Investigations on fungicides

A number of bis-[(i-formamido-2,2,2-trichloro)ethylamino]-alkanes and their dioxy and dithio analogues were examined for direct and systemic antifungal activity. All compounds showed very low in vitro fungitoxicity and only slight protectant anti-mildew activity when applied as a foliar spray. Certain diamino and dioxy derivatives were, however, systemically active against powdery mildew fungi when applied as a root drench to seedlings of wheat or cucumber; the dithio analogues were inactive. The level of systemic activity shown by these compounds was markedly influenced by the nature of the hydrocarbon ‘bridging’ group.     

In vivo and in vitro effects of copper and cadmium on the plasma membrane H+-ATPase from cucumber (Cucumis sativus L.) and maize (Zea mays L.) roots

The plasmalemma vesicles isolated from cucumber and maize roots were used to study the effect of Cu²⁺ and Cd²⁺ on the hydrolytic and proton pumping activities of ATPase. In vivo application of metal ions to the plant growth solutions resulted in stimulation of the proton transport in maize. In cucumber roots the action of metals was not the same: cadmium stimulated the H⁺ transport through plasmalemma whereas Cu²⁺ almost completely inhibited it. Copper ions decreased the hydrolytic activity of H⁺-ATPase in cucumber, without any effect on this activity in membranes isolated from maize roots. The effect of cadmium on the hydrolytic activities was opposite: ATP-hydrolysis activity in plasmalemma was not altered in cucumber, whereas in maize its stimulation was observed. The amount of accumulated metals was not the main reason of different influence of metals on H⁺-ATPase activity in tested plants. In in vitro experiments Cu²⁺ inhibited H⁺ transport in the cucumber, to a higher degree than Cd²⁺ and both metals did not change this H⁺-ATPase activity of plasmalemma isolated from corn roots. Cu²⁺ added into the incubation medium reduced the hydrolytic activity of ATPase in the plasma membrane isolated from cucumber as well as from corn roots. Cd²⁺ diminished the hydrolytic activity of ATPase in cucumber, and no effect of Cd²⁺ in the plasmalemma isolated from corn roots was found. Our results indicated different in vitro and in vivo action of both metals on H⁺-ATPase and different response of this enzyme to Cu²⁺ and Cd²⁺ in maize and cucumber.     

Mutation in <Emphasis Type="Italic">cyaA</Emphasis> in <Emphasis Type="Italic">Enterobacter cloacae</Emphasis> decreases cucumber root colonization

Strains of Enterobacter cloacae show promise as biological control agents for Pythium ultimum-induced damping-off on cucumber and other crops. Enterobacter cloacae M59 is a mini-Tn5 Km transposon mutant of strain 501R3. Populations of M59 were significantly lower on cucumber roots and decreased much more rapidly than those of strain 501R3 with increasing distance from the soil line. Strain M59 was decreased or deficient in growth and chemotaxis on most individual compounds detected in cucumber root exudate and on a synthetic cucumber root exudate medium. Strain M59 was also slightly less acid resistant than strain 501R3. Molecular characterization of strain M59 demonstrated that mini-Tn5 Km was inserted in cyaA, which encodes adenylate cyclase. Adenylate cyclase catalyzes the formation of cAMP and cAMP levels in cell lysates from strain M59 were approximately 2% those of strain 501R3. Addition of exogenous, nonphysiological concentrations of cAMP to strain M59 restored growth (1 mM) and chemotaxis (5 mM) on synthetic cucumber root exudate and increased cucumber seedling colonization (5 mM) by this strain without serving as a source of reduced carbon, nitrogen, or phosphorous. These results demonstrate a role for cyaA in colonization of cucumber roots by Enterobacter cloacae.     

Investigations on fungicides: The systemic fungicidal activity of certain N-carboxymethyl dithiocarbamic acid derivatives

The systemic activity of thirty-three N-substituted S-esters derived from dithiocarbamic acid was investigated by assessing their ability to reduce the infection of broad-bean seedlings by Botrytis fabae and of wheat seedlings by Erysiphe graminis, following application to the roots or cut shoots of the host. Marked systemic activity against mildews was shown by the N-carboxymethyl dithiocarbamates, by S-carboxymethyl-N, N-dimethyl-dithiocarbamate (G₃₃) and by procaine and 6-azauracil. The effect was not very host-specific since most compounds showing high activity in wheat also showed activity in pea, cucumber and, to a smaller extent, apple. All the materials tested showed a much lower level of systemic activity in broad-bean seedlings against B. fabae. Measurements were also made of the uptake, translocation, phytotoxicity and the stability within plant tissues of some of these compounds. The degree of systemic activity which they show is discussed in relation to these and other properties of the compounds.     

