The latest control measures of wheat trematodes

Wheat midge is a worldwide pest, which is widely distributed in major wheat-growing countries in Asia, Europe and America. Domestic wheat trematodes are also widely distributed in the main wheat producing areas in China. There are two main species of wheat midges in China, namely, red midge and yellow midge. Wheat red midge mainly occurs on both sides of the river in the plain area, while wheat yellow midge mainly occurs in plateau areas and alpine areas.

Morphological characteristics

The female adult of wheat red midge has a body length of 2~2.5mm, a wingspan of about 5mm, and a tangerine body. The front wing is transparent, there are 4 developed wing veins, and the rear wing is degenerated into a balance stick. The antennae are slender and 14 nodes, and the male shrinks in the middle of each node so that each node is in the shape of a gourd knot, and most of the swelling produces a ring of long ring-like hairs. The antennae of the female are beaded with a ring of short circular hairs. The body length of the male is about 2mm. The egg is long 0.09mm, oblong, light red. The larvae are about 3-3.5 mm long, oval, orange-yellow, small head, no feet, maggot-shaped, with a Y-shaped sword bone on the ventral side of the forechest, forked at the front and deep in the depression. The pupa is long 2mm, naked pupa, orange-brown, with 2 white short hairs in front of the head and 1 pair of long breathing tubes.

Wheat yellow midge, the female length is about 2mm, the body is bright yellow. The egg is 0.29mm, banana-shaped. The body length of the larva is 2~2.5mm, yellowish green or ginger, the body surface is smooth, there is a sword bone piece on the ventral side of the chest, the front end of the sword bone piece is curved and lobed, and there are 2 protuberances at the ventral end. The pupa is bright yellow and has a pair of long hairs at the head end.

Damaging symptoms

The larvae lurk in the glume to suck the sap of wheat grains that are being filled, resulting in blighted grains and empty shells. Wheat midge, which uses larvae as flower pests, seeds and or wheat grains, is a destructive pest.

Hazard characteristics

Both species of trematodes have one generation a year, and the larvae in adverse environments have dormant habits for many years, so there are also generations for many years. The mature larvae form round cocoons in the soil to survive the winter and summer. The overwintering larvae in the Huang-Huai River Basin broke their cocoons and rose to the soil surface in the first and middle of March, and pupated in large quantities in the middle and last ten days of April, and the peak period of pupation was from late April to early May. After the emergence of adults, it is at the heading and flowering stage of wheat, followed by a large number of eggs (yellow fluke is slightly earlier than wheat red midge). The yellow trematodes lay eggs in the inner and outer glumes of the first heading wheat plant and on their lateral slices, producing 5-6 eggs in one place, and the egg period was 7-9 days. Most of the red midges lay eggs between spikelets and spikelets which have not yet flowered, with 3-5 grains at a place, and the egg period is 3-5 days. After hatching, the larvae are immediately transferred to the glume and attached to the ovary or freshly grouted wheat grains to absorb juice. After the damage caused by the mature larvae, they climb to the glume and wheat awn, fall on the soil surface with rain, dew or automatic bounce, and drill into the soil 10-20 cm to make round cocoons over the summer and winter.

Influencing factors

1. Temperature. The larvae are tolerant to low temperature and high temperature, and the death rate of overwintering is lower than that of oversummer. The overwintering larvae broke their cocoons at 10 cm soil temperature of 7 ℃, pupated at 12 ℃ ~ 15 ℃, and emerged as adults at 20 ℃ ~ 23 ℃. When the temperature increased more than 30 ℃, the larvae returned to dormancy.

2. Humidity. During the period of cocoon breaking and pupation of overwintering larvae, the emergence rate of Rain Water was high. When the humidity is high, not only the hatching rate of eggs is high, but also the newly hatched larvae are active and easy to invade and bite. The occurrence of trematodes is often caused by more Rain Water, high humidity and suitable temperature before and after wheat flowering. Dry weather and low soil moisture are disadvantageous to its occurrence.

3. Soil. The loam soil is loose and has strong water holding capacity. Clay is disadvantageous to his life, and sand is even more unsuitable for his life. Red midge larvae prefer alkaline soil, while yellow midge prefers more acidic soil.

4. The peak period of adults coincided with the heading and flowering stage of wheat, while the dislocation of the two stages occurred slightly.

Prevention and control experience

For wheat fields with serious trematodes, it is best to rotate with cotton, rape and other crops to avoid insect sources. The method of "one sprinkle plus one spray" can be adopted: before wheat jointing to booting, 50% phoxim 0.5 kg / mu mixed with fine sand 15 kg / mu is evenly sprinkled (watering after spraying) to kill adults, larvae and pupae. During the period from wheat heading to pre-flowering, 4.5% cypermethrin and other pyrethroid pesticides were added with 40.7% Lesbon 800x mixture (20 ml per sprayer), or "Hanke 140ml" 1500 times solution (10ml "singly hit one" per sprayer). It can effectively kill the adults and eggs of trematodes, and can control wheat aphids and red spiders at the same time.

Prevention and cure measures

1. Agricultural prevention and control

(1) selection of insect-resistant varieties

Trematodes are resistant to low temperature but not to high temperature, so the overwintering mortality is lower than the oversummer mortality. Soil moisture is an important factor for overwintering larvae to start activity and a necessary condition for pupation and Eclosion of trematodes. The damage degree of trematode is different in different wheat varieties, such as long and prickly awn, dense spikelet, short and neat florescence and thick pericarp, which are disadvantageous to the oviposition, larval invasion and damage of trematodes.

Therefore, it is necessary to choose wheat varieties with tight spike shape, long and dense inner and outer glumes, thick wheat grain skin and not easy to outflow.

(2) rotation and stubble

The wheat field has been ploughed deeply for years, and the rotation of wheat with crops such as rape, legumes, cotton and rice has a significant effect on reducing the number of insect pests. In and around the serious wheat midge fields, cotton-wheat intercropping or replanting rape, garlic and other crops can be carried out, and the damage will be reduced by planting wheat after the rainy year.

2. Chemical control

(1) soil treatment

Time: ① wheat before sowing, the last shallow tillage; ② wheat jointing stage; ③ wheat booting stage.

Medicament: 2% methyl isosinophos powder, 4.5% methyl enemy powder, 4% enemy horse powder, 1.5% methyl 1605 powder (the drug is a highly toxic pesticide banned by the state), 2kg / mu, or 80% dichlorvos EC 50ml 100ml plus 1kg water 1kg, or with 50% phoxim EC 200ml, add 5kg water sprayed on 20,25kg fine soil, mix evenly to make poisonous soil application, sprinkle while ploughing, turn into the soil.

(2) Chemical control in adult stage

Before wheat heading to flowering, 150 ml of 80% dichlorvos per mu, diluted with 4 kg of water, sprayed on 25 kg of wheat bran and sprinkled with a pile per mu, this method has a long residual period and good control effect. Or spray 40% dimethoate (which is a highly toxic pesticide banned by the state) 1000 times, 2.5% deltamethrin 3000 times, 40% fenitrothion wettable powder 1500 times, and so on.