Tea plants are perennial evergreen shrubs, and environmental pollutants accumulate in tea gardens and within the plants over time. Due to their large leaf surface area, tea plants have a higher initial deposition of Pesticides or adsorb higher concentrations of environmental pollutants under the same dosage and air pollution levels compared to other crops. With multiple harvests per year, the interval between pesticide application and harvest is short, reducing the time for pesticide degradation. After picking, tea leaves are directly processed into dried tea, which is then steeped for consumption, causing any pesticide residues or pollutants to leach into the tea infusion based on their solubility. Therefore, the ecological environment of tea gardens and the quality safety of tea products receive significant attention.
I. Development of Pest Management Technologies in China
1. Traditional Control Stage
Before the 1940s, tea gardens were scattered and sporadic, with relatively few pest outbreaks. Pest control technologies were also rudimentary. Since the founding of the People's Republic of China, although tea production rapidly developed, pest management in tea gardens remained at the stage of agricultural control measures and the use of plant-based pesticides. Although this period was technologically primitive from an ecological perspective, the populations of pest and beneficial organisms were relatively balanced.
2. Chemical Control Stage
The first chemical pesticides used in tea production were organochlorine compounds, followed by organophosphorus pesticides in the 1960s and pyrethroid pesticides in the late 1970s. In the early 21st century, neonicotinoid pesticides began to be applied in tea production. While the widespread use of chemical pesticides improved pest control effectiveness, it also led to pesticide residue issues and risks to tea quality safety. It also caused a reduction in beneficial insect populations and a surge in pest populations in some regions. From the 1960s to the 1990s, China experienced five nationwide shifts in pest populations in tea-growing areas, three of which were due to changes in pesticide types. Although chemical pesticides are still used in tea production, their overall usage has been decreasing.
3. Introduction of Green Control and Ecological Regulation Concepts
The purpose of pest control in tea gardens is to prevent economic losses due to pest damage. Gradually, people realized that during pest management, secondary pest outbreaks, impacts on beneficial organisms, and environmental pollution must also be considered. Therefore, while controlling pests, sustainable development principles and harmonious coexistence must be emphasized. The concept of ecological regulation should replace the concept of eradication. Starting from the 1980s to the 1990s, international efforts aimed to reduce chemical pesticide use through ecological regulation techniques.
III. Technical Content and Implementation of Green Pest Management in Tea Gardens
1. Physical Control
Physical control technologies are designed based on the principle that insects are attracted to specific wavelengths, light, and colors. They use sticky traps and light traps to lure and capture pests. Currently, yellow-red dual-color sticky boards (to attract and kill green tea aphids and thrips), blue sticky boards (to attract and kill thrips), and green sticky boards (to attract and kill leafhoppers) are used in tea gardens. In recent years, narrow-spectrum lights have replaced broad-spectrum lights in light trapping technology, reducing accidental harm to natural enemies.
Introduction to Green Pest Management Technologies and Products by the Tea Pest Management Team of the Chinese Academy of Agricultural Sciences Tea Research Institute
2. Chemical Ecological Control
(1) Pheromone Control Technology
Pheromones are chemicals that mediate communication between organisms. Pheromone control technology involves using synthetic volatile substances to lure, repel, or disrupt the behavior and mating of pests to achieve pest control. For example, sex pheromone control technology uses synthetic compounds that mimic the pheromones released by female pests to attract males. Since 2005, the Tea Research Institute of the Chinese Academy of Agricultural Sciences has successfully analyzed, identified, synthesized, and field-applied sex pheromones for several tea pests, including tea looper, gray tea looper, tea caterpillar, tea leafroller, tea black moth, and tea silkmoth. These applications have covered tens of thousands of hectares and have been well-received by tea producers.
In addition to sex pheromones, aggregation pheromones can also be used to control pests like thrips, which secrete aggregation pheromones to form clusters, making them easier to manage.
(2) Use of Plant Volatile Lures
Plant volatiles are the “language” of plants. Plants release different volatile compounds under different conditions to communicate with other organisms. The study of information exchange in nature has become a new discipline in modern science, and its application in green pest control is worth noting. At a test site in Shaoxing, Zhejiang Province, local tea gardens suffered severe infestations of tea longicorn beetles. Researchers used plant volatiles, specifically alcohols and aldehydes containing 5-6 carbon atoms, mixed with vinegar, rice wine, and Sugar to create a low-cost lure. When placed in pots in the tea gardens, it effectively lured the beetles. Over three years, more than 330,000 tea longicorn beetles were captured in the tea gardens using these lures. Further tests are ongoing. It is expected that the use of various volatile lures for pest control will become an important chemical ecological control technology in tea gardens within the next 5-10 years.
3. Biological Control
(1) Utilization of Natural Enemies
Natural enemies include predatory and parasitic organisms. Parasitoids lay their eggs inside the eggs, larvae, pupae, or adults of pests, leading to the death of the host, such as various parasitic wasps and flies. Predators consume pests, such as ladybugs. Protecting natural enemies in tea gardens and introducing and releasing natural enemies can help achieve pest control objectives.
(2) Use of Biopesticides
Biopesticides are products derived from living organisms (fungi, bacteria, viruses) or their metabolites used to control pests. Commonly used biopesticides in tea gardens include Bacillus thuringiensis (BT), Beauveria bassiana, and Metarhizium anisopliae, primarily targeting leaf-eating pests like tea looper, gray tea looper, tea caterpillar, and obliquebanded leafroller, as well as weevils. Pyrethrum and rotenone, among others, and viral preparations for tea looper were introduced in the 1980s. Since the turn of the century, viral preparations for gray tea looper, matrine, azadirachtin, and campneosines have also been applied in tea production.
4. Agricultural Control
Agricultural control is based on improving the ecological environment of tea gardens, focusing on agricultural measures and biological and ecological theories. This method enhances natural control capabilities, achieving a relative balance between pest and natural enemy populations, and will gradually become an essential measure for pest management in tea gardens. To implement this approach, tea plants should be grown in mountainous areas with favorable ecological conditions and resistant varieties selected. A protective forest of taller trees can be planted around tea gardens to prevent pest entry and migration. Beneficial plants that attract natural enemies can be interplanted in the tea rows to increase the diversity of natural enemies and aid in pest control. Attention should also be given to appropriate fertilization, particularly increasing phosphorus and potassium, to enhance the resistance of tea plants, especially against small piercing and sucking pests