Application of tobacco root exudate extract in prevention and treatment of aphids

Abstract

The invention relates to the technical field of biopesticides, in particular to application of tobacco root exudate extract in prevention and treatment of aphid diseases of Chinese roses, tobaccos, wheat and cruciferous vegetables, and a preparation method of the tobacco root exudate extract comprises the following steps: extracting tobacco root exudate by adopting a solvent, and concentrating to obtain the tobacco root exudate extract; the solvent is ethyl acetate or dichloromethane; the volume ratio of the solvent to the tobacco root exudates is (0.5-1.5): 1. According to the invention, the dichloromethane extract of the tobacco root exudates is used for preventing and treating the plant aphids for the first time, the extract can effectively kill and inhibit the plant aphids, and the insecticidal activity rate of the extract on the plant aphids is gradually increased along with the increase of the concentration of the extract of the tobacco root exudates. The tobacco root exudates are derived from plants, are easy to degrade in nature, are safe to the environment, and do not pollute grains, and pests are not easy to generate 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 aphid, also known as green peach aphid, is an important pest in tobacco production and occurs in all major tobacco-growing areas in my country. Tobacco aphid is a widespread and rapidly reproducing pest that poses a serious threat to tobacco crops. Not only do they directly damage the plants by sucking the sap from the leaves and rhizomes of tobacco plants, they can also indirectly damage the plants by secreting honeydew, causing sooty mold and spreading tobacco virus diseases.

[0003] Chemical control is the most commonly used method in tobacco production because it is quick and effective. Long-term use of chemical pesticides to control tobacco aphids can easily cause tobacco aphids in a certain area to develop pesticide resistance and also cause problems such as pesticide residues and environmental pollution. Therefore, domestic and foreign researchers are committed to developing botanical insecticides.

[0004] For example, Chinese patent 202410424411.7 provides a botanical green pesticide for preventing and controlling aphids on crops and a preparation method thereof. The botanical green pesticide is prepared by extracting the following Chinese medicines 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 natural preservatives. The botanical green pesticide provided by the invention can effectively prevent and control aphid pests on crops. The content ratio of each component is reasonable, which can effectively exert the efficacy of the composition of the present invention in preventing and 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, and delays the generation of pest resistance and prolongs the persistence of the agent; its preparation process is simple and effective, green and harmless, and has good stability; the resulting concentrated solution reduces the amount of pesticide used and reduces agricultural costs.

[0005] Chinese Patent 202110163736.0 discloses the application of marigold volatile β-cyclohomocitral to control wolfberry aphids, wherein 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 application of the aphid control composition containing marigold volatiles in controlling wolfberry aphids. The invention provides experimental data support for the effective prevention and control of wolfberry aphids, the development of a new generation of efficient and environmentally friendly botanical pesticides, and a scientific basis for the further development and utilization of marigolds.

[0006] Chinese patent 202111260931.1 discloses a natural plant-derived pesticide, which is made of Euphorbia, Gourd vine, Ganoderma lucidum, Zhenlong root, tobacco, Jiucong root, Allium sibiricum, Corn, Chuanwu, Ziziphus jujuba, and Psoralea corylifolia. The invented natural plant-derived pesticide adopts the theory of monarch, minister, assistant and envoy in traditional Chinese medicine, and uses natural Chinese herbal medicine for reasonable compatibility. The components work synergistically, that is, they can strongly destroy the digestive system and metabolic function of pests, and also destroy the vagus nerve of pests and inhibit the respiratory system. It can kill all soft-bodied chewing pests and piercing and sucking pests; it has strong medicinal power, stable efficacy, long efficacy (not less than 14 days), and is easy to degrade, does not pollute the environment, has no odor, no residue, is pollution-free, green, safe, and environmentally friendly.

[0007] Existing technology (Feng Chao. Identification of tobacco root secretion components and their effects on tobacco phytophthora[J]. Anhui Agricultural Science, 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 isolates were less than 500 μg / mL, among which tartaric acid was the most potent with an EC50 value of 159.68 μg / mL.

[0008] However, there are no research 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 controlling and applying a tobacco root secretion extract to aphids.

