Biological insecticide and preparation method thereof

Abstract

The invention relates to a biological insecticide and a preparation method thereof, and relates to the field of biological insecticides, the biological insecticide comprises the following components by weight: 15-20% of bacillus thuringiensis microcapsules, 5-10% of a wetting dispersant, and the balance of water, totaling 100%; the bacillus thuringiensis microcapsule is prepared from bacillus thuringiensis raw powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride and tannic acid according to the weight ratio of (5 to 10): (3 to 5): (1 to 1.5): (8 to 15): (4 to 8): (8 to 15): (1 to 2). The biological insecticide has the advantages that the ultraviolet resistance of the bacillus thuringiensis is improved, so that the insecticidal effect of the biological insecticide is improved.

Description

Technical Field

[0001] This application relates to the field of biological insecticides, and particularly to a biological insecticide and its preparation method. Background Art

[0002] Bacillus thuringiensis is the most studied, widely used, safe for humans and animals, and non - destructive to the ecological balance microbial insecticide in the world. Bacillus thuringiensis is a Gram - positive bacterium widely distributed in nature. Its prominent feature is that during the process of spore formation, it can produce parasporal crystal proteins. The parasporal crystal proteins are composed of one or more proteins and have highly specific insecticidal activity. This kind of protein is usually called insecticidal crystal protein. The parasporal crystal protein exists in the state of protoxin. When it enters the digestive tract of sensitive insects, it dissolves in an alkaline environment and is activated by protease into toxic polypeptides. The activated toxic polypeptides combine with the receptors on the brush border membrane of the midgut of insects and form pores on the cell membrane, destroying the osmotic balance of the cells, causing cell lysis, and ultimately leading to the death of larvae.

[0003] Bacillus thuringiensis has significant advantages as a biological insecticide. However, since the main insecticidal component of Bacillus thuringiensis is insecticidal crystal protein, its ability to resist ultraviolet rays and adverse environments is poor, resulting in disadvantages such as a short effective period and the control effect being easily restricted by external climatic and ecological conditions such as sunlight and temperature. Therefore, how to solve the problems of unstable drug efficacy and poor environmental adaptability of biological insecticides with Bacillus thuringiensis as the active ingredient has become an urgent problem to be solved in the development of biological insecticides. Summary of the Invention

[0004] In order to solve the above - mentioned technical problems, this application provides a biological insecticide and its preparation method.

[0005] A biological insecticide and its preparation method provided by this application adopt the following technical scheme: A biological insecticide is composed of the following components in weight ratio: 15 - 20% of Bacillus thuringiensis microcapsules, 5 - 10% of wetting and dispersing agents, and water is added to make up 100%; the Bacillus thuringiensis microcapsules include Bacillus thuringiensis original powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and tannic acid in a weight ratio of (5 - 10):(3 - 5):(1 - 1.5):(8 - 15):(4 - 8):(8 - 15):(1 - 2).

[0006] By adopting the above technical solution, the present application uses sodium alginate, whey protein, calcium chloride, and tannic acid as the wall materials of the microcapsules, and uses Bacillus thuringiensis powder, chlorbenzuron, and melanin as the core materials of the microcapsules to prepare Bacillus thuringiensis microcapsules with good environmental adaptability and ultraviolet resistance. Applying the Bacillus thuringiensis microcapsules to biological insecticides has a good and stable insecticidal effect.

[0007] When Bacillus thuringiensis and chlorbenzuron are used in combination, they give full play to the synergistic effect, so they have a good insecticidal effect. By adding melanin, the ultraviolet resistance of Bacillus thuringiensis is greatly improved, and the stability of Bacillus thuringiensis in the external environment is enhanced. By using sodium alginate, whey protein, calcium chloride, and tannic acid as the wall materials of the microcapsules, effective protection of Bacillus thuringiensis is achieved, further improving the ultraviolet resistance of the Bacillus thuringiensis microcapsules and further enhancing the stability of the Bacillus thuringiensis microcapsules in the external environment.

[0008] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and tannic acid with a weight ratio of 7:4:1.2:12:6:12:1.5. The prepared Bacillus thuringiensis microcapsules are applied to the preparation of biological insecticides, and the biological insecticides include 15% of Bacillus thuringiensis microcapsules, 10% of wetting and dispersing agents, and 75% of water.

