Occurrence and Damage Characteristics of Tea Tussock Moth and Integrated Control Methods

In recent years, with the development of pollution-free tea and organic tea production, the frequency and amount of chemical pesticides used in tea gardens have decreased, and some tea gardens even do not use chemical pesticides, resulting in aggravated damage by the tea tussock moth in a short period. In the county where the author works, tea tussock moth damage has occurred for several consecutive years, and after being damaged, the tea plants were left with only bare branches, greatly affecting the economic income of tea farmers.

1. Damage symptoms

The tea tussock moth larvae bite and feed on leaves, causing leaf notches and bare branches. 1st-2nd instar larvae gather on the underside of leaves to feed on the mesophyll, leaving only the epidermis and veins, and the damaged leaves appear as transparent dry membranes; after the 3rd instar, food intake increases greatly, and they begin to disperse in groups to damage the upper leaves of the tea bush, feeding on leaves to form notches. When the damage is severe, buds, leaves, flowers, and young fruits are all eaten clean, leaving only bare branches. In addition, the venomous hairs, molted skins, and cocoon silk on the larvae's bodies are toxic and, when touched by humans, cause redness, swelling, pain, and itching, hindering tea picking and tea garden management.

2. Integrated control

For the control of the tea tussock moth, the plant protection policy of "prevention first, integrated control" should be adhered to, protecting and utilizing natural enemies, and using low-toxicity, low-residue pesticides for control, so that the pesticide residues in tea leaves meet the standards for pollution-free tea.

2.1 Agricultural control: First, balanced fertilization should be carried out. Apply sufficient base fertilizer, combine organic fertilizer with chemical fertilizer, and control the application of chemical nitrogen fertilizer as much as possible, promoting normal growth of tea plants and improving their resistance to pests and diseases. Second, manual removal should be carried out. From November of the current year to April of the following year, pick off leaves with yellow egg masses on the underside, and before the larvae hatch in early spring, pile them in a small basin, place a large basin with water (with pesticide added to the water) outside, and put it near the tea garden. This can kill the tea tussock moth and protect the parasitic wasps parasitizing inside the egg masses, so that after emergence they fly back to the tea garden and eliminate the tea tussock moth. Manually remove the clustered larvae leaves before the 2nd instar, trample them to death on the spot, or soak and kill them with a pesticide solution. Third, intertillage and hilling should be carried out. During the peak pupation period, combined with intertillage in the tea garden, a large number of pupae that have entered the soil can be hoed and killed, and hilling about 6cm around the roots can prevent adult emergence. Fourth, trapping and killing control should be carried out. In the early stage of moth emergence for each generation, light lamps at night to trap and kill adults.

2.2 Biological control: This is an important measure that does not pollute the tea garden, meets the requirements of pollution-free tea production, reduces pesticide residues, and effectively controls the tea tussock moth. Before the 2nd instar larval stage, spray control can be carried out with 16000IU/mg Bt formulation at 10000 times dilution, 2.5% rotenone emulsifiable concentrate at 300-500 times dilution, or 0.36% matrine emulsifiable concentrate at 1000 times dilution. In addition, selecting suitable concentrations of Bacillus thuringiensis var. aizawai, Bacillus thuringiensis var. galleriae, and self-made tea tussock moth nuclear polyhedrosis virus also has very significant control effects. When controlling, spraying on a windless cloudy day or just after rain clears is most effective.

2.3 Chemical control: On the basis of agricultural control and biological control, when the damage by the tea tussock moth is still severe, chemical pesticide control must be used. Before the 3rd instar larval stage, spray control with 80% dichlorvos emulsifiable concentrate at 800-1000 times dilution or 10% cypermethrin at 4000-6000 times dilution, and strictly observe the pesticide safety interval; tea must not be picked during the safety interval.