[0010] In order to achieve the above object, the present invention adopts the following technical solution.

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

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

[0013] In one preferred embodiment, the tobacco root secretions are obtained by the following method: wash the tobacco root part, place it in a sealed light-proof container, add deionized water, seal it, and culture it at room temperature and natural light conditions for 1-3 days, collect the liquid, and obtain the tobacco root secretions.

[0014] In the process of cultivating the tobacco root secretions, a light-proof condition is selected, and light will degrade the root secretions.

[0015] In a preferred embodiment, the tobacco is preferably tobacco root secretions in the vigorous 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 solution for irrigation and soaking 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 system 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 under sunlight.

[0020] In a 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 fixed to 1-5 mL with dichloromethane solvent.

[0022] Based on the same invention, the present invention also claims to protect the 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 tobacco root secretion extract in preventing and controlling aphid diseases of 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 a 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 to protect an insecticide composition comprising the tobacco root secretion extract.

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

[0028] The present invention adopts the dichloromethane extract of tobacco root secretions for the first time to prevent and control plant pests aphids. The extract can effectively kill and inhibit aphids in plants. As the concentration of the tobacco root secretions extract increases, its insecticidal activity rate against aphids gradually increases. When the tobacco root secretions extract is concentrated to a fixed volume of 1-5 mL, its insecticidal activity rate is 100% at 24 hours. The tobacco root secretions extract is derived from the plant itself, is easily degraded in nature, is safe for the environment, does not pollute food, and pests are not easy to develop drug resistance. 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 graphs 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 by immersion;

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

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

[0034] Example 1

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

[0036] Step 1: Collection of tobacco root exudates

[0037] When the tobacco (variety K326) planted in the field grows to different stages (i.e., root extension stage, vigorous growth stage and mature stage), the tobacco plants with good growth status and uniform plant size are dug out from the field, and the integrity of the root system is maintained as much as possible. The tobacco root system is washed with clean water and then rinsed with deionized water. Each tobacco plant is placed in a 500mL beaker, and 20mL, 40mL, and 80mL of deionized water are added respectively. The beaker and the roots of the tobacco plants are completely wrapped with black plastic bags, and then placed in the sun for cultivation. The collected liquid is the crude extract of tobacco root secretions for 2 consecutive days. Each treatment is 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. Select fresh tobacco leaves of the same size and good growth, and soak them in the crude extract of tobacco root secretions collected in step 1 above for 5 seconds, 20mL, 40mL, and 80mL of deionized water, respectively. At the same time, a control test (only distilled water) was performed, and each treatment or control was repeated 3 times. Take out the excess crude extract of tobacco root secretions and absorb it with absorbent paper. Transfer 30 wingless tobacco aphids to each tobacco leaf, put the tobacco leaves in a culture dish for observation, use filter paper to absorb water and keep moisture at the roots of the tobacco leaves, seal them with plastic wrap, and puncture 50 ventilation holes with a needle. Observe and count after 12h, 24h, and 48h, and record the survival of tobacco aphids. (The death standard is that the tobacco aphid cannot move normally or there is no reaction when the insect body is gently touched with a needle). The mortality rate and corrected mortality rate are 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] Adjusted 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 of 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 collected by 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 collected in a volume of 20 mL, after treatment for 12 h, 24 h, and 48 h, the corrected mortality rates of tobacco aphids were 34.5%, 44.4%, and 57.7%, respectively. When the concentration of tobacco root secretions collected at the vigorous growth stage was collected in a volume of 20 mL, after treatment for 12 h, 24 h, and 48 h, the mortality rates of tobacco aphids were 37.6%, 47.6%, and 62.3%, respectively. The tobacco root secretions collected at the mature stage caused the mortality rates of tobacco aphids to be 36.6%, 45.5%, and 60.4%, respectively. This indicates that at a higher concentration, the crude extract of tobacco root secretions has a certain toxic and inhibitory effect on tobacco aphids, has a good insecticidal activity, and the toxic effect becomes more obvious with time. The insecticidal activity of tobacco root secretions collected at different times on tobacco aphids was different, and the insecticidal activity of tobacco root secretions collected during the vigorous growth period was the best. When the concentration was low (80 mL of tobacco root secretions collected), the crude extract of tobacco root secretions had a certain promoting effect on the growth of tobacco aphids. This may be because the low concentration of crude extract of tobacco root secretions provided nutrients for the growth, development and reproduction of tobacco aphids, which increased the number of tobacco aphids.