[0009] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and chlorogenic acid with a weight ratio of 7:4:1.2:12:6:12:1.5. The prepared Bacillus thuringiensis microcapsules are applied to the preparation of biological insecticides, and the biological insecticides include 15% of Bacillus thuringiensis microcapsules, 10% of wetting and dispersing agents, and 75% of water.

[0010] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, chitosan, calcium chloride, and tannic acid with a weight ratio of 7:4:1.2:12:6:12:1.5. The prepared Bacillus thuringiensis microcapsules are applied to the preparation of biological insecticides, and the biological insecticides include 15% of Bacillus thuringiensis microcapsules, 10% of wetting and dispersing agents, and 75% of water.

[0011] Among them, the component composition of the Bacillus thuringiensis microcapsules prepared with the component ratio provided by this application has an encapsulation efficiency increased by 9.5 - 10.4% compared to the Bacillus thuringiensis microcapsules prepared with chlorogenic acid and chitosan, and the survival rate under ultraviolet irradiation increased by 13.5 - 15.4%, indicating that the Bacillus thuringiensis microcapsules provided by this application have higher ultraviolet resistance. The bio-insecticide prepared with the Bacillus thuringiensis microcapsules prepared with the component ratio provided by this application has a 48-hour insect mortality rate increased by 9.9 - 13.1% and a 72-hour insect mortality rate increased by 11.5 - 16% compared to the bio-insecticide prepared with the Bacillus thuringiensis microcapsules prepared with chlorogenic acid and chitosan, indicating that the bio-insecticide prepared with the Bacillus thuringiensis microcapsules provided by this application has better insecticidal effects.

[0012] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and tannic acid with a weight ratio of 5:5:1:15:4:15:1. And the prepared Bacillus thuringiensis microcapsules are applied to the preparation of a bio-insecticide, and the bio-insecticide includes 15% of the Bacillus thuringiensis microcapsules, 10% of a wetting and dispersing agent, and 75% of water.

[0013] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and tannic acid with a weight ratio of 7:4:1.2:12:6:12:1.5. And the prepared Bacillus thuringiensis microcapsules are applied to the preparation of a bio-insecticide, and the bio-insecticide includes 15% of the Bacillus thuringiensis microcapsules, 10% of a wetting and dispersing agent, and 75% of water.

[0014] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and tannic acid with a weight ratio of 8:3.5:1.3:10:7:10:1.8. And the prepared Bacillus thuringiensis microcapsules are applied to the preparation of a bio-insecticide, and the bio-insecticide includes 15% of the Bacillus thuringiensis microcapsules, 10% of a wetting and dispersing agent, and 75% of water.

[0015] In a specific embodiment, the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride, and tannic acid with a weight ratio of 10:3:1.5:8:8:8:2. And the prepared Bacillus thuringiensis microcapsules are applied to the preparation of a bio-insecticide, and the bio-insecticide includes 15% of the Bacillus thuringiensis microcapsules, 10% of a wetting and dispersing agent, and 75% of water.

[0016] Among them, the weight ratio of the Bacillus thuringiensis original powder, chlorbenzuron, melanin, sodium alginate, whey protein, calcium chloride and tannic acid being 7:4:1.2:12:6:12:1.5 is the optimal technical solution. Compared with other technical solutions, the encapsulation rate is increased by 4.4 - 5.3%, and the survival rate under ultraviolet irradiation is increased by 7.6 - 9.5%. This shows that the preferred value of the component ratio of the Bacillus thuringiensis microcapsule provided in this application has a better effect on improving the encapsulation rate and the survival rate under ultraviolet irradiation of the Bacillus thuringiensis microcapsule. Compared with other technical solutions, the mortality rate of test insects at 48 h is increased by 6.1 - 7.2%, and the mortality rate of test insects at 72 h is increased by 2.6 - 3.7%. This shows that the biological insecticide prepared from the Bacillus thuringiensis microcapsule prepared according to the preferred ratio of the component composition provided in this application has a better insecticidal effect.

