A method for evaluating the wettability of spider mite surface

Abstract

The present invention relates to the field of agricultural technology, and in particular to a method for evaluating the wettability of the spider mite surface. The steps are: closely stick spider mites on a glass slide to prepare a spider mite aggregate surface; use a contact angle meter to test the contact angle, use the center point of the spider mite aggregate surface to lightly touch the droplets dripped by the motor, and record the video immediately after adhesion, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle; judge the wettability of the droplet on the spider mite surface by the size of the equilibrium contact angle, and if the equilibrium contact angle is not greater than 65°, it is judged that the wettability of the droplet on the spider mite surface is good. The present invention can measure the equilibrium contact angle of the droplet on the spider mite surface, thereby evaluating the wettability of the droplet on the spider mite surface. It has the advantages of convenient operation and good data repeatability, and solves the difficult problems of evaluating the wettability of the spider mite surface, screening of adjuvants, and evaluation of the performance of acaricides.

Description

Technical Field

[0001] The invention relates to the technical field of agriculture, and in particular to a method for evaluating wettability of spider mite body surface. Background Art

[0002] Spider mites, commonly known as red spiders, belong to the order Acarina of the subclass Acari. There are more than 900 known species in the world, and more than 140 species in China. Spider mites are very small, with a body length of 200 to 600 microns, and body colors include red, orange, brown, yellow, green, etc. Spider mites are a type of worldwide herbivorous agricultural pests that harm important economic crops and ornamental plants such as fruits, vegetables, and flowers, causing serious economic losses. It is estimated that about 5% of agricultural production losses worldwide are caused by various spider mites. Spider mites are difficult to control because of their high reproduction rate and resistance to pesticides. At present, chemical pesticide control (acaricides) is still an effective means of controlling spider mites. Common acaricides include contact pesticides such as bifenazate and spiroclofen.

[0003] In the process of using chemical pesticides to control spider mites, the pesticide is generally diluted with water and then sprayed. The liquid medicine is atomized by the spray equipment and contacts the target interface such as plant leaves and spider mite bodies through space transmission. Since acaricides are generally contact-killing, it is particularly important to wet the target during the action of the liquid medicine with the target. The better the wettability of the liquid medicine with the target, the higher the activity of the acaricide. Fountain et al. (Crop Protection, 2010, 29 (11): 1286-1292) reported a comparative test on the efficacy of adding and not adding the surfactant Silwett L-77 (0.05% silicone (50 mL / ha)) to control mites on strawberries under the same conditions as other component additives. The test results show that after adding Silwett L-77, especially when used in combination with abamectin, etoxazole and cypermethrin, the control effect is significant. Since the liquid medicine with organic silicon has good wettability, it can not only wet and penetrate into the folds of the leaves, but also better wet the hairy strawberry leaves, so the efficacy is significantly improved. It can be seen that studying the wettability of the liquid medicine on the surface of spider mites is of great value in judging the efficacy of the liquid medicine.

[0004] The classic method for studying wettability is to measure the contact angle. The common contact angle measurement method is the sessile drop method. The specific operation process is to drop the detection liquid on the surface of the target to be measured, and measure the angle at the gas-liquid-solid triple line by photography. The volume of the detection liquid used is generally 0.2μL~3μL. If the droplet is too small, it will evaporate too quickly. If the droplet is too large, it will deform due to gravity. Therefore, if the droplet is too small or too large, it will cause a certain error. This method has been widely used in the measurement of the contact angle of the liquid on the leaves of plants. However, when measuring the contact angle of the spider mite body surface, due to the small body length of the spider mite and its flexible movement, the volume of the detection liquid is larger than the volume of the spider mite, resulting in the inability to measure the wettability of the spider mite body surface. And because spider mites are biological organisms, the method of compacting powder into a plane cannot be used for measurement.

[0005] Therefore, there is no good evaluation method in the prior art to characterize the wettability of spider mite surface, which in turn limits the screening of adjuvants for the wettability of spider mite surface, the evaluation of acaricide performance, and the optimization of existing acaricide formulations. Summary of the invention

[0006] In view of this, it is necessary to provide a method for evaluating the wettability of the spider mite surface in order to address the problem that the wettability of the spider mite surface is difficult to characterize. By this method, the equilibrium contact angle of the spider mite surface can be measured to simply and accurately determine the wettability of the spider mite surface.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for evaluating the wettability of spider mite surface comprises the following steps:

