Control methods of Liriomyza sinensis

Liriomyza huidobrensis belongs to the family Liriomyidae. Also known as soybean root maggot, soybean root miner, etc., this insect is a monophagous pest, only to harm soybean and wild soybean. Distributed in Heilongjiang, Liaoning, Inner Mongolia, Shandong and Hebei and other places. The yield of the injured plant is more than 40% lower than that of the healthy plant.

1. Morphological characteristics

(1) the adult is about 3 mm long, bright black, and its wings are light purple with metallic luster. Compound eyes are bright red.

(2) the egg is about 0.015 mm long and 0.04mm wide, reniform, white and transparent.

(3) the length of the larva is about 3.2 ml 4.2 mm, which is yellowish, translucent, cylindrical and the tail is slightly thinner.

(4) the pupa is about 2.1 Mel 3.0 mm long, ovoid, black.

two。 The damage characteristics of adults punctured and eaten the cotyledons and true leaves of soybean seedlings, and the feeding place was in the shape of withered spots. After hatching, the larvae enter the root of the seedling to feed, harming the cortex and essential part of the main root, causing scars. The damage to the root of the plant was characterized by underdeveloped root system, thickening and browning of the root, cracking or abnormal proliferation of the cortex, or tumorigenesis. The aboveground parts of the damaged plants showed weak seedling growth, short plants and yellowish leaves. In the light victims, after the pupation of the larvae, the root wound healed and the plant grew again, but the root nodule was smaller and less, the parietal leaf yellowed and fewer pods, and the quality and yield decreased. The severely injured plants gradually withered. In addition, the larvae cause wounds and also infect root diseases, which aggravates the damage of soybean.

3. The occurrence regularity occurs one generation a year in the northern soybean area, and the pupa overwinters in the soil near the bean stubble or the injured root. In the following year, the overwintering pupae emerged from late May to early June, and adults flourished in early June. The egg peak stage entered in the middle of June, and the peak egg hatching period was from mid-June to late June, which was also the peak stage of larva damage, which lasted for 20 mi for 40 days. The mature larvae began to pupate in late June. The larvae damage the cortex of the main root of soybean seedlings, and the adults feed on the cotyledon or leaf juice of soybean seedlings. The adult of Liriomyza huidobrensis moves among bean plants after Eclosion, and lays eggs in the root or stem cortex near the soil surface of bean seedlings after mating. The eggs are scattered, one egg per plant, and the oviposition period is 4ml for 7 days, and each adult lays 2040 eggs. After hatching, the larvae move along the Hypocotyl epidermis to the root and cause food damage. The last instar larvae pupate over the winter in a space of 5m / 10cm on the surface.

The occurrence of Liriomyza huidobrensis is closely related to climatic factors and farming system.

The main results are as follows: (1) the effects of air temperature and humidity on the emergence, mating and oviposition of adults of Liriomyza huidobrensis were affected by climatic factors, and the optimum temperature was 20 ℃. Moist soil after rainfall was beneficial to Eclosion and adult occurrence.

(2) ① stubble of tillage system: the occurrence degree of soybean root miner is different with different stubble. The number of overwintering insect sources in the continuous cropping land is more, and the occurrence is serious, while the occurrence in the stubble and positive stubble land is relatively light. According to the survey, the damage rate of continuous cropping land is 30%, that of facing stubble land is 15%, and that of positive stubble land is 7.5%. ② soil fertility: the degree of soil fertility affects the growth potential of soybean seedlings, and then affects the recovery ability of the damaged plants. The survey found that the content of soil organic matter is less than 5%, lack of fertilizer, the growth of seedlings is thin, and the damage is aggravated. The content of soil organic matter is more than 5%, and the water and fertilizer is sufficient, which promotes the seedlings to develop early, grow and develop healthily, reduce the damage, and recover quickly even if damaged. ⑧ sowing time: different sowing time, different degree of occurrence. The sowing was too late, and the land sown after May 20 became heavy. Because in the late sowing plot, when the soybean root leafminer larvae are in full bloom, the root stem epidermis of soybean seedlings is delicate, which is beneficial to its occurrence and harm. ④ tillage method: deep ploughing in autumn or light occurrence of stubble in autumn. Turning over more than 20 cm in autumn can bury the fly pupae into the deeper soil layer and reduce the emergence rate: autumn mackerel can bring the overwintering pupae under the bean stubble to the surface, and the death rate of overwintering pupae will also increase due to the influence of long-term low temperature and dry climate in winter.

four. Prevention and cure method

(1) rational rotation of ① for agricultural control: Liriomyza sativae feed only on soybean and wild soybean, so reasonable rotation with gramineous crops can reduce the number of insect sources in the soil. Generally, rotation with Gramineae crops for more than 2 years can reduce the degree of damage. ② clean field: the removal of weeds in the field and the field can reduce the source of insects. Autumn waterlogging or deep ploughing of ③ soybean stubble in autumn: the soybean field is turned deep in autumn, but it cannot be feathered when it is turned into the soil at a depth of 30 cm; autumn waterlogging can bring overwintering pupae to the surface, and the mortality of overwintering pupae increases after long-term low temperature and dry climate in winter, thus reducing the number of insect sources and adults. Early sowing at the right time for ④: applying sufficient fertilizer and sowing early at the right time can make soybean seedlings develop early. when the larvae flourish, the Lignification degree of the main root is higher, and the damage is mild if it can tolerate the larval boring; on the contrary, the delicate damage of the seedling rhizome is severe.

(2) seed treatment can be treated with medicament or seed coating agent. Seed coating agent treatment seeds: 8% A multi-coating agent or 35% Kefu suspension seed coating agent, seed coating according to seed weight 1.2%-2.0%. Soybean seed coating agent 26 was seed coated according to the drug ratio at 1:75. EC medicament treatment: 5% methyl thiocarbophos or 35% ethyl thiocarbophos, seed dressing according to 0.5% of seed weight; 40% dimethoate EC (EC) 700ml plus water 4ml 5kg mixed soybean seeds 100kg, sow immediately after drying.

(3) the control of adults in the field. During the peak period of adults, that is, before the first compound leaf of soybean, macula appeared on the surface of cotyledons, and when adults (small flies) were seen in the field, spraying to control adults. The insects were sprayed once every 10 days when the number of worms was large. Spray pyrethroid pesticides with water spray at about 450ml per hectare, 1000 times with 40% dimethoate or 80% dichlorvos EC or with 90% trichlorfon crystals.