[0017] Preferably, the preparation method of the Bacillus thuringiensis microcapsule includes the following steps: S1. Add the Bacillus thuringiensis original powder, chlorbenzuron and melanin into water, mix and stir evenly to obtain a bacterial suspension. Stir sodium alginate and tannic acid in water until dissolved, then mix with the bacterial suspension, with a stirring speed of 450 - 500 r / min, stir for 50 - 60 min to obtain a mixed solution. Slowly drop the mixed solution into the calcium chloride solution to obtain a suspension, and obtain a precipitate as an intermediate product through multiple centrifugal filtrations; S2. Dissolve whey protein in water to obtain a whey protein solution with a concentration of 0.8 - 1.2 wt%. Adjust the pH to 4.8 - 5.2 with acetic acid. Mix the intermediate product obtained in step S1 with the whey protein solution, with a stirring speed of 450 - 500 r / min, stir for 40 - 50 min, then centrifuge, filter and freeze-dry to obtain the Bacillus thuringiensis microcapsule.

[0018] By adopting the above technical solution, in this application, the Bacillus thuringiensis original powder, chlorbenzuron and melanin are initially encapsulated by sodium alginate and tannic acid, and then secondarily encapsulated by whey protein, thereby improving the structural stability of the Bacillus thuringiensis microcapsule, enabling the Bacillus thuringiensis microcapsule to have good ultraviolet resistance, and further improving the insecticidal effect of the biological insecticide in the external environment.

[0019] In a specific embodiment, the concentration of the calcium chloride solution in step S1 is 1 wt%.

[0020] In a specific embodiment, the concentration of the calcium chloride solution in step S1 is 1.5 wt%.

[0021] In a specific embodiment, the concentration of the calcium chloride solution in step S1 is 1.8 wt%.

[0022] In a specific embodiment, the concentration of the calcium chloride solution in step S1 is 2 wt%.

[0023] In a specific embodiment, the concentration of the calcium chloride solution in step S1 is 2.5 wt%.

[0024] In a specific embodiment, the concentration of the calcium chloride solution in step S1 is 3 wt%.

[0025] Among them, when the concentration of the calcium chloride solution is in the range of 1.5 - 2.5 wt%, the encapsulation rate of the Bacillus thuringiensis microcapsules prepared is increased by 5.7 - 6.8% compared with those prepared outside the range, and the survival rate under ultraviolet irradiation is increased by 6.9 - 8.3%. This shows that the concentration range of the calcium chloride solution provided in this application has a good effect on improving the ultraviolet resistance of the Bacillus thuringiensis microcapsules.

[0026] The concentration of the calcium chloride solution being 2 wt% is the optimal technical solution. Compared with the Bacillus thuringiensis microcapsules prepared by other technical solutions within the range of 1.5 - 2.5 wt%, the encapsulation rate is increased by 7 - 7.5%, and the survival rate under ultraviolet irradiation is increased by 11.1 - 11.8%. This shows that the preferred value of the concentration of the calcium chloride solution provided in this application has a better effect on improving the ultraviolet resistance of the Bacillus thuringiensis microcapsules.

[0027] In a specific embodiment, the concentration of sodium alginate in the mixed solution is 1 wt%.

[0028] In a specific embodiment, the concentration of sodium alginate in the mixed solution is 1.5 wt%.

[0029] In a specific embodiment, the concentration of sodium alginate in the mixed solution is 1.6 wt%.

[0030] In a specific embodiment, the concentration of sodium alginate in the mixed solution is 1.7 wt%.

[0031] In a specific embodiment, the concentration of sodium alginate in the mixed solution is 1.9 wt%.

[0032] In a specific embodiment, the concentration of sodium alginate in the mixed solution is 2.5 wt%.

[0033] Among them, when the concentration of sodium alginate in the mixed solution is in the range of 1.5 - 1.9 wt%, the encapsulation rate of the Bacillus thuringiensis microcapsules prepared is increased by 1.5 - 2.9% compared with that of the Bacillus thuringiensis microcapsules prepared outside the range, and the survival rate under ultraviolet irradiation is increased by 2.3 - 4.3%. This shows that the concentration range of sodium alginate in the mixed solution provided by this application has a good effect on improving the ultraviolet resistance of Bacillus thuringiensis microcapsules.

[0034] The concentration of sodium alginate in the mixed solution being 1.7 wt% is the optimal technical solution. Compared with other technical solutions within the range of 1.5 - 1.9 wt%, the encapsulation rate is increased by 8 - 8.8%, and the survival rate under ultraviolet irradiation is increased by 13.7 - 15.1%. This shows that the preferred value of the concentration of sodium alginate in the mixed solution provided by this application has a better effect on improving the ultraviolet resistance of Bacillus thuringiensis microcapsules.

