Microcapsule pesticides 1. Microcapsule pesticides
1.1 Microcapsule Pesticide Introduction In general, microcapsule pesticide refers to the use of polymer materials as the wall or capsule to encapsulate the active substance of the pesticide by chemical, physical or physical chemical methods to form a semi-permeable membrane. Capsules, and pesticide formulations uniformly dispersed in various additives, such as microcapsule suspensions are dispersed in water, and the powder is dispersed in a certain solid filler. Compared with other pesticide preparations, the most important feature of microcapsule pesticides is sustained release, which can extend the duration of pesticides, increase the utilization rate, reduce or avoid the decomposition and loss of pesticides due to the external environment, reduce toxicity and phytotoxicity, Reduce environmental pollution and poisoning of operators [2]. In terms of use, after the common pesticide preparation is used, the active ingredient is directly in contact with the crop or the target organism, and the active ingredient of the microcapsule pesticide and the target organism are separated by a layer of wall material. It is this difference that makes microcapsule pesticides have some excellent properties that are not available in other pesticide formulations.
1.2 Development status of microcapsule pesticides in China The research on microcapsule pesticides in China started late. Since 1978, microcapsule pesticides have been developed and some progress has been made, such as the development of parathion, phoxim and methyl sulfonate. Microcapsule products such as phosphorus and malathion [3]. Because the development cost of developing new pesticide formulations is much lower than the development of new pesticide varieties [4], coupled with the increasing attention of researchers on microcapsule technology, pesticide microcapsule technology has developed rapidly in the past decade, and lambda-cypermethrin, New microcapsule pesticide products such as chlorpyrifos, avermectin and bifenthrin have been introduced, and the number has increased from more than ten in 2004 to dozens today. The application scope covers field weeding, agricultural pests, forestry pests, underground pests. , health pests, fruit preservation and many other fields. At the same time, the improvement of microcapsule preparation technology and the emergence of new preparation technology have promoted the birth of nano-scale microcapsule pesticides, and also made the performance of micro-capsule pesticides more stable, less toxic to humans and animals, longer lasting effect, and wider application range. [5]. Pesticide microcapsule technology has become a development trend of new pesticide formulations.
2. Termite prevention methods and drug use status
2.1 Methods for termite prevention The termite prevention methods for building construction mainly include physical barriers, chemical barriers, and monitoring and control technologies.
2.1.1 Physical barrier Physical barrier mainly refers to the prevention method of using sand or gravel particles, metal mesh or guard plate as a physical or mechanical barrier to prevent termites from invading the room. Its purpose is to separate termites from food, rather than driving away or killing termites close to the building. For example, stainless steel mesh barriers for new homes that have been commercialized in the United States and Australia are based on this technology [6]. The physical barrier method is safe and environmentally friendly, and has a long-lasting effect. However, the setting process is complicated, and it has high requirements for construction technology and barrier materials.
2.1.2 Chemical barriers Chemical barriers are a long-established traditional termite control strategy that applies insecticides to soil, wood or other termite-active environments, in termite sources and conservation targets (such as buildings). A medicament treatment belt is formed to prevent the damage of termite invasion. The new chemical barrier application technology also allows the insecticide to be directly bonded to the mat or plastic sheet of fiber to avoid direct chemical bonding to the soil. Although the chemical barrier method is easy to operate, a large number of applications also increase the potential environmental and health risks, and the chemical barrier formed by one-time application is difficult to meet the requirements of the state's minimum effective barrier for the 15-year period of protection [7].
2.1.3 Monitoring and Control Technology Termite monitoring and control technology is a new type of termite control technology. Various products developed based on this technology can be called termite monitoring and control system, and the specific monitoring station, monitoring trapping material and bait Or powders and other components that control termites and practices. The more representative products are the domestic Fukang® termite population monitoring and control system and the foreign Sentricon® group elimination system [8]. The detection and control technology is more in line with the termite IPM control concept and has broad application prospects in termite control.
2.2 Use and development of termite preventive agents From the perspective of pharmaceutical ingredients, termite preventive agents at home and abroad have experienced a transition from inorganic insecticides to organic pesticides. Traditional commonly used termite control agents are mainly inorganic insecticides and organochlorine insecticides. The main type of inorganic insecticides is arsenic trioxide, and the development of synthetic organic insecticides has undergone changes in organochlorine, organophosphorus, carbamate, pyrethroid, insect growth regulators and microbial insecticides. Organochlorine agents include chlordane, mirex, aldrin, dieldrin, etc., and are now almost completely discontinued. The types of agents that have been used for a long time and in large quantities in domestic termite control work are mainly arsenic, sodium arsenite, chlordane, mirex, copper-chromium arsenic and chlorpyrifos [9]. In recent years, termite preventive agents registered, researched and applied in China mainly include organic phosphorus, such as chlorpyrifos; pyrethroids such as fenvalerate, bifenthrin, etc.; carbamates, such as Zhong Dingwei Silanes, such as silylindene; phenylpyrazoles, such as fipronil; nicotines, such as imidacloprid. Their application in termite prevention in China has played an important role in the control of termite damage in China, effectively controlling the damage of termites.
