Preparation and application of spraying type chitosan-based liquid film agent for physically blocking plant pests

Abstract

The invention provides preparation and application of a spraying type chitosan-based liquid film agent for physically blocking plant pests, and belongs to the technical field of pest control. The chitosan-based liquid film agent comprises chitosan and a film-forming aid, the film-forming aid comprises sodium carboxymethyl cellulose or konjac powder, the mass ratio of the chitosan to the film-forming aid is (1-4): (1-4), and the concentration of the chitosan-based liquid film agent is 0.1-2%. The chitosan-based liquid film agent disclosed by the invention can be used for quickly forming a film and effectively blocking pests without influencing normal photosynthesis of plants, so that on one hand, a physical isolation and protection technology is provided for the plants, and on the other hand, the agricultural production cost is reduced and the environmental pollution is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pest control, and particularly relates to preparation and application of a spraying type chitosan-based liquid film agent for physically blocking plant pests. BACKGROUND

[0002] In the production process of vegetables and fruit trees, traditional physical isolation means of pests can be divided into three categories according to the action position: one is to form a physical barrier in the periphery, such as a mosquito net and a greenhouse tent technology; two is a bagging technology located on the surface of the plant, and three is a mulching film technology which plays a role on the surface of the soil.

[0003] Bagging technology originated in Japan in the early 20th century, mainly to prevent the apple and grape on the borer. Similar simple bagging means in our country before and after the founding of new China appeared small-scale use and promotion, but with the popularization and application of high-efficiency pesticides and mechanical spraying, it once shrunk, only in the prevention of apple rust was paid attention to (Wang Shaomin, Gao Huajun. Fruit tree bagging key technology atlas. Shandong: Science and Technology Press, 2002.). This phenomenon has continued until the reform and opening up, in order to adapt to the increasingly competitive fruit market, to cultivate higher appearance quality of fruit, Japan and South Korea mature bagging technology system was introduced again. The scientific bagging cultivation technology of fruit trees and fruit vegetables and its effect mechanism were also opened (Chen Zhijie, Zhang Shulian, Liang Yinli, Zhang Feng, Xu Fulie, Yan Yongdang. Effect evaluation of fruit vegetables bagging technology. Northwest Plant Science, 2004 (05): 850-854.; Wang Guiping, Xue Xiaomin, Wang Jinzheng. Research progress and development trend of apple bagging technology in China. Hebei Agricultural Sciences, 2021, 25 (04): 44-48.). In addition to preventing various borer, bagging can significantly control the damage of fruit fly, Helicoverpa armigera and other insects (Liang Fan, Liang Guangqin, Zhao Jupeng, Zhou Qingxian, Hu Xuedan, Liu Zhibin, Ouyang Hanquan, Liang Zhenyu. Occurrence and comprehensive prevention and control measures of Bactrocera dorsalis in Guangzhou area. Guangdong Agricultural Sciences, 2008 (03): 58-61.; Li Jingrui. Investigation and prevention and control of main diseases and pests of grape in Zhumadian area. [Master's thesis]. Hebei University of Engineering, 2017.; Ma Qi, Zhang Ruiping, Chen Yaohua, Luo Shi, Zeng Xinian. Biological characteristics and comprehensive prevention and control of guava fruit fly. Guangdong Agricultural Sciences, 2010, 37 (08): 131-135.); The prevention of diseases mainly embodies the prevention of the damage of anthracnose, alternaria disease, fruit rot and other air-borne diseases to the fruiting part (Li Baohua, Wang Caixia, Dong Xiangli. Research progress of main apple diseases in China and problems in disease control. Plant Protection, 2013, 39 (05): 46-54.; Bi Runxia, Hao Zhaoxiang, Chen Ying, Wang Qingjun, Ma Min. Occurrence and prevention of common diseases of pomegranate fruit. Deciduous Fruit Trees, 2018, 50 (06): 68-69.; Buganic Jr R D, Lizida M C C, De Ramos M B. Disease control in Philippine‘carabao’ mango with preharvest bagging and postharvest hot water treatment. Acta Horticulturae, 1997, 455: 797-780.).Currently, paper bags, plastic film bags, and non-woven bags are commonly used (Zhang S Y. Fruit bagging types and performance. Shanxi Fruit Trees, 2003(03): 45.; Wang G P, Xue X M, Wang J Z. Research progress and development trend of apple bagging technology application in China. Hebei Agricultural Sciences, 2021, 25(04): 44-48.). Due to the isolation of bagged fruits from the outside world, the contact between fruits and pesticides is greatly reduced, and the pursuit of non-pollution or high-quality fruits often leads to the indirect reduction of the use of chemical pesticides and the chemical pesticide residues on the fruit skin (Liu J H, Li B Z, Zhang L S, Li H H, Tan B J. Effects of bagging on fruit quality and pesticide residues of red fuji apple. Journal of Northwest Sci-Tech University of Agriculture and Forestry (Natural Science Edition), 2003, 31: 16-18, 21.; Chen Q Q, Wang X S, Zhao Y Y, Xing T T, Zhang Z C. Effects of peach fruit bagging on the deposition and distribution of six typical pesticides and residues. Journal of Pesticide Science, 2021, 23(06): 1205-1212.). In addition to controlling diseases and pests, physical isolation caused by fruit bagging also has other positive significance. Because bagging affects air circulation, it changes the temperature, humidity, and light conditions in the fruit bag, so reasonable bagging management has a significant improvement effect on the appearance of fruits (Chen Z J, Zhang S L, Liang Y L, Zhang F, Xu F L, Yan Y G. Fruit and vegetable bagging technology effect evaluation. Acta Botanica Boreali-Occidentalia Sinica, 2004(05): 850-854.). Stable microenvironment significantly reduces the occurrence of fruit distortion, while light protection significantly reduces the browning of fruits caused by sunburn, and the fruit skin is smoother and more delicate, with fewer epidermal fruit points (Zhang J G. Apple (Malus domestica Borkh.) fruit sunburn causes, mechanisms and prevention. [PhD thesis]. Hebei Agricultural University, 2005.; Gong M Y, Zhang F M. Reasons and countermeasures affecting the quality of bagged apples. Shanxi Fruit Trees, 2002(02): 26-27.). Therefore, bagging technology is more in line with consumers' pursuit of agricultural product safety and appearance quality, and is more in line with the trend of green prevention and control.