[0035] Preferably, adding the Bacillus thuringiensis microcapsules and a wetting and dispersing agent to water and stirring and mixing evenly can prepare the biological insecticide.

[0036] In summary, this application has the following beneficial technical effects: This application uses sodium alginate, whey protein, calcium chloride, and tannic acid as the wall materials of the microcapsules, and uses Bacillus thuringiensis original powder, chlorbenzuron, and melanin as the core materials of the microcapsules to prepare Bacillus thuringiensis microcapsules, significantly improving the ultraviolet resistance of Bacillus thuringiensis, thereby improving the insecticidal effect of the biological insecticide in the external environment. Specific Embodiments

[0037] The specific embodiments are only explanations of this application and not limitations thereof. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as they are within the scope of the claims of this application, they are protected by the patent law.

[0038] Material Sources Sodium lignosulfonate, industrial grade, purchased from Guangzhou Hongda Cellulose Co., Ltd.; The original powder of Bacillus thuringiensis is of model KN - Bt - 01, purchased from Wuhan Kenuo Biotechnology Co., Ltd.; Chlorbenzuron is of model RF - MYU - 80WP, purchased from Shandong Weifang Runfeng Chemical Industry Co., Ltd.; Melanin is purchased from Shanghai Macklin Biochemical Co., Ltd.; Sodium alginate is of pharmaceutical grade, purchased from Henan Xinfu Industry Co., Ltd.; Whey protein is purchased from Fonterra Co - operative Group Limited, New Zealand; Calcium chloride is purchased from Tianjin Botian Chemical Co., Ltd.; Tannic acid was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Acetic acid was purchased from Shandong Hualu Hengsheng Chemical Industry Co., Ltd.; The wetting dispersant used in the preparation of the biological insecticide in this application is sodium lignosulfonate.

[0039] Preparation Example 1 The preparation method of Bacillus thuringiensis microcapsules includes the following steps: S1. Add 5 g of Bacillus thuringiensis original powder, 5 g of chlorbenzuron and 1 g of melanin into water, mix and stir evenly to obtain a bacterial suspension. Stir 15 g of sodium alginate and 4 g of tannic acid in water until dissolved, then mix with the bacterial suspension, stir at a speed of 500 r / min for 50 min to obtain a mixed solution. Slowly drop the mixed solution into the calcium chloride solution to obtain a suspension, then centrifuge at 500 r / min for 5 min, discard the supernatant, add distilled water and then centrifuge again. Centrifuge and filter three times to obtain a precipitate as an intermediate product; S2. Dissolve 4 g of whey protein in water to obtain a whey protein solution with a concentration of 0.8 wt%. Adjust the pH to 5.2 with acetic acid. Mix the intermediate product obtained in step S1 with the whey protein solution, stir at a speed of 450 r / min for 50 min, then centrifuge at 500 r / min for 5 min, discard the supernatant, add distilled water and then centrifuge again. Centrifuge and filter three times and freeze-dry at -60 °C in a freeze dryer for 24 h to obtain Bacillus thuringiensis microcapsules.

[0040] Among them, in step S1, the mass of calcium chloride is 15 g, the concentration of the calcium chloride solution is 2 wt%, and the concentration of sodium alginate in the mixed solution is 1.7 wt%.

[0041] Preparation Example 2 The preparation method of Bacillus thuringiensis microcapsules includes the following steps: S1. Add 10 g of Bacillus thuringiensis original powder, 3 g of chlorbenzuron and 1.5 g of melanin into water, mix and stir evenly to obtain a bacterial suspension. Stir 8 g of sodium alginate and 2 g of tannic acid in water until dissolved, then mix with the bacterial suspension, stir at a speed of 450 r / min for 60 min to obtain a mixed solution. Slowly drop the mixed solution into the calcium chloride solution to obtain a suspension, then centrifuge at 500 r / min for 5 min, discard the supernatant, add distilled water and then centrifuge again. Centrifuge and filter three times to obtain a precipitate as an intermediate product; S2. Dissolve 8 g of whey protein in water to obtain a whey protein solution with a concentration of 1.2 wt%. Adjust the pH to 4.8 with acetic acid. Mix the intermediate product prepared in step S1 with the whey protein solution, stir at a speed of 500 r / min for 40 min, then centrifuge at 500 r / min for 5 min and discard the supernatant. Add distilled water and then centrifuge again. Centrifuge and filter three times and conduct freeze-drying at -60°C in a freeze dryer for 24 h to obtain the Bacillus thuringiensis microcapsules.

