Methyl Isonicotinate Research Articles

Ligand Environment and Light: Two Triggers for Controlling Cytotoxicity of Ruthenium Nitrosyl Complexes

AbstractPhotoinduced nitric oxide (NO) release for complexes [RuNO(L)2(NO2)2OH], where L=methyl isonicotinate (1), ethyl isonicotinate (2), methyl nicotinate (3) and ethyl nicotinate (4) was studied in DMSO, MeCN and water solutions (PBS, CTAB) using spectroscopic methods (UV‐vis, IR, EPR) and spectrometric techniques (ESI‐MS). Additionally, we present methodological evidence for improving the calculation of the quantum yield (QY) of NO release through the utilization of a combined IR‐UV‐vis‐spectroscopy flow‐through setup. According to DFT calculations, the production of nitric oxide occurs through the photoinduced cleavage of the Ru−NO bond, triggered by irradiation at 445 or 532 nm. This cleavage is a consequence of charge transfer from the orbitals of the Ru−OH group and the equatorial ligands (HOMO, HOMO‐1) to the Ru−NO antibonding orbital (LUMO). The cytotoxicity and photoinduced cytotoxicity of the investigated compounds were assessed against the breast adenocarcinoma cell line MCF‐7. Moreover, the investigation of the lipophilic properties of compounds 1–4 unveiled a significant influence of their lipophilicity on cytotoxic behavior, allowing for the modification of cytotoxicity through changes in the ligand L or by light irradiation.

Identification of the odorant binding proteins of Western Flower Thrips (Frankliniella occidentalis), characterization and binding analysis of FoccOBP3 with molecular modelling, molecular dynamics simulations and a confirmatory field trial

Olfactory systems are indispensable for insects as they, including Western Flower Thrips (Frankliniella occidentalis), use olfactory cues for ovipositing and feeding. F. occidentalis use odorant binding proteins (OBPs) to transport semiochemicals to odorant receptors to induce a behavioural response from the sensillum lymph of the insect’s antennae. This study identifies four OBPs of F. occidentalis and analyses their expression at three stages of growth: larvae, adult males and adult females. Further, it investigates the presence of conserved motifs and their phylogenetic relationship to other insect species. Moreover, FoccOBP3 was in silico characterized to analyse its structure along with molecular docking and molecular dynamics simulations to understand its binding with semiochemicals of F. occidentalis. Molecular docking revealed the interactions of methyl isonicotinate, p-anisaldehyde and (S)-(-)-verbenone with FoccOBP3. Moreover, molecular dynamics simulations showed bonding stability of these ligands with FoccOBP3, and field trials validated that Lurem TR (commercial product) and p-anisaldehyde had greater attraction as compared to (S)-(-)-verbenone, given the compound’s binding with FoccOBP3. The current study helps in understanding the tertiary structure and interaction of FoccOBP3 with lures using computational and field data and will help in the identification of novel lures of insects in the future, given the importance of binding with OBPs. Communicated by Ramaswamy H. Sarma

The cytotoxic and antiproliferative properties of ruthenium nitrosyl complexes and their modulation effect on cytochrome P450 in the HepG2 cell line.