[0047] Example 2

[0048] Determination of insecticidal activity of crude extracts of tobacco root exudates at different concentrations against tobacco aphid

[0049] According to the experiment of Example 1, the concentration effect conclusion of low concentration of crude extract of tobacco root secretion is promoted and high concentration is suppressed. We will further test the crude extract of tobacco root secretion collected with 20mL deionized water in the vigorous period. We collected the crude extract of tobacco root secretion collected with 20mL deionized water in the vigorous period again, and then put it into a rotary evaporator to concentrate it to dryness, and used 0.5mL, 1mL and 2mL of deionized water to make up the volume, and configured it into different concentrations of tobacco root secretion to test tobacco aphid. The leaf immersion method was also used for determination. The fresh young leaves were soaked in deionized water (control), 2mL, 1mL, and 0.5mL of crude extract of tobacco root secretion for 5s, and the excess crude extract of tobacco analysis secretion 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. Observation and counting were carried out after 12h, 24h and 48h respectively, and the survival of tobacco aphids was recorded. The results are shown in Table 2 and 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 is the control, A, B, and C represent the tobacco root secretions fixed to volume with 0.5mL, 1mL, and 2mL of deionized water, respectively. The results show that different concentrations of crude extracts of tobacco root secretions have good toxicity to tobacco aphids, with mortality rates ranging from 13.0% to 81.0%. After the same treatment time (12, 24, and 48h), the mortality rate of tobacco aphids increased with the increase of the concentration of tobacco root secretions. When the fixed volume of tobacco root secretions was 0.5mL, the mortality rates of tobacco root secretions on tobacco aphids were 30.6%, 41.1%, and 81.0% after treatment for 12h, 24h, and 48h, respectively, and the insecticidal activity was good. When the fixed volume of tobacco root secretions was 2mL, the mortality rates of tobacco root secretions on tobacco aphids at different treatment times were 13.0%, 20.8%, and 54.3%, respectively, and the insecticidal activity was relatively poor. In addition, at the same concentration of tobacco root secretions, as the treatment time prolonged, the mortality rate of tobacco root secretions on tobacco aphids all showed an upward trend. And when the constant volume of tobacco root secretions was 0.5mL, the corrected mortality rate was significantly different from that of the control. This proves that tobacco root secretions have an inhibitory effect on the growth of tobacco aphids, and as the concentration increases, the inhibitory effect becomes stronger.

[0054] Example 3

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

[0056] Step 1 Collection of tobacco root secretions

[0057] When the tobacco (variety K326) planted in the field grows to 20 days and 40 days, dig out the tobacco plants with good growth status and uniform plant size from the field, and try to keep the integrity of the root system. Wash the tobacco root part with clean water, and then rinse it with deionized water. Put each tobacco plant in a 500mL beaker, add 20mL deionized water, and completely wrap the beaker and the roots of the tobacco plant with a black plastic bag, and then place it in the sun for cultivation. Collect it for 2 days continuously. The collected liquid is the tobacco root secretion.

[0058] Step 2 Extraction of tobacco root secretions

[0059] The multiple 20 mL of tobacco root secretions collected in step 1 were transferred to different pear-shaped separatory funnels, and the tobacco root secretions were extracted with ethyl acetate and dichloromethane, respectively, and the amount of extractant added was 1:1 in volume ratio to the tobacco root secretions. Then all 20 mL of ethyl acetate and dichloromethane organic phase liquids were collected.