外源亚精胺对淹涝胁迫下黄瓜根HSP70表达的影响

采用逆转录聚合酶链式反应(RT-PCR)及蛋白免疫印迹杂交(Western Blot)技术,研究0.5 mmol/L亚精胺浸种的黄瓜幼苗在淹水胁迫下,根热激蛋白70基因(HSP70)mRNA和蛋白质的表达量的变化。结果表明:淹水胁迫使黄瓜根HSP70的mRNA和蛋白的表达呈现先上升后下降的趋势,在淹水4 h时,HSP70的mRNA和蛋白表达量均极显著高于未淹水处理; 亚精胺浸种的黄瓜根HSP70的mRNA和蛋白的表达量在24 h内呈一直上升的趋势,在淹水24 h时,HSP70的mRNA和蛋白表达量均极显著高于未淹水处理。淹涝胁迫下,亚精胺浸种的黄瓜根HSP70的mRNA和蛋白表达量在淹水12 h和24 h时极显著高于蒸馏水浸种。外源亚精胺能诱导淹涝胁迫下黄瓜幼苗根HSP70 mRNA和蛋白质的表达量的增加,缓解淹涝胁迫对黄瓜造成的伤害。     

Expression of recombinant Digitalis lanata EHRH. cardenolide 16′-O-glucohydrolase in Cucumis sativus L. hairy roots

The coding sequence for the Digitalis lanata EHRH. cardenolide 16′-O-glucohydrolase was inserted downstream of the 35S promoter in the binary vector pBI121 resulting in plant expression vector pBI121cgh. Cotyledon explants excised from 10-day-old seedlings of Cucumis sativus L. were transformed using Agrobacterium rhizogenes 15834 harbouring pBI121cgh. Hairy roots were obtained from infected cotyledon explants in vitro 10 days after inoculation. PCR amplification of coding sequences for cgh I, rolB and rolC from Ri plasmid showed that the aimed sequences were inserted into the genome of transformed cucumber hairy roots. Glycolytic activity of the transgenic CGH I was measured by HPLC using Lanatoside glycosides as substrate. Therefore, the cgh I transformed cucumber hairy roots may provide a valuable model for biotransformation of natural compounds by recombinant enzymes.This report is dedicated to Prof. W. Roos on the occasion of his 60th birthday.     

Specific detection of Lysobacter enzymogenes (Christensen and Cook 1978) strain 3.1T8 with TaqMan® PCR

Aims: To develop a strain‐specific TaqMan^® PCR method for detecting and quantifying the biocontrol strain Lysobacter enzymogenes 3.1T8. Methods and Results: A primer–probe combination was designed on the basis of a strain‐specific sequence selected using REP‐PCR (repetitive extragenic palindromic‐polymerase chain reaction). The specificity of this combination was demonstrated by 14 other Lysobacter strains that did not react with the selected primer–probe combination. To quantify strain 3.1T8 in cucumber root samples, a calibration curve was prepared by spiking roots with a 10‐fold dilution series of the strain. Detection of the biocontrol strain 3.1T8 with this method showed that the strain survived well for 22 days on root tips as well as on older cucumber roots. Survival was higher when the strain was inoculated to younger plants. In a cucumber production system with large volumes of substrate, strain 3.1T8 was detected in high numbers on cucumber roots 3 weeks after inoculation. Conclusions: The primer–probe combination developed was strain specific, because it did not react with other strains of the same species and genus. The TaqMan^® PCR method successfully quantified the inoculated biocontrol strain on cucumber roots grown in different cropping systems. Significance and Impact of the Study: The developed TaqMan^® PCR method is a strain‐specific real‐time detection method that can be used to assess the population dynamics of L. enzymogenes strain 3.1T8 for further optimization of its biocontrol efficacy.     