[0009] Step 1: Stick double-sided tape on a glass slide, gently touch the area on the glass slide with the double-sided tape to the spider mite, and stick the spider mites tightly one by one to prepare the spider mite aggregation surface;

[0010] Step 2: Place the glass slide with multiple spider mites attached on the stage of the contact angle measuring instrument, draw the test liquid with a syringe and fix it on the injection unit, use a motor to drip the droplet and make the droplet suspended in the air, raise the stage and use the center point of the surface of the spider mite aggregate to touch the droplet lightly, record the video immediately after adhesion, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle;

[0011] Step 3: The wettability of the liquid drop on the spider mite surface is determined by the size of the equilibrium contact angle. If the equilibrium contact angle is not greater than 65°, it is determined that the wettability of the liquid drop on the spider mite surface is good.

[0012] Furthermore, in the above method for evaluating wettability of spider mite body surface, the plurality of equilibrium contact angles are 5 to 15, preferably 8 to 12.

[0013] Furthermore, the spider mite is one or more of two-spotted spider mite, cinnabarinus spider mite, cotton spider mite, and hawthorn spider mite.

[0014] Furthermore, the number of the spider mites is 4 to 20, preferably 8 to 15.

[0015] Furthermore, the volume of the droplets added by the motor is 0.2 μL to 1.0 μL, preferably 0.5 μL.

[0016] Furthermore, the test liquid includes but is not limited to a solvent, a surfactant aqueous solution or a miticide; when the test liquid is a miticide, it is preferably diluted with water to its recommended concentration.

[0017] Furthermore, in step 1, the gap between adjacent spider mites in the spider mite aggregate is less than 20 μm.

[0018] The beneficial effects of the present invention are:

[0019] The method of the present invention is simple to operate, does not require special contact angle equipment and complicated operations, and can quickly evaluate and judge the wettability of the spider mite body surface using commonly used laboratory consumables and existing equipment. The method has a small measurement error and high repeatability of measurement data. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further clearly and completely described in combination with the embodiments of the present invention. It should be noted that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] The materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0022] The equilibrium contact angle in this application refers to the contact angle when the contact angle hardly changes after the liquid drop contacts the spider mite surface for a certain period of time. Different liquids have different wettability to the spider mite surface, and the time to reach the equilibrium contact angle is slightly different. Therefore, in this application, for different test liquids, the contact angle when the contact angle no longer changes is selected as the equilibrium contact angle based on the video.

[0023] Example 1: Determination of the wettability of water on the surface of Tetranychus cinnabarinus

[0024] Step 1: Stick double-sided tape on a glass slide, gently touch the area on the slide with the double-sided tape to the spider mite, and stick 4 spider mites tightly one by one to prepare the spider mite aggregation surface;

[0025] Step 2: Place the glass slide with four spider mites attached on the stage of the OCA20 contact angle meter, use a 1mL syringe with a flat needle to draw water and fix it on the injection unit, use a motor to drip 0.2μL droplets to make the droplets suspended in the air, raise the stage and use the center point of the surface of the spider mites to touch the droplets lightly, record the video immediately after contact, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle;

[0026] Step 3: Repeat steps 1 to 2 for 5 times to obtain 5 equilibrium contact angle data: 138.54°, 140.34°, 138.71°, 139.25°, 138.95°, with an average value of 139.16° and a standard deviation of 0.71°.

[0027] The average value of the equilibrium contact angles measured 5 times was 139.16°, which was greater than 65°, so it was judged that water had poor wettability on the surface of Tetranychus cinnabarinus.

[0028] Example 2: Determination of the wettability of formamide on the surface of cotton spider mites

[0029] Step 1: Stick double-sided tape on a glass slide, gently touch the area with double-sided tape on the slide to the spider mite, and stick 15 cotton spider mites tightly one by one to prepare the spider mite aggregation surface;

[0030] Step 2: Place a glass slide with 15 cotton spider mites attached on the stage of the OCA20 contact angle meter, use a 1mL syringe with a flat needle to absorb formamide and fix it on the injection unit, use a motor to drip 1μL formamide droplets to make the droplets suspended in the air, and use the lifting stage to touch the droplets with the center point of the spider mite aggregate surface. Record the video immediately after contact, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle;

[0031] Step 3: Repeat steps 1 to 2 20 times to obtain 20 equilibrium contact angle data: 107.23°, 109.56°, 107.96°, 108.52°, 107.63°, 108.27°, 109.23°, 108.64°, 107.93°, 108.72°, 109.46°, 108.65°, 108.43°, 109.31°, 107.45°, 108.45°, 107.46°, 109.45°, 109.45°, 109.87°, with an average value of 108.58° and a standard deviation of 0.80°.

