Causes of outbreak of tea inchworm and its pollution-free control

Tea inchworm, also known as Archworm, measure-inch worm, hanging filariasis, belongs to the family Lepidoptera. The pest is mainly distributed in Bihu, Lixin and other tea areas in Liandu District. It is a kind of overeating pest. If the prevention and control is not in time, the output of summer and autumn tea will be seriously reduced, and the tree potential will decline, which will seriously affect the tea production. It happened every year in the past few years, but it didn't do much harm. In August 2007, the pest occurred in a large area in the tea garden in Huangling, Lixin Township, which not only seriously affected the tea yield in the current season, but also caused tree potential decline, poor cold tolerance, vulnerable to freezing injury, and affected the tea production in the following year.

1 what happens

On August 19, 2007, a small number of larvae were found in the tea garden on Huangling, Lixin Township. Seven days later, the tea garden was damaged in a large area. All the green leaves and twigs of the tea trees were eaten up. Most of the tea trees in the affected tea garden only left their main veins, shaped like fire, and there was no tea to pick.

2 habits and harmful characteristics

2.1 Life habits

Most of the tea inchworm overwintered as pupae in the tea rhizosphere topsoil and a few as larvae in the tea bushes. Most of the overwintering pupae are in the state of diapause, with strong stress resistance and low mortality, and the emergence rate after overwintering is greatly affected by soil moisture.

There are 6 to 7 generations a year in Zhejiang, the first and second generations have obvious "hair center" phenomenon, the third generation overlap, the fourth generation occurs in a large amount, which is the most harmful generation in the whole year. If the environmental conditions of autumn are suitable (temperature, food and control are not timely), the sixth generation of tea inchworm will occur in large quantity and the loss of autumn tea will be serious. If the temperature is above 20 ℃ in winter, seven generations may occur. After hatching, the tea inchworm larvae formed an obvious occurrence center on the surface of the tea canopy, and the silking and drooping of the larvae spread with the wind. The 1st and 2nd instar larvae mostly harmed on the leaf surface, and the 4th or 5th instar entered the stage of overeating.

2.2 Hazard characteristics

Those with good tea growth, fertile soil, deep soil layer, loose structure and good water retention generally have a large insect population, high density and heavy damage; tea gardens with shelter from the wind and the sun occur earlier and suffer more seriously; flat and sloping tea gardens occur more seriously than mountain tea gardens; hilly tea gardens occur more seriously than alpine tea gardens.

3 the cause of the outbreak

3.1 Climatic factors

Due to the warm winter weather in 2006, tea inchworm has more overwintering insects, higher maturity and higher overwintering survival rate. It provides a sufficient population for the outbreak of tea inchworm.

3.2 Food factors

Due to the increase of new tea gardens, the improvement of fertilization and management in tea gardens and the change of picking system, there is too much tea in summer and autumn, which provides rich food for the outbreak of tea inchworm.

3.3 untimely prevention and treatment

Due to the occurrence of irregular and small scale over the years, it does not constitute a disaster, so it has not attracted much attention in production. At the same time, due to the lack of understanding of the occurrence characteristics and control period of tea inchworm, when tea inchworm entered the stage of overeating in the elderly, attention was paid to it, and the control has entered the stage of overeating in the elderly, resulting in serious losses and increasing the difficulty of control.

4 pollution-free prevention and control

4.1 strengthen forecasting and forecasting

In view of the occurrence characteristics of tea inchworm, it is necessary to strengthen the monitoring of insect situation, grasp the occurrence dynamics of insect pests in time, do a good job in the transmission of pest information, and accurately release the forecast of pest trend, so as to provide scientific basis for pest control. It is convenient for tea farmers to take appropriate control measures in time according to the situation.

4.2 timely picking and deep ploughing

Tea geometrid larvae mainly feed on the tender leaves of tea trees, and picking fresh leaves in time can take away some of the larvae and reduce the harm. Combined with deep digging and fertilization in autumn and winter, tea inchworm can be deeply buried in the pupa of tea rhizosphere topsoil, so that it can not be unearthed and the harm can be reduced.

4.3 entrapment

Tea inchworm adults have phototaxis, and the adults have phototaxis. Frequency vibrating insecticidal lamps can be used to trap and kill adults in the moth stage to reduce the number of eggs laid. The isotropic method can also be used to interfere with mating, that is, a large amount of extra-sex hormones are released in the tea garden, destroying the normal information relationship between male and female adults, making the male lose the ability to find the female and unable to mate, thus reducing the incidence of larvae.

4.4 artificial hunting and killing

According to the habit of silking and sagging after being frightened, the larvae can be knocked down in the evening or before dawn to be eliminated.

4.5 spraying virus

Tea inchworm nuclear polyhedrosis virus has a strong infection rate to tea inchworm larvae, and the disease rate is the highest in the first, fifth and sixth generations of tea inchworm in the whole year, with a dosage of 15 billion ~ 70 billion polyhedrosis per mu.

4.6 Protection and utilization of natural enemies

The natural enemies of tea inchworm are parasitic flies, parasitic wasps, spiders, lacewings and ants. Tea gardens should try to reduce the number of times of drug use and reduce the amount of pesticides in order to protect natural enemies and give full play to the control role of natural enemies.

4.7 Chemical control

The first and second generations of the insect occurred neatly, and the three generations overlap. The elimination of tea inchworm before three generations in production is important to control the damage in the whole year. Pesticide control should be carried out strictly according to the control index. When the control index of adult tea garden is 4500 larvae per mu or 10 long tea rows of sea rice, spraying control should be carried out in the tea garden. The suitable period of application is in the larval stage before the 3rd instar. The key generation of comprehensive application was the fourth generation, followed by the third and fifth generation, and the first and second generation advocated selective treatment. The suitable way of application is to sweep and spray with low capacity. The medicament can choose 2.5% cyhalothrin, 20~25mL per mu, safety interval 5 days; 2.5% deltamethrin, 20~25mL per mu, safety interval 5 days.