The effects of <Emphasis Type="Italic">β</Emphasis>-amino-butyric acid on resistance of cucumber against root-knot nematode, <Emphasis Type="Italic">Meloidogyne javanica</Emphasis>

In this study, the effects of β-amino-butyric acid (BABA) on root-knot nematode(Meloidogyne javanica) infection of cucumber and accumulation of total phenolic compounds, hydrogen peroxide and activity of some enzymes related to plant defense mechanisms, i.e., guaiacol peroxidase (GPOX), polyphenol oxidase (PPO), catalase (CAT) in cucumber roots infected with nematode were investigated. Results of this study show that treating the cucumber seedlings with the above elicitor significantly reduces the nematode infection level (the nematode galls, number of egg masses per plant and number of eggs per individual egg mass) compared to control. Additionally, treatment of cucumber roots by BABA and BABA + nematode, significantly increased peroxidase, polyphenol oxidase and catalase activities in root tissues, 1 day after nematode inoculation in comparison to nematode inoculated plants as control and sterile water-treated plants. Enzyme activities reached to a maximum level at 4, 4 and 3 days after nematode inoculation, respectively. Additionally, the amount of H₂O₂, a product of oxidative stress, was significantly increased in the BABA and BABA + nematode treatments in comparison to control. Such increases have occurred in two phases and maximum levels of it were observed at 5 days after inoculation. Inoculation of cucumber plants by BABA also significantly increased accumulation of total phenol in comparison to control and maximum level of it was observed at 7 days after nematode inoculation. The results suggest that the inhibitory effect of BABA on the root-knot nematode (M. javanica) may be related to its ability to enhance defense responses in the cucumber roots.     

Antimicrobial Activity of 3-Phenylimidazolidine-2,4-diones and Related Compounds

The structure-activity relationships of 3-(3′,5′-dichlorophenyl)imidazolidine-2,4-dione derivatives were investigated by the agar dilution method using Sclerotinia sclerotiorum as a test microbe. Several compounds were tested for antimicrobial spectrum in vitro with other pathogenic microbes and for foliage protective activity in green house tests with rice sheath blight, rice brown spot, damping-off of cucumber and kidney bean stem rot. It was found that the antimicrobial activity was enhanced when the 1-position of imidazolidine ring was substituted by an alkyl group but was reduced when the 5-position was substituted by alkyl groups. Generally, 3-(3′,5′-dichlorophenyl)imidazolidine-2,4-dione derivatives were active against Scierotiniaceae, Corticiaceae, Dematiaceae, Polystigmataceae or Pleosporaceae. In green house tests, some of these compounds showed high protective activity against rice sheath blight, rice brown spot, damping-off of cucumber and kidney bean stem rot. Results of the green house tests on the above mentioned diseases correlate well with those of in vitro tests except in the case of kidney bean stem rot.     

Free and glucosylated phenolics, phenol β-glucosyltransferase activity and membrane permeability in cucumber roots affected by derivatives of cinnamic and benzoic acids

Seven-day-old seedlings of cucumber (Cucumis sativus L.) cv. Wisconsin were treated with 0.01, 0.1 and 0.5 mM solutions of derivatives of cinnamic acid (ferulic and p-coumaric acids) and benzoic acid (p-hydroxybenzoic and vanillic acids) as stress factors. In cucumber roots phenolics (free and glucosylated), phenol β-glucosyltransferase (E.C. 2.4.1.35) activity as well as membrane permeability were examined. The most intensive glucosylation took place in the first hour of stress duration in roots treated with 0.01 mM ferulic and p-coumaric acids and with 0.01 and 0.1 mM p-hydroxybenzoic and vanillic acids. At these concentrations a high phenol β-glucosyltransferase activity was found. The deterioration of capacity for phenolic glucosylation as well as the decrease of the phenol β-glucosyltransferase was observed at the higher concentrations. It was associated with increased membrane permeability.     

Accumulation and secretion of exoglucanase activity in yeast secretory mutants

Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum (sec 18), from the Golgi body (sec 7) and in transport of secretory vesicles (sec 1), accumulated exoglucanase, a constitutive yeast activity, when incubated at the restrictive temperature (37°C). Different proportions of the accumulated activity were released by mutant cells under permissive conditions. The presence or absence of cycloheximide during the secretion period made no differences in the results. More than 90% of the internal activity was bound to membrane in wild type cells. However, only the soluble pool underwent changes during the accumulation or secretion periods. The bulk of secretory invertase accumulated by sec 1 was also soluble. By contrast sec 7 and sec 18 accumulated membrane-bound as well as soluble invertase forms and both were secreted in similar proportions in each mutant. More than 90% of the accumulated invertase was secreted at the permissive temperature in sec 18 cells. That percentage was significantly lower for exoglucanase (<65%). Concomitantly, invertase accumulated by this mutant exited from the cells with a lower half time (t 1/2=150 min). These results may be interpreted assuming that exoglucanase is exported by a passive flow of the soluble pool.Non-standard abbreviations p-NPG p-nitrophenyl--d-glucopyranoside - Con A concanavalin A - Tris tris(hydroxymethyl)-amino-methane     