Ruthenium nitrosyl complexes are actively investigated as antitumor agents. Evaluation of potential interactions between cytochromes P450 (CYPs) with new compounds is carried out regularly during early drug development. In this study we have investigated the cytotoxic and antiproliferative activities of ruthenium nitrosyl complexes with methyl/ethyl esters of nicotinic and isonicotinic acids and γ-picoline against 2D and 3D cultures of human hepatocellular carcinoma HepG2 and non-cancer human lung fibroblasts MRC-5, assessed their photoinduced activity at λrad = 445 nm, and also evaluated their modulating effect on CYP3A4, CYP2C9, and CYP2C19. The study of cytotoxic and antiproliferative activities against 2D and 3D cell models was performed using phenotypic-based high content screening (HCS). The expression of CYP3A4, CYP2C9, and CYP2C19 mRNAs and CYP3A4 protein was examined using target-based HCS. The results of CYP3A4 mRNA expression were confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR). The ruthenium nitrosyl complexes exhibited a dose-dependent cytotoxic effect against HepG2 and MRC-5 cells. The cytotoxic activity of complexes with ethyl isonicotinate (1) and nicotinate (3, 4) was significantly lower for MRC-5 than for HepG2, for a complex with methyl isonicotinate (2) it was higher for MRC-5 than for HepG2, for a complex with γ-picoline (5) it was comparable for both lines. The antiproliferative effect of complexes 2 and 5 was one order of magnitude higher for MRC-5; for complexes 1, 3, and 4 it was comparable for both lines. The cytotoxic activity of all compounds for 3D HepG2 was lower than for 2D HepG2, with the exception of 4. Photoactivation affected the activity of complex 1 only. Its cytotoxic activity decreased, while the antiproliferative activity increased. The ruthenium nitrosyl complexes 1-4 acted as inducers of CYP3A4 and CYP2C19, while the complex with γ-picoline (5) induced of CYP3A4. Among the studied ruthenium nitrosyl complexes, the most promising potential antitumor compound is the ruthenium compound with methyl nicotinate (4).

CO2-actuated spin transition tuning in an interdigitated Hofmann-type coordination polymer.

The increased anthropogenic emission level of CO2 urges the development of CO2-responsive materials, but is it possible to regulate the inherent electronic properties through weak physisorption of a ubiquitous gas such as CO2? Herein, we intended to answer this imperative question by the first case of CO2-actuated variable spin-state stabilisation in an interdigitated Hofmann-type coordination polymer [FeIIPd(CN)4L2] (1, L = methyl isonicotinate), showing a wide shift in transition temperature (T eq) from 178 K at P CO2 = 0 kPa to 229 K at P CO2 = 100 kPa. Interestingly, the emergence of a stepped behaviour in the heating process below P CO2 = 10 kPa and overlapping magnetic susceptibility values above P CO2 = 10 kPa elucidate the selective LS state stabilisation solely correlated with the extent of CO2 accommodation. Based on the magnetic response and phase transition diagrams obtained under respective P CO2 , a plausible scenario of the spin-state switching can be interpreted as (1ls + ) → (1hs + ) → 1hs at P CO2 ≤ 10 kPa, → 1hs at 100 kPa < P CO2 ≥ 32 kPa and → → 1hs at 100 kPa, where 1 and 1' represent CO2-free and CO2-encapsulated states, respectively. The cooperative CO2 sorption with SCO based on the varied CO2 pressure corroborates a novel case for developing CO2-responsive magnetic materials henceforth.

Attraction of Frankliniella occidentalis Females towards the Aggregation Pheromone Neryl (S)-2-Methylbutanoate and Kairomones in a Y-Olfactometer.

An understanding of insect olfaction allows for more specific alternative methods of pest control. We evaluated the responses of the western flower thrips (WFT, Frankliniella occidentalis) in a Y-olfactometer to estimate gas-phase concentrations of the aggregation pheromone neryl (S)-2-methylbutanoate and known kairomones such as methyl isonicotinate, (S)-(-)-verbenone, and p-anisaldehyde. The gas-phase concentrations of these compounds were obtained from the release rates measured in dynamic headspace cells. The compounds were collected from the headspace using dried solid-phase extraction (SPE) cartridges and analyzed with a triple quadrupole GC-MS/MS. We observed that the aggregation pheromone significantly attracted WFT females at doses of 10 and 100 µg, whereas methyl isonicotinate and p-anisaldehyde significantly attracted WFT females at the highest dose. Verbenone did not produce any significant results. A completely different picture was obtained when the gas-phase concentrations were considered. The minimal gas-phase concentrations of the pheromone required to attract WFT females was 0.027 ng/mL, at least 100 times lower than that of the other two compounds. The relevance and implications of our results are discussed in light of the insect's biology and pest management methods.

