Insect pheromones are extremely trace amounts of chemicals secreted by insect-specific glands, and are the medium for chemical communication between insects. Many insect life activities such as mating, host orientation and selection, identification of spawning sites, alerting, and defense are regulated by their chemical information. Synthetic insect pheromones are also called insect behavior modifiers. Generally, these synthetic insect pheromones cannot directly kill the pests, but achieve the purpose of controlling pests by interfering with the insect's normal behaviors such as mating behavior, spawning behavior, feeding behavior, assembly behavior, self-defense behavior, etc. With the deepening of the understanding of the mechanism of chemical information connection between organisms, the use of insect pheromones to change and disrupt the normal life activities of pests has opened a new way for pest control.
Research progress of insect pheromone
The most studied insect pheromones are sex pheromones, cluster pheromones, spawning attractants, kairomone, and so on. Insect pheromones require comprehensive research in multiple disciplines including entomology, chemistry, ecology, physiology, biochemistry, behavior, etc.
Insect pheromone biological research includes the courtship and mating behavior of insects, the morphology and ultrastructure of glands that secrete pheromones, and the sex pheromone biosynthesis and endocrine regulation. The first issue in insect pheromone chemistry research is to understand the chemical structure and composition of these pheromones. Due to the small content of these substances and their complex components, it is not easy to understand their structure and composition. The initial test subjects may require hundreds of thousands of insects. Later, due to the introduction of high-sensitivity analytical instruments, the number of insects used in the analysis was reduced to hundreds or even dozens. In order for insect pheromones to function properly when applied in the field and to be released into space at a certain rate, it is necessary to have various slow-release formulation. The most commonly used slow-release formulations use natural rubber or plastic as a carrier. Researching effective pest control technologies that have no side effects on the environment, humans and animals is an important basis for establishing a comprehensive pest management system.
Application of pheromone in pest control
The purpose of controlling pests can be achieved by preventing food search, intra-specific contact and reproduction of pests, and promoting the breeding of natural enemies of pests. Insect attractants used for pest monitoring have the advantages of high sensitivity, strong specificity, and low cost. More than 100 commercial insect attractants have been used for pest detection.
Generally, 3-5 traps are hung at each measurement point, and the number of lure moths is recorded daily. According to the number of adult worms monitored, the number of eggs, the number of larvae, and other control thresholds can be used to decide whether or not to spray and optimum spraying period. A large number of traps can be used to capture part of the male moth, so that the female moth has no chance of mating, thereby reducing the pest density. For this method to be effective, 85% to 90% of the male moths need to be trapped, so a certain number of traps are required. If the pest density is too high, the trapping method will be difficult to work. At this time, other methods must be used to reduce the pest density before using the trapping method. It is alsopossible to reduce the density of pests by setting a large number of sex attractant dispensers or spraying sex attractants. This method allows the scent of sexual attractants to be emitted into the air to disrupt insect activity and reduces the chance of pest mating, thereby reducing pest density. The amount of sexual attractant to be used in this method is relatively large, and 1500-7500 dispensers or 30-75 grams of sustained-release dosage forms need to be set per hectare, which is very costly. And for some insects, if the pheromone dose exceeds the optimal threshold, the number of trapped pests will decrease. For example, when the pheromone content is in the range of 0.5-200 micrograms, the core trap of diploid pupae will be attractive to male moths, but when the pheromone content is in the range of 25-75 micrograms, the number of captured male moth reaches the maximum.
Insect pheromones are highly specialized, do not harm natural enemies of pests, have no side effects on the environment, and are easy to use. Since artificial insect pheromone can be synthesized in large quantities at low cost, it can be used as an effective tool for controlling pests. However, some biological characteristics and external environmental factors related to insect information links have limited the application of insect pheromones to a certain extent. Populations of the same species in different geographies, or different individuals in the same population may form different pheromone communication systems during the evolution process. Therefore, insect pheromones are mainly used for pest monitoring at the present stage. And under certain conditions, pheromones can be applied in combination with other measures. For example, using pesticides to reduce the density of pests, and then using pheromones to interfere with and trap the pests.