Wheat midge is a devastating pest that is a major pest of wheat. From the larvae, the larvae lurk in the glume of the sap of the wheat stalk that is being grouted, or damage the sap, causing pods and empty shells, and the production is reduced by 20% to 50%, and the weight is reduced by 60% to 90%. It has a great influence on the yield and quality of wheat. The worm body is small, hidden, difficult to find, easy to miss the control period.

In recent years, because of the farming system, cultivation methods and changes in wheat varieties, wheat midge significantly recovered, new areas of occurrence continued to occur, the area of ​​occurrence continued to expand, the density of population population increased dramatically, and the degree of damage increased year by year, resulting in the formation of new insect pests. The phenomenon of worms becoming catastrophic has become one of the factors that affect the high yield, high quality and high efficiency of wheat.

Second, life history and habits

Wheat midge occurs one generation in a year. Overwintering larvae grow in summer and winter in the soil. In the jointing period of wheat in late March of the following year, the larvae rise to 3 to 10 cm in soil after preparation for pupa. In mid-April wheat booting season, The larvae successively made earthworms in about 3 cm soil layers. In early April, the heading of wheat emerged at the heading stage, and the filling stage of the flowering flower often coincided with the larval hatching period. Adult eclosion can spawn on the same day, and spawning is performed at 6 to 9 o'clock in the evening. Ears that have not been flowered are spawned by spawning, and wheat ears that have been flowered are sparsely oviposited due to closed pods. This kind of strict selection of spawning habits for the wheat growing stage is often the main reason for the difference in the hazards between the plots and varieties in the same area. After hatching, the larvae invade from the inner and outer striated joints and attach to the ovary or the grouting grain to suck the slurry. 15 to 20 days after maturity, fall into the soil, in the depth of 6 to 10 centimeters after 3 to 10 days of knots (sleep dormant) over the summer and winter.

Third, the impact of the factors

1. climatic conditions

The temperature mainly affects the occurrence period of wheat midge, and the rainfall or soil moisture is the dominant factor influencing the number of occurring. In mid-April and late April, there is abundant rainfall, rainy days and frequent flooding. There is little rainfall, soil drought is unfavorable to the activity of larvae in the soil, and larvae can regenerate and sleep, increasing the number of insects in the coming year.

2. Wheat variety and growth period

The wheat has long, spiny, straight, spikelets arranged neatly, thick glumes, thick inner and outer glumes, or thicker epidermis, with obvious resistance. The adult spawning of midge insects is also strictly selective to the wheat growth stage. For those headings that are orderly, the grouting is rapid, the heading period is high, and the breeds that are not encountered at the time of adult emergence are lightly damaged; otherwise, the victims are heavy.

3. Rotation and Cultivation Measures

The dry fields, continuous wheat crops, wheat crops and soybean crops are heavy in the wheat fields, and the crops are lightly affected in areas where paddy-wheat and maize crop rotations occur. Wheat crops after ploughing and exposing wheat fields have higher larval mortality rates;

4. Soil and topography

Wheat midge in the loam soil is more harmful than the clay and sandy soil; usually there are more slopes in the lowland than in the slope, and the shade is more acidic than in the sunny slope; the wheat red midge is suitable for the acidic soil, and the wheat yellowworm is suitable for the alkaline soil.

5. Natural enemies

The wheat midge parasitoids are Tetrastichus sp. and platygaster error Fitch, and the parasitism rate is up to 75%. The larvae have natural enemies with fungal parasitism, causing their death; the predators have natural enemies. Ants, spiders, hummer, etc.

Fourth, prevention and control measures

In addition to adopting agricultural measures such as adjusting crop layout, implementing crop rotation, avoiding continuous cropping of wheat, wheat stubble ploughing and sun exposure, chemical control measures are still important means for the prevention and control of wheat midge insects.

1. Soil treatment before planting

Before the sowing of wheat, the soil is treated with toxic soil, which can treat both underground pests and wheat spiders. Per acre with 6% lindane powder 1.5 kg or 5% methylisothiacin granules 1.5 ~ 2 kg or 3% phoxim granules 1.5 ~ 2.5 kg, mixed with fine soil 30 kg, mixed evenly, sprinkled on the surface, While spreading and ploughing, turning into the soil, or spreading on the ridge head after ploughing, and with the spittoon, can effectively control the larvae in the soil.

2. Control of larval stage

From late March to early April, the jointing period of wheat uses 5% methylisothiphos granules 1.5 to 2kg per mu, 3% phorate granules 2 to 2.5kg, and 3% phoxim granules 1.5 to 2.5 Kilograms were mixed with 20 kg of fine soil, and evenly spread on the surface of the soil between the ridges of the ridges. In combination with the depression, the toxic soil was mixed into the surface layer. This period coincided with the beginning of the upward movement of the wheat midge, which could kill a large number of larvae and suppress the adult emergence. If the combination of irrigation or rainfall after application, the effect is better.

3. Flood control

The flood season is the most critical period for the prevention of wheat midge. In this period, the wheat plant is already high. After application, it is necessary to try to shoot the soil on the wheat leaf to the ground. The specific method is: 2.5% per acre with 2.5 kg of Sejining, 20 kg of evenly mixed fine soil, or 40% of methyl isofluosa EC per acre 200 ml or 50% phoxim EC 200 ml of water 5 kg mixed 25 kg of soil, thrown into the wheat field, then watering or snatch before the rain, can receive good results.

4. Adult stage control

This period is the last line of defense to control the harm of wheat midge, and it is also the most difficult time to grasp the beneficial control period. Because one family planting, different wheat varieties, different sowing dates, heading flowers early or late, so accurate measurement and reporting is the key to doing a good job of adult control. Should be mastered in the early stage of wheat heading and flowering, that is, the beginning of adult emergence. Each acre can use 10-15 grams of acetamiprid or 2.5% of 2.5% of deltamethrin vinegar, or 80% of dichlorvos emulsifiable concentrate, 40% of omethoate EC 100 ml, evenly add 15-20 kilograms of water for low-volume spray. If rain occurs within 25 hours after application, additional treatment should be considered. The above comprehensive prevention and control measures can achieve a control effect of more than 95%.

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