Application of tobacco root exudate extract in controlling aphids

Abstract

The present invention belongs to the field of biological pesticide technology, specifically, it relates to the application of tobacco root secretion extract in preventing and controlling aphid diseases of roses, tobacco, wheat, and cruciferous vegetables. The preparation method of the tobacco root secretion extract comprises: extracting and concentrating the tobacco root secretion with a solvent; the solvent is ethyl acetate or dichloromethane; the volume ratio of the solvent to the tobacco root secretion is 0.5-1.5:1. The present invention is the first to use the dichloromethane extract of tobacco root secretion to prevent and control plant aphids. The extract can effectively kill and inhibit plant aphids. As the concentration of the tobacco root secretion extract increases, its insecticidal activity rate against plant aphids also gradually increases. The tobacco root secretion extract is derived from the plant itself, is easily degraded in nature, is safe to the environment, does not contaminate food, and pests are not likely to develop drug resistance.

Description

Technical Field

[0001] The invention relates to the technical field of biological pesticides, in particular to the application of tobacco root secretions in preventing and controlling aphids. Background Art

[0002] Tobacco aphids, also known as green peach aphids, are a significant pest in tobacco production, occurring in all major tobacco-growing areas of my country. Widely distributed and rapidly reproducing, they pose a serious threat to tobacco crops. They not only directly damage plants by feeding on sap from leaves and rhizomes, but can also indirectly harm plants by secreting honeydew, causing sooty mold and spreading tobacco viral diseases.

[0003] Chemical control is the most commonly used method in tobacco production due to its rapid and effective effectiveness. However, the long-term use of chemical pesticides for tobacco aphid control can easily lead to the development of pesticide resistance in a given area, while also causing problems such as pesticide residues and environmental pollution. Consequently, researchers both domestically and internationally are dedicated to developing botanical insecticides.

[0004] For example, Chinese Patent No. 202410424411.7 provides a botanical green pesticide for controlling aphids on crops and its preparation method. The botanical green pesticide is prepared by extracting the following Chinese medicinal herbs in parts by weight: 2-6 parts of coptis root, 3-8 parts of cinnamon bark, 3-10 parts of sophora flavescens, 2-8 parts of turmeric, 2-6 parts of mint, 4-8 parts of garlic, and 1-2 parts of a natural preservative. The botanical green pesticide provided by this invention can effectively control aphid pests on crops. The content ratio of each component is reasonable, which can effectively exert the efficacy of the composition in controlling aphids and has a certain ability to repel other pests. It is friendly to crops, non-target organisms, and the environment, increases the rapid effect of the agent on pests, delays the development of pest resistance, and prolongs the agent's long-lasting effect. Its preparation process is simple, effective, green, harmless, and stable. The resulting concentrated solution reduces the amount of pesticide used and reduces agricultural costs.

[0005] Chinese Patent 202110163736.0 discloses the use of marigold volatile β-cyclohomocitral to control wolfberry aphids. The marigold volatile component is β-cyclohomocitral, which is collected from marigold flowers, stems and leaves, or whole marigold plants. The invention also provides the use of the aphid control composition containing marigold volatiles in controlling wolfberry aphids. This invention effectively controls the damage caused by wolfberry aphids and provides experimental data support for the development of a new generation of efficient and environmentally friendly botanical pesticides. It also provides a scientific basis for the further development and utilization of marigolds.

[0006] Chinese Patent No. 202111260931.1 discloses a natural botanical pesticide made from Euphorbia pulcherrima, Cucurbitaceae, Glehnia littoralis, Zhenlong root, Tobacco, Nine-cong root, Allium sibiricum, Cornus officinalis, Aconite root, Jujube fruit, and Strychnos nux vomica. This natural botanical pesticide utilizes the theory of monarch, minister, assistant, and envoy in Traditional Chinese Medicine (TCM). It utilizes a rational combination of natural Chinese herbs. The synergistic effects of the various components powerfully disrupt the insect's digestive system and metabolic function, while also disrupting the insect's vagus nerve and suppressing its respiratory system. This pesticide can kill all soft-bodied, chewing, and sucking pests. It has a high potency, stable efficacy, and a long-lasting effect (at least 14 days). It is easily degradable, environmentally friendly, odorless, and residue-free. It is pollution-free, safe, and environmentally friendly.

