Application of citronellyl acetate and geranyl acetate in controlling thrips

Abstract

The application discloses application of citronellyl acetate and geranyl acetate in prevention and treatment of Frankliniella intonsa. The application identifies and screens the volatile substances citronellyl acetate and geranyl acetate from leaves of the aromatic plant Citronella, which have a significant repelling effect on Frankliniella intonsa and a significant attracting effect on the dominant natural enemy of the Frankliniella intonsa, i.e. Scirtetinus insularis, and can be used for prevention and treatment of the Frankliniella intonsa. The citronellyl acetate and the geranyl acetate are derived from plants, green and environmentally friendly, and the application provides a scientific basis for a green prevention and control strategy of the Frankliniella intonsa, development of a plant-derived repellent and application of an ecological regulation technology, and has a strong application value.

Description

Technical Field

[0001] This invention belongs to the technical field of green control of flower thrips using plant volatiles, specifically involving the application of citronellol acetate and geraniol acetate in the control of flower thrips. Background Technology

[0002] Aromatic plants refer to a broad group of cultivated or wild plants that secrete volatile aromatic substances and provide essential oils. Their applications span multiple fields, including food processing, pharmaceuticals, daily chemical products, and ecological pest control. Numerous studies have shown that aromatic plants and their volatile compounds play an important role in repelling or interfering with thrips behavior. For example, research has shown that the aromatic plant peppermint... Mentha piperita Perilla Perilla frutescens Nepeta cataria Schizonepeta tenuifolia Western flower thrips Frankliniella occidentalis It exhibited a clear repellent effect, and further investigation revealed that β-caryophyllene, a common volatile component of these plants, had a significant repellent effect on western flower thrips; lemongrass Cymbopogon citratus Freshly cut leaves of *Thrips fasciatus* Megalurothrips sjostadti It has a significant repellent effect. Further analysis revealed that the volatile substances such as myrcene and geraniol, which are present in high amounts in citronella, have significant repellent activity against thrips.

[0003] Flower thrips Frankliniella intonsa Flower thrips (Trybom) is a significant agricultural pest globally, and in recent years it has caused widespread damage to various economic crops in my country, including mangoes, chili peppers, and cantaloupes. This insect primarily damages crops by rasping and sucking plant sap and transmitting plant viral diseases, leading to yield reductions of 15% to 30%, and in severe cases, complete crop failure. Currently, there is a lack of systematic research on using aromatic plants or their volatile compounds to regulate flower thrips behavior. Summary of the Invention

[0004] In response to the current outbreak of flower thrips in tropical regions, behavioral regulation technology is an important measure for its control. However, behavioral regulators with attraction or repellency effects rarely take into account their impact on natural enemies, and there is a lack of highly effective behavioral regulators. This invention aims to develop behavioral regulators that have a significant repellency effect on flower thrips but attract their dominant natural enemy, the island bug, and to provide the application of citronellol acetate and geraniol acetate in the control of flower thrips.

[0005] The first objective of this invention is to provide the use of citronellol acetate and / or geraniol acetate in the control of flower thrips.

[0006] Preferably, the application is the use of citronellol acetate and / or geraniol acetate in repelling thrips.

[0007] Preferably, the application is the use of citronellol acetate and / or geraniol acetate in attracting island volcano bugs.

[0008] A second objective of this invention is to provide the use of citronellol acetate and / or geraniol acetate in the preparation of thrips control agents.

[0009] Preferably, in the application described, citronellol acetate is used to prepare a thrips control agent, wherein the concentration of citronellol acetate in the control agent is 0.1-10 μg / μL.

[0010] More preferably, the concentration of citronellol acetate in the control agent is 1-10 μg / μL.

[0011] Preferably, in the application described, geraniol acetate is prepared into a thrips control agent, and the concentration of geraniol acetate in the control agent is 0.1-10 μg / μL.

[0012] More preferably, the concentration of geraniol acetate in the control agent is 0.1-1 μg / μL.

[0013] The present invention has the following beneficial effects:

[0014] This invention identifies and screens volatile compounds, citronellol acetate and geraniol acetate, from the leaves of the aromatic plant lemongrass. These compounds exhibit significant repellent activity against flower thrips and significant attraction to its dominant natural enemy, the island bug. They can be used for the control of flower thrips. Citronellol acetate and geraniol acetate are derived from plants, making them environmentally friendly. This invention provides a scientific basis for green control strategies for flower thrips, the development of plant-derived repellents, and the application of ecological regulation technologies, and has significant application value. Attached Figure Description

[0015] Figure 1 The selection rate of flower thrips for lemongrass and the blank control is shown.