[0042] Among them, in step S1, the mass of calcium chloride is 8 g, the concentration of the calcium chloride solution is 2 wt%, and the concentration of sodium alginate in the mixed solution is 1.7 wt%.

[0043] Preparation Example 3 The difference from Preparation Example 1 is that the original powder of Bacillus thuringiensis is 7 g, chlorbenzuron is 4 g, melanin is 1.2 g, sodium alginate is 12 g, tannic acid is 1.5 g, calcium chloride is 12 g, and whey protein is 6 g.

[0044] Preparation Example 4 The difference from Preparation Example 3 is that the concentration of the calcium chloride solution in step S1 is 1.5 wt%.

[0045] Preparation Example 5 The difference from Preparation Example 3 is that the concentration of the calcium chloride solution in step S1 is 2.5 wt%.

[0046] Preparation Example 6 The difference from Preparation Example 3 is that the concentration of the calcium chloride solution in step S1 is 1 wt%.

[0047] Preparation Example 7 The difference from Preparation Example 3 is that the concentration of the calcium chloride solution in step S1 is 3 wt%.

[0048] Preparation Example 8 The difference from Preparation Example 3 is that the concentration of sodium alginate in the mixed solution is 1.5 wt%.

[0049] Preparation Example 9 The difference from Preparation Example 3 is that the concentration of sodium alginate in the mixed solution is 1.9 wt%.

[0050] Preparation Example 10 The difference from Preparation Example 3 is that the concentration of sodium alginate in the mixed solution is 1 wt%.

[0051] Preparation Example 11 The difference from Preparation Example 3 is that the concentration of sodium alginate in the mixed solution is 2.5 wt%.

[0052] Comparative Preparation Example 1 The difference from Preparation Example 3 is that tannic acid is replaced with an equal amount of chlorogenic acid.

[0053] Comparative Preparation Example 2 The difference from Preparation Example 3 is that in step S2, whey protein is replaced with an equal amount of chitosan.

[0054] Example 1 The preparation method of the biological insecticide comprises the following steps: Mix 1.5 g of Bacillus thuringiensis microcapsules, 1 g of sodium lignosulfonate and 7.5 g of water and stir evenly to obtain the biological insecticide.

[0055] The used Bacillus thuringiensis microcapsules are the ones prepared in Preparation Example 1.

[0056] Example 2 The preparation method of the biological insecticide comprises the following steps: Mix 2 g of Bacillus thuringiensis microcapsules, 0.5 g of sodium lignosulfonate and 7.5 g of water and stir evenly to obtain the biological insecticide.

[0057] The used Bacillus thuringiensis microcapsules are the ones prepared in Preparation Example 1.

[0058] Examples 3 - 12 The difference from Example 1 is that the used Bacillus thuringiensis microcapsules are respectively the ones prepared in Preparation Examples 2 - 11.

[0059] Comparative Examples 1 - 2 The difference from Example 1 is that the used Bacillus thuringiensis microcapsules are respectively the ones prepared in Comparative Preparation Examples 1 - 2.

[0060] Performance Detection 1. Detect the encapsulation efficiency of the Bacillus thuringiensis microcapsules prepared in Preparation Examples 1 - 11 and Comparative Preparation Examples 1 - 2. Collect the supernatant and precipitate obtained by centrifugation in step S2. Gradient dilute the supernatant by the viable count method, take the dilution and spread it on the LB agar plate, culture at 37 °C for 24 h, count the number of colonies (CFU), calculate the cell concentration of Bacillus thuringiensis in the supernatant, cell concentration (CFU / mL) = number of colonies * dilution factor / spreading volume (mL). Similarly, measure the initial cell concentration in the cell suspension in step S1 by the viable count method, and repeat each experiment three times. Encapsulation efficiency (%) = (initial cell concentration of Bacillus thuringiensis - cell concentration of Bacillus thuringiensis in the supernatant) * 100 / initial cell concentration of Bacillus thuringiensis.

