What are the occurrence patterns and control measures of the tea tussock moth?

The tea tussock moth is an important pest in China's tea-growing regions, an insect of the genus Euproctis in the family Erebidae of the order Lepidoptera, also known as the tea yellow tussock moth, head-swinging worm, etc. It is distributed in all tea-producing provinces of China, mainly damaging tea leaves, and can also damage tea-oil camellia, citrus, etc. When outbreaks are severe, the leaves of tea plants are eaten almost completely. So, what are the control measures for the tea tussock moth? What are its occurrence patterns? The following provides a detailed introduction.

I. Occurrence patterns of the tea tussock moth

The adult tea tussock moth has a body length of about 10 mm and a wingspan of about 28 mm. The female moth is slightly larger, with a yellow-brown body and wings; the male moth is slightly smaller and brownish. There are 2 pale yellow transverse bands in the middle of the forewing, and 2 black spots in the pale yellow area at the wing tip. The tip of the female moth's abdomen has a yellow hair tuft. Eggs are laid in masses; the egg mass is oval and covered with yellow fuzz. The mature larva has a body length of about 20 mm and is yellow-brown. The three thoracic segments are slightly smaller. Each body segment has 8 yellow (early stage) or black hair tubercles, bearing yellow-brown venomous hairs. The whole body is also densely covered with yellow venomous hairs of uneven length. The pupa is yellow-brown, about 9 mm long, enclosed in a thin soil-yellow silk cocoon about 13 mm long.

The occurrence pattern of the tea tussock moth is multivoltine, with differences in the number of generations across regions. In Hunan, it has 3 generations per year and overwinters as egg masses on the undersides of old leaves. The larval damage periods of each generation occur from April to May, June to July, and August to October, respectively. Damage is generally severe in spring and autumn. After the larvae mature, they form cocoons and pupate under fallen leaves at the base of the tea bush or beneath the soil surface. Female moths lay eggs on the undersides of old leaves. The larvae have 6-7 instars and are gregarious; before the 3rd instar they are strongly gregarious, often with dozens to hundreds gathered on the undersides of leaves feeding on the lower epidermis and mesophyll, leaving the upper epidermis as a translucent yellow-green membranous film. After the 3rd instar, they begin to disperse in groups and cause damage, chewing the leaves and creating notches. After the larvae mature, they crawl to the base of the tea bush under dead branches and fallen leaves or into shallow soil to form cocoons and pupate. The adults are phototactic.

II. Control measures

(1) From November each year to April of the following year, manually remove overwintering egg masses.

(2) Remove the newly hatched larval clusters of each generation.

(3) During the adult emergence period, use lights to trap moths, or use sex pheromones to trap and kill male moths.

(4) In combination with cultivation, bury cocooned pupae deeply.

(5) Biological control: use the tea tussock moth black egg parasitoid and the braconid wasp to control egg masses and larvae. During the larval stage, spray Bacillus thuringiensis or tea tussock moth nuclear polyhedrosis virus.

(6) Chemical control: during the larval stage, spray 90% trichlorfon, 80% dichlorvos, 50% malathion, 50% fenitrothion, 50% phoxim each at 1000-1500 times dilution, or 10% permethrin, 20% fenvalerate, 2.5% deltamethrin each at 5000-6000 times dilution, or 25% diflubenzuron at 1000 times dilution.