The preparation of 24% spirochetes diester suspension agent for control of citrus red spider was studied. By wet grinding process, the effects of wetting dispersant, thickening stabilizer, antifreeze agent and water quality on the properties of the system were investigated. The process parameters were optimized. The field control effect of the preparation against citrus red spider was tested. The optimal formula (all mass fractions) : snail mite diester 24%, SP-30205%, 700# 3%, ethylene glycol 3%, Xanthan gum o. 2%, magnesium aluminum silicate 1%, tap water supplement to 100%; The optimal process parameters are as follows: the mass ratio of 1mm and 2mm zirconia beads is 1:1, the mass ratio of material to zirconia beads is 1:1.5, and the grinding time is 2.5 h. The field efficacy test showed that its rapidity and control effect against citrus red spider were better than the control agent 24% spirofenester suspension, and it had a good application prospect.
Spirofenester, as the highest sales of acaricides, has excellent control effect and retention period against different mites of many crops. Spirofenin is a growth and development inhibitor, which has a tactile effect, no endosuction activity and poor rapidity. And with the long-term or frequent use, the pest mites developed different degrees of resistance to spirofenester, and the control effect gradually decreased, the duration of the effect gradually became shorter. In view of this, the development of new acaricide varieties is an effective way to control the resistance of mites.
Spirodicaracide is a new acaricide designed and synthesized by our research group on the basis of fully studying the structure-activity relationship of spirodicaracide, which has obtained patent authorization. Pyrogen diester is a non-inhalation acaricide, which can control eggs, weak mites and female adult mites through contact and stomach toxicity. Its mechanism of action is to inhibit the fat synthesis and block energy metabolism in the body of mites, and there is no serious cross-resistance with conventional acaricides. It has good control effect on the genera of panonychus, tetranychus, etotetranychus and gall mite, and can be used for mite control in citrus, grape, eggplant, pepper and other crops. The activity of spiroroid diester was higher than spiroroid diester. Laboratory toxicity tests showed that the toxicity of the insecticide to tetranychus cinnabarinus eggs was 0.7g·mL, while the toxicity of the control agent spirofenester was 4.4 g·mL. For convenient use in different areas and enlarge the using range of technical development in the early stage of the micro emulsions on the basis of the further development to turn it into a suspending agent, water emulsion, suspending agent can be dispersed oil, such as a variety of dosage forms, this work focuses on its suspending agent, by investigating the spiral mite double ester containing the components and the influence of different process parameters on the preparation performance, The formulation and optimum process of 24% spirorodiester suspension agent with qualified physical properties were determined. The activity of the suspension agent against Citrus red spider was higher than that of the control agent.
Ⅰ. The Experiment
1. Reagents and Instruments
- 98.5% spiromite diester, homemade;
- Sodium methylene dinaphthalene sulfonate (NNO), Nanhe Henderson Corporation;
- Alkyl naphthalene sulfonate polycondensation (MOR-WETD425), mixture of alkyl naphthalene sulfonate and anionic wetting agent (MorwetEFw), Akzo Nobel;
- Fatty alcohol polyoxyethylene ether dispersant (Tersperse4894), Huntsman Additives;
- Polycarboxylic acid salt dispersive agent (SP-2728), geminoid dispersant (SP-SC3), phosphate salt dispersive agent (SP_SC3060), Qingyu Additives Co., LTD.;
- Fatty alcohol polyoxyethylene ether (AE07), alkyl phenol polyoxyethylene ether formaldehyde condensation (700#), alkyl phenol polyoxyethylene ether formaldehyde condensation phosphate ester salt (700# P), Xingtai Blue Sky Company;
- Ethylene glycol, propylene glycol, urea, magnesium aluminum silicate, silica, xanthan gum.
- Laboratory small vertical sand mill, Shenyang Grisi Machinery Company;
High Performance Liquid Chromatograph, Waters 1525, USA;
- Rotary viscometer, Blerfield Company; PH meter, HS-3C, Shanghai Leichi Company;
- High shear emulsifier, FRuck FM200, Shanghai Fruck Company;
- Laser particle size Distributor, BT 1 9300H, Dandong Baxter Company. Zirconium beads for grinding are 1mmT and 2mm.
2. The Experiment Method
(1) Preparation Method of Suspension Agent
The preparation components were accurately weighed by wet grinding process, coarse dispersion was carried out by high shear dispersion emulsifier, and transferred to vertical sand mill. An appropriate amount of zirconia beads were added to grind for a certain time to obtain 24% spiromite diester suspension agent.
(2) Test Method for Performance of Suspension Agent
According to HG/T2467.5-2003 Pesticide Suspension Product Standard Preparation Specification, the physical and chemical properties of 24% snail mite diester suspension agent were tested. The particle size and viscosity of the preparation were measured by laser particle size meter and rotary viscometer.