[0004] However, the rural population is aging, and the cost of manual bagging is increasing (Feng G T. Orchard cost and labor situation investigation and analysis in Zhuanglang County. Fruit Farmer, 2012(04): 34-35.). The white pollution caused by bagging and the consumption of wood and chemical products are contrary to the ecological concept (Wang C X, Liu H L, Yang L. Prospects and countermeasures for apple bagless cultivation. Modern Agricultural Science and Technology, 2013(15): 122-123.). In this context, the development and application of "spray film-forming plant pest physical barrier" are simpler than traditional bagging operations, have fewer uncertain factors of damaging fruits, and have the potential to replace traditional bagging.

[0005] It is found that high-fat film has obvious inhibitory effect on diseases such as powdery mildew, annular disease, anthracnose, rust and the like on vegetables, fruits and flowers, and therefore is applied in the storage and transportation process of fruits to play the function of preservative (Hu Liang. Preliminary report on the application of non-toxic high-fat film in the storage and preservation of citrus fruits. China Citrus, 1984, (04): 9-10.; Qu Zezhou, Li San-kai, Wu Yuansu, Sun Pingfei, Hu Jingping. Experimental technology for the storage and preservation of jujube. Chinese Journal of Agricultural Sciences, 1987, (02): 86-91.; Deng Dinghui. Application of high-fat film in plant protection. Agricultural Technology Service, 2001, (10): 20-21.; Zhou Haisheng, Yang Weijun, Ding Chaoying. Efficiency test of "new high-fat film powder" in the storage and preservation of Xiangxi ponkan. Hunan Agricultural Sciences, 2016 (12): 66-67+72.) With the in-depth study of high-fat film, the potential of the film bag is further revealed. Compared with the paper bag treatment, the apple treated with the high-fat film liquid film bag is better in appearance quality such as color rate and brightness, and the internal nutrient composition and flavor are also significantly improved due to the increase of flavonoids and total phenol content (Li Aimei. Effect of high-fat film liquid film bag on the quality and aroma of apple fruit. [Master's thesis]. Northwest A&F University, 2018.). However, whether the high-fat film can replace the traditional bagging effect of insect prevention still lacks systematic theoretical support. SUMMARY

[0006] Therefore, the present application aims to provide a preparation and application of a spraying type chitosan-based liquid film agent for physically blocking plant pests, and comprehensively evaluate the film-forming physical properties, pest blocking activity and plant protection effect. On the one hand, it provides a physical isolation and protection technology for plants, and on the other hand, it reduces the cost of agricultural production and reduces environmental pollution.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The present application provides a chitosan-based liquid film agent, which comprises chitosan and a film-forming aid, and the film-forming aid comprises sodium carboxymethyl cellulose or konjac powder.