[0007] Existing technology (Feng Chao. Identification of tobacco root secretion components and their effects on tobacco Phytophthora[J]. Anhui Agricultural Sciences, 2018, 46(17):5.DOI:10.13989 / j.cnki.0517-6611.2018.17.044.) explored the effects of different components of tobacco root secretions on tobacco Phytophthora. The results showed that among the 32 tobacco root secretions with relatively high content, 12 secretions had an inhibitory effect on tobacco Phytophthora, and 5 had a growth-promoting effect; at a concentration of 800 μg / mL, the inhibition rates of tartaric acid, salicylic acid, 2-furancarboxylic acid and scutellaria lactone on tobacco Phytophthora were 92.87%, 97.14%, 91.33% and 93.76%, respectively, with salicylic acid having the best antibacterial effect. Compared with the control, the EC50 values ​​of all the bacteria were less than 500 μg / mL, among which tartaric acid was the most toxic with an EC50 of 159.68 μg / mL.

[0008] However, there are currently no reports on the application of tobacco root exudate extracts in the prevention and control of aphids. Summary of the Invention

[0009] The invention aims to provide a method for preventing and controlling aphids by using a tobacco root secretion extract.

[0010] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0011] The present invention provides application of tobacco root secretion extract in preventing and controlling aphid diseases of roses, tobacco, wheat and cruciferous vegetables.

[0012] In one preferred embodiment, the preparation method of the tobacco root exudate extract comprises: extracting and concentrating the tobacco root exudate with a solvent; the solvent is ethyl acetate or dichloromethane; and the volume ratio of the solvent to the tobacco root exudate is 0.5-1.5:1.

[0013] In one preferred embodiment, the tobacco root secretions are obtained by the following method: washing the tobacco root part, placing it in a sealed light-proof container, adding deionized water, sealing it, and culturing it at room temperature and natural light conditions for 1-3 days, collecting the liquid, and thus obtaining the tobacco root secretions.

[0014] The tobacco root secretions are cultured in a light-proof environment, as light will degrade the root secretions.

[0015] In one preferred embodiment, the tobacco is preferably tobacco root secretions during the tobacco growth period.

[0016] In one preferred embodiment, 20-80 mL of deionized water is added to each tobacco plant.

[0017] If too much water is added, the concentration of root secretions will be too low and the effect will be poor. If too little water is added, the amount of watering and soaking solution will be insufficient and the effect will also be poor.

[0018] In one preferred embodiment, the sealed light-proof container is a beaker covered with a black plastic bag.

[0019] Place the tobacco root part and water in a container, completely wrap the container and the roots of the tobacco plant with a black plastic bag, and cultivate the plant in sunlight.

[0020] In one preferred embodiment, the solvent is preferably dichloromethane.

[0021] In one preferred embodiment, the liquid obtained by extracting tobacco root secretions with dichloromethane solvent is concentrated to dryness, and the volume is adjusted to 1-5 mL with dichloromethane solvent.

[0022] Based on the same invention, the present invention also claims protection for a method for controlling aphids using the tobacco root secretion extract prepared by the above preparation method.

[0023] Based on the same invention, the present invention also claims to protect the use of the above-mentioned tobacco root secretion extract in preventing and controlling aphid diseases in roses, tobacco, wheat, and cruciferous vegetables.

[0024] In a preferred embodiment, the application is to spray the tobacco root secretion extract onto the leaves of roses, tobacco, wheat, and cruciferous vegetables.

[0025] In one preferred embodiment, the application is to soak the leaves of roses, tobacco, wheat, and cruciferous vegetables in the above-mentioned tobacco root secretion extract.

[0026] Based on the same inventive concept, the present invention also claims protection for an insecticide composition comprising the tobacco root exudate extract.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention is the first to use a dichloromethane extract of tobacco root secretions for the prevention and control of plant pests called aphids. This extract effectively kills and inhibits aphids in plants, and its insecticidal activity against aphids gradually increases with increasing concentration of the tobacco root secretion extract. When the tobacco root secretion extract is concentrated to a volume of 1-5 mL, its insecticidal activity remains at 100% after 24 hours. The tobacco root secretion extract is derived from the plant itself, is easily degraded in nature, is safe for the environment, does not contaminate food, and is less likely to develop pesticide resistance in pests. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The effect of crude extracts of tobacco root exudates on tobacco aphids;

[0030] Figure 2 GC-MS images of tobacco root exudates under different treatments;

[0031] Figure 3 The effect of ethyl acetate and dichloromethane extraction of tobacco root secretions on tobacco aphids was studied.

