Occurrence and damage of tea caterpillar and its integrated control

In recent years, with the development of pollution-free tea and organic tea production, the number and number of chemical pesticides used in tea gardens decreased, and some tea gardens even did not use chemical pesticides, which led to the aggravation of tea caterpillar damage in a short time. The tea caterpillar damage occurred in the tea garden of the author's county for several years in a row, and only bald branches were left in the damaged tea trees, which greatly affected the economic income of tea farmers.

1. Harmful symptoms

The tea caterpillar bites the leaves with larvae, causing the leaves to be engraved and bald branches. 1 the 2nd instar larvae gathered on the back of the leaves to feed on the mesophyll, leaving only the epidermis and veins, and the injured leaves were transparent and withered; after the 3rd instar, the food intake increased greatly and began to disperse into groups to harm the upper leaves of the tea bushes. When the damage was serious, the buds, leaves, flowers and young fruits were all eaten up, leaving only bald branches. In addition, the poisonous hairs, molting shells and cocoon filaments on the larvae are all poisonous, touching the human body, causing redness, swelling, pain and itching, hindering tea picking and tea garden management.

2. Comprehensive prevention and control

The prevention and control of tea caterpillar should adhere to the plant protection policy of "prevention first, comprehensive control", protect and utilize natural enemies, and use low-toxic and low-residue pesticides to make the pesticide residues in tea meet the standard of pollution-free tea.

2.1 Agricultural control: first, balanced fertilization should be carried out. It is necessary to apply sufficient base fertilizer, to achieve the combined application of organic fertilizer and chemical fertilizer, and to control the application of chemical nitrogen fertilizer as far as possible, so as to promote the normal growth of tea trees and improve their resistance to diseases and insect pests. The second is to carry out manual removal. From November of that year to April of the next year, the leaves with yellow eggs on the back were picked and stacked in a small basin before the dry spring larvae hatched, and a large basin with water (pesticides in the water) was placed near the tea garden, which could kill the tea caterpillar, protect the parasitic wasps parasitic in the egg mass, and make them fly back to the tea garden after Eclosion to destroy the tea caterpillar. The leaves of the larvae clustered before the 2nd instar were removed manually and trampled to death on the spot or immersed in the solution. Third, ploughing and soil cultivation should be carried out. In the peak period of pupation, combined with tea garden ploughing, a large number of pupae can be wiped out, and 6cm can be cultivated in the rhizosphere to prevent adult emergence. Fourth, entrapment and prevention should be carried out. At the early stage of each generation of moths, the adults were trapped and killed by lighting lamps at night.

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 tea caterpillars. Pre-2nd instar larvae can be sprayed with 10000 times of 16000IU/mgBt preparation, 2.5% rotenone EC 300 Mel 500 times or 0.36% matrine EC 1000 times. In addition, the control effect of suitable concentration of fenitrobacter, cyanobacteria and self-made tea caterpillar nuclear polyhedrosis virus was also significant. In prevention and treatment, the spray effect is the best when there is no wind in cloudy days or when it clears up at the beginning of rain.

2.3 Chemical control: on the basis of agricultural control and biological control, when the damage of tea caterpillar is still serious, chemical pesticides must be used. In the pre-3rd instar larva stage, spray control with 80% dichlorvos EC 800ml 1000 times or 10% cypermethrin 4000ml 6000 times, and strictly control the pesticide safety interval, do not pick tea during the safe interval.