[0016] Figure 2 This is a total ion chromatogram of volatiles of lemongrass, standard, and blank control; the numbers 1-4 on the graph represent compounds (+)-citronellol, citronellol, citronellol acetate, and geraniol acetate, respectively.

[0017] Figure 3 These are the EAG reaction curves and reaction values ​​of thrips to different lemongrass volatiles; Note: AD is the EAG reaction curve of thrips to different lemongrass volatiles, and EH is the EAG reaction value of thrips to different lemongrass volatiles.

[0018] Figure 4 It is the reaction rate of flower thrips to different volatiles.

[0019] Figure 5 The response rates of the island bug to geraniol acetate and citronellol acetate are shown in Figure 1. Note: A and B represent geraniol acetate and citronellol acetate, respectively.

[0020] Figure 6 The study describes the repellent effect of spraying two citronella volatiles, geraniol acetate and citronellol acetate, on thrips. Detailed Implementation

[0021] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0022] Example 1

[0023] I. Methods

[0024] Volatile substances from lemongrass leaves were collected and identified using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Volatile substances that had a significant repellent effect on flower thrips but an attraction effect on island cricket were selected using an antennal potentiometer, a Y-type olfactometer, and field repellency tests.

[0025] 1. The repellent effect of lemongrass leaves on flower thrips

[0026] The "Y"-shaped olfactory apparatus mainly consists of a "Y"-shaped tube, a flavor source bottle, a gas washing bottle (air humidification device), an activated carbon air filter tower, an atmospheric flow meter, and an air pump. The various devices are connected using odorless silicone tubing. The basic connection sequence is as follows: air pump → activated carbon air filter tower → atmospheric flow meter → gas washing bottle → flavor source bottle → "Y"-shaped olfactory apparatus. Before the experiment, the glassware and odorless silicone tubing are cleaned with 75% ethanol, rinsed with water, and dried. Distilled water is added to the gas washing bottle, filling it to no more than two-thirds full. The airflow in both arms is controlled at 100 mL / min to ensure that the experimental conditions are essentially the same. 2 g of fresh lemongrass leaves are weighed and placed in one flavor source bottle, while the other flavor source bottle remains empty (i.e., only air flows in). Sixty newly emerged flower thrips are selected and tested one by one. The selectivity of the flower thrips is observed over 5 minutes. A flower thrips is considered selective when it enters two-thirds of the side wall and remains there for more than 30 seconds. If the flower thrips did not make a choice within 5 minutes, the behavioral observation was terminated. To eliminate the influence of light, the entire "Y"-shaped olfactory instrument was covered with a black cloth at the beginning of the test. The position of the "Y"-shaped tube was changed every 5 thrips to counteract the influence of orientation. Every 10 thrips, a new "Y"-shaped tube, rubber tube, and flavor source material were used to prevent residual odors in the tube and changes in the concentration of flavor source material from affecting the flower thrips' selection behavior.

[0027] 2. Collection and identification of volatiles from lemongrass leaves

[0028] Preheat the GC-MS to 200℃ at the injection port. Insert the SPME extraction tip into the injection port and age it for 30 min. Collect 2.0 g of fresh, insect-damaged lemongrass leaves and place them in a 20 mL headspace vial. Puncture the top gasket of the transparent headspace vial with the aged extraction tip, place it in a preheated 40℃ metal water bath, and after removing the adsorption coating, secure the handle to maintain stability (to prevent the adsorption layer from detaching due to shaking). Incubate at 40℃ for 1 h.

[0029] ① GC conditions—The column type was an HP-5 MS flexible quartz glass capillary column (30 mm × 0.25 mm × 0.25 μm), the gas chromatographic detector was a FID flame ionization detector, the carrier gas was high-purity nitrogen (>99.99%), the flow rate was 2 mL / min, the auxiliary gas parameters were set to hydrogen 30 mL / min and air 400 mL / min, and the injection mode was split (split ratio 10:1). The injection port temperature was constant at 250℃, and the column temperature was controlled by a gradient program: initially 40℃ and held for 4 min, then increased to 160℃ at a rate of 5℃ / min and held for 5 min, then increased to 260℃ at a rate of 10℃ / min and held for 5 min. ② MS conditions: solvent delay time 3 min, transfer line temperature 280℃, quadrupole temperature 150℃, ion source temperature 230℃; ionization mode: EI; ionization energy 70 eV; data acquisition via full scan, scan range 45-550 amu. ③ Identification and screening of aromatic plant volatiles: Agilent Mass Hunter Qualitative Analysis software was used. Based on the mass spectra corresponding to each chromatographic peak, the NIST 14 standard mass spectrometry library established by the National Institute of Standards and Technology (NIST) was connected to retrieve and analyze the mass spectrometry data of each component. Compounds with high mass spectrometry matching were selected to determine the chemical composition of the volatiles. Quantitative analysis was performed using the peak area normalization method to determine the relative content of each component.