[0008] Preferably, the mass ratio of the chitosan and the film-forming aid is 1-4:1-4.

[0009] Preferably, the concentration of the chitosan-based liquid film agent is 0.1-2%.

[0010] The present application also provides a preparation method of the chitosan-based liquid film agent, which comprises the following steps: (1) mixing chitosan and water to obtain a chitosan aqueous solution; (2) mixing a film-forming aid and water to obtain a dispersion liquid; (3) mixing the chitosan aqueous solution and the dispersion liquid to obtain the chitosan-based liquid film agent.

[0011] The application further provides application of the chitosan-based liquid film agent or the chitosan-based liquid film agent prepared by the preparation method in blocking plant pests.

[0012] Preferably, the plant pests include small sap-sucking pests, and the small sap-sucking pests include aphids, thrips and red spiders.

[0013] Compared with the prior art, the application has the following beneficial effects: The chitosan-based liquid film agent can quickly form a film, effectively block pests and does not affect the normal photosynthesis of plants, thereby providing physical isolation and protection technology for plants, reducing agricultural production costs and environmental pollution.

[0014] The application explores the film forming effect of chitosan as a film forming agent mixed with four kinds of film forming aids, and detects the film thickness and the blocking effect on plant pests. When the same concentration is used, the film formed by sodium carboxymethyl cellulose + chitosan is thicker, and the konjac powder + chitosan film is the second. Based on chitosan, 0.5% chitosan: sodium carboxymethyl cellulose film forming liquid is configured, and the blocking effect on pea aphids is the best when the ratio of the two is 1:1. When different treatment times are used, the blocking effect of chitosan combined with sodium carboxymethyl cellulose is the best, the blocking effect of chitosan combined with konjac powder is the second, and the blocking effect of chitosan combined with sodium carboxymethyl cellulose and konjac powder is significantly higher than that of the control when the treatment time is 24 hours. The influence of different film agents on the photosynthesis of the host plant of pea aphids is not significantly different. Therefore, two kinds of chitosan-based film forming type plant pest physical blocking agents are obtained, which are chitosan combined with sodium carboxymethyl cellulose and chitosan combined with konjac powder, and can be popularized and applied subsequently. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic diagram of film forming of different liquid film agents at a concentration of 0.5% (note: from left to right, high-fat film, sodium carboxymethyl cellulose + chitosan, konjac powder + chitosan, sodium alginate + chitosan, and gum arabic + chitosan); Figure 2 is the film thickness of film forming of different liquid film agents at different concentrations; Figure 3 is a leaf disc method detail display; Figure 4 is the blocking effect of different ratios of chitosan-based spraying films on aphids; Figure 5 is the blocking effect of different liquid film agents on aphids after different treatment times; Figure 6 is the blocking effect of different liquid film agents on aphids after 24 hours of treatment; Figure 7 is the influence of different film agents on the net photosynthetic rate of broad bean seedlings. Detailed Implementation

[0016] The present invention provides a chitosan-based liquid film agent, comprising chitosan and a film-forming aid, wherein the film-forming aid comprises sodium carboxymethyl cellulose or konjac flour.

[0017] In this invention, the mass ratio of chitosan to film-forming agent is preferably 1-4:1-4, more preferably 1:1; the concentration of chitosan-based liquid film agent is preferably 0.1-2%, more preferably 0.2-1%, and even more preferably 0.5%.

[0018] The present invention also provides a method for preparing the chitosan-based liquid film agent, comprising the following steps: (1) Mix chitosan and water to obtain a chitosan aqueous solution; (2) Mix the film-forming agent and water to obtain a dispersion; (3) Mix the chitosan aqueous solution and the dispersion to obtain the chitosan-based liquid film agent.