[0032] Figure 4 The effect of spraying tobacco root secretions extracted with ethyl acetate and dichloromethane on tobacco aphids was studied. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0034] Example 1

[0035] Insecticidal activity of crude extracts from tobacco root exudates against tobacco aphid

[0036] Step 1: Collection of tobacco root exudates

[0037] When tobacco plants (variety K326) grown in the field reached different stages (i.e., root extension stage, vigorous growth stage, and maturity stage), tobacco plants with good growth status and uniform plant size were dug out from the field, and the root system was kept as intact as possible. The tobacco roots were washed with clean water and then rinsed with deionized water. Each tobacco plant was placed in a 500mL beaker, and 20mL, 40mL, and 80mL of deionized water were added respectively. The beaker and the tobacco plant roots were completely wrapped with black plastic bags and then placed in the sun for cultivation. The collected liquid was collected for 2 consecutive days. The collected liquid is the crude extract of tobacco root secretions. Each treatment was repeated 3 times.

[0038] Step 2: Determination of insecticidal activity of crude extracts of tobacco root exudates at different stages against tobacco aphids

[0039] The insecticidal activity of tobacco root secretions against tobacco aphids was determined by leaf immersion method. Fresh tobacco leaves of the same size and good growth were selected and immersed in the crude extract of tobacco root secretions collected in step 1 above for 5 seconds, 20 mL, 40 mL, and 80 mL of deionized water, respectively. A control experiment (only distilled water) was also performed. Each treatment or control was repeated 3 times. The excess crude extract of tobacco root secretions was removed and absorbed with absorbent paper. 30 wingless tobacco aphids were transferred to each tobacco leaf and placed in a culture dish for observation. The roots of the tobacco leaves were moisturized with filter paper, sealed with plastic wrap, and 50 ventilation holes were punctured with a needle. After 12 hours, 24 hours, and 48 hours, the tobacco aphids were observed and counted, and the survival of the tobacco aphids was recorded. (The death standard was that the tobacco aphid could not move normally or did not respond when the insect body was gently touched with a needle). The mortality rate and the adjusted mortality rate were calculated using the following formulas (1) and (2):

[0040] Mortality rate = number of dead insects / (number of live insects + number of dead insects) × 100% (1)

[0041] Corrected mortality rate = [treatment mortality rate - control mortality rate / (1 - control mortality rate)] × 100% (2)

[0042] The results are shown in Table 1.

[0043] Table 1 Insecticidal activity of crude extracts from tobacco root exudates at different stages against tobacco aphids (%

[0044]

[0045]

[0046] As shown in Table 1, after the same treatment time (12, 24, and 48 h), the mortality rate of tobacco aphids increased with the decrease in the volume of deionized water used to collect tobacco root secretions, that is, the higher the concentration of tobacco root secretions, the higher the mortality rate. When the concentration of tobacco root secretions collected at the root extension stage was 20 mL, the corrected mortality rates of tobacco aphids were 34.5%, 44.4%, and 57.7% after treatment for 12 h, 24 h, and 48 h, respectively. When the concentration of tobacco root secretions collected at the vigorous growth stage was 20 mL, the mortality rates of tobacco aphids were 37.6%, 47.6%, and 62.3% after treatment for 12 h, 24 h, and 48 h, respectively. The mortality rates of tobacco aphids collected at the mature stage were 36.6%, 45.5%, and 60.4%, respectively. This indicates that at higher concentrations, the crude extract of tobacco root secretions has certain toxic and inhibitory effects on tobacco aphids, with good insecticidal activity, and the toxic effect becomes more obvious with time. Tobacco root secretions collected at different times showed different insecticidal activity against tobacco aphids, with those collected during the vigorous growth period showing the best insecticidal activity. At lower concentrations (80 mL of tobacco root secretions), crude extracts of tobacco root secretions promoted the growth of tobacco aphids to a certain extent. This may be because low concentrations of crude extracts of tobacco root secretions provide nutrients for the growth, development, and reproduction of tobacco aphids, leading to an increase in the number of aphids.