[0061] 2. The Bacillus thuringiensis microcapsules prepared in Preparation Examples 1-11 and Comparative Preparation Examples 1-2 were irradiated under 30 W of ultraviolet light for 1 h, and then the survival rate was detected by the viable count method.

[0062] 3. Third-instar Plutella xylostella larvae with consistent growth and good health were selected as test insects and artificially inoculated into the test field to ensure uniform distribution. The biological insecticides prepared in Examples 1-12 and Comparative Examples 1-2 were diluted 1000 times and then applied to the test field. The mortality rates of Plutella xylostella were measured 48 h and 72 h after the application of the biological insecticides.

[0063] Table 1 Detection results of Bacillus thuringiensis microcapsules Object to be detected Entrapment efficiency (%) Survival rate after UV irradiation (%) Preparation Example 1 94.1 79.3 Preparation Example 2 93.2 77.4 Preparation Example 3 98.5 86.9 Preparation Example 4 91.5 75.8 Preparation Example 5 91.0 75.1 Preparation Example 6 85.3 68.2 Preparation Example 7 84.7 67.5 Preparation Example 8 90.5 73.2 Preparation Example 9 89.7 71.8 Preparation Example 10 88.2 69.5 Preparation Example 11 87.6 68.9 Comparative Preparation Example 1 83.7 63.9 Comparative Preparation Example 2 82.6 62.7 As can be seen from Table 1, the encapsulation rates of the Bacillus thuringiensis microcapsules prepared in Preparation Example 1 and Preparation Example 2 were 94.1% and 93.2% respectively, and the survival rates under ultraviolet irradiation were 79.3% and 77.4% respectively. Compared with Comparative Preparation Example 1, the encapsulation rates increased by 10.4% and 9.5% respectively, and the survival rates under ultraviolet irradiation increased by 15.4% and 13.5% respectively. Compared with Comparative Preparation Example 2, the encapsulation rates increased by 11.5% and 10.6% respectively, and the survival rates under ultraviolet irradiation increased by 16.6% and 14.7% respectively. This shows that the composition of the Bacillus thuringiensis microcapsules provided in this application has a good effect on improving the encapsulation rate and the survival rate under ultraviolet irradiation of the Bacillus thuringiensis microcapsules.

[0064] Compared with Preparation Example 1 and Preparation Example 2, the encapsulation rate of Preparation Example 3 of this application increased by 4.4% and 5.3% respectively, and the survival rate under ultraviolet irradiation increased by 7.6% and 9.5% respectively. This shows that the preferred values of the component ratios of the Bacillus thuringiensis microcapsules provided in this application have a better effect on improving the encapsulation rate and the survival rate under ultraviolet irradiation of the Bacillus thuringiensis microcapsules.

[0065] Compared with Preparation Example 6 and Preparation Example 7, the encapsulation rate of Preparation Example 4 of this application increased by 6.2% and 6.8% respectively, and the survival rate under ultraviolet irradiation increased by 7.6% and 8.3% respectively. Compared with Preparation Example 6 and Preparation Example 7, the encapsulation rate of Preparation Example 5 of this application increased by 5.7% and 6.3% respectively, and the survival rate under ultraviolet irradiation increased by 6.9% and 7.6% respectively. This shows that the range of the calcium chloride solution concentration provided in this application has a good effect on improving the encapsulation rate and the survival rate under ultraviolet irradiation of the Bacillus thuringiensis microcapsules.

[0066] In Preparation Example 4 and Preparation Example 5 of the present application, the encapsulation efficiency decreased by 7% and 7.5% respectively compared with Preparation Example 3, and the survival rate under ultraviolet irradiation decreased by 11.1% and 11.8% respectively. This shows that the preferred value of the calcium chloride solution concentration provided in the present application has a better effect on improving the encapsulation efficiency and the survival rate under ultraviolet irradiation of Bacillus thuringiensis microcapsules.