[0019] This invention also provides the application of the chitosan-based liquid film agent or the chitosan-based liquid film agent prepared by the aforementioned preparation method in the blocking of plant pests. In this invention, the chitosan-based liquid film agent is applied by spraying; the plant pests include the pea aphid.

[0020] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0021] The instruments, equipment, and consumables involved in this invention include: a magnetic stirrer, glass rod, glass slides, spray bottle, micrometer, analytical balance, measuring cup, and commercially available high-lipid film powder, potassium humate, konjac flour, gum arabic, chitosan, sodium alginate, sodium carboxymethyl cellulose, and agar powder. The broad bean seedlings were self-grown. Transparent cellophane, petri dishes, and a hole punch were also used in the experiment.

[0022] Example 1

[0023] A chitosan-based liquid film agent is composed of chitosan and sodium carboxymethyl cellulose, wherein the mass ratio of chitosan to sodium carboxymethyl cellulose is 1:1, and the concentration of the chitosan-based liquid film agent is 0.5%.

[0024] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0025] Example 2

[0026] A chitosan-based liquid film agent is composed of chitosan and sodium carboxymethyl cellulose, wherein the mass ratio of chitosan to sodium carboxymethyl cellulose is 2:1, and the concentration of the chitosan-based liquid film agent is 0.1%.

[0027] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0028] Example 3

[0029] A chitosan-based liquid film agent is composed of chitosan and sodium carboxymethyl cellulose, wherein the mass ratio of chitosan to sodium carboxymethyl cellulose is 4:1, and the concentration of the chitosan-based liquid film agent is 0.2%.

[0030] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0031] Example 4

[0032] A chitosan-based liquid film agent is composed of chitosan and sodium carboxymethyl cellulose, wherein the mass ratio of chitosan to sodium carboxymethyl cellulose is 1:2, and the concentration of the chitosan-based liquid film agent is 1%.

[0033] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0034] Example 5

[0035] A chitosan-based liquid film agent is composed of chitosan and sodium carboxymethyl cellulose, wherein the mass ratio of chitosan to sodium carboxymethyl cellulose is 1:4, and the concentration of the chitosan-based liquid film agent is 2%.

[0036] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0037] Example 6

[0038] A chitosan-based liquid film agent is composed of chitosan and konjac flour, wherein the mass ratio of chitosan to konjac flour is 1:1, and the concentration of the chitosan-based liquid film agent is 0.5%.

[0039] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0040] Example 7

[0041] A chitosan-based liquid film agent is composed of chitosan and konjac flour, wherein the mass ratio of chitosan to konjac flour is 2:1, and the concentration of the chitosan-based liquid film agent is 0.1%.

[0042] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0043] Example 8

[0044] A chitosan-based liquid film agent is composed of chitosan and konjac flour, wherein the mass ratio of chitosan to konjac flour is 4:1, and the concentration of the chitosan-based liquid film agent is 0.2%.

[0045] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0046] Example 9

[0047] A chitosan-based liquid film agent is composed of chitosan and konjac flour, wherein the mass ratio of chitosan to konjac flour is 1:2, and the concentration of the chitosan-based liquid film agent is 1%.

[0048] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0049] Example 10

[0050] A chitosan-based liquid film agent is composed of chitosan and konjac flour, wherein the mass ratio of chitosan to konjac flour is 1:4, and the concentration of the chitosan-based liquid film agent is 2%.

[0051] The preparation method of the chitosan-based liquid film agent is as follows: (1) Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; (2) Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; (3) Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent.

[0052] Experimental Example 1

[0053] Comparison of film formation and film thickness of different liquid film-forming agents

[0054] The specific steps are as follows: (1) Use a spiral micrometer to measure the initial thickness of the glass slide. Select five areas for measurement: four right angles and the center of each slide.

[0055] (2) Prepare high-lipid film aqueous solutions with concentrations of 0.1%, 0.2%, 0.5%, 1%, and 2%, and four chitosan-based film-forming solutions (the mass ratio of chitosan to film-forming agent is 1:1). The preparation method of the chitosan-based film-forming solutions is as follows: ① Add chitosan to water and stir until the chitosan is completely dissolved to obtain a chitosan aqueous solution; ② Disperse the film-forming agent in water and stir until uniform to obtain a dispersion; ③ Mix the two thoroughly and stir until the system is homogeneous to obtain the chitosan-based liquid film agent. Stir the prepared film-forming solution for 20 minutes and then pour it into a spray bottle.