Semiochemicals Associated with the Western Flower Thrips Attraction: A Systematic Literature Review and Meta-Analysis

The study of the semiochemicals of the western flower thrips (WFT), Frankliniella occidentalis, Pergande (Thysanoptera: Thripidae), is a relevant topic that spans the last two decades. Approximately a hundred articles published on this subject from 2000 to 2022 can be found in academic databases, representing approximately 5% of the research on this important pest. These topics have generated a platform for novel research with a high potential for development. However, to move on to a new research step, an effectiveness evaluation of the compounds discovered so far is necessary. This review conducted a systematic analysis of the research focused on the semiochemicals (kairomones, pheromones, and attractants) for this pest. Papers from the past three decades on WFT attraction to semiochemicals were collected from databases using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The number of individuals attracted to compounds was extracted from the papers and compiled for analysis. With this information, an attraction ratio was calculated. Forty-one possible attractants were found in the literature, with methyl isonicotinate being the most-studied compound so far, with the third-highest attraction ratio. δ-Decalactone was the compound with the highest attraction ratio, but it was one of the least studied. A meta-analysis of the WFT choosing proportion was performed for the compounds with more trials found in the literature. The predicted mean choice percentages for methyl isonicotinate (MIN) and Lurem-TR, the MIN's commercial product, were 76.6% and 66.6%, respectively. There was a convergence among the analyzed studies showing a high degree of research focus on the same group of nitrogen-containing compounds (mainly the pyridine structure). These findings call for future research to diversify the discovery and evaluation of attractive compounds in this relevant study area.

Guest-Induced Multistep-to-One-Step Reversible Spin Transition with Enhanced Hysteresis in a 2D Hofmann Framework.

The interplay of host-guest interactions and controlled modulation of spin-crossover (SCO) behavior is one of the most exploited topics regarding data storage, molecular sensing, and optical technologies. In this work, we demonstrate the experimental approach of tuning the SCO behavior via controlled modulation of the spin-state cooperativity in a 2D Hofmann coordination polymer, [FeIIPd(CN)4(L)2]·1.3MeOH (1·1.3MeOH; L = methyl isonicotinate). Removal of the solvent changes the four-step transition to a complete one-step spin transition with an enhanced hysteresis width (∼20 K). Structural analysis of solvated (1·1.3MeOH) and partially desolvated (1·0.3MeOH) compounds reveals that the crystal system changes from a monoclinic C2/c space group to an orthorhombic Imma space group, where the FeII sites are present in a more symmetrically equivalent environment. Consequently, the axial ligand-field (LF) strength and face-to-face interactions of the ligands were increased by removing the guest, which is reflected in the highly cooperative SCO in 1 (desolvated compound). Also, the shift of the CN bond stretching frequencies and decrease of their relative intensities from the variable-temperature Raman spectroscopic measurements further corroborate the SCO behavior. Besides, theoretical calculations reveal that the singlet (1Γ) LF terms decrease by removing guest molecules, enhancing the molecular population in the low-spin state at low temperature, as experimentally observed for 1. Notably, fine tuning of the SCO behavior via host-guests interactions provides a great opportunity to design potential chemosensors.

Visually and olfactorily enhanced attractive devices for thrips management.