[0060] Step 3 Identification of tobacco root exudate extracts

[0061] The tobacco root exudates were extracted by ethyl acetate and dichloromethane respectively, then concentrated to dryness by rotary evaporator under reduced pressure, and then diluted to 1.5 mL with chromatographic pure dichloromethane, and filtered through 0.45 μm organic filter membrane. The tobacco root exudates were qualitatively and quantitatively analyzed by Agilent 7890A / 5975C gas chromatograph-mass spectrometer (GC-MS). A DB-5ms capillary column (30m×0.25mm, coating thickness 0.25 μm) was used for chromatographic separation; the injection port temperature was set to 280; the column temperature program was 50 for 3 minutes, then heated to 290 at a rate of 10℃ / min and maintained for 20 minutes; the carrier gas was helium (He), with 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% between tobacco root secretions and the library and a relative content of more than 0.2% are shown in Table 3, and the total ion chromatogram is shown in Figure 2 .

[0062] Table 3 Main components of tobacco root secretions collected at different times extracted by different extractants

[0063]

[0064] Note: DCM-20d, DCM-40d, EAC-20d, and EAC-40d are the abbreviations for the tobacco root secretions collected at 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 2The results show that with the extension of tobacco growth period, the diversity and concentration of tobacco root secretions increased significantly. A total of 63 root secretions were identified and classified into hydrocarbons, lipids, phenols, organic acids, etc. In the first 20 days of growth, 30 and 14 tobacco root secretions were identified using dichloromethane (DCM) and ethyl acetate (EAC) extraction methods, respectively. By the 40th day, the types of root secretions increased to 54 and 33, respectively. There were significant differences in the extraction of tobacco root secretions by these two extractants, dichloromethane (DCM) and ethyl acetate (EAC). On the 20th day, tobacco root secretions extracted with DCM showed a wide spectrum of organic compounds, with hydrocarbons (19 species) and lipids (6 species) being the most abundant compounds. It is worth noting that 3-octyl methyl epoxyoctanoate accounted for the highest proportion, reaching 25.79%. Organic compounds lipids (7 species) dominated the 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-phthalic acid, di(2-methylpropyl) ester, 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), among which di(2-ethylhexyl) phthalate was the most common, accounting for 24.28%. The content of (Z)-docosa-9-enenitrile in the root exudates extracted by EAC was the highest, reaching 38.85%. The results showed that in all treatments, hydrocarbons, esters, phenols and organic acids accounted for about 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 extractant treatments, the method using DCM as the extraction solution detected the most types of tobacco root secretions, especially 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 and can effectively extract multiple components from the sample. On the other hand, EAC also showed excellent performance in the extraction of compounds such as organic acids and lipids. This is quite different from the nicotine, the main active ingredient in the tobacco leaf extract disclosed in the prior art. The main components of root secretions are hydrocarbons, benzene, thiazole, acid, ketone, amide, ester, alcohol and phenol. The 33 compounds with relatively high contents include 2 hydrocarbons (castorene and polyethylene oxide), 12 organic acids (l-2-amino-3-methylbutyric acid, valeric acid, decanedioic acid, etc.), 2 ketones (jasmone and 6,7-dihydroxycoumarin), 2 amines (cyclohexylamine and dinitramide), 8 esters (2,4-pentadiene-4-lactone, S-hydroxymethyl thiobenzoate, isopentyl 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 exudates against tobacco aphids

[0067] The tobacco root secretions collected and extracted in the above 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 by leaf dipping method and uniform spraying method.

[0068] Leaf immersion method: Soak fresh young leaves in deionized water, ethyl acetate CK, tobacco root secretions extracted with ethyl acetate, dichloromethane CK, and tobacco root secretions extracted with dichloromethane for 5 seconds, take out and absorb the excess tobacco root secretion extract with absorbent paper. Transfer 30 wingless tobacco aphids to each tobacco leaf, put the tobacco leaf in a culture dish for observation, use filter paper to absorb water and keep it moist 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 the treatment time of tobacco root secretions. However, at 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. At 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 became dry (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, and dichloromethane extracted tobacco root secretions were evenly sprayed on the surface of fresh tobacco leaves, and the solution on the leaf surface evaporated. 30 wingless tobacco aphids were transferred to each tobacco leaf, and the tobacco leaves were placed in a culture dish for observation, sealed with plastic wrap, and 50 vents were punctured with a needle. Observation and counting 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] It can be seen from Table 5 that after the same treatment time (12, 24, and 48h), the extract containing tobacco root secretions was significantly different from CK. When treated for 12h, 24h, and 48h, the mortality rates of tobacco aphids extracted with dichloromethane were 19.3%, 28%, and 86.4%, respectively, with good insecticidal activity. The mortality rates of tobacco aphids extracted with ethyl acetate were 23.1%, 36.1%, and 90.9%, respectively, with better insecticidal activity, but 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 with dichloromethane have a high content of lipids and organic acids, which may be key substances for inhibiting aphids. Moreover, the insecticidal activity of tobacco root secretions extracted with 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 insecticidal activity of tobacco root exudates extracted with dichloromethane at different concentrations against tobacco aphid