[0056] (3) Spray the film-forming liquid evenly onto the glass slide with a spray bottle and put it into the oven to dry for 2 hours.

[0057] (4) Remeasure the thickness and record the experimental data.

[0058] Experimental results: such as Figure 1 and Figure 2 As shown. By Figure 1 It can be seen that all four materials used can form films when mixed with chitosan, but the film thicknesses differ. From Figure 2 It can be seen that, when sprayed at the same concentration, the thickness of sodium carboxymethyl cellulose + chitosan film and konjac flour + chitosan film is significantly higher than that of the new high-lipid film, sodium alginate + chitosan film and gum arabic + chitosan film. (Multiple comparison tests, p<0.05). When sprayed at a 0.5% concentration, the film thicknesses of the two were approximately 44.4 μm and 31.8 μm, respectively, which were 2.65 times and 3.70 times the thickness of the new high-lipid film. Therefore, it is inferred that the mixture of chitosan and sodium carboxymethyl cellulose or konjac flour has a better barrier effect against pests.

[0059] Experimental Example 2

[0060] Tests on the barrier effect of liquid film spraying agents with different mass ratios on pea aphids.

[0061] Test material: pea aphid Acrythosiphon pisum It is an indoor multi-generation breeding population.

[0062] The barrier effect of the film on aphids was tested using the leaf dish method. The specific steps for preparing the leaf dishes are as follows: Take a 9cm diameter petri dish, pour in an appropriate amount of 1.5% agar hydrothermal solution, and allow it to cool and solidify. Prepare leaf discs (1.5cm in diameter) using a perforator, and place the leaf discs into the aforementioned petri dishes, with two leaves from the treatment group and two from the control group in each dish, randomly distributed. Prepare perforated transparent cellophane, punching four evenly distributed holes (1.0cm in diameter) in the cellophane, referencing the positions of the leaf discs in the petri dish. Cover the petri dish with the perforated transparent cellophane, leaving only four leaf discs exposed. Details of the leaf dish method are shown below. Figure 3 As shown.

[0063] Considering that the plant epidermis is the main line of defense against aphid penetration, and the thinnest herbaceous plant epidermis is 0.01 mm thick, to ensure that each film-forming agent can completely adhere to the epidermis and play a certain defensive role, it can be considered that the thickness of the film-forming agent should be at least 0.01 mm to conservatively assume that the film-forming agent may have a defensive effect. Therefore, 0.5% was chosen as the lowest concentration at which various film-forming agents may have a control effect for further exploration. Following the method in Experiment 1, a 0.5% film-forming solution of chitosan and sodium carboxymethyl cellulose was prepared, with different ratios including 1:4, 1:2, 1:1, 2:1, and 4:1. The film solution was evenly applied to broad bean seedling leaves, with 6 replicates for each treatment. Water was applied to other leaves as a blank control. After the film solution was completely air-dried, leaves were harvested and leaf discs (1.5 cm in diameter) were made using a perforator. Once the leaf discs were prepared, adult aphids starved for 6 hours were inoculated into the leaf discs, with 15 aphids in each disc. Cover the petri dish and invert it into a constant temperature incubator (temperature (25±1)℃, relative humidity (60±5)%). Count the number of aphids on each leaf at 4, 8, 12, 16, 20 and 24 hours and calculate the barrier index.

[0064]

[0065] Experimental results: such as Figure 4 As shown, a 0.5% film-forming solution of chitosan and sodium carboxymethyl cellulose was prepared based on chitosan. Different ratios of chitosan and sodium carboxymethyl cellulose included 1:4, 1:2, 1:1, 2:1, and 4:1. The prepared round leaves showed the best aphid-blocking effect within 24 hours at a ratio of 1:1, with a highly significant difference compared to other treatment groups (p<0.01). Therefore, a ratio of 1:1 was determined to be the most suitable for subsequent use.

[0066] Experimental Example 3

[0067] Testing the barrier effect of different types of liquid film spraying agents on pea aphids

[0068] Five aqueous solutions of film-forming agents with a total mass fraction of 0.5% were prepared (high-lipid film, chitosan + gum arabic, chitosan + konjac flour, chitosan + sodium alginate, and chitosan + sodium carboxymethyl cellulose; when two film-forming agents were used, their mass fraction ratio was 1:1). The barrier effect against pea aphids was determined according to the leaf dish method in Experiment Example 2.