[0047] Example 2

[0048] Determination of the insecticidal activity of different concentrations of crude extracts from tobacco root exudates against tobacco aphids

[0049] According to the conclusion of the concentration effect of low concentration of crude extract of tobacco root secretion and high concentration of high inhibition, we will conduct further experiments on crude extract of tobacco root secretion collected with 20mL deionized water during the vigorous growth period. We collected crude extract of tobacco root secretion collected with 20mL deionized water during the vigorous growth period again, then placed it in a rotary evaporator and concentrated it to dryness, and fixed the volume with 0.5mL, 1mL and 2mL of deionized water respectively, and configured it into different concentrations of tobacco root secretion to test tobacco aphids. The leaf immersion method was also used for determination. Fresh young leaves were soaked in deionized water (control), 2mL, 1mL, and 0.5mL of crude extract of tobacco root secretion for 5s, and excess tobacco analysis secretion crude extract was absorbed with absorbent paper. 30 wingless tobacco aphids were transferred to each tobacco leaf, and the tobacco leaf was placed in a culture dish for observation. The root of the tobacco leaf was moisturized with filter paper, sealed with plastic wrap, and 50 vents were punctured. Each treatment or control was repeated 3 times. Observe and count the number of tobacco aphids after 12h, 24h and 48h respectively, and record the survival of the tobacco aphids. Figure 1 shown.

[0050] Table 2 Insecticidal activity of crude extracts of tobacco root exudates at different concentrations against tobacco aphids (%)

[0051]

[0052]

[0053] Table 2 and Figure 1 The insecticidal activity of tobacco root secretions at different concentrations against tobacco aphids is listed. Figure 1 In the figure, D represents the control, while A, B, and C represent tobacco root exudates diluted with 0.5 mL, 1 mL, and 2 mL of deionized water, respectively. The results showed that different concentrations of crude tobacco root exudate extracts exhibited strong toxicity against tobacco aphids, with mortality rates ranging from 13.0% to 81.0%. After the same treatment time (12, 24, and 48 hours), the mortality rate of tobacco aphids increased with increasing tobacco root exudate concentration. When the tobacco root exudate concentration was 0.5 mL, the mortality rates against tobacco aphids were 30.6%, 41.1%, and 81.0% after 12, 24, and 48 hours of treatment, respectively, demonstrating strong insecticidal activity. When the tobacco root exudate concentration was 2 mL, the mortality rates against tobacco aphids at different treatment times were 13.0%, 20.8%, and 54.3%, respectively, demonstrating relatively poor insecticidal activity. Furthermore, at the same tobacco root exudate concentration, the mortality rate of tobacco aphids increased with treatment time. Furthermore, when the tobacco root exudate concentration was set at 0.5 mL, the adjusted mortality rate was significantly different from the control. This demonstrates that tobacco root exudates inhibit the growth of tobacco aphids, and the inhibitory effect increases with increasing concentration.

[0054] Example 3

[0055] Determination of the insecticidal activity of tobacco root exudates extracted with different extractants against tobacco aphids

[0056] Step 1 Collection of tobacco root secretions

[0057] When field-grown tobacco (variety K326) is 20 and 40 days old, dig out healthy, uniformly sized tobacco plants from the field, maintaining the integrity of the root system as much as possible. Wash the tobacco roots with clean water and then rinse with deionized water. Place each tobacco plant in a 500mL beaker, add 20mL of deionized water, and completely wrap the beaker and the tobacco plant roots with a black plastic bag. Place the beaker in the sun and incubate for 2 consecutive days. The collected liquid is the tobacco root secretions.

[0058] Step 2 Extraction of tobacco root secretions

[0059] Transfer multiple 20 mL aliquots of tobacco root exudates collected in step 1 above to separate pear-shaped separatory funnels and extract the tobacco root exudates with ethyl acetate and dichloromethane, respectively, at a 1:1 ratio of extractant to the volume of the tobacco root exudates. Collect all 20 mL of the ethyl acetate and dichloromethane organic phases.

