Effective control of soybean root Liriomyza sinensis

Soybean root miner Ophiomyiashibatsuji (kato), also known as Liriomyza huidobrensis, belongs to Diptera, Liriomyidae. Commonly known as soybean root maggots, bean root snake flies, root flies and so on.

First, distribution and harm. Soybean root miner is mainly distributed in the main soybean producing areas, and is distributed in three provinces of Northeast China, Inner Mongolia, Hebei, Shandong and Shanxi, among which Heilongjiang, Jilin and Inner Mongolia are the most prominent. Liriomyza sativa is mainly harmed in soybean seedling stage, and its feeding habit is single, only harmful to soybean and wild soybean. The larvae did harm to the root cortex and xylem of soybean seedlings and excreted feces, resulting in root cortex rot and strip scars. The damaged roots became thicker, browned, cortical cracking or abnormal proliferation, and the feces and feeding of larvae stimulated phloem cork to form tumors, resulting in soybean roots being damaged and unable to normally grow and absorb various nutrients in the soil. The adults pierced and ate the cotyledons and true leaves of soybean seedlings and formed small white spots or transparent pores or withered spots at the feeding place.

Second, morphological characteristics. ⑴ adult: about 3mm in length, 1.5mm in wingspan, bright black, thicker. The compound eyes are large and dark red. The flagellum of the antennae is flat and short and the end is obtusely round. The wings are light purple with metallic luster. Dark brown feet. ⑵ eggs: about 0.4mm long, olive-shaped, white and transparent. ⑶ larvae: about 4 mm long, cylindrical, milky white maggots, and then all appear light yellow, translucent; the head shrinks into the anterior cavity, the mouth hook is black, curved at right angles, and its tip bends slightly inward. One pair of front valves and one pair of rear valves, larger, protruding from the tail end, perpendicular to the tail shaft, parallel to each other, the valve opening is like cauliflower. There are 28-41 valve holes on the surface. ⑷ pupa: 2.5-3mm long, long oval, black, front and rear valve protruding, boot-shaped, tail end with two needle-like whiskers (rear valve).

III. Life history and occurrence regularity

The main results are as follows: 1. Life history: Liriomyza sativa occurs one generation a year, and its pupa overwinters in the soybean root (in the soybean root nodule) or in the soil near the damaged root, and the pupa period is as long as 10-11 months. The overwintering pupae gradually increased in ground temperature in late April of the following year, reached more than 8 ℃ at a depth of 10 cm, began to develop when the soil moisture was about 35%, emerged into adults from the end of May to the beginning of June, and the peak period of Eclosion was in the middle of June. The deeper the pupa is in the soil layer, the lower the emergence rate is. When the temperature is high in May, the adults appear 5-6 days earlier, and the harm is more serious. Adults can mate 2-3 days after Eclosion and lay eggs on the same day. Spawning usually begins in early June, and the peak spawning period is mid-June. The eggs began to hatch after 3-4 days of development, and the peak incubation period was in the middle to late June. The hatched larvae move down the stem. Dive into the root to drill into the harm. The larval stage is about 20 days, and the mature larvae begin to pupate in late June. Pupation reached its peak from the end of June to the beginning of July, and the pupae lived in the soil for as long as 10 months.

2. Occurrence regularity: the occurrence of Liriomyza sativa is closely related to the environmental conditions, and the suitable temperature for its development is 20-25 ℃. The occurrence of late final frost period, high air temperature and soil drought is lighter than that of low temperature and high soil moisture. Fertile plots are more harmful than barren plots. The harm of the hilly land is more serious than that of the depression, the slope land is heavier than the flat fertile land, the sandy soil is heavier than the brown loam, and the harm is serious near the grass wasteland and continuous cropping land. The occurrence degree of soybean root Liriomyza sinensis 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. The deep turning in autumn or the stubble in autumn is light. If the pupae are turned more than 20 cm deep in autumn, the pupae can be buried deeply in the soil and the emergence rate can be reduced. Qiuzhu can bring the overwintering pupae under the ground of bean stubble to the surface, and the death rate increases due to the influence of long-term low temperature and dryness in winter.

Fourth, the method of prediction. According to the research of Chen Shenkuan et al. (2004), the occurrence quantity can be predicted by the following methods.

1. Large occurrence index: the number of overwintering pupae per square meter is more than 20, the emergence rate of flies is more than 70%, the number of flies caught by 5 nets is more than 50, and the plant damage rate is more than 76%. The loss can reach more than 20%.

2. Occurrence index: the number of overwintering pupae per square meter is 10-20, the emergence rate of flies is 60-70%, the number of flies caught by 5 nets is 20-50, the plant damage rate is 50-75%, and the yield loss is 10-20%.

3. Light occurrence index: the number of overwintering pupae per square meter is less than 10, the emergence rate of flies is less than 60%, the catch of flies in 5 nets is less than 20, the damage rate of plants is less than 50%, and the loss is less than 10%.

V. Prevention and control measures

1. Agricultural prevention and control law: rotation for more than 3 years to reduce the density of insect sources; deep turning in autumn to reduce the emergence rate of the following year; timely sowing, sowing when the soil temperature is stable more than 8 ℃, never more than May 20. Suppressed after sowing, the sowing depth is 3-4 cm. In addition, the proper application of phosphorus and potassium fertilizer and rotten organic fertilizer can promote the growth of seedlings and Lignification of root bark, which can enhance the damage resistance of soybean plants.

2. Drug prevention and treatment: ⑴ soil treatment. The soil was treated with 3% carbofuran granules, 15-100 kg per hectare, mixed with fine fluvo-aquic soil and sprinkled into the sowing hole or ditch, and then sown soybean seeds. ⑵ uses seed coating agent. Coated with seed coating agent containing furan (carbofuran), 1 kg seed coating agent mixed with 90-100 kg seed coating agent; seed coating with 8% A multi-coating agent or 35% doxorubicin suspension seed coating agent, seed coating was carried out according to seed weight 1.2-2%. Seed dressing with ⑶ medicament. With 50% phoxim and 0.3% dofol mixture, stir the seeds with a sprayer on the indoor floor until well mixed. But to avoid direct sunlight, to prevent phoxim photolysis, dry after sowing. ⑷ uses pesticides to control larvae. 80% dichlorvos emulsion 800-1000 times, or sprayed or irrigated with 90% crystal trichlorfon 700-1000 times. When filling the root, the liquid must be infiltrated into the root. ⑸ spray to control adults. During the peak period of adults, that is, before the first compound leaf of soybean, macula appeared on the surface of cotyledons. When adults appeared in the visual field, 40% dimethoate EC or 80% dichlorvos EC 1000 times, or 90% trichlorfon was sprayed, about 750L per hectare. The occurrence period of adult ⑹. Fumigation with 80% dichlorvos sustained-release cards to control adults.