[0069] Experimental results: such as Figure 5 and Figure 6 As shown.

[0070] Depend on Figure 5It was found that, at different treatment times, chitosan combined with sodium carboxymethyl cellulose consistently exhibited the best blocking effect, while chitosan combined with sodium alginate showed the worst effect. The P-values ​​for treatment times of 4, 8, 12, 16, 20, and 24 hours were 0.0005, 0.0255, 0.0321, 0.0425, 0.0124, and 0.0307, ​​respectively. Chitosan combined with konjac flour showed the second best blocking effect, significantly different from that of chitosan combined with sodium alginate. The P-values ​​for treatment times of 4, 8, 12, 16, 20, and 24 hours were 0.0051, 0.0005, 0.0003, 0.0095, 0.0162, and 0.0408, respectively. While chitosan combined with gum arabic was better than chitosan combined with sodium alginate, its effect was lower than the control at all treatment times except for 4 hours.

[0071] Depend on Figure 6 The barrier index of the control was 0.44 ± 0.02. The barrier effects of chitosan combined with sodium carboxymethyl cellulose and konjac flour were significantly higher than the control. The combination of chitosan and sodium carboxymethyl cellulose showed the best barrier effect, 1.55 times that of the control, and significantly higher than the combination of chitosan and konjac flour, by 15.25 percentage points. However, the effects of chitosan combined with gum arabic and sodium alginate were lower than the control. The barrier effect of chitosan combined with gum arabic was only 84.09% of the control, and the barrier effect of chitosan combined with sodium alginate was even worse, only 56.82% of the control.

[0072] Experiment Example 4

[0073] Detection of the effect of chitosan-based spray coating film on photosynthesis of pea aphid host plants

[0074] The method for determining the effect of film-forming agents on plant photosynthesis was as follows: Five pots of broad bean seedlings approximately 21 days old were taken, and five robust seedlings were selected from each pot. The third leaf from the bottom of each seedling was selected as the experimental subject. The net photosynthetic rate of each leaf was measured using a portable fluorescence photosynthesis measurement system LI-6800. Measurement conditions: temperature 26°C; relative humidity 50%; light intensity 1400 μmol·m⁻¹. -2 ·s- 1 Carbon dioxide release rate (CO2_s): 400 μmol·mol. The film agent was evenly applied to the marked leaves, with 5 replicates for each treatment. After air drying, the net photosynthetic rate of each leaf was measured again, and the relative change in net photosynthetic rate after each film agent treatment was calculated.

[0075] Experimental results: such as Figure 7 As shown, different film agents did not have a significant effect on the net photosynthetic rate of broad bean seedlings. P The value was 0.0568; the effects of chitosan-bound konjac flour and chitosan-bound sodium alginate on the net photosynthetic rate of broad bean seedlings were relatively small.

[0076] The chitosan-based liquid film agent of the present invention can form a film quickly, effectively blocking pests without affecting the normal photosynthesis of plants. On the one hand, it provides physical isolation and protection technology for plants, and on the other hand, it reduces agricultural production costs and environmental pollution.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A chitosan-based liquid film agent, characterized in that, It includes chitosan and a film-forming aid, wherein the film-forming aid includes sodium carboxymethyl cellulose or konjac flour.

2. The chitosan-based liquid film agent according to claim 1, characterized in that, The mass ratio of chitosan to film-forming agent is 1~4:1~4.

3. The chitosan-based liquid film agent according to claim 1, characterized in that, The concentration of the chitosan-based liquid film agent is 0.1-2%.

4. The method for preparing the chitosan-based liquid film agent according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Mix chitosan and water to obtain a chitosan aqueous solution; (2) Mix the film-forming agent and water to obtain a dispersion; (3) Mix the chitosan aqueous solution and the dispersion to obtain the chitosan-based liquid film agent.

5. The application of the chitosan-based liquid film agent according to any one of claims 1 to 3 or the chitosan-based liquid film agent prepared by the preparation method according to claim 4 in the blocking of plant pests.

6. The application according to claim 5, characterized in that, The plant pests include small sap-sucking pests, such as aphids, thrips, and spider mites.

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