncoides was β‐caryophyllene, one of the major volatile components of flowering rice panicles. β‐Elemene was a common volatile found in flowering rice panicles and flowering S. juncoides spikelets. Therefore, we investigated the attractiveness of synthetic blends of flowering rice panicles and S. juncoides spikelets composed of β‐caryophyllene and β‐elemene. The synthetic blend of flowering S. juncoides spikelets significantly attracted males but not females. The synthetic blend of flowering rice panicles composed of β‐caryophyllene and β‐elemene did not attract either sex. These results suggest that β‐caryophyllene and β‐elemene are common active compounds responsible for attractiveness of flowering rice panicles and S. juncoides spikelets although some of the other volatile components act synergistically with these two compounds in natural plant odours.     

Volatile induction of infected and neighbouring uninfected plants potentially influence attraction/repellence of a cereal herbivore

Pathogen infection can induce plant volatile organic compounds (VOCs). We infected ‘McNeal’ wheat and ‘Harrington’ barley with a Fusarium spp. blend (F. graminearum,F. avenaceum and F. culmorum). Both cereals had the greatest VOC induction 14 days after pathogen innoculation, only slightly lower induction occurred at 7 days, but displayed no induction at 1 days. The induced VOC bouquet for both cereals included six green leaf volatiles (GLVs; e.g. (Z)‐3‐hexenol and (Z)‐3‐hexenyl acetate), four terpenes (linalool, linalool oxide, (Z)‐β‐ocimene and (E)‐β‐caryophyllene) and benzyl acetate. Neighbouring, uninfected individuals of both cereals had significant VOC induction when exposed to an infected, conspecific plant. The temporal pattern and VOC blend were qualitatively similar to infected plants but with quantitative reductions for all induced VOCs. The degree of neighbouring, uninfected plant induction was negatively related to distance from an infected plant. Plant VOC induction in response to pathogen infection potentially influences herbivore attraction or repellency. Y‐tube tests showed that herbivorous female and male Oulema cyanella Voet. (Chrysomelidae: Coleoptera) were significantly attracted to (Z)‐3‐hexenal and (Z)‐3‐hexenyl acetate at 300 and 1500 ng/h but were repelled by both GLVs as well as (Z)‐β‐ocimene and linalool at 7500 ng/h. These O. cyanella behavioural responses were significantly at higher concentrations than those emitted by single plants with pathogen‐induced VOCs, so adults might only be able to respond to a dense group of infected plants. Also, O. cyanella dose responses differ from the previously tested congeneric O. melanopus (cereal leaf beetle), which was attracted to three VOCs induced by Fusarium infection of maize, barley and wheat. Future behavioural tests may indicate whether different herbivore dose responses measured with each VOC singly can help to predict attraction or repellency to injured and uninjured VOC bouquets from different host plant species.     

Repellent activity of Cymbopogon citratus and Tagetes minuta and their specific volatiles against Megalurothrips sjostedti

Cowpea is an important source of protein for people in Africa. However, the crop suffers major damage and yield losses due to bean flower thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae). Although companion plants are known to reduce the damage caused by insect pests, the role of their volatiles in repelling pests from target plants has been the subject of few investigations. Here, we used the Y‐tube olfactometer experiments and chemical analyses to investigate the effect of volatiles from cowpea flowers and two companion plants; lemongrass, Cymbopogon citratus and Mexican marigold, Tagetes minuta on the olfactory responses of M. sjostedti. The results revealed that M. sjostedti males and females were repelled by the volatiles from freshly cut leaves of C. citratus. The combination of freshly cut leaves of C. citratus and cowpea flower was repellent to females but not to males. The female thrips, but not males, were repelled by the volatiles from the vegetative stage of T. minuta. Fifty‐four compounds were identified in the volatiles from two herbal plants. Among the major compounds, citral and a 4‐component blend comprised of dihydrotagetone, (Z)‐3‐hexenyl acetate, limonene and (Z)‐β‐ocimene repelled females but dihydrotagetone alone attracted females. While myrcene combined with cowpea flower volatiles enhanced the attraction of females M. sjostedti, when tested alone was not attractive. These results highlight the potential of volatiles from C. citratus and T. minuta to repel M. sjostedti females. The use of these plants as companion plants in a cowpea cropping system could reduce M. sjostedti infestation.     