‘Lure‐and‐infect’ is an insect pest management strategy with high potential but so far there are few examples of its application. Using traps as surrogates for auto‐dissemination devices, we tested the attractiveness to naturally occurring thrips (Thysanoptera: Thripidae) of three trap types differing in colour and structure, with and without the thrips lure methyl isonicotinate (MI), and sticky plate traps as a control. The aim was to find more effective traps that could be further developed into devices for auto‐dissemination and lure‐and‐infect of thrips. The number of thrips captured varied substantially with trap type and the presence of the MI lure. We found a high visual response to a sticky ‘white ruffle’ trap (i.e., a 30‐cm‐long cylindrical outline of folded fabric), compared to a commonly used blue sticky plate trap (Bug‐scan) as the control. This effect was seen both in a greenhouse with roses (Rosa spp.), where we encountered western flower thrips, Frankliniella occidentalis (Pergande), and in a grass field, where we encountered onion thrips, Thrips tabaci Lindeman, and New Zealand flower thrips, Thrips obscuratus (Crawford). In the absence of MI, the white ruffle trap caught 7–22× more thrips than the control Bug‐scan trap. A similarly designed blue ruffle trap and a modified Lynfield trap caught lower thrips numbers than the white ruffle and the control Bug‐scan traps. Presence of MI substantially increased the captures of T. tabaci in all three trap types in the field (2.5–18×). In the greenhouse, without MI the white ruffle trap caught 3.5–14× more thrips than the Bug‐scan, blue ruffle, or modified Lynfield traps. Presence of MI increased the captures of F. occidentalis males and females in the Lynfield and blue ruffle traps (1.4–2.8×), but not in the white ruffle trap in the greenhouse (ca. 1.1×). The importance of visual and olfactory factors for the design of effective auto‐dissemination and lure‐and‐infect strategies for thrips management is discussed.

Tuning of cytotoxic activity by bio-mimetic ligands in ruthenium nitrosyl complexes

Three novel ruthenium nitrosyl complexes [Ru(NO)Cl3(InicMe)2] (1b), [RuNOCl3(NicEt)2] (1c) and [RuNOCl3(NicMe)2] (1d) (InicMe = methyl isonicotinate, NicEt = ethyl nicotinate, NicMe = = methyl nicotinate)were prepared and crystal structure of the complexes were determined by single crystal XRD analysis. In all complexes, the organic ligands are coordinated by a pyridine nitrogen atom and located in trans-position each to other and in cis-position to NO group. In the crystal package of all compounds stacking interactions of two types were determined: πarene-πarene and πCOO-πarene stacking. Finally, cytotoxicity of the compounds was tested on Hep2 and HepG2 cell lines. In the set of similar compounds mer-[RuNO(L)2Cl3] (L = Py, γ-Pic, β-Pic, Inic-Alk, Nic-Alk), complexes with iso-nicotinic acid esters are the most toxic, while nicotinic acid derivatives are less toxic and compared with pyridine complex.

Push-pull Strategy for Control of Sweet-potato Whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) in a Tomato Greenhouse

This study was conducted to develop a technology for environmentally friendly control of sweet-potato whitefly, Bemisia tabaci, by controlling their behavior using a push-pull strategy in a tomato greenhouse. B. tabaci was attracted the most by yellow color, light source of 520 nm, whereas it avoided the complex light treatment of 450 + 660 nm. The two natural enemies of B. tabaci, Cyrtopeltis tenuis and Orius laevigatus, were attracted the most by 520 nm light source. B. tabaci was repelled by the volatile organic compounds ocimene and carvacrol and was the most attracted by methyl isonicotinate. When buckwheat was added into the tomato greenhouse, the density of C. tenuis was maintained at about 16 times higher than when untreated for 15 days. As a result of the combined treatment of push-pull strategy, the density per trap of B. tabaci was three times lower than when no treatment was applied, and the control of this pest increased with time and reached up to 68.7%.

Volatile compounds as insect lures: factors affecting release from passive dispenser systems

ABSTRACTKnowledge about the behaviour of passive dispensers used to release semiochemicals for insect pest management is essential to ensure the efficacy of monitoring and control methods based on the use of the semiochemicals. The release characteristics of different passive dispenser types (commercial sachet, altered commercial sachet, polyethylene bags and cotton rolls) were investigated in the laboratory under various conditions. Using the volatile compound methyl isonicotinate (MI), a known lure for western flower thrips Frankliniella occidentalis (Pergande) and two additional homologues ethyl and n-propyl isonicotinate the effect of loading amount (0.5, 1.0 or 2.5 ml), temperatures (15°C, 25°C or 35°C) and air flow (0.1–0.15 m/s or 0.25–0.3 m/s) were tested in a low-speed laminar-flow wind tunnel. The results showed zero-order release kinetics for all tested dispenser types. Release rate kinetics relies on the type of molecule, dispenser type, and the climatic conditions with temperature being a major determinant of release rate. The results of the release characteristics of the different dispensers are discussed in regards to their practical use under greenhouse and field conditions.