Boron toxicity is alleviated by hydrogen sulfide in cucumber (Cucumis sativus L.) seedlings

Boron (B) is an essential micronutrient for plants, which when occurs in excess in the growth medium, becomes toxic to plants. Rapid inhibition of root elongation is one of the most distinct symptoms of B toxicity. Hydrogen sulfide (H₂S) is emerging as a potential messenger molecule involved in modulation of physiological processes in plants. In the present study, we investigated the role of H₂S in B toxicity in cucumber (Cucumis sativus) seedlings. Root elongation was significantly inhibited by exposure of cucumber seedlings to solutions containing 5 mM B. The inhibitory effect of B on root elongation was substantially alleviated by treatment with H₂S donor sodium hydrosulfide (NaHS). There was an increase in the activity of pectin methylesterase (PME) and up-regulated expression of genes encoding PME (CsPME) and expansin (CsExp) on exposure to high B concentration. The increase in PME activity and up-regulation of expression of CsPME and CsExp induced by high B concentration were markedly reduced in the presence of H₂S donor. There was a rapid increase in soluble B concentrations in roots on exposure to high concentration B solutions. Treatment with H₂S donor led to a transient reduction in soluble B concentration in roots such that no differences in soluble B concentrations in roots in the absence and presence of NaHS were found after 8 h exposure to the high concentration B solutions. These findings suggest that increases in activities of PME and expansin may underlie the inhibition of root elongation by toxic B, and that H₂S plays an ameliorative role in protection of plants from B toxicity by counteracting B-induced up-regulation of cell wall-associated proteins of PME and expansins.     

The Decreased Cold-Resistance of Chilling-Sensitive Plants Is Related to Suppressed CO2 Assimilation in Leaves and Sugar Accumulation in Roots

Tomato (Lycopersicon esculentum L., cv. Sibirskii skorospelyi) and cucumber (Cucumis sativus L., cv. Konkurent) plants were grown in a soil culture in a greenhouse at an average daily temperature of 20°C and ambient illumination until the development of five and eight true leaves, respectively. During the subsequent three days, some plants were kept in a climatic chamber at 6°C in the light, whereas other plants remained in a greenhouse (control). The cold-resistance of cucumber leaves and roots, as assayed from the electrolyte leakage, was reduced after cold exposure stronger than cold-resistance of tomato organs. The ratio photosynthesis/dark respiration was lower in cucumber than in tomato leaves at all measurement temperatures. The concentrations of sugars (sucrose + glucose + fructose) increased in chilled tomato roots but decreased in cucumber roots. Cold exposure changed the activities of various invertase forms (soluble and insoluble acidic and alkaline invertases). The total invertase activity and the ratio of mono- to disaccharides increased. The lower cucumber cold-resistance is related to the higher sensitivity of its photosynthetic apparatus to chilling and, as a consequence, insufficient root supply with sugars.     

Microwave-assisted synthesis of sec/tert-butyl 2-arylbenzimidazoles and their unexpected antiproliferative activity towards ER negative breast cancer cells

A new series of N-sec/tert-butyl 2-arylbenzimidazole derivatives was synthesised in 85–96% yields within 2–3.5?min by condensing ethyl 3-amino-4-butylamino benzoate with various substituted metabisulfite adducts of benzaldehyde under focused microwave irradiation. The benzimidazole analogues were characterised using ¹H NMR, ¹³C NMR, high resolution MS and melting points. Evaluation of antiproliferative activity of the benzimidazole analogues against MCF-7 and MDA-MB-231 revealed several compounds with unexpected selective inhibitions of MDA-MB-231 in micromolar range. All analogues were found inactive towards MCF-7. The most potent inhibition against MDA-MB-231 human breast cancer cell line came from the unsubstituted 2-phenylbenzimidazole 10a.     