The pollination system of the widely distributed mammal‐pollinated Mucuna macrocarpa (Fabaceae) in the tropics

Although the pollinators of some plant species differ across regions, only a few mammal‐pollinated plant species have regional pollinator differences in Asia. Mucuna macrocarpa (Fabaceae) is pollinated by squirrels, flying foxes, and macaques in subtropical and temperate islands. In this study, the pollination system of M. macrocarpa was identified in tropical Asia, where the genus originally diversified. This species requires “explosive opening” of the flower, where the wing petals must be pressed down and the banner petal pushed upward to fully expose the stamens and pistil. A bagging experiment showed that fruits did not develop in inflorescences (n = 66) with unopened flowers, whereas fruits developed in 68.7% of inflorescences (n = 131) with opened flowers. This indicated that the explosive opening is needed for the species to reproduce. Four potential pollinator mammals were identified by a video camera‐trap survey, and 78.3% and 60.1% of monitored inflorescences (n = 138) were opened by gray‐bellied squirrels (Callosciurus caniceps) and Finlayson's squirrels (C. finlaysonii), respectively, even though more than 10 mammal species visited flowers. Nectar was surrounded by the calyx, and the volume and sugar concentration of secreted nectar did not change during the day. This nectar secretion pattern is similar to those reported by previous studies in other regions. These results showed that the main pollinators of M. macrocarpa in the tropics are squirrels. However, the species' nectar secretion pattern is not specifically adapted to this particular pollinator. Pollinators of M. macrocarpa differ throughout the distribution range based on the fauna present, but there might not have been no distinctive changes in the attractive traits that accompanied these changes in pollinators.     

Chemical Composition,Antibacterial, Schistosomicidal,and Cytotoxic Activities of the Essential Oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae)

We have investigated the chemical composition and the antibacterial activity of the essential oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae) (DA‐EO) against a representative panel of cariogenic bacteria. We have also assessed the in vitro schistosomicidal effects of DA‐EO on Schistosoma mansoni and its cytotoxicity to GM07492‐A cells in vitro. Gas chromatography (GC) and gas chromatography‐mass spectrometry (GC/MS) revealed that the monoterpenes cis‐piperitone oxide (35.2%), p‐cymene (14.5%), isoascaridole (14.1%), and α‐terpinene (11.6%) were identified by as the major constituents of DA‐EO. DA‐EO displayed weak activity against Streptococcus sobrinus and Enterococcus faecalis (minimum inhibitory concentration (MIC) = 1000 μg/ml). On the other hand, DA‐EO at 25 and 12.5 μg/ml presented remarkable schistosomicidal action in vitro and killed 100% of adult worm pairs within 24 and 72 h, respectively. The LC₅₀ values of DA‐EO were 6.50 ± 0.38, 3.66 ± 1.06, and 3.65 ± 0.76 μg/ml at 24, 48, and 72 h, respectively. However, DA‐EO at concentrations higher than 312.5 μg/ml significantly reduced the viability of GM07492‐A cells (IC₅₀ = 207.1 ± 4.4 μg/ml). The selectivity index showed that DA‐EO was 31.8 times more toxic to the adult S. mansoni worms than GM07492‐A cells. Taken together, these results demonstrate the promising schistosomicidal potential of the essential oil of Dysphania ambrosioides.     

Volatile organic compounds released by Rumex confertus following Hypera rumicis herbivory and weevil responses to volatiles

We report in this study large induction of volatile organic compounds (VOCs) from a single inflorescence of mossy sorrel (Rumex confertus Willd., Polygonaceae), by herbivory of the weevil (Hypera rumicis L., Coleoptera: Curculionidae). VOCs blend induced by the weevil herbivory included 1 green leaf volatiles (GLVs) ((Z)‐3‐hexen‐1‐yl acetate), five terpenes ((Z)‐β‐ocimene, linalool, geranyl acetate, β‐caryophyllene and (E)‐β‐farnesene), three esters (benzyl acetate, methyl salicylate and methyl anthranilate) and one aromatic heterocyclic organic compound (indole). Uninjured plants produced only detectable amounts of VOCs. A Y‐tube experiment revealed that both females and males of H. rumicis were not attracted to any of tested concentrations (1, 5, 25, 125 ng/min). Also both females and males were significantly repelled by the highest concentrations (25 and 125 ng/min). Additionally, concentration of 5 ng/min proved to be repellent for females of H. rumicis.     