(3) Method of Field Efficacy Test
The field efficacy test of control citrus red spider was carried out in Ganzhou, Jiangxi province. Seven treatments of 24% spirofenester suspension agent (5000, 4000, 3000), 24% spirofenester suspension agent (5000, 4000, 3000, CK) were set in the experiment. Use a regular manual sprayer to spray 2 navel orange trees per treatment. Before spraying, 3,7 and 15 days after spraying, the live insect numbers of 20 leaves from 4 leaves of one branch were investigated from 5 directions of each tree, respectively, and the pest decline rate (%) and control effect (%) were calculated.
Ⅱ. Results and Discussion
1. Formula Screening
(1) Preliminary Screening of Wetting Dispersant
Wetting dispersant is the most important additive component in suspension agent. Because pesticide suspension agent is a thermodynamically unstable system, the role of wetting dispersant is to form a protective layer around pesticide particles, prevent pesticide particles from getting close to each other, so as to ensure the stability of the preparation during storage. According to the physical and chemical properties of spirochaete diester and the experience of developing suspension agent, the addition amount of 6% (mass fraction) was tested. A variety of anionic and non-ionic wetting dispersants including NN0, MorweD425, MorwetEFW, Tersperse4894, SP_2728, SP_SC3, SP-3060, 700# P, AE07, 700# were screened. The optimum wetting dispersant was selected by investigating the suspension rate, dispersity, sieving and thermal water storage rate of the preparation system with wetting dispersant. The preliminary screening results of wetting dispersants are shown in Table 1.
It can be seen from Table 1 that sp-3060 and 700# are used as 7 of wetting dispersant under the same dosage of additives. The properties of the formula are relatively good, but the properties of the two preparations, suspension rate and thermal storage and water extraction rate, need to be further improved, so the ratio and dosage of SP – 3060 and 700# were optimized.
(2) Quantitative Screening of Wetting Dispersant
The proportion and dosage of sp-3060 and 700# wetting dispersants in the formula were further optimized to improve the performance of the preparation. The experimental results are shown in Table 2.
It can be seen from Table 2 that the performance of formula 28 is worse than that of formula 18 in all aspects, that is, the less dosage of additives has a great influence on the system performance. The properties of 38, 48, 58 and 68 formulations were better than those of 18,34 and 48. It can be seen that increasing the dosage of any kind of auxiliary agent will improve the performance of the preparation to a certain extent. Sp-3060 (5%) and 700#(3%) of formula 38 were selected as wetting dispersant system considering the performance and production cost.
(3) Screening of Thickening Stabilizer
Thickening stabilizer is an important factor affecting the viscosity of suspension agent, and the viscosity has an important effect on the stability of suspension agent. The viscosity is too small, the preparation is easy to stratify, physical stability is poor; The viscosity is too large, the fluidity of the preparation is poor, which is unfavorable to the processing and use of mangles. In the formulation development of 24% roxanthan diester suspension agent, xanthan gum, white carbon black and magnesium aluminum silicate were selected for type and dosage screening. By analyzing the fluidity, dispersity, thermal storage and water extraction rate of the preparation, the thickening stabilizer was selected to ensure the good performance of the preparation. The experimental results are shown in Table 3.
The results showed that when the three thickening stabilizers were used alone, the thermal water storage and precipitation rates of the preparation were all more than 10%. When xanthan gum and silica were used together, the viscosity of the system was high, the fluidity and the dispersibility of human water were poor. When xanthan gum 0.2% and magnesium aluminum silicate 1% are used together, the system has moderate viscosity, good fluidity and water entry dispersion, and the thermal water storage and separation rate is 3%.
(4) Screening of Antifreeze Agents
The suspension agent with water as dispersion medium should not only be used in the high temperature condition in the south, but also in the cold condition in the north. Antifreeze agent should be added to ensure that the preparation has good performance in the cold condition. The antifreezing effect of ethylene glycol, propylene glycol and urea was investigated in the experiment. When the mass fraction of ethylene glycol was 3%, 5% and propylene glycol was 5%, the preparation had good stability at low temperature, but the antifreezing effect of urea was not ideal. From an economic point of view, ethylene glycol was chosen as antifreeze agent with a mass fraction of 3%.
(5) Impact of Water Quality
The effect of water hardness on the properties of the preparation system was investigated. The tap water used in the screening of the additives was changed into distilled water, 342mg·L ^-1standard hard water, 500mg·L ^-1standard hard water and 1000mg·L^-1respectively. The suspension agent was prepared with standard hard water, and the performance of the preparation was investigated. The experimental results are shown in Table 4.