[0032] The average value of the equilibrium contact angles measured 10 times was 108.58°, which was greater than 65°, so it was judged that formamide had poor wettability on the surface of cotton spider mites.

[0033] Example 3: Determination of the wettability of ethylene glycol on the surface of the hawthorn spider mite

[0034] Step 1: Stick double-sided tape on a glass slide, gently touch the area with double-sided tape on the slide to the spider mite, and stick 20 hawthorn spider mites one by one to prepare the spider mite aggregation surface;

[0035] Step 2: Place the glass slide with 20 hawthorn spider mites on the stage of the OCA20 contact angle meter, use a 1mL syringe with a flat needle to absorb ethylene glycol and fix it on the injection unit, use a motor to drip 0.5μL ethylene glycol droplets to make the droplets suspended in the air, and use the lifting stage to touch the droplets with the center point on the surface of the hawthorn spider mite aggregate. Record the video immediately after contact, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle;

[0036] Step 3: Repeat steps 1 to 2 15 times to obtain 15 equilibrium contact angle data: 130.89°, 129.56°, 130.87°, 131.97°, 130.53°, 129.63°, 131.12°, 129.85°, 128.99°, 130.97°, 129.82°, 130.37°, 129.96°, 128.88°, 129.19°, with an average value of 130.17° and a standard deviation of 0.88°.

[0037] The average value of the equilibrium contact angles measured 15 times was 130.17°, which was greater than 65°. Therefore, it was judged that ethylene glycol had poor wettability on the surface of the hawthorn spider mite.

[0038] Example 4: Determination of wettability of 0.01 wt% organic silicon Silwet 408 aqueous solution on the surface of spider mite

[0039] Step 1: Stick double-sided tape on a glass slide, gently touch the area with the double-sided tape on the slide to the spider mite, and stick 20 two-spotted spider mites tightly one by one to prepare the spider mite aggregation surface;

[0040] Step 2: Place the glass slide with 20 spider mites attached on the stage of the OCA20 contact angle meter, use a 1mL syringe with a flat needle to absorb the silicone solution and fix it on the injection unit, use a motor to drip 0.5μL droplets to make the droplets suspended in the air, and use the lifting stage to touch the droplets with the center point on the surface of the spider mite aggregate. Record the video immediately after contact, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle;

[0041] Step 3: Repeat steps 1 to 2 for 5 times to obtain 5 equilibrium contact angle data: 42.83°, 43.81°, 41.98°, 41.78°, 42.56°, with an average value of 42.59° and a standard deviation of 0.80°.

[0042] The average value of the equilibrium contact angles measured 5 times is 42.59°, which is less than 65°. Therefore, it is judged that the 0.01wt% organic silicon Silwet408 aqueous solution has good wettability on the surface of the spider mite.

[0043] Example 5: Determination of wettability of commercially available 24% bifenazate and 12% spiroclofen suspension on the surface of spider mites

[0044] Step 1: Stick double-sided tape on a glass slide, gently touch the area with the double-sided tape on the slide to the spider mite, and stick 15 two-spotted spider mites tightly one by one to prepare the spider mite aggregation surface;

[0045] Step 2: Place a glass slide with 15 spider mites attached to it on the stage of the OCA20 contact angle measuring instrument, dilute the 24% bifenazate·12% spirodiclofen suspension with water to 0.033wt% according to the recommended concentration, use a 1mL syringe with a flat needle to draw the suspension dilution and fix it on the injection unit, use a motor to drip 0.5μL droplets to make the droplets suspended in the air, lift the stage to touch the droplets with the center point on the surface of the spider mite aggregate, record the video immediately after contact, and select the contact angle when the contact angle no longer changes as the equilibrium contact angle;

[0046] Step 3: Repeat steps 1 to 2 10 times to obtain 10 equilibrium contact angle data: 128.72°, 127.89°, 126.99°, 127.98°, 128.34°, 127.88°, 126.89°, 127.63°, 127.45°, 128.59°, with an average value of 127.84° and a standard deviation of 0.62.

[0047] The average value of the equilibrium contact angles measured 5 times was 127.84°, which was greater than 65°. Therefore, it was judged that the wettability of the 24% bifenazate·12% spiroclofen suspension on the surface of the two-spotted spider mite was poor, and it was necessary to improve the formula or add a tank-mixing adjuvant.