[0060] Step 3 Identification of tobacco root exudate extracts

[0061] Tobacco root exudates were extracted with ethyl acetate and dichloromethane, respectively, and then concentrated to dryness on a rotary evaporator under reduced pressure. The volume was then adjusted to 1.5 mL with chromatographically grade dichloromethane and filtered through a 0.45 μm organic filter. Qualitative and quantitative analysis of the tobacco root exudate composition was performed using an Agilent 7890A / 5975C gas chromatograph-mass spectrometer (GC-MS). Chromatographic separation was performed using a DB-5ms capillary column (30 m × 0.25 mm, film thickness 0.25 μm). The inlet temperature was set at 280°C. The column temperature program was 50°C for 3 minutes, followed by a temperature increase of 10°C / min to 290°C and hold for 20 minutes. Helium (He) was used as the carrier gas at a flow rate of 1 mL / min. The injection volume was 1 μL. The mass spectrometry analysis conditions include: electron impact source (EI) energy 70eV; mass spectrometry scanning range 35-800m / z; scanning speed 0.2s for the entire range; ion source temperature 200; interface temperature 250℃; detection voltage 1kV; solvent removal time 3 minutes. The total ion spectrum was manually analyzed and compared with the standard spectrum of the NIST 107 mass spectrum database, combined with computer retrieval, to achieve qualitative identification of unknown compounds. The statistical results of the components with a similarity of more than 80% and a relative content of more than 0.2% between tobacco root secretions and the database are shown in Table 3, and the total ion chromatogram is shown in Table 3. Figure 2 .

[0062] Table 3 Main components of tobacco root secretions collected at different times after extraction with different extractants

[0063]

[0064] Note: DCM-20d, DCM-40d, EAC-20d, and EAC-40d are abbreviations for tobacco root secretions collected 20 days and 40 days after transplanting, respectively, and extracted with dichloromethane and ethyl acetate; (*) indicates that the correlation reached a significant level.

[0065] From Table 3 and Figure 2Results indicate that the diversity and concentration of tobacco root exudates increase significantly with the extension of the tobacco growth period. A total of 63 root exudate species were identified and categorized as hydrocarbons, lipids, phenols, and organic acids. Within the first 20 days of growth, 30 and 14 root exudate species were identified using dichloromethane (DCM) and ethyl acetate (EAC) extraction methods, respectively. By the 40th day, the number of root exudate species increased to 54 and 33, respectively. Significant differences were observed in the extraction of tobacco root exudates using the two extractants, dichloromethane (DCM) and ethyl acetate (EAC). On the 20th day, tobacco root exudates extracted using DCM displayed a broad spectrum of organic compounds, with hydrocarbons (19 species) and lipids (6 species) being the most abundant. Notably, 3-octylmethyl epoxyoctanoate accounted for the highest proportion, reaching 25.79%. Lipids (7 species) dominated the organic compounds in tobacco root exudates extracted using EAC, accounting for 80.46%, while hydrocarbons (3 species) were relatively rare. The most significant compound was identified as 1,2-dimethylpropyl 1,2-phthalate, accounting for 55.82% of the total. On the 40th day, root exudates extracted using DCM showed abundant hydrocarbons (24 species) and lipids (10 species), of which di(2-ethylhexyl) phthalate was the most prevalent, accounting for 24.28%. (Z)-docosa-9-enenitrile was the highest content in root exudates extracted using EAC, reaching 38.85%. The results showed that in all treatments, hydrocarbons, esters, phenols, and organic acids accounted for approximately 80% of all detected compounds and were the main root exudate components. With the extension of the growth period, the types and relative contents of compounds in tobacco root exudates increased significantly. Under different extraction agent treatments, the method using DCM as the extraction solution detected the most types of tobacco root secretions, particularly hydrocarbons. However, the method using EAC as the extraction solution detected more organic acids and lipids. This may be because DCM has good solubility for many organic compounds, effectively extracting multiple components from the sample. On the other hand, EAC also demonstrated excellent performance in extracting compounds such as organic acids and lipids. This is significantly different from the prior art's disclosure of nicotine, the main active ingredient in tobacco leaf extracts. The main components of root secretions are hydrocarbons, benzene, thiazole, acid, ketone, amide, ester, alcohol and phenol. The 33 compounds with relatively high content include 2 hydrocarbons (castorene, polyethylene oxide), 12 organic acids (l-2-amino-3-methyl-n-butyric acid, valeric acid, decanedioic acid, etc.), 2 ketones (jasmone, 6,7-dihydroxycoumarin), 2 amines (cyclohexylamine, dinitramide), 8 esters (2,4-pentadiene-4-lactone, S-hydroxymethyl thiobenzoate, isoamyl cinnamate, etc.), 1 alcohol (rosin alcohol), 1 phenol (6-gingerol), 1 pyrrole (2-acetylpyrrole), 1 base, 1 purine and 1 quinone.