[0030] 3. Electrophysiological activity of flower thrips on volatiles from lemongrass leaves

[0031] Using glass electrode connections, prepare glass capillaries at both ends of the antennae to be tested, aspirate Ringer's saline solution, and connect silver wire electrodes to the probe connections of the measuring electrodes at both ends. After being fixed with a micromanipulator, the flower thrips head is microscopically dissected through the prothorax-head junction and placed in the reference electrode slot. Recording electrode microtubes are inserted into the tips of both antennae (the tube walls are blotted dry with filter paper to ensure no air bubbles or impurities interfere). The outlet of the airflow system is aligned with the antennae, 1 cm away, and the continuous gas flow rate is controlled at 200 mL / min, while the stimulation gas flow rate is 40 mL / min. Fine-tune the antennal connection to stabilize the signal recording baseline. Perform electrophysiological response experiments on the flower thrips antennae using liquid paraffin as a reference sample. Gradient solutions were prepared using liquid paraffin (analytical grade) as the solvent for volatile standard solutions. Four high-content components of citronella (+)-citronellol, citronellol, citronellol acetate, and geraniol acetate) were dissolved in the liquid paraffin and thoroughly mixed on a vortex mixer. Three solutions with concentrations of 0.1 μg / μL, 1 μg / μL, and 10 μg / μL were prepared by volume ratio and used immediately. Liquid paraffin without any added volatile substances served as a control. A 2.5 cm × 0.5 cm filter paper strip was used as the adsorption medium. After fixing it to the inner wall of a sterilizing pipette tip, 15 μL of the test solution was accurately transferred to the center of the strip using a pipette. The sterilizing pipette tip was then assembled into the orifice of a Pasteur tube. Before the experiment, liquid paraffin was used as a reference value (mean of three replicates). The stimulation parameter was set to 0.5 s, and the time interval between two stimulations should be greater than or equal to 60 s to avoid adaptation error. The testing procedure strictly followed the principle of increasing concentration gradient (from low to high concentration). Each concentration gradient was measured three times in parallel on the same antenna, and each antenna was used only for testing a single compound. During the antennal measurement process, the antennal response weakened, and individual differences existed between different antennae. The test involved first stimulating the antenna with paraffin wax once, then testing each sample sequentially with a 1-minute interval between each stimulation, and finally stimulating with paraffin wax again. The EAG and CK values ​​for each compound concentration were the average of three replicates, and valid data were obtained from at least 10 antennae for each compound.

[0032] 4. Flower thrips' behavior towards different lemongrass volatiles

[0033] A Y-type olfactometer was used for determination. Volatile monomer chemical standards prepared by dilution of liquid paraffin were used as odor sources, with concentration gradients set at 0.1 μg / μL, 1 μg / μL, and 10 μg / μL. Small petri dishes containing filter paper were placed in the odor source bottles on both sides of the Y-type olfactometer. Using a pipette, 30 µL of control solution (liquid paraffin) and odor source solutions of different concentrations were evenly added to the surface of the qualitative filter paper. The operation procedure of the Y-type olfactometer was performed as described above.

[0034] 5. The effect of lemongrass volatiles, which have a repellent effect on flower thrips, on the selective behavior of the non-target species, the small flower bug, on islands.

[0035] To evaluate the effects of citronellol acetate and geraniol acetate, which have been screened as repellents to flower thrips, on non-target targets, the study further evaluated the influence of four volatile compounds on the selective behavior of *Symplocos spp.*, a dominant natural enemy of flower thrips. Measurements were performed using a Y-type olfactometer, and the operating procedure for the Y-type olfactometer was as described above.

[0036] 6. Verification of the repellent effect of aromatic plant volatiles on flower thrips in mango orchards

[0037] The field experiment was conducted in a mango orchard in Ledong Li Autonomous County, Hainan Province (39°73'N, 116°44'E). The experiment took place during the peak flowering period of the mangoes. Geraniol acetate and citronellol acetate were diluted with mineral oil to three concentration gradients: 0.1 μg / μL, 1 μg / μL, and 10 μg / μL, respectively. These were then sprayed evenly onto the mango flower spikes. Twenty-four hours later, one 10 cm flower spike was cut from each of the east, south, west, and north sides of each mango tree, and the number of thrips was counted. A control group was used, with only mineral oil sprayed. Both the control and treatment groups were replicated three times.