[0048] Example 6: Commercially available 24% bifenazate·12% spiroclofonate suspension + silicone Silwet 408 in Tetranychus urticae Determination of body surface wettability

[0049] 24% bifenazate·12% spiroclofen suspension was diluted with water to 0.033wt% according to the recommended concentration, and then a certain amount of organic silicon Silwet 408 was added to prepare a mixed dilution, and the steps of Example 5 were followed. In step 3, the operations of steps 1 to 2 were repeated 5 times, and the remaining steps were the same. The results are as follows:

[0050] Table 1 Wettability of 24% bifenazate·12% spiroclofen SC+Silwet 408 on the surface of Tetranychus urticae

[0051]

[0052] Examples 5 and 6 were used for indoor efficacy tests on two-spotted spider mites. Clean bean leaves were punched into discs with a diameter of 3.0 cm, and the front side was pasted into an insect feeding box with a diameter of 6.0 cm. The edges of the leaves were sealed with agar, and then adult two-spotted spider mites were carefully transferred to the leaves with a brush. Use a Potter spray tower (Burkard Manufacturing Co. Ltd) for spraying at a pressure of 68.9 kPa. The amount of liquid medicine was 3 mL, and it was allowed to stand for 30 seconds after spraying. The box was placed in an environment of 25°C and 60% relative humidity. The mortality rate was evaluated after 48 hours. Repeat 4 times. LC was analyzed using DPS v12.01 50 , the results are shown in Table 2.

[0053] Table 2 LC of drug solution 50

[0054] Group <![CDATA[LC 50 (95% confidence interval, mg / L)]]> Example 5 42.28 Example 6A 42.12 Example 6B 41.99 Example 6C 30.74

[0055] Comparative Examples 1 to 6 show that water, organic solvents ethylene glycol and formamide have poor wettability on the spider mite surface, and only the organosilicon solution and the drug solution with added organosilicon have good wettability on the spider mite surface and have better prevention effect.

[0056] Comparison of Examples 5 and 6 shows that adding different concentrations of organosilicon solution to the 24% bifenazate and 12% spiroclofen suspension can effectively improve the wettability of the suspension on the spider mite surface. When the concentration of the organosilicon solution added to the suspension is 0.01wt%, the wettability of the suspension is good according to the evaluation method of the present invention. The LC 50 It is 30.74mg / L.

[0057] It can be seen from the above examples that the method for evaluating the wettability of the spider mite surface provided by the present invention has good data repeatability and is convenient, and can provide a good evaluation method for auxiliary agent screening, evaluation of acaricides, optimization of acaricide formulations and use methods thereof.

[0058] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. Application of a method for evaluating the wettability of spider mite surface in screening and performance evaluation of acaricide adjuvants, characterized in that: The evaluation method includes the following steps: Step 1: stick a double-sided tape on a glass slide, lightly touch the area on the glass slide with the double-sided tape to the spider mite, and stick the spider mites tightly one by one to prepare the surface of the spider mite aggregation; the gap between adjacent spider mites in the spider mite aggregation is less than 20 μm; the number of the spider mites is 4 to 20; Step 2: placing a glass slide with multiple spider mites attached to it on the stage of the contact angle measuring instrument, sucking the test liquid with a syringe and fixing it on the injection unit, dripping the liquid droplets with a motor and making the liquid droplets suspended in the air, raising the stage and lightly touching the liquid droplets with the center point of the surface of the spider mite aggregate, and recording the video immediately after adhesion, and selecting the contact angle when the contact angle no longer changes as the equilibrium contact angle; the equilibrium contact angle is the average value of multiple equilibrium contact angles obtained by multiple measurements, and the multiple equilibrium contact angles are 5 to 15; the test liquid includes a solvent, a surfactant aqueous solution or a miticide; Step 3: The wettability of the droplet on the spider mite surface is determined by the size of the equilibrium contact angle. If the equilibrium contact angle is not greater than 65°, the wettability of the droplet on the spider mite surface is good; this is used to screen adjuvants, evaluate acaricides, or optimize acaricide formulations; Wherein, the spider mite is one or more of two-spotted spider mite, cinnabarinus spider mite, cotton spider mite, and hawthorn spider mite; The volume of the droplets added by the motor is 0.2 μL to 1.0 μL.

2. The use according to claim 1, characterized in that: The volume of the droplet added by the motor is 0.5 μL.

3. The use according to claim 1, characterized in that: The plurality of equilibrium contact angles is 8 to 12.

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