Spodoptera exigua

Spodoptera exigua Hiibner, commonly known as Beet armyworm, belongs to the order Lepidoptera, Noctuidae, and it is a omnivorous pest that is distributed worldwide and intermittently and that harms vegetables. On green onions, cabbage, cabbage, celery, cauliflower, carrots, asparagus, leeks, leeks, peppers, kidney beans, cauliflower, eggplant, kale, tomatoes, cabbage, cabbage, broccoli, spinach, radish and other vegetables harm.

What are the hazards? Generally eaten leafy leaves, endangering welsh onions and peppers as they enter the onion tube and peppers for feeding. The newly hatched larvae clustered on the back of the leaves, spun silk, fed the leaves, leaving the epidermis, transparent holes, scattered after 3rd age damage, eat the leaves into holes or nicks, severe leaves only leaves veins and petiole, Lead to the death of vegetable seedlings, resulting in lack of seedlings and ridges, and even destroy the seed. Instar larvae can also drill sweet peppers and tomato fruits, causing fruit drop and rot.

Morphological features: Adult body length 12-14 mm, wingspan 26-30 mm, grayish brown. There is one kidney-shaped spot on the outer edge of the front wing of the fore-fin and there is one ring-shaped spot on the inner side and the outer edge line is composed of a black triangle spot. The hind wings are white, and the veins and edges are dark brown.

Eggs are spherical, white, with radial ridges on the surface. Eggs are lumpy. Each egg generally has more than 10 eggs. The single layer or 2 to 3 layers overlap and the white hairs are covered by female moths.

The larvae, the instar larvae, are about 22 to 27 mm in length. Body color changes greatly, with green, dark green, yellow-brown, brown to dark brown, abdominal valve below the line is a clear yellow-white vertical band, sometimes with pink, straight to the end of the abdomen, do not bend to the hip foot, each section There is a clear white point above the valve.

The carcass is about 12 mm long, yellow-brown, and the mid-thorax valve is located on the posterior border of the anterior chest. There are two bristles on the hip spine and two very short bristles on the ventral base.

Occurrence characteristics: North China takes 3 to 4 generations, and the Yangtze River Basin has 5 to 6 generations. Generations overlap. In the area north of the Yangtze River, the earthworms live in the earth in the winter. There is no obvious wintering phenomenon in the south of China, and they can be bred all year round. Adults grow into nighttime and hide in the shade of weeds, clods, earth seams, and litters during the day. They have the most vigorous nighttime activities. They have strong phototaxis and weak chemotaxis. Eggs are produced on the back of leaves, petiole, or weeds. On the top, the eggs are arranged in a layer of 3 to cover white fluff. Each female can produce 100 to 600 eggs. Egg period 2 to 6 days. Larvae are 5 instars and 6 instars. The newly hatched larvae are harmed on the back of the colon, drawing on the nets and feeding on the leaves. Dispersed after 3rd instar, after 4th instar, the amount of food increased greatly, and it lodged overnight, with a false dead habit. When the population density is too large, the larvae can kill each other. Mature larvae into the soil, spit silk room building, depth of about 0.5-3 cm. It is also possible to phlegm at the base of plants.