[0078] Further the tobacco root secretion of dichloromethane extraction is concentrated, then the tobacco root secretion of dichloromethane extraction of higher different concentrations is formed, and its insecticidal activity to tobacco aphid is studied.According to the 20mL dichloromethane organic phase liquid obtained in step 1 and step 2 among embodiment 3, be put on rotary evaporator and concentrate dry, then carry out constant volume dissolution with dichloromethane of different volumes (1mL, 2mL and 5mL), form the tobacco root secretion of dichloromethane extraction of different concentrations.Then adopt uniform spraying method to measure its insecticidal activity to tobacco aphid: respectively the extraction solution of tobacco root secretion of dichloromethane solvent (as contrast), dichloromethane extraction of different concentrations is evenly sprayed on fresh tobacco tender leaf blade surface, after the solution on the leaf surface evaporates dry.Take 30 wingless tobacco aphids on each tobacco leaf, tobacco leaf is put into culture dish and observed, sealed with plastic wrap, 50 acupuncture vents. Observation and counting were carried out after 12h, 24h and 48h respectively, and the survival of tobacco aphids was recorded. The survival of 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 dichloromethane-extracted tobacco root secretions were concentrated to form different concentrations of dichloromethane-extracted tobacco root secretions, which had significantly improved the insecticidal activity efficiency against tobacco aphids. When the constant volume was 5 mL, the mortality rates of tobacco aphids extracted by dichloromethane after treatment for 12 h, 24 h, and 48 h were 86%, 94%, and 100%, respectively, and the insecticidal activity was very good. With the increase of concentration, the mortality rate of aphids increased significantly. When the constant volume was 2 mL and 1 mL, the mortality rates of tobacco aphids extracted by dichloromethane after treatment for 12 h, 24 h, and 48 h were 100%, 100%, and 100%, respectively, and the insecticidal activity was very significant.

[0082] In summary, when different solvents are used as extractants to extract tobacco root secretions, the composition of the root secretions is significantly different. 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 certain toxic and inhibitory effects 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 by ethyl acetate on aphids is higher than that extracted by dichloromethane, but the insecticidal activity of ethyl acetate solvent itself (i.e., control experiment) on aphids is also very large, while the insecticidal activity of dichloromethane solvent itself on aphids is relatively small. When sprayed in a spraying manner, the tobacco root secretions extracted by dichloromethane have good insecticidal activity on aphids.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any form. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and technical solution of the present invention, which should all fall within the scope of the present invention.

Claims

1. Application of tobacco root secretion extracts in the prevention and control of aphid diseases in roses, tobacco, wheat and cruciferous vegetables.

2. The use according to claim 1, 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.

3. 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, The tobacco root secretions are obtained by culturing the tobacco root secretions at room temperature and under natural light for 1-3 days and collecting the liquid.

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

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

6. The use according to claim 5, characterized in that: The application is to spray the tobacco root secretion extract on the leaves of roses, tobacco, wheat and cruciferous vegetables.

7. The use according to claim 5, characterized in that: The application is to soak the leaves of rose, tobacco, wheat and cruciferous vegetables in the tobacco root secretion extract.

8. An aphid-killing composition, characterized in that: It includes tobacco root exudate extract.

9. The aphid-killing composition according to claim 8, 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.

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