Synthesis and Lateral Root-Inducing Activity of Novel N-Substituted-2-Piperidones with a 1,4-Benzodioxan Ring

Novel N-substituted-2-piperidones with a 1,4-benzodioxan ring were prepared and evaluated for their activity to induce lateral roots in lettuce seedlings. Compounds were obtained by aldol condensation of the lithium enolate of N-substituted-2-piperidones with 1,4-benzodioxan-6-carbaldehyde. Of the series compounds tested, N-cinnamyl-3-[1-(1,4-benzodioxan-6-yl)-1-hydroxymethyl]-2-piperidone (2e) had the highest activity. In seedlings treated with 10 ppm of 2e, all of the primary roots formed lateral roots. Only erythro-2e showed lateral root-inducing activity, while threo-2e was inactive.     

Antisense suppression of cucumber (Cucumis sativus L.) sucrose synthase 3 (CsSUS3) reduces hypoxic stress tolerance

Sucrose synthase (SUS; EC 2.4.1.13) plays important roles in sugar metabolism and abiotic stress response. But the genes encoding SUS in cucumber (Cucumis sativus L.) have not been well studied. Here, we isolated four cucumber sucrose synthase genes (CsSUS). Among them, CsSUS3, which highly expressed in the roots, was chosen for further study. Immunolocalization and subcellular localization analysis indicated that CsSUS3 localized in the cytosol and the plasma membrane, and mainly existed in the companion cells of phloem in the roots. When suffering hypoxia stress from flooding, CsSUS3 expression and SUS activity in roots increased, especially in the lateral roots; moreover, the soluble SUS activity increased clearly, but the membrane fraction hardly changed. Compared with the wild‐type cucumbers, the transgenic lines with antisense expression of CsSUS3 were more sensitive to flooding. After 6 d of flooding, the SUS activity, soluble sugar and uridine 5′‐diphosphate glucose (UDPG) content and the ratio of ATP/ADP in the roots of transgenic plants were significantly lower than that in wild‐type plants. Moreover, the transgenic lines grew more slowly with more yellow necrosis in the leaves. These findings suggested CsSUS3 participated in resisting hypoxic stress. Furthermore, the mechanism of CsSUS3 in resisting hypoxic stress was also discussed.     

Scanning ion‐selective electrode technique and X‐ray microanalysis provide direct evidence of contrasting Na+ transport ability from root to shoot in salt‐sensitive cucumber and salt‐tolerant pumpkin under NaCl stress

Grafting onto salt‐tolerant pumpkin rootstock can increase cucumber salt tolerance. Previous studies have suggested that this can be attributed to pumpkin roots with higher capacity to limit the transport of Na⁺ to the shoot than cucumber roots. However, the mechanism remains unclear. This study investigated the transport of Na⁺ in salt‐tolerant pumpkin and salt‐sensitive cucumber plants under high (200 mM) or moderate (90 mM) NaCl stress. Scanning ion‐selective electrode technique showed that pumpkin roots exhibited a higher capacity to extrude Na⁺, and a correspondingly increased H⁺ influx under 200 or 90 mM NaCl stress. The 200 mM NaCl induced Na⁺/H⁺ exchange in the root was inhibited by amiloride (a Na⁺/H⁺ antiporter inhibitor) or vanadate [a plasma membrane (PM) H⁺‐ATPase inhibitor], indicating that Na⁺ exclusion in salt stressed pumpkin and cucumber roots was the result of an active Na⁺/H⁺ antiporter across the PM, and the Na⁺/H⁺ antiporter system in salt stressed pumpkin roots was sufficient to exclude Na⁺. X‐ray microanalysis showed higher Na⁺ in the cortex, but lower Na⁺ in the stele of pumpkin roots than that in cucumber roots under 90 mM NaCl stress, suggesting that the highly vacuolated root cortical cells of pumpkin roots could sequester more Na⁺, limit the radial transport of Na⁺ to the stele and thus restrict the transport of Na⁺ to the shoot. These results provide direct evidence for pumpkin roots with higher capacity to limit the transport of Na⁺ to the shoot than cucumber roots.     