[0066] Step 4: Determination of the insecticidal activity of tobacco root secretions against tobacco aphids

[0067] The tobacco root secretions collected and extracted in steps 1 and 2 during the vigorous growth period (equivalent to about 40 days after transplanting) were used to determine their insecticidal activity against tobacco aphids using leaf dipping and uniform spraying methods.

[0068] Leaf immersion method: Soak fresh young leaves in deionized water, ethyl acetate CK, ethyl acetate extracted tobacco root secretions, dichloromethane CK, and dichloromethane extracted tobacco root secretions for 5 seconds, remove and absorb excess tobacco root secretion extract with absorbent paper. Transfer 30 wingless tobacco aphids to each tobacco leaf, place the tobacco leaf in a petri dish for observation, use filter paper to absorb water and moisture at the root of the tobacco leaf, seal it with plastic wrap, and puncture 50 ventilation holes. Observe and count after 12h, 24h, and 48h, and record the survival of tobacco aphids. The results are shown in Table 4 and Figure 3 shown.

[0069] Table 4 Insecticidal activity of tobacco root secretions extracted with different extractants against tobacco aphids by soaking tobacco leaves (%

[0070]

[0071] From Table 4 and Figure 3 It can be seen that after the same treatment time (12, 24, and 48 hours), the mortality rate of tobacco aphids increased with the increase of tobacco root secretion treatment time. However, after 48 hours of treatment, the mortality rates of tobacco aphids caused by the CK group of ethyl acetate and the tobacco root secretions extracted with ethyl acetate were 88.8% and 94.5%, respectively. The difference between the two was not significant, and it was impossible to explain the contact killing effect of tobacco root secretions on tobacco aphids. After 48 hours of treatment, the mortality rates of tobacco aphids caused by the CK group of dichloromethane and the tobacco root secretions extracted with dichloromethane were 44.5% and 77.8%, respectively, and the insecticidal effect was good. However, after the immersion method, all the fresh tobacco leaves treated with dichloromethane and ethyl acetate withered, turned yellow, and dried up (such as Figure 3 This impregnation method is very harmful to tobacco leaves.

[0072] Uniform spraying method: Deionized water, ethyl acetate solvent (as a control), ethyl acetate extracted tobacco root secretions, dichloromethane CK, dichloromethane extracted tobacco root secretions were evenly sprayed on the surface of fresh tobacco leaves, and the solution on the leaf surface was evaporated and dried. 30 wingless tobacco aphids were transferred to each tobacco leaf, and the tobacco leaf was placed in a culture dish for observation, sealed with plastic wrap, and 50 ventilation holes were punctured with a needle. The number of observations and counts were carried out after 12h, 24h, and 48h, and the survival of tobacco aphids was recorded. The results are shown in Table 5 and Figure 4 shown.

[0073] Table 5 Insecticidal activity of tobacco root secretions extracted by spraying different extractants against tobacco aphids (%)

[0074]

[0075] As shown in Table 5, after the same treatment time (12, 24, and 48 hours), the extractant containing tobacco root secretions was significantly different from CK. When treated for 12 hours, 24 hours, and 48 hours, the mortality rates of tobacco aphids extracted from tobacco root secretions by dichloromethane were 19.3%, 28%, and 86.4%, respectively, with good insecticidal activity. The mortality rates of tobacco aphids extracted from tobacco root secretions by ethyl acetate were 23.1%, 36.1%, and 90.9%, respectively, with better insecticidal activity. However, the ethyl acetate solvent itself is also highly toxic to aphids. In comparison, dichloromethane is more effective as an extractant. This may be because the tobacco root secretions extracted by dichloromethane contain a high content of lipids and organic acids, which may be key substances for inhibiting aphids. The insecticidal activity of tobacco root secretions extracted by ethyl acetate and dichloromethane are significantly better than that of tobacco root secretions at the same concentration. In addition, from Figure 4 It can be seen that changing to a spraying method to spray dichloromethane and ethyl acetate to extract tobacco root secretions has no obvious effect on tobacco leaves.

