Application Research of Insect Pheromones

The research on pheromones is aimed at understanding the regulatory mechanism of insect behavior and physiology on the one hand, and at artificial use of pheromones on the other hand, such as pest control and biological monitoring. In particular, the introduction of the concepts of green plant protection and reverse chemical ecology has made pheromones more and more concerned in production practice. By the end of 2016, there were more than 600 commercialized insect pheromone products in the world.

• Pheromone Based on Functional Groups
• Pheromone Based on Carbon Number (Main Chain)
• Pheromone Plant Growth Regulators

Pest Control

Insect sex pheromones have the characteristics of high accuracy, strong specificity, low cost, convenient use and safety. They are widely used in pest control. The main control methods include trapping, avoidance and blocking mating. Trapping is to use pheromones to attract pests to a designated location and kill them by physical, chemical and other methods. The pheromones used in this way mainly include sex pheromones and aggregation pheromones. For example, the gray tea looper Ectropis grisescens is the main leaf-eating pest on tea trees, which causes serious damage to tea leaves. Its pheromones (Z,Z)-3,9-6,7-epoxyoctadecadiene and (Z,Z,Z)-3,6,9-octadecatri-ene are mixed in a mass ratio of 4:1 and hung 40 cm from the top of the tea tree, which has a good trapping and killing effect on the gray tea looper. Repelling is to use pheromones to drive pests away from the target area. The alarm pheromones of the insects themselves or their natural enemies, high concentrations of aggregation or sex pheromones can be used for repelling. For example, Culex quinquefasciatus is an insect that spreads viruses, and N,N-diethyl-3-p-toluamide has a good repelling and repelling effect on it. At present, combining trapping and repelling is the most commonly used pest control method. If trapping and avoidance are passive pest control methods, then pheromone-mediated mating blocking is a more direct pest control method, which has a good application in the control of moth pests. For example, Lobesia botrana is a pest on European grapes. The artificially synthesized female pheromone component E7, Z9-12∶Ac of Lobesia botrana can interfere with the mating of female and male adults, and has a significant effect on controlling its population. However, it is often difficult to achieve the expected effect by relying on one method to control pests. The integrated pest control measures that combine multiple methods are the higher goal of pest control research. In addition to pheromones, the developed pheromones are also well used in pest control. Due to the poor stability, short action time and high synthesis cost of natural pheromones, researchers have found some pheromone analogs, which have better physical and chemical properties and toxicity, and have great potential application value. In addition, research on pheromone microcapsule technology, slow-release agents and traps can also improve the effect of pheromones in pest control.

Biodiversity Monitoring and Protection

With the serious decline of global biodiversity, biodiversity surveys and species protection have gradually been paid attention to. At present, countries around the world have done a lot of work to prevent the decline of biodiversity, but the effect is not obvious. Developing a pheromone-based monitoring system is an effective management method for protecting endangered species and resource insects, and it is cost-effective. The first pheromone used to protect insects was (R)-γ-decalactone found in the male adult of Osmoderma eremita, which can be used to attract female adults for mating and male adults for species counting. At present, moth pheromones are the most studied and applied in species protection. Moths eat weeds, can pollinate, and are a food source for many birds and reptiles. They play an important role in maintaining the food chain. Due to the influence of facility agriculture and urbanization, the number of moths has dropped sharply, seriously affecting the dynamic balance of the ecology. Female moth sex pheromones have been well used in the distribution survey and protection of species such as Graellsia isabellae, Callosamia promethea and Rhodinia fugax. Compared with pest control, pheromones have not received much attention in species monitoring and protection, mainly because of their limited commercial value. However, pheromones are very sensitive as indicators to indicate whether a species exists in a certain area, especially for the survey and protection of rare insect species, and have the potential for in-depth research.

Promote Insect Pollination

Another great value of insect pheromones is that they can enhance the ability of insects to pollinate flowering plants. In nature, 80% of flowering plant species require animals to pollinate them, and insects are the main mediators. However, environmental climate change and the promotion of facility agriculture have changed the living space of insects and the traditional insect pollination mode. For example, plants attract insects for pollination by secreting some insect pheromones. The pollinating insects of many orchid plants are relatively single, and they have formed a unique mechanism to attract insects during the co-evolution process. Epipactis veratrifolia attracts vetch aphids for pollination by releasing pheromone components of Megoura viciae, such as α-pinene and β-myrcene. The spider orchid Caladenia crebra attracts wasps for pollination by secreting the pheromone methylthiophenol of the wasp Campylothynnus flavopictus. Dendrobium sinense attracts the bee predator Philanthus triangulum for pollination by secreting the bee alarm pheromone component (Z)-11-eicosen-1-ol. Pachysan‐dra axillaris is a winter flowering plant. The main reason why honey bees like to pollinate it is that its volatiles have a high proportion of benzyl acetate. Benzyl acetate is a component of the alarm pheromone of honey bees, which can attract honey bees to gather. Based on these studies, insect pheromones can be extracted or artificially synthesized to stimulate insect pollination behavior, which has broad application prospects in improving the ecological environment and increasing the yield and quality of crops, fruits and vegetables.

Other Applications

The functional diversity of insect pheromones determines their wide application. Many of them are closely related to people's lives and have significant effects. For example, when Italian honey bees are disturbed, they release alarm pheromones to attack intruders, but smoke can inhibit the worker bees' olfactory receptors from receiving alarm pheromones, so beekeepers use smoke to reduce the bees' aggressiveness before managing them; Cinnamo‐mum camphora is a perennial evergreen tree, and its roots, stems, branches and leaves are rich in camphor and essential oils, which have an insect repellent effect. Artificially extracted or synthetic camphor is used in daily life for mite removal and insecticide; Argentine ants Linepithema humile are widely spread in the world, and the viruses they carry can harm a variety of crops. The use of pheromones in vineyards can reduce the activity of ants and reduce their damage to grapes; in libraries, the wood moth Tineola bisselliella, the medicinal herb beetle Stegobium paniceum and the striped beetle Anobium punctatum cause serious damage to books and cultural relics, making manual pest control very difficult, and pesticides cannot be used in these places. The use of pheromones to lure and kill insects has a significant effect on book protection. Therefore, the functions of insect pheromones are multifaceted, and their rational use will be beneficial to human production and life.

In nature, insects are the most diverse and widely distributed animal group on the earth, and they have a very close relationship with humans. Studying the chemical language of insects is of great significance to understanding and transforming nature. Insect pheromones are their most important chemical signals, and researchers have found more than 3,000 pheromones in different insects. Most of the pheromones used now are artificially synthesized, which are different from the pheromones in the natural environment in terms of composition, proportion and material structure, and the amount used is several times or even dozens of times that of the pheromones released by insects. Their impact on the ecological environment should be considered.