Spodoptera exigua is an intermittently occurring pest that varies greatly in different years. Each insect state has high temperature resistance and is not strong against cold. The high winter mortality rate in the north is the main reason for the small number of spring adults and the small distribution range. In the south, if there is little rain in spring, the plum rain obviously advances, and in summer, it is serious in autumn. The starting temperature for the development of eggs, larvae and pupae of Spodoptera exigua was 10.9°C and 12.2°C, respectively. At 25°C, the eggs, larvae, and pupal stages were 3, 18, and 8.5 days, respectively. In general, the period from July to September is the period of damage. From July to August, the amount of precipitation is small and the humidity is low. Spodoptera exigua larvae are susceptible to drug resistance. In recent years, the insects in the south have developed high resistance to insecticides such as pyrethroids and organophosphorus, resulting in frequent outbreaks and becoming important pests.
?? Prevention methods
1. Agricultural control of autumn or winter plowing, deep plowing of the soil can eliminate part of the overwintering pupae; spring weeding in March to April to eliminate the weeds on the first instar larvae; combined with field management, artificial eggs, removal of newly hatched larvae Clustered blades, centralized processing.
2. Protection and utilization of natural enemies Spodoptera exigua has a large variety of natural enemies and is an important natural controlling factor. In early stages, it uses broad-spectrum pesticides to protect natural enemies in vegetable fields.
3. Chemical control of larvae: Spodoptera exigua has the weakest drug resistance before the second instar and is the best period for drug control. After the second instar, the resistance of the insect is enhanced. The larger the insect body is, the stronger the drug resistance is, and the more effective the chemical control is. Poor, so when it comes to prevention and control, we must follow the principle of “prevention and cure early?” and early prevention and treatment. The most effective method for the prevention and control of beet armyworm is contact. Therefore, it should be selected before 8 o'clock in the morning or after 6 o'clock in the afternoon. When the surface of the leaves is active, the effect is best, and when the sunlight is strong and the temperature is high, it is not suitable to use drugs, because the pests have long been lurking in the earth seams and grasses, and the direct contact killing effect is not achieved, and the control effect is not obvious.
At present, the effective non-polluted pesticides for controlling Spodoptera exigua are 48% of Lethbone EC 1000 times, 2.5% of vegetable suspensions 1000--1500 times, and 52.25% of farmland EC 1000--1500 times. , 10% dilute the suspension 1000--1500 times the liquid, 20% of the rice full suspension agent 1000--1500 times the liquid, which Miman, farmland music and divertion control Spodoptera exigua has special effects. However, when using the above pesticides, they should be used alternately. Generally, pesticides should be sprayed from the early stage of pest occurrence, once every 7-10 days, and sprayed 2--3 times. At the same time, the spraying should be uniform and detailed, so that the buckle can be turned upside down, and it can be penetrated on all sides. Since the insect is extremely resistant, it is necessary to pay attention to alternation of insecticides with different insecticidal mechanisms, such as chlortetracycline, chlorprocarb, carbitol, etc. However, the number and dose of these new pesticides must be strictly limited to avoid and delay the use of insecticides. The beet armyworm is resistant to them.
? 4, prevention and control of adults? Sex lures control Spodoptera exigua, can kill a large number of males. According to experiments, the control area can reduce Spodoptera exigua above 60% compared to the non-control area, and the adult seminal vesicles fall by 41.96%, and almost no Spodoptera exigua larvae and eggs can be seen. Because the adults are nocturnal, they tend to have a strong tendency towards light. In regions where conditions permit, blacklights or high-pressure mercury lamps can be used to attract insects, lamps can be placed under water basins, and a small amount of washing powder can be added, so that adults cannot escape after falling into water. Adult worms have strong tropism for sweet vinegar and poplar odors, so they can be eliminated with sweet vinegar and poplars before they are trapped.

Attachment: Occurrence of Spodoptera exigua and its pollution-free control technology?
Mu Wei Wu Kongming (Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100094)

Spodoptera exigua Hubner, commonly known as the cabbage brown hawk moth, belongs to Lepidoptera and Noctuidae and is a omnivorous pest that is distributed worldwide and intermittently to endanger vegetables. Domestically, in the 1960s, there were reports of its damage, but they were secondary pests. Since the 1980s, the damage has gradually increased. Especially in the early 1990s, they were successively located in Taiwan, Guangdong, Yunnan, Jiangxi, Hunan, Zhejiang, Jiangsu, and Shanghai. There have been devastating occurrences of various vegetables such as Shandong and Beijing, and cash crops such as cotton, soybeans and beets, which have caused heavy losses to local agricultural production. The author started from the biology and occurrence rule of Spodoptera exigua, and explored its pollution-free control technology. ?

