Occurrence characteristics and control techniques of black whitefly in tea plant

The black thorn whitefly mainly uses the larvae to absorb the tea tree juice on the back of the leaves, which causes coal bacteria parasitism and coal disease, and when it is serious, the tea tree is pitch black. The damaged tea trees had lower photosynthetic efficiency, lower germination density, late germination, thin bud leaves and serious defoliation, which not only affected the yield and quality of tea, but also seriously affected the potential of tea trees.

I. occurrence characteristics

The insect has four generations a year, overwintering as mature larvae on the back of tea leaves, pupating in March in the second year, and the peak periods of the first to fourth generation larvae are in late May, mid-July, late August and late September to early October, respectively. The flying ability of adults is weak, most of the eggs are laid on the back of adults and old leaves, and the newly hatched larvae can crawl, but they are soon fixed near the hatching shell. The insect likes to be depressed and closed, and it is easy to occur in the tea gardens with more leaves in the middle and lower part of the tea bushes and in the tea gardens after several years of table cutting. the insect population distribution in the tea bushes is more in the lower part and less in the upper part. The key factors affecting the population growth and decline of whitefly whitefly are environmental conditions and natural enemies.

The most influential factors in the environmental conditions are human factors and tea garden environment. The so-called human factors are mainly the unreasonable use of chemical pesticides, especially the frequent application of pesticides in tea gardens, killing a large number of natural enemies of whitefly whitefly, resulting in disaster. The black thorn whitefly in the tea garden environment is generally more serious in the tea garden where the tea tree is dark and wet, and the pest density in the tea garden in the sunny depression is often higher.

It is reported that there are 66 species of natural enemies, including 20 species of predatory spiders, 27 species of predatory insects, 8 species of parasitoids and 11 species of parasitic bacteria.

Second, prevention and control technology

1. Protect the natural enemies: reduce the times of pesticide application and the amount of pesticides in the tea garden as far as possible, in order to protect and promote the reproduction of natural enemies and give full play to the control role of natural enemies.

2. Agricultural control: light pruning can be carried out in locally occurring tea gardens, table cutting can be carried out in tea gardens with serious occurrence of whitefly whitefly, and the cut branches and leaves can be centrally treated to reduce the number of insects in the field.

3. Biological control: Sporosporium Weber has strong pathogenicity to the larvae of whitefly whitefly, the suitable concentration is 200 million ~ 300 million spores per milliliter, and the suitable period for control is in the stage of 1st and 2nd instar larvae.

4. Chemical control: the control indexes of whitefly are 2 leaflet varieties / mu ~ 3 / mu and 4 large leaf varieties / mu ~ 7 / mu. When the number of insects in the field exceeds the control index, chemical control should be considered. The key to chemical control is to master the appropriate period for control, and the appropriate period for the control of the pest is the peak stage of egg hatching. For the insect population density is too high, it can also be considered as a period of auxiliary application in the peak period of adult insects.

Control agents can be selected: 10% imidacloprid wettable powder 20-30 g / mu, 98% Batan wettable powder 40-50 g / mu, 50% phoxim EC 100 ml / mu, the above pesticide safety intervals are: 7 days, 7 days and 5 days respectively. Spraying must be aimed at the target in order to improve the utilization rate of the agent. It is suitable to control adults by low-volume spray. Lateral spraying is recommended in the larval stage, and the liquid is mainly sprayed on the back of the middle and lower leaves of the tea tree.