Influence of Plant Root Exudates, Germ Tube Orientation and Passive Conidia Transport on Biological Control of Fusarium Wilt by Strains of Nonpathogenic Fusarium oxysporum

In earlier studies, biological control of Fusarium wilt of cucumber induced by Fusarium oxysporum f. sp. cucumerinum was demonstrated using nonpathogenic strains C5 and C14 of Fusarium oxysporum. Strain C14 induced resistance and competed for infection sites whether roots were wounded or intact, whereas strain C5 required wounds to achieve biocontrol. In the current work, additional attributes involved in enhanced resistance by nonpathogenic biocontrol agents strains to Fusarium wilt of cucumber and pea were further investigated. In pre-penetration assays, pathogenic formae specials exhibited a significantly higher percentage of spore germination in 4-day-old root exudates of cucumber and pea than nonpathogens. Also, strain C5 exhibited the lowest significant reduction in spore germination in contrast to strain C14 or control. One-day-old cucumber roots injected with strain C14 resulted in significant reduction in germ tube orientation towards the root surface, 48–96 h after inoculation with F. o. cucumerinum spores, whereas strain C5 induced significantly lower spore orientation of the pathogen and only at 72 and 96 h after inoculation. In post-penetration tests, passive transport of microconidia of pathogenic and nonpathogens in stems from base to apex were examined when severed plant roots were immersed in spore suspension. In repeated trials, strain C5, F. o. cucumerinum and F. o. pisi were consistently isolated from stem tissues of both cucumber and pea at increasing heights over a 17 days incubation period. Strain C14 however, was recovered at a maximum translocation distance of 4.6 cm at day 6 and later height of isolation significantly declined thereafter to 1.2 cm at day 17. In pea stem, the decline was even less. Significant induction of resistance to challenge inoculation by the pathogen in cucumber occurred 72 and 96 h after pre-inoculation with biocontrol agents. Nonetheless, strain C14 induced protection as early as 48 h and the maximum resistance was reached at 96 h. The presented data confirm the previous findings that attributes important for nonpathogenic fusaria to induce resistant are: rapid spore germination and orientation in response to root exudate; active root penetration and passive conidia transport in stem to initiate defence reaction without pathogenicity and enough lag period between induction and challenge inoculation. Strain C14 possesses all these qualifications and hence its ability to enhance host resistance is superior than strain C5.     

Effects of Seselin and Coumarin on Growth, Indoleacetic Acid Oxidase, and Peroxidase, with Special Reference to Cucumber (Cucumis sativa L.) Radicles

Seselin, a natural coumarin derivative isolated from citrus roots, inhibited radicle growth in seedlings of cucumber (Cucumis sativa), lettuce (Lactuca sativum), radish (Raphanus sativus), and wheat (Triticum aestivum) grown in the dark. Coumarin similarly inhibited radicle growth of cucumber seedlings. Growth retardation of the cucumber radicles was accompanied by an increased activity of peroxidase and indole-3-acetic acid oxidase. Both compounds antagonized indole-3-acetic acid-induced growth of wheat coleoptiles, whereas coumarin was much less effective than seselin in antagonizing gibberellic acid-induced release of reducing sugars from barley endosperm. It is suggested that seselin plays an important role in the regulation of root growth, and that it is the indole-3-acetic acid oxidase cofactor previously detected in citrus roots.     

Influence of salicylaldehyde and methyl salicylate on post-landing behaviour of Frankliniella occidentalis Pergande

This study investigates behavioural responses of adult western flower thrips (Frankliniella occidentalis Pergande; Thysan., Thripidae) females to direct contact with repellent phenylpropanoid plant compounds (salicylaldehyde and methyl salicylate) applied on bean and cucumber leaves. The residence time of F. occidentalis females until take off was significantly shorter on bean or cucumber leaf discs treated with salicylaldehyde at 1% concentration compared with control leaf discs. A methyl salicylate (1%) treatment of cucumber resulted in shorter time periods until thrips took off the treated leaf discs compared with the control leaf discs. In a choice experiment thrips avoided to settle on a 1% salicylaldehyde treatment of bean and cucumber leaf discs for a maximum of 3 h, on a 1% methyl salicylate treatment for a 5‐h period. Within a 24‐h period neither the egg‐laying nor the feeding activity of F. occidentalis was affected after salicylaldehyde application (0.1%, 1%) on bean or cucumber. In contrast, methyl salicylate (1%) applied on bean and cucumber significantly prevented thrips females from oviposition and reduced the percentage of damaged area caused by their feeding activity for 24 h. As olfactory repellent plant volatiles applied on crop plants may elicit diverse post‐landing responses of F. occidentalis, short‐ and long‐term effects should be considered when evaluating the factual applicability of secondary plant compounds in a successful thrips management strategy.