The application of insect pheromones in pest control has become an important development direction for green control in the process of modern organic agriculture. Compared with traditional pesticides, pheromones have more advantages such as easy degradation, high efficiency, non-toxicity, etc. Insect pheromones can be mainly used for pest monitoring, trapping and mating disruption. Among them, mating disruption is the main means of pest control. It interferes with the mating of insects by altering the concentration of specific insect pheromones around the crops.
Although insect pheromones have high biological activity and safety, pheromones cannot be used directly in practical application. Most synthetic pheromone molecules are highly volatile and are susceptible to environmental factors such as temperature, sunlight, wind and rain, etc., so the application of insect pheromones has been severely limited. Therefore, it is necessary to develop the controlled release technology of insect pheromones to realize the precise delivery and maintain a certain concentration level of pheromones in the control area.
Controlled Release Technology
Controlled release technology refers to slowing down the release rate of pheromones by a specific method, so that the effective concentration of pheromones in the control area can be maintained for a long time and the control effect is improved. The physical and chemical properties of the controlled release system is more stable and the system is easier to preserve. What's more, the technology can prevent pests more effectively, reduce the amount of pheromone applied as well as reduce agricultural costs. In recent years, controlled release technology of insect pheromone has been a research hotspot in the field of materials chemistry.
According to the mode of action between the controlled release agents and the active substances, the controlled release technology can be divided into physical release and chemical release.
Physically release typically involves dissolving the active substance and dispersing or encapsulating it in a sustained release agent to hinder the release of the active substance. There are three ways of physical controlled release.
The pheromone active molecule is uniformly dissolved or dispersed into the release agents, and the active substances on the surface of the dispersion system are first released while the remaining active substances are gradually diffused to the surface and then released.
The active substance is embedded in a membrane to form a capsule, which is released to the environment through the envelope, and the release rate is controlled by the thickness, composition and others of the membrane.
The active molecule forms a gel with the controlled release agent, and the release rate is controlled by the concentration of the cross-linking agent and the polymerization conditions during gel preparation.
Chemical release refers to the chemical bonds between the active molecules and the controlled release agents, and the release of the active substance is carried out by breaking the chemical bonds in the release system. Chemical release can be divided into the following three ways.
- Active substances and the controlled release agents are directly or indirectly linked by covalent bonds.
- Active monomers are converted into polymerizable monomer derivatives and polymerized to become polymers, which then release active substances under the specific condition.
- Polymers are obtained by direct polymerization between reactive monomers with double reactive groups. When the chain-end of the polymer is broken, the active substance can be released, and the release rate is controlled by the degree of polymerization.
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