As can be seen from Table 4, when distilled water, 342mg·L^-1 standard hard water and 500mg·L^-1 standard hard water are used, the properties of the preparation are equivalent to tap water. When 1000mg· l^-1 standard hard water is used, the viscosity of the system becomes larger, the fluidity becomes worse, and the water segregation is obvious. When the amount of calcium and magnesium ions increases, the interaction with the wetting dispersant in the system is strengthened, and the double electric layer of the system is destroyed to a certain extent, leading to the deterioration of the preparation performance. The adaptability of the formula to water with high hardness needs to be improved, but tap water with ordinary hardness of 300-500mg ·L has no obvious effect on the system performance, so it is suggested to use more economical tap water in production.
(6) Optimum Formula and Property Index
Various factors affecting the performance of the 24% spirochus diester suspension agent were comprehensively investigated. After repeated experiments, the optimal formulation was finally determined, as shown in Table 5. According to HG/T2467.5-2003 Pesticide Suspension Product Standard Preparation Specification, the physical and chemical properties of the prepared 24% spiromite double ester suspension agent were tested, and the particle size and viscosity of the preparation were tested by laser particle size meter and rotary viscometer. The test results are shown in Table 6.
As can be seen from Table 6, the physical properties of the 24% spiromite diester suspension developed in this study all meet the requirements of relevant standards.
2. Optimization of Preparation Process
(1) Selection of Zirconia Beads
Fixed grinding time for 3h, xanthan gum (o. 2% aqueous solution) was added at the initial stage of material preparation, and the particle size of zirconia beads and the effect of mass ratio between materials and zirconia beads on the performance of the system were investigated. The results are shown in Table 7.
It can be seen from Table 7 that the grinding effect is best when zirconia beads with particle sizes of 1mm and 2mm are used together. When the mass ratio of material to zirconia bead is 1:1, the particle size of the preparation is larger, and the thermal storage and water extraction rate is higher. When the ratio of material to zirconia bead is 1:1.5 and 1:2, the performance of the preparation is not different. Therefore, in the laboratory test, 1mm and 2mm zirconia beads were mixed according to the mass ratio of 1:1, and the mass ratio of materials and zirconia beads was determined to be 1:1.5.
(2) Determination of Grinding Time
During the suspension grinding process, samples were taken at different time points for particle size testing, and the thermal storage and water extraction rate was investigated to select the best grinding time in the preparation process. The results are shown in Table 8.
It can be seen from Table 8 that from o. 5h to 2h, with the increase of grinding time, the particle size of the preparation decreased significantly, and the thermal water storage and separation rate decreased significantly. From 2h to 3h, the grinding time extended, the particle size and water extraction rate of the preparation decreased, but tended to be gentle, and there was little difference between 2.5h and 3h data. After many experiments, it was found that there was no obvious difference in other properties between 2.5h and 3h preparations. In the experiment, the grinding time was fixed at 2.5h.
3. Acaricidal Activity
24% spiromite diester suspension showed excellent control effect on citrus red spider in field, and the test results were shown in Table 9. Three days after treatment, the control effect of 24% spirorodiester suspension reached more than 75% at 5000, 4000 and 3000 times liquid, which was 10% higher than that of the control agent 24% spirorodiester suspension at the same dilution ratio, indicating that the 24% spirorodiester suspension was better than 24% spirorodiester suspension.
On the 7th day after treatment, the control effect of 24% and 24% spirofenester suspension reached the peak, and the control effect of 24% spirofenester suspension at the same dilution ratio was better. After 15 days of treatment, the control efficiency of 24% spirofenester suspension and 24% spirofenester suspension were both higher than 70%, showing excellent retention. Under the same dilution ratio, the control effect of 24% spirofenester suspension was higher than that of 24% spirofenester suspension. In general, 24% spirorodiester suspension has better control effect than the control agent 24% spirorodiester suspension, and has obvious advantages in rapidity.
Through the screening of wetting dispersant, thickening stabilizer, antifreeze agent and other additives, this study investigated the influence of different water quality on the system performance, and determined the optimal formula (mass fraction) of 24% spiromite double ester suspension agent: Snail mite diester 24%, SP-30205%, 700# 3%, ethylene glycol 3%, Xanthan gum o. 2%, magnesium aluminum silicate 1%, tap water supplement to 100%.
Better process: the mass ratio of 1mm and 2mm zirconia beads is 1:1, the mass ratio of material and zirconia beads is 1:1.5, and the grinding time is 2.5h. The preparation with preferential formula and better process has good performance and all indexes meet the requirements of suspension agent. Acaricidal activity: Under the conditions of 5000, 4000 and 3000 times liquid, the control effect of 24% spirofenester suspension on citrus red spider was higher than that of 24% spirofenester suspension at the same dilution ratio, and the 24% spirofenester suspension was more advantageous in terms of rapidity. With the increase of spirofenester resistance, The biester of snail mite has the advantages of good rapidity and high control efficiency and has a good application prospect.