Short communication: Efficacy of a non-pheromone semiochemical for trapping of western flower thrips in the presence of competing plant volatiles in a nectarine orchard

Non-pheromone semiochemicals or allelochemicals (kairomones, synomones, allomones) are often derived from, or are similar to, host plant odours and depending on their use, these semiochemicals may have to compete with the same or similar odours emanating from adjacent host plants with unknown consequences on trapping efficacy. The aim of this study was to examine the efficacy of the non-pheromone thrips attractant methyl isonicotinate (MI) as a lure for Western flower thrips (WFT; Frankliniella occidentalis) over a range of Prunus persicae nectarine plant growth stages (flowering, green fruit, ripe fruit), when competition from different host plant odours may vary, and different numbers of thrips can be present, in a Catalan nectarine orchard in 2014 and 2015. Significant 2.4–3.9 × increases in WFT numbers in traps with MI compared with those without MI were consistent over the season (flowering, green fruit, mature fruit) despite overall differences in thrips numbers on these different occasions. These results suggest that MI is an effective lure throughout the nectarine growth stages despite the presumed presence of competing and changing host plant odours. Trap type and colour and MI release rate may be important for improving overall trap efficacy.

The separation of Ni(II) over base metal ions in acidic polymetallic medium: Synergistic extraction and structural evidence

The selective extraction of Ni(II) from a polymetallic solution was achieved with an extractant mixture containing dinonylnaphthalene disulfonic acid (H2DNNDS) and 2-ethylhexyl 4-pyridinecarboxylate ester (4PC, LII). The equilibrium results indicated that Ni(II) extraction was sensitive to the molar fraction of 4PC in the mixture containing H2DNNDS and 4PC. It was found that individual H2DNNDS or 4PC resulted in low extraction efficiency of Ni(II). Interestingly, when the mole fraction of 4PC in the mixture surpassed 50%, significant synergistic effect was observed for Ni(II) separation over Fe(III), Al(III), Ca(II), Mg(II) and Mn(II), thus highlighting the synergistic role of 4PC. In order to provide structural evidence for synergistic mechanism, two nickel model complexes were synthesized with 1,5-naphthalene disulfonic acid (H2NDS) in the absence/presence of methyl isonicotinate (LI), which were the corresponding short-chain analogues of H2DNNDS and 4PC, respectively. Combined with single crystal X-ray diffraction of nickel model complexes, the coordination chemistry of nickel complex in the loaded organic phases was disclosed with the Fourier Transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results showed that Ni(II) was directly coordinated with two monodentate ligands LI and four water molecules, while no direct interaction existed between Ni(II) and the O atoms of the deprotonated H2NDS in both two nickel model complexes. Hydrogen-bonding interaction between the H atom of coordinated water and the O atom of the deprotonated H2NDS played important role in stabilization of coordination configuration. The selective extraction of Ni(II) might be attributed to the incorporation of the pyridine based nitrogen donor into the inner coordination sphere of Ni(II) to supplant coordinated water.

Chiral Cyclodimeric Zinc(II) Complexes: Enantio-recognition via Differential Pulse Voltammetry

Self-assembly of a series of ZnX2 (X– = Cl–, Br–, and I–) with (S)-(1-isonicotinoylpyrrolidin-2-yl)methyl isonicotinate (L) as a new chiral hemicircular bidentate ligand yields a system comprising 30-membered metallacyclodimeric species [ZnX2L]2 with two chiral centers. In the solid state, the metallacyclodimers’ packing arrays differ according to the anions and nestled solvate molecules. In the present study, the differential pulse voltammetry (DPV) technique was employed for chiral discrimination of amino acid enantiomers with S-chiral [ZnX2L]2 and was found to be an effective tool for enantio-recognition of amino acids.

