Occurrence and Control of Rice Water fly in Aksu area

Rice water fly (EphydramacellafiaEgger) belongs to Ephydridae of Diptera family, which occurs very seriously in newly reclaimed saline-alkalized rice area and is one of the important pests of rice production in Aksu area. The insect bites on primary and secondary roots, resulting in stunted growth of rice seedlings or death of floating seedlings. A survey of rice in Aksu Prefecture from 2002 to 2003 found that the yield loss of light stripe fields reached 5.8% to 8.1%, while that of heavy stripe fields reached 40.5% to 56.1%, which seriously affected rice production in this area. In this paper, the morphological characteristics, living habits, occurrence regularity and control methods of rice fly were investigated and studied.

1. Morphological characteristics

The adult body is 6mm long, the wingspan is 8mm, the body is grayish brown to black-gray, and the head is lead-gray. The compound eyes are covered with short black hair, the top is golden-green, and the back of the chest is purple. The egg is 0.5-0.7 mm long, nearly round, colostrum white, and then yellowish white. The larva has 11 nodes, the soil is gray, and there are eight pairs of pseudopods in each of the 4-11 nodes on the ventral side. The body surface is smooth and bristled. The pin is dark brown and the back ends are bifurcated. The pupa is a peripupa, and the front end of the pupa shell is annularly split during Eclosion, which belongs to the ring cleft class. It is 8-10 mm long and 2-3 mm wide, with 11 nodes, cylindrical, initially yellowish brown, and then yellowish brown or brown. Its tail 9-11 pseudopod forms a ring hook suitable for fixing on the roots, stems and leaves of rice and weeds during the process from larva to pupa.

II. Distribution and harm

In China, the damage caused by rice flies has been reported in Ningxia, Hebei, Liaoning, Gansu, Shaanxi, Shandong, Inner Mongolia and other provinces. The hosts of rice flies in this area are Reed grass, trigonous grass, paspalum grass, wild rice, horse tang, Setaria, sedge and other Gramineae weeds. Rice water fly is a major pest in the seedling stage of rice in saline-alkali soil. The larvae endanger the freshly exposed rice seeds, cause rotten seeds, bite the primary and secondary roots of rice, absorb juice and nutrients, and cause floating seedlings. In addition, the larvae pupated and sandwiched on the rice root seriously affected the normal development of rice. In Aksu area, rice flies are mainly harmed in the two periods of rice dew and standing needle.

Third, occurrence regularity

1. Life history

Rice water flies occur four generations a year in Aksu area, and each generation occurs for about 40 days, and the generations overlap. The adults overwintered in the cracks of large soil clods, under the salt crust on the edge and under the deciduous layer of poplar, Elaeagnus angustifolia and weeds. At the end of March and the beginning of April in the second year, when the temperature rose to 14: 15 ℃, the adults first moved on the alkaline zone and stagnant puddle water surface of the paddy field, feeding on humus. After the rice field is flooded, the overwintering adults lay eggs on sundries and floating objects in the paddy field, and the larvae feed on humus first and then harm rice. Rice whitening and needle-setting stage is the main damage period, to rice tillering, rice root system firmly in the ground, plant development is strong, no longer damaged, and it propagates on weeds on the edge of the paddy field.

two。 Main habits

The adults of rice flies have strong phototaxis. The adults of rice flies can be attracted by a large number of black lights with a wavelength of 3650 A. The adults like to live on the dirty foam layer of the water surface and move on the sewage surface, and there are adult activities wherever stagnant water accumulates. They are especially active when the temperature rises, chasing each other, feeding on the decaying organic matter floating on the water surface and laying eggs on the floating matter. The places with more floating objects on the water surface attract and gather more adults, lay more eggs and have a high density of larvae. Because the floating objects are often blown to the ridges at the edge of the field, the larvae and pupae are mostly distributed in the edge and corner of the paddy field, and often occur in stagnant puddles, alkali drains, newly opened wasteland and saline-alkali heavy paddy fields, and the prevention and control is also the key.

IV. The relationship between occurrence and environment

1. The relationship between temperature and occurrence

The occurrence of rice water fly is closely related to temperature. The developmental threshold temperature of each state of rice water fly is 9.3 ℃ for adults, 10 ℃ for eggs, 12.7 ℃ for larvae and 12.4 ℃ for pupae. The effective accumulated temperature of the whole generation is 302.4 ℃.

two。 Effects of different soil pH values

The soil in this area has a high degree of salinization, and rice water flies occur frequently in dead puddles, alkaline canals, newly opened wasteland and saline-alkali heavy paddy fields. Rice water flies like saline-alkali and only live in water with a pH value of 7.5 to 9, but can not survive in an environment with a pH value greater than 9.

3. The influence of flat land level

The occurrence and damage degree of rice water flies have a great influence on the level of tillage. The land is flat and light, on the contrary, the harm is serious.

4. Effects of natural enemies on the occurrence of rice flies

It is observed that the main natural enemies of rice flies in this area are frogs, fish, ants, walking beetles, spiders, birds and so on. Among them, frogs are the main natural enemies, adult frogs feed on adults of rice water flies, and their larvae and tadpoles feed on rice.

V. Prevention and control methods

1. Agricultural prevention and control

Strengthen field management: flat land preparation to clean up the previous crops, regularly remove the floating objects on the water layer.

Soaking soda, frequent drainage and irrigation, keeping field water clean, soaking soda in newly opened wasteland and heavy salt land, in order to reduce PH value. Frequent irrigation and turning stagnant water into living water can not only rinse saline-alkali and cause harm to the living environment of rice fly maggots, but also wash away the floating matter from the water surface and keep the water surface clean.

To cultivate strong seedlings, the varieties with fast growth, firm and erect leaves and strong cold tolerance were selected.

two。 Biological control

Protection and use of natural enemies for prevention and control. The use of carbofuran in this area has low toxicity to frogs and has good control effect.

3. Chemical control

The paddy field in early spring should be prevented and treated with dead puddles and alkali drains at the edge of the paddy field, and the early breeding sites should be eliminated with enemy killing or 80% dichlorvos EC.

In the later stage of growth, the paddy field can be controlled with granules or poisonous soil: 667 square meters with 3% carbofuran granules 2kg. It can also be diluted with 150 grams of 80% dichlorvos EC, diluted with an appropriate amount of water, mixed with fine soil and sprinkled with 20-25 kg.