1 The distribution of Spodoptera exigua and its occurrence in various parts of China?

Spodoptera exigua originates from South Asia and occurs throughout the subtropical region all year round, and occurs frequently in temperate regions. Damaged vegetables, hemp, and tobacco in India, and vegetables, cotton, broad beans, and other crops in Egypt, North Africa, and the Middle East. Hawaii, which moved into the United States around 1880, spread throughout the United States in less than 50 years and expanded southwards to Mexico and other Central American countries. British CAB (1972) describes the world map of Spodoptera exigua, covering Europe, Asia, and North America in the vast latitudes south of the 57th latitude and throughout Africa and Australia. In Europe and Asia, Spodoptera exigua can not overwinter in the north of 44 degrees north latitude. The worm has the ability to migrate long distances. The migration of Spodoptera exigua (Hübner) may occur intermittently. The generation of Spodoptera exigua declines gradually with the increase of latitude in China. Spodoptera exigua Hibernian hibernation, the main hazard period is concentrated in the high temperature period and the food sufficient crop growth period. For example, Hebei, Henan, Beijing, Shandong, Anhui, Jiangsu, etc., in the northern regions from July to September (2rd to 4th generations), Shanghai and Hunan from June to October (3rd to 5th generations) are severely harmed, and Guangdong and Fujian can occur one year. 8th generation, Shengfa period from May to September. Tropical and some sub-tropical regions such as Hainan and Shenzhen can be bred year-round without overwintering. With the exception of Hainan and Shenzhen, the 1st and 2nd generations are more obvious in each region, and overlapping generations occur later.

2 Biological characteristics?

• Spodoptera exigua single female eggs per 100 to 600 grains, up to more than 1800 grains. Eggs are usually produced on the back of the more tender leaves of the plant. The egg masses are covered with white scales. The eggs are pale green when they are first born. They are gray before hatching. The larvae of the primordial eggs feed on the egg shells. The knotted nets are clustered in them and the leaf epidermis is shed between the overlapping leaves, resulting in a translucent mesh. Window spots, after 3rd age, disperses hazards, causes holes or nicks, eats less in 1 to 3 years of age, increases in food intake after 4th instar, enters gluttony in 4 to 5 years, and feeds in 3 to 4 days in the entire larval period. 80% to 90%. The young larvae of the beet armyworm are mainly concentrated in the middle and upper parts of the plant. With the increase of the larval age, the distribution center of the larvae on the plant gradually decreases, and the old larvae have the tendency to shift to the backlight of the leaves and the soil surface. ?

The young instar larvae of Spodoptera exigua feed on daytime, whereas the older larvae lurk in the back of the leaves, in the lower part of the plant, in the soil or in the grass during the daytime, and they are transferred to the plants before and after the evening for feeding hazards, and they mostly harm on the back of the leaves. Larvae have a dead-dead habit. After the larvae are mature, ellipsoid earthworms can be used to make larvae 5 to 10 cm below the surface of the earth. It is also possible to phlegm the soil surface and weeds, and the larvae often avoid places with excessive humidity. Adults live 6 to 10 days, 1 to 2.5 days before spawning, and 4 to 6 days to spawn. Different host plants had no significant effect on biological characteristics such as longevity, pre-oviposition period, spawning period and hatchability of females. Adults have feeding habits and have strong tropism towards black light and sweet and sour liquid. Adults grow into nighttime, lurking in earthy seams, weeds, and shades of plants and leaves during the day, and they begin their activities in the evening. Field trapping tests showed that adults were most active 6 to 8 hours after sunset. Indoor observations of male and female females each had two peaks of emergence during the night, at 17:00 to 22:00 and 1:00 to 5:00, respectively. Two-day-old adults had the highest mating rate, and their egg production and hatching rate were the highest. Delayed mating will affect the fecundity of adults, but the life span of uncopulated adults and the prolonged spawning period will be conducive to the outward migration of non-adulted adults and the search for mate. It takes about 22 to 30 days (at 25 to 30°C) for the first generation of Spodoptera exigua. ?

?3 hazard crop species?