Structural insights into the extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester

In this work, to elucidate the synergistic extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (L), hexaaquacobalt(II) naphthalene-2-sulfonate (compound 1) was prepared using naphthalene-2-sulfonic acid (HNS, the short chain analog of HDNNS) and di-methyl isonicotinate tetraaquacobalt(II) naphthalene-2-sulfonate (compound 2) was prepared using methyl isonicotinate (LI, a short chain analog of 2-ethylhexyl 4-pyridinecarboxylate ester) and HNS; the compounds were studied by single crystal X-ray diffraction. Moreover, 2 and the actual extracted cobalt(II) complex were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results indicated that the actual extracted cobalt(II) complex possesses a similar coordination structure as 2. Combined with the results obtained by single crystal X-ray diffraction of 1 and 2, FT-IR and ESI-MS of 2 and the actual extracted cobalt(II) complex, it is reasonable to conclude that the extracted cobalt(II) complex with the actual synergistic mixture is much more stable than the cobalt(II) complex with HDNNS alone. Therefore, the extraction selectivity cobalt(II) is effectively enhanced with the addition of 2-ethylhexyl 4-pyridinecarboxylate ester to HDNNS.

Using 2 H labelling to improve the NMR detectability of pyridine and its derivatives by SABRE.

By introducing a range of 2H labels into pyridine and the para‐substituted agents, methyl isonicotinate and isonicotinamide, we significantly improve their NMR detectability in conjunction with the signal amplification by reversible exchange process. We describe how the rates of T 1 relaxation for the remaining 1H nuclei are increased and show how this leads to a concomitant increase in the level of 1H and 13C hyperpolarization that can ultimately be detected.

Insights into the extraction mechanism from the coordination chemistry of copper(II) with a synergistic mixture which mimics Versatic10 and 2-ethylhexyl 4-pyridinecarboxylate ester

In the present work, a copper(II) synergist complex with methyl isonicotinate (LI, a short chain analog of 2-ethylhexyl 4-pyridinecarboxylate ester) and isobutyric acid (HBI, a short chain analog of Versatic10) was synthesized and studied by X-ray single-crystal diffraction. The results indicated that the copper(II) synergist complex obtained with isobutyric acid and methyl isonicotinate crystallizes in the monoclinic C2/c space group and confirmed the composition [Cu(BI)2(LI)]2. The crystal structure consisted of centrosymmetric dimeric units, in which the two Cu ions are bridged in pairs by four carboxylate groups of the deprotonated isobutyric acid. In order to bridge the gap between the solid-state structure of the copper(II) synergist complex obtained with isobutyric acid and methyl isonicotinate and the solution structure of the extracted copper(II) complex in the non-polar organic phase, the two copper(II) complexes were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results indicated that the extracted copper(II) complex in the non-polar organic phase has a similar coordination structure as the copper(II) synergist complex obtained with isobutyric acid and methyl isonicotinate.

Structural Insights into the Coordination and Extraction Mechanism of Nickel(II) with Dinonylnaphthalene Sulfonic Acid and n‐Hexyl 3‐Pyridinecarboxylate Ester as Extractants