[0076] Example 4

[0077] Determination of the insecticidal activity of tobacco root exudates extracted with dichloromethane at different concentrations against tobacco aphids

[0078] Further the tobacco root secretion of dichloromethane extraction is concentrated, then form the tobacco root secretion of dichloromethane extraction of higher variable concentrations, study its insecticidal activity to tobacco aphid.The 20mL dichloromethane organic phase liquid that obtains according to step 1 and step 2 among the embodiment 3 is put on the rotary evaporator and concentrate dry, then use the dichloromethane of different volumes (1mL, 2mL and 5mL) carry out constant volume dissolution, form the tobacco root secretion of dichloromethane extraction of variable concentrations.Adopt the uniform spraying method to measure its insecticidal activity to tobacco aphid then: respectively the extraction solution of the tobacco root secretion of the variable concentrations of dichloromethane solvent (in contrast), dichloromethane extraction is evenly sprayed on the fresh tobacco young leaf blade surface, after the solution volatilization on the leaf surface does.Pipette 30 wingless tobacco aphids on each tobacco leaf, tobacco leaf is put into culture dish and observes, with preservative film sealing, 50 acupuncture vents. Observation and counting were performed after 12 h, 24 h, and 48 h, and the survival of the tobacco aphids was recorded. The survival of the tobacco aphids was recorded. The results are shown in Table 6.

[0079] Table 6 Insecticidal activity of tobacco root secretions extracted by spraying different concentrations of dichloromethane against tobacco aphids (%)

[0080]

[0081] As shown in Table 4, the insecticidal activity of different concentrations of dichloromethane-extracted tobacco root secretions against Myzus persicae (Pseudomonas aeruginosa) was significantly improved after concentration of dichloromethane-extracted tobacco root secretions. When the volume was 5 mL, the mortality rates against Myzus persicae (Pseudomonas aeruginosa) after treatment for 12, 24, and 48 hours were 86%, 94%, and 100%, respectively, demonstrating excellent insecticidal activity. Aphid mortality rates increased significantly with increasing concentrations. When the volume was 2 mL and 1 mL, the mortality rates against Myzus persicae (Pseudomonas aeruginosa) after treatment for 12, 24, and 48 hours were 100%, 100%, and 100%, respectively, demonstrating highly significant insecticidal activity.

[0082] In summary, when different solvents are used as extractants to extract tobacco root secretions in the present invention, there are significant differences in the components of the root secretions. Among them, the dichloromethane extraction method detects the most types of compounds, especially hydrocarbons; the ethyl acetate extraction method detects more organic acids and lipids. Tobacco root secretions have a certain toxic and inhibitory effect on tobacco aphids, and this toxic effect becomes more obvious as time goes by. In experiments with different extraction reagents, the insecticidal activity of tobacco root secretions extracted with ethyl acetate against aphids is higher than that extracted with dichloromethane, but the insecticidal activity of ethyl acetate solvent itself against aphids is also very large (i.e., the control experiment), while the insecticidal activity of dichloromethane solvent itself against aphids is relatively small. When sprayed, the tobacco root secretions extracted with dichloromethane have good insecticidal activity against aphids.

[0083] The foregoing description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. Any person skilled in the art may, without departing from the spirit and technical solutions of the present invention, utilize the methods and technical contents disclosed above to make numerous possible variations and modifications to the technical solutions of the present invention, all of which fall within the scope of the present invention.

Claims

1. Application of tobacco root secretion extract in preventing and controlling tobacco aphid disease, characterized in that: The preparation method of tobacco root secretion extract comprises: extracting and concentrating tobacco root secretion with a solvent; the solvent is ethyl acetate or dichloromethane; and the volume ratio of the solvent to the tobacco root secretion is 0.5-1.5:

1.

2. The use according to claim 1, characterized in that The tobacco root secretion is obtained by the following method: washing the tobacco root part, placing it in a sealed light-proof container, adding deionized water, sealing it, culturing it at room temperature under natural light conditions for 1-3 days, and collecting the liquid to obtain the tobacco root secretion.

3. The use according to claim 1, characterized in that Add 20-80 mL of deionized water to each tobacco plant.

4. The use according to any one of claims 1 to 3, characterized in that The tobacco root exudates are extracted with a solvent and the resulting liquid is concentrated to 1-5 mL.

5. The use according to claim 4, characterized in that The application is to spray the tobacco root secretion extract on the tobacco leaves.

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