Spodoptera exigua is an omnivorous pest, on scallions, cabbage, cabbage, celery, cauliflower, carrots, asparagus, leeks, leeks, peppers, kidney beans, cauliflower, eggplant, kale, tomatoes, cabbage, cabbage, broccoli Spinach, radish, cotton, beets, peanuts, corn, sorghum, geraniol, tea trees, soybeans, mung beans, red adzuki beans, sweet potatoes are all harmful. The leaves are generally dominated, but in the event of harm to cotton, the buds and young bells are occasionally eaten, and the green onions and peppers are jeopardized when they enter the onion tube and the peppers.

4 No pollution prevention measures?

4.1 Improve the farming system and cultivation management?

As China's vegetable growing area and multiple cropping index increase year by year, the intercropping between different crops provides sufficient foodstuffs for Spodoptera exigua, and the occurrence of insects increases year by year and the generation overlaps seriously. In recent years, the rapid expansion of vegetable greenhouses has provided conditions for the wintering of the beak in the north, causing the insects to occur throughout the year. If the management level of the farmland is low and weeds are there, it will provide more convenience for the reproduction of the beet armyworm and its continuation from generation to generation. The adults of Spodoptera exigua prefer to lay spawning weeds such as low earthworms and earthworms, and rely on these “bridge hosts” to move into vegetable fields, cotton fields, and bean fields. Large amount of insects, timely removal of weeds in the field can delay the laying of eggs for 5 to 7 days. Removing weeds can not only reduce and postpone spawning, but also bring a lot of eggs out of the field, greatly reducing the pressure of prevention. We can also use this feature to intercropping crops with leeks, quails, etc. to induce larval control, which can reduce Spodoptera exigua larvae in crops by approximately 60% compared to controls. In addition, the worm lands or weeds in the weeds. Therefore, we must do a good job in the field health, sowing the soil before sowing and killing all weeds with phytosanitary herbicide before ploughing, so that the beet armyworm loses its food source. , can eliminate the vast majority of insect sources. As the insect shakes the plant, it can also shake the leaf, and the larvae will step on it after landing. Because Spodoptera exigua is relatively shallow (0.5 to 3 cm) and cannot resist low temperatures for a long period of time, ploughing soil or winter irrigation is very effective in depressing the population of the next generation.

4.2 Reasonable use of insect growth regulators?

Any pest control must follow the principle of comprehensive prevention and control. In comprehensive prevention and control strategies, the use of natural enemies is very important, but due to a large number of incorrect use of chemical pesticides for a long time, the natural control of natural enemies is largely hindered. Based on the analysis of the formation and exclusion of the life table of the natural population of Spodoptera exigua, it was concluded that natural enemies are important factors affecting the population dynamics of S. exigua. In particular, predatory natural enemies with spiders as the dominant group played a very important role in inhibiting the population of Spodoptera exigua. If the role of predatory and parasitic natural enemies is eliminated, the population of the next generation will be 70 to 100 times that of the present. How to organically combine chemical control with the use of natural enemies for biological control, selecting insect growth regulators that are less virulent to natural enemies is an effective measure. Compared with common chemical insecticides, insect growth regulators have many advantages, such as low toxicity, safety to natural enemies, mammals, fish, and birds, low dosages, fewer drug applications, long residual effects, and post-effects. In line with the requirements of green food production, it is expected that such pharmaceuticals will have greater potential for use in the future.

The Spodoptera exigua is breeding in 1 to 2 generations in the spring under suitable climatic conditions, and it has an outbreak in the summer and July to September. In the spring, in May and June, the occurrence of large amounts of diamondback moth and cabbage caterpillars on cruciferous vegetables is large. Requires repeated use of insecticides for prevention and control, massive killing of natural enemies in the field, and loss of natural control of Spodoptera exigua in the field after July. In addition to protecting natural enemies, insect growth regulators are particularly suitable for the control of Spodoptera exigua. Insect growth regulators such as tebufenozide are effective for both eggs and larvae. First, the agent can infiltrate into the egg, play a physiological effect during embryonic development, inhibit the hatching of the egg, and the newly hatched larvae have the habit of feeding the eggshell, so when the insect growth regulator treats the egg, the normal life activities of the first instar larvae are Destruction, increased mortality. The generation of Spodoptera exigua is overlapped by generations. Insect growth regulators can affect larvae molting on different instar larvae, eventually leading to larval death. In addition, due to the beet armyworm eggs produced in the back of the leaves, the egg shell is covered with villi, second instar larvae some of the spinning knot network, and in the net feeding damage, this time spraying, the liquid is not easy with the body Contact, control effect is not ideal.