In this work, a nickel(II) synergist complex with methyl isonicotinate (BI, a short chain analog of n‐hexyl 3‐pyridinecarboxylate ester) and naphthalene‐2‐sulfonic acid (HNS, a short chain analog of dinonylnaphthalene sulfonic acid) was synthesized and studied by single‐crystal X‐ray diffraction. The nickel(II) complex crystallizes in the monoclinic P21/n space group with the composition [Ni(H2O)4(BI)2](NS)2·2H2O. The Ni(II) ions of these crystallographically independent molecules lie on an inversion center, forming a trans‐form distorted octahedral coordination structure. The nickel(II) ions can coordinate with four water molecules and two BI ligands, resulting in a mono‐metallic structure [Ni(H2O)4(BI)2]2+. There is no direct interaction between nickel(II) and sulfonic oxygen atoms of the sulfonate anions, but hydrogen bonds form between sulfonic oxygen atoms and water molecules in the synergist complex. In order to further elucidate the solution structure of the nickel(II) complexes with the actual synergistic mixture containing n‐hexyl 3‐pyridinecarboxylate ester and dinonylnaphthalene sulfonic acid in the nonpolar organic phase, the nickel(II) complexes were studied by electrospray ionization mass spectrometry. The results indicated that the extracted nickel(II) complexes in the nonpolar solvent have a similar coordination structure as that of the crystalline nickel(II) synergist complex.

Methyl isonicotinate – a non-pheromone thrips semiochemical – and its potential for pest management

AbstractMethyl isonicotinate is one of several patented 4-pyridyl carbonyl compounds being investigated for a variety of uses in thrips pest management. It is probably the most extensively studied thrips non-pheromone semiochemical, with field and glasshouse trapping experiments, and wind tunnel and Y-tube olfactometer studies in several countries demonstrating a behavioural response that results in increased trap capture of at least 12 thrips species, including the cosmopolitan virus vectors such as western flower thrips and onion thrips. Methyl isonicotinate has several of the characteristics that are required for an effective semiochemical tool and is being mainly used as a lure in combination with coloured sticky traps for enhanced monitoring of thrips in greenhouses. Research indicates that this non-pheromone semiochemical has the potential to be used for other thrips management strategies such as mass trapping, lure and kill, lure and infect, and as a behavioural synergist in conjunction with insecticides, in a range of indoor and outdoor crops.

The effect of background plant odours on the behavioural responses of Frankliniella occidentalis to attractive or repellent compounds in a Y‐tube olfactometer

AbstractThe western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), causes major losses in agricultural and horticultural crops worldwide. The volatile compounds methyl isonicotinate, p‐anisaldehyde, eugenol, and linalool are known as olfactory attractants, and salicylaldehyde is known as a repellent for F. occidentalis under clean‐air conditions in laboratory experiments. In the present study we assessed the responses of F. occidentalis to these compounds when presented alone, in combination, and in the presence of background odours emanating from cucumber (Cucumis sativus L., Cucurbitaceae), capsicum (Capiscum anuum L., Solanaceae), chrysanthemum (Chrysanthemum morifolium Ramat., Asteraceae), clove basil (Ocimum gratissimum L.), and lavender (Lavandula angustifolia L., both Lamiaceae) plants in a Y‐tube olfactometer. In the presence of any background plant odour, the attractiveness of pure methyl isonicotinate to F. occidentalis proved to be consistently significant. Compared to clean‐air conditions, a slightly lower percentage of thrips chose the Y‐tube arm loaded with 10% p‐anisaldehyde in the presence of cucumber leaf odour. With non‐flowering clove basil plants in the background, F. occidentalis responses to 1% eugenol, a constituent of clove basil essential oil, were neutral, and the same applied to responses to pure linalool, a constituent of lavender essential oil, in the presence of flowering lavender plants. Also, thrips responses to pure or diluted salicylaldehyde were clearly influenced by plant background odours. We simulated a push‐pull situation and found a trend indicating that the percentage of F. occidentalis choosing the airflow loaded with the attractant methyl isonicotinate was higher when the airflow in the other arm of the Y‐tube was loaded with the repellent salicylaldehyde compared to clean air, and vice versa. We showed interactions between attractive or repellent volatile compounds and the environmental odours in the chemical ecology of F. occidentalis and the potential of a combined use of these compounds in thrips pest management.