Scientific name Mythimna separata (Walker) Lepidoptera, Noctuidae. Synonyms Leucania separata Walker is known as the night robber, razor worm. Common name of multicolored insects, wheat silkworms and so on. Distribution in addition to Xinjiang has not been reported, all over the country.

Host cereals such as wheat, rice, millet, and corn, and more than 104 plants of 16 families including cotton, beans, and vegetables.

Damage characteristics larvae eat leaves, when the big crops can eat all the light, causing serious losses. Because of its flocculation, migration, omnivorous, and bulimia, it has become a nationally important agricultural pest.

Morphological characteristics Adult body length 15-17mm, wingspan 36-40mm. Head and chest beige, dark brown belly. The pre-wing ash is brownish-yellow, yellow, or orange, with many changes; the inner horizontal line is often only a few black spots, the ring pattern and the kidney pattern are brownish-yellow, the boundary is not significant, and there is a white point at the back of the kidney pattern, and each side has a Black points; the outer horizontal line is a black dot; the sub-line is inclined from the top corner to Mz; the edge line is a black dot. The hind wings are dark brown and fade to the base. The egg is about 0.5mm long, hemispherical, and it has a white, yellowish, shiny appearance. The monolayers of eggs are arranged in rows and blocks. The mature larvae are 38mm long. The head is reddish-brown, with a reticular pattern on the head and a flat frontal, with thick vertical lines on both sides, a slightly octagonal shape, and a brown netting on the outside. The body color varies from light green to dark, with great changes (usually due to changes in food and environment)

In the event of an outbreak, the back often appears black, the ventral surface is lightly coloured, the midline of the dorsal midline is white, and there is a slight blue between the subline and the valve upper line, and the valve line and the valve lower line are pink to grayish white. There is a dark brown wide longitudinal band on the outside of the gastropod, and a semi-ringed dark brown toe hook at the tip of the foot. About 19 mm long; reddish-brown; abdomen 5-7 section of the back of the front edge of a row of dentate bite; hip thorn on the spiny 4 roots, the central 2 thick, slightly sting on both sides slightly curved.

Life habits occur in different generations throughout the country. The number of generations from north to south is: 2-3 generations in the Northeast, Inner Mongolia, 3-4 generations in the south-central part of North China, 4-5 generations in the Huaihe River Valley in Jiangsu, and 5-6 generations in the Yangtze River Basin. , South China 6-8 generations. Mythimnasis is a migratory pest and its winter crossing line is 33 degrees north latitude. No insects can overwinter in the area north of 33 degrees; in the areas of Hunan, Jiangxi, and Zhejiang, larvae and earthworms are overwintered in rice piles, field weeds, green manure fields, wheat fields, and other places; and they breed in Guangdong and southern Fujian all year round. No overwintering phenomenon. A large number of adults emerged in the spring in the north from the south. Adults lay eggs at the tips of leaves or leaves, and between the creases of the heart and leaves, often causing the leaves to become vertical. The newly hatched larvae have not fully developed their gastropods, so they walk like a ruler; the young instar larvae can only feed on the leaves and make the leaves appear white spots; after 3rd instar, the leaves can be eroded and become incomplete, and 5-6 instar larvae enter the gluttony phase. Larvae are 6 instar. Mature larvae in the rhizosphere top soil 1-3cm do earthworms. Developmental starting temperature: egg 13.1 soil 1°C, larvae 7.7 soil 1.3°C, alfalfa 12.0 soil 0.5°C, adult spawning 9.0 soil 0.8°C; whole life history 9.6 soil 1°C. The effective accumulated temperature was 4.3 days in the egg period, 402.1 days in the larval period, 121.0 days in the flood period, and 111 days in the adult oviposit. The entire life cycle was 685.2 days. Adults are nocturnal and they begin their activities in the evening. Serve at dusk, spawn at midnight, and find shelter at dawn. Adults tend to have strong tropism for sweet and sour liquids, and their production tends to yellow dry leaves. In the field of wheat fields, the eggs are laid in the creases at the tips of the yellow leaves at the base of the wheat plant; in the rice fields, many eggs are produced on the tip of the upper half of the yellow leaves, and the leaves of the eggs fall into strips. Each egg block is generally 20-40 pieces, in strips or overlaps, with 200-300 grains in total, and 1000-2000 grains per woman. The newly hatched larvae are clustered. The 1st and 2nd instar larvae damage the back of the wheat plant or the backlight of the tiller leaves. After 3rd instar, the food intake is greatly increased. The 5-6 years old enters the binge eating stage. Its food intake accounts for about 90% of the entire larval period. The third-instar larvae have a false death. They are rapidly disturbed by the shock, fall down to the ground, and are photophobic. The sunny daylight larvae lurk in the earth seam at the wheat root, and climb to the plants in the evening or on a cloudy day. When the larvae occur in a large amount of food, the larvae often migrate to the nearby plots to continue the damage and the old mature larvae enter the earth. The temperature of the pest is suitably 10-25°C and the relative humidity is 85%. The optimal spawning temperature is 19-22°C, and the relative humidity is about 90%. The temperature is lower than 15°C or higher than 25°C, and spawning is obviously reduced. The temperature is higher than 35°C and no eggs can be laid. Humidity directly affects the survival rate of newly hatched larvae. The adult worm needs to take nectar to supplement the nutrients, and it has abundant honey source and high egg production. The larvae feed on the grass quickly, and the fecundity of adults is high. Adults like to lay eggs in intensive fields, producing good growing wheat, millet, paddy fields, densely planted dense planted fields, and more fertilizer and well-irrigated fields, which is conducive to the occurrence of this pest. There are mainly natural enemies such as walkers, frogs, birds, parasitic bees, and parasitic flies.

Control methods (1) Trapping adult worms. The use of adults in the spawning habits of cereal crops on the leaves, in the wheat field to put the straw or straw, 667m260-100, replace the new grass every 5 days, put the replaced grass to burn. In addition, sweet and sour vinegar pots, black light, etc. can also be used to seduce adult worms and reduce insect populations. (2) According to the forecast, it is necessary to spray 2.5% trichlorfon powder or 5% insecticide-fighting powder before the third instar of the larvae, and spray 1.5-2.5kg per 667m2. Conditional spraying of 90% crystal trichlorfon 1000 times or 50% malathion EC 1000-1500 times, 90% crystal trichlorfon 1500 times plus 40% Dimethoate 1500 times, spray per 667m2 Good medicine 75kg. Advocate the application of hormone pesticides, 667m2 with 20% diflubenzuron suspension 10ml, 12.5kg water, spraying with Dongfanghong 18 type mist sprayer. Conditional Yun-6 aircraft can be used for ultra-low volume spray, with 20% diflubenzuron 1 colloidal suspension 10ml per 667m2, 0.5kg water, suitable for large-scale joint defense. (3) Control of the armyworm herbicides Bichexin, phoxim, and amitraz alone control the armyworm control efficiency from high to low in the order of phoxim is greater than butyl sulfur carbofuran greater than the double glands. Carbofuran and phoxim were mixed at a ratio of 1:4, and the synergistic effect was significant. A combination of amitraz and butylthiocarbamate and amitraz and phoxim is a 1:1 synergistic effect.

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