[0038] II. Results

[0039] 1. The repellent effect of lemongrass leaves on flower thrips

[0040] The repellent effect of lemongrass leaves on flower thrips was determined using a Y-type olfactory analyzer. Figure 1 The results showed that the selection rate of thrips for lemongrass was 31.7%, while the selection rate for the blank control was 68.3%, indicating that lemongrass has a significant repellent effect on thrips.

[0041] 2. Identification of volatiles from lemongrass leaves

[0042] Volatile compounds from lemongrass leaves were collected and identified using SPME combined with GC-MS. The relative content of compounds was calculated using peak area normalization, and the results were verified against the NIST-14 mass spectrometry library. Finally, the chemical names, retention times, molecular formulas, and CAS numbers of each component were obtained. Analysis showed that 20 highly matched compounds (qualitative values ​​> 90) were identified in the lemongrass volatiles, covering four types: two aldehydes, two esters, four alcohols, and twelve terpenes. Figure 2(See Table 1). Based on screening criteria such as repeated stable occurrence and high content, we selected four high-content components ((+)-citronellol, citronellol, citronellol acetate, and geraniol acetate) from citronellol volatiles for validation analysis. Liquid chromatography-mass spectrometry (LC-GC-MS) was used to detect the above target compound standards, and their chromatographic retention time parameters were measured and recorded. Comparative analysis revealed that the retention times of the standard peaks were highly consistent with the chromatographic behavior of the corresponding components in the total ion chromatogram (TIC) of citronellol volatiles. Figure 2 As shown in Table 1, the retention times of the target compound standard are highly consistent with those of the target compound in lemongrass volatiles. The experimental data fully confirm the accuracy of the qualitative analysis results of the above four volatile components and provide a reliable basis for subsequent quantitative research.

[0043] Table 1. Identification results of volatile chemical components of lemongrass

[0044]

[0045] 3. Electrophysiological activity of flower thrips on volatiles from lemongrass leaves

[0046] The electrophysiological activities of thrips on four volatile compounds from lemongrass leaves—(+)-citronellol, citronellol, citronellol acetate, and geraniol acetate—were determined using EAG. Figure 3 It was found that thrips exhibited electrophysiological activity in response to all four volatiles, especially under high concentration conditions, where the induced amplitude was the largest.

[0047] 4. Flower thrips' behavior towards different lemongrass volatiles

[0048] The selective behavior of flower thrips towards (+)-citronellol, citronellol, citronellol acetate, and geraniol acetate was determined using a Y-type olfactometer. Figure 4 The study found that, except for citronellol which had no significant effect on the selection of flower thrips, (+)-citronellol, citronellol acetate, and geraniol acetate at concentrations of 0.1–1 μg / μL all showed significant repellent effects on flower thrips.

[0049] Based on cost considerations, given that (+)-citronellol is extremely expensive among the three volatile compounds, citronellol acetate and geraniol acetate, which are less expensive, were chosen as the subjects for subsequent testing.

[0050] 5. The effect of lemongrass volatiles, which have a repellent effect on flower thrips, on the selective behavior of the non-target species, the small flower bug, on islands.

[0051] The selective behavior of the dominant natural enemy of thrips, the island pistil, towards lemongrass volatiles was determined using a Y-type olfactory instrument. Figure 5Geraniol acetate at concentrations of 0.1 μg / μL and citronellol acetate at concentrations of 1 μg / μL had a significant attraction effect on the island bug.

[0052] 6. Verification of the repellent effect of aromatic plant volatiles on flower thrips in mango orchards

[0053] By spraying mineral oil containing geraniol or citronellol acetate onto mango flower spikes, the number of flower thrips was significantly reduced on the spikes treated with either volatile compound compared to the control (mineral oil only). Figure 6 The number of flower thrips decreased by 42.19%, 44.38%, and 31.15% after 24 h of treatment with geraniol acetate at concentrations of 0.1, 1, and 10 μg / μL, respectively. The number of flower thrips decreased by 48.62%, 73%, and 70.08% after 24 h of treatment with citronellol acetate at concentrations of 0.1, 1, and 10 μg / μL, respectively. This indicates that the two citronellol volatiles have a significant repellent effect on flower thrips and can be used to control flower thrips.

Claims

1. Application of citronellol acetate in repelling thrips.

2. Application of geraniol acetate in attracting island volcano bugs.

3. Application of citronellol acetate in the preparation of thrips repellent.

4. The application according to claim 3, characterized in that, Citronellol acetate was used to prepare a thrips repellent, with the concentration of citronellol acetate in the repellent being 0.1-10 μg / μL.

5. The application according to claim 4, characterized in that, The concentration of citronellol acetate in the repellent is 1-10 μg / μL.

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