[0067] In Preparation Example 8 of the present application, the encapsulation efficiency increased by 2.3% and 2.9% respectively compared with Preparation Example 10 and Preparation Example 11 of the present application, and the survival rate under ultraviolet irradiation increased by 3.7% and 4.3% respectively. In Preparation Example 9 of the present application, the encapsulation efficiency increased by 1.5% and 2.1% respectively compared with Preparation Example 10 and Preparation Example 11 of the present application, and the survival rate under ultraviolet irradiation increased by 2.3% and 2.9% respectively. This shows that the concentration range of sodium alginate provided in the present application in the mixed solution has a good effect on improving the encapsulation efficiency and the survival rate under ultraviolet irradiation of Bacillus thuringiensis microcapsules.

[0068] In Preparation Example 8 and Preparation Example 9 of the present application, the encapsulation efficiency decreased by 8% and 8.8% respectively compared with Preparation Example 3, and the survival rate under ultraviolet irradiation decreased by 13.7% and 15.1% respectively. This shows that the preferred value of the concentration of sodium alginate provided in the present application in the mixed solution has a better effect on improving the encapsulation efficiency and the survival rate under ultraviolet irradiation of Bacillus thuringiensis microcapsules.

[0069] In Comparative Preparation Example 1 of the present application, the encapsulation efficiency decreased by 14.8% compared with Preparation Example 3, and the survival rate under ultraviolet irradiation decreased by 23%. This shows that the tannic acid provided in the present application has a better effect on improving the encapsulation efficiency and the survival rate under ultraviolet irradiation of Bacillus thuringiensis microcapsules compared with chlorogenic acid.

[0070] In Comparative Preparation Example 2 of the present application, the encapsulation efficiency decreased by 15.9% compared with Preparation Example 3, and the survival rate under ultraviolet irradiation decreased by 24.2%. This shows that the whey protein provided in the present application has a better effect on improving the encapsulation efficiency and the survival rate under ultraviolet irradiation of Bacillus thuringiensis microcapsules compared with chitosan.

[0071] Table 2 Detection results of the mortality rate of Plutella xylostella As can be seen from Table 2, the 48-hour insect mortality rates of Examples 1, 2, and 3 of this application were 88.5%, 89.3%, and 88.2% respectively, and the 72-hour insect mortality rates were 96.4%, 97.2%, and 96.1% respectively. Compared with Comparative Example 1, the 48-hour insect mortality rates increased by 10.2%, 11%, and 9.9% respectively, and the 72-hour insect mortality rates increased by 11.8%, 12.6%, and 11.5% respectively. Compared with Comparative Example 2, the 48-hour insect mortality rates increased by 12.3%, 13.1%, and 12% respectively, and the 72-hour insect mortality rates increased by 15.2%, 16%, and 14.9% respectively. This shows that the composition of the Bacillus thuringiensis microcapsules provided in this application has a significant effect on improving the insecticidal effect of biological insecticides.

[0072] Compared with Examples 1, 2, and 3 of this application, the 48-hour insect mortality rates of Example 4 of this application increased by 6.9%, 6.1%, and 7.2% respectively, and the 72-hour insect mortality rates increased by 3.4%, 2.6%, and 3.7% respectively. This shows that the preferred ratio of the composition of the Bacillus thuringiensis microcapsules provided in this application has a better effect on improving the insecticidal effect of biological insecticides.

[0073] Compared with Examples 7 and 8, the 48-hour insect mortality rates of Example 5 of this application increased by 7.1% and 7.8% respectively, and the 72-hour insect mortality rates increased by 5.8% and 6.5% respectively. Compared with Examples 7 and 8, the 48-hour insect mortality rates of Example 6 of this application increased by 6.6% and 7.3% respectively, and the 72-hour insect mortality rates increased by 5.2% and 5.9% respectively. This shows that the Bacillus thuringiensis microcapsules prepared according to the calcium chloride solution concentration range provided in this application have a good effect on improving the insecticidal effect of biological insecticides.

[0074] Compared with Example 4, the 48-hour insect mortality rates of Example 5 and Example 6 of this application decreased by 6.1% and 7.2% respectively, and the 72-hour insect mortality rates decreased by 6.1% and 7.2% respectively. This shows that the Bacillus thuringiensis microcapsules prepared according to the preferred value of the calcium chloride solution concentration provided in this application have a better effect on improving the insecticidal effect of biological insecticides.