After the third instar, the body wall of the larvae is thickened, and drug resistance is enhanced. The farmers are often accustomed to spraying medicine during the daytime. Most of the larvae use contact poisons. The liquid medicine cannot directly contact the worm body, and the control effect is even worse. The insect has a feign death. When spraying, it touches a little, that is, landing, which is not conducive to the exertion of efficacy. The insect growth regulator can interrupt the life activities of larvae through stomach poisoning, interfere with the development of insects, and even cause Insects die, so as long as pests feed crops, there is the possibility of poisoning. The difference from common pesticides is that the effect of insect growth regulators on Spodoptera exigua (Hübner) is obvious. After the treatment of certain doses, even if the larvae do not die, the feed intake will decrease, the larvae drop rate will decrease, and the weight loss will decrease. Decline in eggs, which can significantly reduce the next generation population base. There are three points to note when using these agents: First, try to apply the drug at the younger age of Spodoptera exigua as it has no effect on larval feeding on the day of application, and it can reach the maximum within 3 to 5 days after the drug is applied. Control effect, if the larvae enter the gluttony period, even if the insect is controlled, it will cause loss. Second, due to the poor availability and high price, it can be used in combination with low-toxicity and more efficient chemical pesticides such as phoxim and beta-cypermethrin to improve the instant effect. Third, the dilution of the drug should not be too low. At very low doses, these agents have no effect on the larvae and the next generation of eggs. When the mixture is used for control, the proportion of insect growth regulators in the mixture should be appropriate. ?

Although insect growth regulators can effectively control Spodoptera exigua, it is also necessary to limit the number of times they are used and their doses, alternately using insecticides with different insecticidal mechanisms to avoid and delay the development of insecticide resistance against Spodoptera exigua. Extend the useful life of such agents. ?

At present, insect growth regulators that can be used for the control of beet armyworm are tebufenozide (Brazil), flufenoxuron (calcamide), hexaflumuron, and diflubenzuron (Taibao), generally 1500-2000 times of the field. Liquid spray, spray thoroughly spray the drug, 3 to 5 days can reach 90%? Control effect. ?

4.3 virus control?

The viruses used for control of Spodoptera exigua are beet armyworm particle virus (LeGV), NPV, Autographa californica nuclear polyhedrosis virus (AcMNPV) and celery spider mite nuclear polyhedrosis virus (SfaMNPV), plus some virus Anti-ultraviolet protection agents, such as 1% uric acid, 1% activated carbon and 1% folic acid, can significantly reduce the passivation effect of ultraviolet rays on the virus and improve the control effect.

4.4 control of adult?

As a new prevention and control method, sexual attractants have the ability to not kill natural enemies, do not pollute the environment, and have a specific target for prevention and control. They are safe for humans and animals and can be used in the production of pollution-free vegetables. The sex attractant produced by the Shanghai Institute of Entomology, Chinese Academy of Sciences, controls Spodoptera exigua and can kill males in large quantities. According to experiments, the control area can reduce Spodoptera exigua above 60% compared to the non-control area, and the adult seminal vesicles fall by 41.96%, and almost no Spodoptera exigua larvae and eggs can be seen. A 10:1 mixture of sex pheromone (Z,E)-9,12-tetradecadienyl acetate and (Z)-9-tetradecene-1-ol was found in the study. There is a strong tendency. Because the adults are nocturnal, they tend to have a strong tendency toward lighting. In regions with conditions, blacklights or high-pressure mercury lamps can be used to attract insects, lamps can be placed under water basins, and a small amount of washing powder can be added, so that adults cannot escape after falling into the water. Adult worms have strong tropism for sweet vinegar and poplar odors, so they can be eliminated with sweet vinegar and poplars before they are trapped.

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