First Report of Sclerotinia nivalis Causing White Mold Disease on Sedum sarmentosum in China

In 2010 and 2011, a disease exhibiting characteristics of white mold was found on Sedum sarmentosum, a crassulaceous weed under canopies of tea trees, in Zhushan County, Hubei Province, China. Based on the cultural and morphological characteristics, the pathogen was identified as Sclerotinia nivalis Saito. In the phylogenetic tree inferred from the internal transcribed spacer (ITS)‐rDNA sequences, the pathogen was clustered with five previously characterized isolates of S. nivalis, forming a unique clade, thus confirming the morpho‐cultural identification. Koch’s postulates were fulfilled by pathogenicity tests using the isolate SsSn‐24 and Let‐19 of S. nivalis on plants of S. sarmentosum. To our knowledge, this is the first report of S. nivalis on S. sarmentosum in the family Crassulaceae.     

Pollinators shift to nectar robbers when florivory occurs,with effects on reproductive success in Iris bulleyana (Iridaceae)

• Studies have indicated that florivory and nectar robbing may reduce reproductive success of host plants. However, whether and how these effects might interact when plants are simultaneously attacked by both florivores and nectar robbers still needs further investigation.
• We used Iris bulleyana to detect the interactions among florivory, nectar robbing and pollination, and moreover, their effects on plant reproductive success. Field investigations and hand‐pollination treatments were conducted on two experimental plots from a natural population, in which Experimental plot was protected from florivores and Control plot was not manipulated.
• The flower calyx was bitten by sawflies to consume the nectary, and three bumblebee species were pollinators. In addition, the short‐tongued pollinator, Bombus friseanus, was the only robber when there was a hole made by a sawfly. The bumblebee had significantly shortened flower handling time when robbing, as compared to legitimate visits. Pollinator visitation and seed production decreased significantly in damaged flowers. However, seed production per flower after supplementary hand‐pollination did not differ significantly between damaged and undamaged flowers. Compared to the Experimental plot, bumblebees visited fewer flowers per plant in a foraging bout in the Control plot.
• The flowers damaged by florivory allowed B. friseanus to shift to a nectar robber. Florivory and nectar robbing collectively decreased plant reproductive success by consuming nectar resources, which may reduce attractiveness to pollinators of the damaged flowers. However, the changes in pollinator behaviour might be beneficial to the plant by reducing the risk of geitonogamous mating.

     

An astigmatid defence volatile against a phytoseiid mite

Numerous semiochemicals have been isolated from several species of astigmatid mites with various identified or unidentified functions. Alarm pheromonal activity is widespread with neryl formate and neral, being the most common compounds eliciting alarm response in conspecifics. The cosmopolitan astigmatid mite Suidasia medanensis (= S. pontifica) Oudemans (Acari: Suidasidae) has been reported to use neral as an alarm pheromone, but neral can also act as an allomone towards predators of oribatid mites. Suidasia medanensis can be utilised as a factitious prey for mass‐rearing of the phytoseiid predatory mite Amblyseius (= Typhlodromips) swirskii (Athias‐Henriot) (Acari: Phytoseiidae), which is used for biological control of insect and mite pests in protected crops. This study investigated the potential defence properties of the S. medanensis volatiles against A. swirskii, comparing the repellency to pollen‐reared (naïve) vs. S. medanensis‐reared (experienced) predators using a synthetic blend of the isomers neral and geranial (1:1) as a model compound. In a repellency bioassay, the synthetic blend elicited a significant repellence to A. swirskii with no difference between naïve and experienced predators. During capture success studies, S. medanensis under repeated attack could release sufficient quantities of the defence volatile to deter 1–5 attacks from A. swirskii, whereas hexane‐treated S. medanensis artificially depleted of volatiles were significantly more vulnerable to an attack. This is the first report of an astigmatid defence volatile with repellent activity to a phytoseiid mite and the starting point to understanding semiochemical interactions in any current or novel factitious predator‐prey mass‐rearing system.