[0075] In Example 9 of this application, the mortality rates of test insects at 48 h were increased by 3.8% and 4.4% respectively compared with those in Example 11 and Example 12, and the mortality rates of test insects at 72 h were increased by 3.5% and 4.1% respectively. In Example 10 of this application, the mortality rates of test insects at 48 h were increased by 2.6% and 3.2% respectively compared with those in Example 11 and Example 12, and the mortality rates of test insects at 72 h were increased by 2.3% and 2.9% respectively. This shows that the Bacillus thuringiensis microcapsules prepared according to the concentration range of sodium alginate in the mixed solution provided by this application have a good effect on improving the insecticidal effect of biological pesticides.

[0076] In Example 9 and Example 10 of this application, the mortality rates of test insects at 48 h were decreased by 9.3% and 10.5% respectively compared with those in Example 4, and the mortality rates of test insects at 72 h were decreased by 5.8% and 7% respectively. This shows that the Bacillus thuringiensis microcapsules prepared according to the preferred values of the concentration of sodium alginate in the mixed solution provided by this application have a better effect on improving the insecticidal effect of biological pesticides.

[0077] In Comparative Example 1 of this application, the mortality rate of test insects at 48 h was decreased by 17.1% compared with that in Example 4, and the mortality rate of test insects at 72 h was decreased by 15.2%. This shows that the biological pesticide prepared with the Bacillus thuringiensis microcapsules prepared with the tannic acid provided by this application has a better insecticidal effect than the biological pesticide prepared with the Bacillus thuringiensis microcapsules prepared with chlorogenic acid.

[0078] In Comparative Example 2 of this application, the mortality rate of test insects at 48 h was decreased by 19.2% compared with that in Example 4, and the mortality rate of test insects at 72 h was decreased by 18.6%. This shows that the biological pesticide prepared with the Bacillus thuringiensis microcapsules prepared with the whey protein provided by this application has a better insecticidal effect than the biological pesticide prepared with the Bacillus thuringiensis microcapsules prepared with chitosan.

Claims

1. A biological insecticide, characterized in that: The invention is composed of the following components by weight: 15-20% of Bacillus thuringiensis microcapsules, 5-10% of a wetting and dispersing agent and water to make up to 100%; the Bacillus thuringiensis microcapsules include Bacillus thuringiensis powder, carbendazim, melanin, sodium alginate, whey protein, calcium chloride and tannic acid in a weight ratio of (5-10):(3-5):(1-1.5):(8-15):(4-8):(8-15):(1-2).

2. A biological insecticide according to claim 1, characterized in that: The weight ratio of the Bacillus thuringiensis powder, carbendazim, melanin, sodium alginate, whey protein, calcium chloride and tannic acid is 7:4:1.2:12:6:12:1.

5.

3. A biological insecticide according to claim 1, characterized in that: The preparation method of the Bacillus thuringiensis microcapsules comprises the following steps: S1. Add Bacillus thuringiensis powder, carbendazim and melanin into water, mix and stir evenly to obtain a bacterial suspension, stir sodium alginate and tannic acid in water until dissolved, and then mix with the bacterial suspension at a stirring speed of 450-500 r / min for 50-60 min to obtain a mixed solution, slowly dropwise add the mixed solution into a calcium chloride solution to obtain a suspension, and obtain a precipitate as an intermediate product by multiple centrifugal filtration; S2, dissolving whey protein in water to obtain a whey protein solution with a concentration of 0.8-1.2wt%, adjusting the pH to 4.8-5.2 with acetic acid, mixing the intermediate product obtained in step S1 with the whey protein solution, stirring at a speed of 450-500r / min, stirring for 40-50min, then centrifugally filtering and freeze-drying to obtain Bacillus thuringiensis microcapsules.

4. A biological insecticide according to claim 3, characterized in that: The concentration of the calcium chloride solution in step S1 is 1.5-2.5 wt %.

5. A biological insecticide according to claim 4, characterized in that: The concentration of the calcium chloride solution in step S1 is 2 wt %.

6. A biological insecticide according to claim 3, characterized in that: The concentration of sodium alginate in the mixed solution is 1.5-1.9 wt %.

7. A biological insecticide according to claim 6, characterized in that: The concentration of sodium alginate in the mixed solution is 1.7 wt %.

8. A method for preparing a biological insecticide according to any one of claims 1 to 7, characterized in that: The biopesticide is prepared by adding bacillus thuringiensis microcapsules and a wetting dispersant into water and stirring and mixing them evenly.

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