3. Registration status of microcapsule pesticides in China In recent years, with the continuous development and maturity of microcapsule technology, the number of domestically registered microcapsule products has increased year by year. Among the registered microcapsule pesticide products, the development of water-based microcapsule suspensions is the most rapid, and the application range includes field weeding, agricultural pests, forestry pests, underground pests, sanitary pests, and fruit preservation.
Through the China Pesticide Information Network, the microcapsule suspensions that have obtained pesticide registration certificates in China and are valid for the period of validity are inquired. As of October 2011, 28 domestic and foreign manufacturers have registered 40 microcapsule suspensions within the validity period. product. Among them, there are 6 herbicide products, 10 sanitary insecticides, 1 termite control agent, 10 underground pest insecticides, 6 agricultural pest insecticides, and 7 forestry pest insecticides. The registered microcapsule suspension products are mainly sanitary pests, underground pest insecticides, followed by agricultural pests, forestry pest insecticides, and these application fields have high demand for the efficacy of the medicament. Termite control also has high requirements for the efficacy of the drug, but currently only one registered product is registered as 5% bifenthrin microcapsule suspension agent registered by Jiangsu Changzhou Fukang Chemical Products Co., Ltd., registration number is WL20110123 . According to another enquiry, Sumitomo Chemical Co., Ltd. registered a microcapsule pesticide 15% white-capture special microcapsule suspension agent for termite control in China in 2007. The registration number is WL200014, which has expired.
At present, the mainstream dosage forms of domestic termite prevention agents are mainly suspending agents, emulsifiable concentrates, microemulsions, water emulsions, water dispersing agents, etc. [9], the competition among different termite control agents is fierce, and the pursuit of preventive effects and environmental influences At the same time, it is necessary to produce cost considerations. The more balanced pharmaceuticals in all aspects ultimately dominate the market. The development of termite prevention microcapsule products is also the result of market competition.
4. Feasibility of application of microcapsule pesticides to termite prevention In recent years, although a series of environmentally friendly termite prevention products have emerged, such as commercial barrier termite technology and commercial application of termite monitoring and control technology, their degree of promotion in China Still low, the chemical barrier method will remain the main measure for termite prevention in China within a certain period of time. In view of the rapid development of pesticide processing technology and the successful application of microcapsule technology in many fields in recent years, actively exploring the application of microcapsule pesticides in termite prevention will become an effective way to solve the existing dilemma of termite prevention. At the same time, domestic termite control workers have also carried out experiments related to the application of termite prevention in microcapsule pesticides. For example, the experiment of termite prevention and control in Baihang special microcapsules in Zhejiang Province was carried out in 1997-2003, and it was found that 1000mg·kg-1 was passed. After 5 years, the anti-ant effect of the treated soil was 100%, and the anti-ant effect was 80% after 6 years. The repellent effect and anti-termite effect were ideal [10].
Compared with other pesticide formulations, microcapsule pesticides have obvious advantages in termite prevention because of their various excellent properties. For example,: 1 new house termite prevention is mostly one-time application, and the sustained release property of microcapsule pesticide is once applied. Drugs and long-term effective prevention of termite damage provide a very meaningful means. 2 microcapsule pesticides can isolate the active ingredients of the drug from the soil environment, reduce the impact of many environmental factors on the degradation of the agent, thereby improving the utilization rate of the pesticide, reducing the amount of preventive application, and greatly reducing the environmental stress. 3 The capsule structure of microcapsule pesticide can isolate the active ingredients of pesticides and reduce the volatilization of pesticides, thus reducing the harm caused by human exposure to pesticides. In theory, microcapsule pesticides are more consistent with the concept of high-efficiency, low-toxic, long-lasting and environmentally friendly termite prevention. The application prospects in termite prevention work should be paid enough attention by the termite control workers.
Of course, there are some problems with microcapsule pesticides. For example, its production process is more complicated than other pesticides, the cost is high, and the promotion is not enough. These problems have restricted their promotion and application in termite prevention to some extent. In addition, whether the release law of microcapsule pesticides in the multi-factor soil environment satisfies our expected effects is still to be further verified in practical applications.
5. Conclusion The status of chemical barriers as the main measures for termite prevention in China will continue, and environmental pressures and health risks will continue to increase. Microcapsule pesticides represent the research and development direction of contemporary new agents, and are also an important way to promote the improvement of termite prevention. It has broad application prospects in termite prevention, but its development status also seriously restricts its promotion and application. To change this situation, it is necessary not only for domestic termite control workers to constantly change their own concept of termite prevention, but also to explore new drugs. It is also necessary for domestic pesticide manufacturers to pay attention to production technology innovation and accurately judge market development trends. Government departments provide policy support for new pharmaceuticals with great environmental protection, sustainability and development potential. Only in this way will the termite prevention technology innovation be substantially developed, and the status of termite prevention in China will be improved.
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