Detailed Guide to the Control Methods of the Tea Green Leafhopper (Empoasca onukii)

The tea green leafhopper (Empoasca onukii), commonly known as "fuchenzi," is one of the major pests on tea plants in all tea-producing regions of our province. Damage from this pest ranges from minor harm to buds and leaves with reduced yields, to severe destruction of buds and leaves resulting in total crop loss.

I. Morphological Characteristics

The tea green leafhopper belongs to the order Homoptera, family Cicadellidae. Its life cycle passes through three stages: egg → nymph → adult.

1. Egg: crescent-shaped, about 0.8 mm long and about 0.15 mm wide, initially milky white, gradually turning pale green; before hatching, a pair of red eye spots is visible through the front end.

2. Nymph: 5 instars in total. Initially milky white, gradually turning pale yellow then green as the instar increases; wing pads begin to appear at the 3rd instar, and at the 5th instar the wing pads extend to the fifth abdominal segment.

3. Adult: 3.1-3.8 mm from head to wing tip, pale green to pale yellow-green. The central area of the crown usually has two green spots, and the front margin of the head has a pair of green rings, also called pseudocelli; the compound eyes are grayish brown. The mesothoracic scutellum has white bands, with the transverse striations straight and level. The forewings are pale yellow-green, the base of the front margin green, and the wing tips transparent or slightly smoky brown. The legs are the same color as the body, but the ends of the tibiae and the tarsi of each leg are green.

II. Damage Mode

Nymphs and adults pierce and suck the sap of tender shoots, buds and leaves, and female adults also lay eggs inside tender shoots, causing damage to the conducting tissues, loss of nutrients and insufficient water supply. After damage, buds and leaves show wilting, reddening of veins, reddening and even scorching of leaf tips and margins, shortened internodes and brittle texture. Among the whole year, the second round of tea suffers the most severe damage.

III. Occurrence Characteristics

The tea green leafhopper has a tendency to prefer tender growth and only damages tender shoots, buds and leaves. It is photophobic and afraid of moisture; in the early morning when the dew has not yet dried, it is not very active, and after the sun comes out it gradually moves into the canopy. Its adults gradually develop eggs, and eggs are laid day by day, 1-2 per day, which determines that its generations are not uniform. In summary, its occurrence has the following characteristics.

1. Number of generations per year: mostly 13 generations per year in Guangdong; it overwinters as adults in northern Guangdong, while in other places there is no obvious overwintering phenomenon.

2. Overlapping generations: in messy tea gardens, adults and nymphs can be seen at the same time. However, there are two population peaks throughout the year: the first peak in May-June, and the second peak in September-October.

3. Climatic factors: temperature, precipitation and the number of rainy days are the main climatic factors affecting the population dynamics of the tea green leafhopper. It is suitable for occurrence under conditions of an average temperature of 17-28°C and alternating sunny and rainy weather.

4. Natural enemies: there are many, more than 60 species, the most important being egg parasitoid wasps, mymarid wasps, spiders and entomophthoralean fungi, etc.

In addition, its occurrence and development are closely related to cultivation management and variety. Baiye Dancong is severely damaged.

IV. Control Methods

There are two different directions for controlling the tea green leafhopper: one is the ecological regulation method, and the other is the chemical pesticide control method.

1. Ecological regulation: so-called ecological regulation means using agricultural cultivation and management measures, such as pruning and plucking, to fully protect natural enemies, give play to the role of natural enemies, and control the occurrence of the tea green leafhopper well. For example, Haiou Farm and Yongshi Farm on the Leizhou Peninsula in our province adopted the ecological regulation method and did not apply pesticides in more than 7,000 mu of tea gardens; for more than ten years, they have kept the tea green leafhopper below the level causing economic loss for a long time. The bud and leaf damage rate is low, the pest population density is low, there are many species and large numbers of spiders, the parasitism rate of mymarid wasps is high, and the tea green leafhopper has been completely controlled. This method is convenient, effective and low in cost, and will not cause pesticide residue contamination in tea. When adopting the ecological regulation method, there will be a certain risk in the initial stage, that is, in the early stage of stopping pesticide application, the pest population will rise to a certain extent, but there is no need to be afraid; when the populations of natural enemies such as parasitoid wasps and spiders increase, they can play a controlling role.

2. Chemical pesticide control: the chemical pesticide control method is commonly used in tea gardens throughout our province. It is effective, but it also has major drawbacks. After application, it kills natural enemies. According to our investigation, in any tea garden where pesticides have been used, it is very difficult to find mymarid wasps, and the number of spiders also drops rapidly, making it difficult for natural enemies to play their role. Moreover, the occurrence of the tea green leafhopper is not uniform, and eggs are laid in tender shoots, so one application often cannot solve the problem, and frequent application is needed, thus creating a vicious cycle: the more pesticides are applied, the more dependent one becomes on pesticides. For example, in some tea farms in our province, pesticides are applied once for every tea plucking, and pesticides are applied many times each year, yet the pest still occurs heavily, while costs increase and pesticide residues also increase. We believe that all localities should overcome the idea of blindly relying on chemical pesticides and use as few pesticides as possible. Even if pesticides must be used, they should be selected accurately and applied according to the target, so as to reduce pesticide residues and lower costs.

At present, pesticides with relatively ideal effects for controlling the tea green leafhopper include Tianswang, Kung Fu, endosulfan, batan, imidacloprid, etc. The specific usage is: 10% imidacloprid 15-20 grams diluted to a 4000-5000 times solution; 35% endosulfan 50-75 milliliters diluted to a 1000 times solution; 98% batan 40-50 grams diluted to a 1000-2000 times solution; 2.5% Tianswang 25-40 milliliters per mu, diluted with water to a 1500-2000 times solution; 2.5% Kung Fu 25-35 milliliters per mu, diluted with water to a 2000 times solution for spraying. Any one of the above pesticides may be selected, and application should be timed before the peak of the tea green leafhopper nymphs.