Ambrose. It is the general name of plants of ragweed in Compositae. Panicum miliaceum. Leaves opposite or alternate, entire or lobed. Small head, unisexual, dioecious; Male heads are densely clustered on branches into leafless spikes or racemes; Female flower heads are solitary or densely clustered in the upper leaf axils to form umbrellas; Male inflorescences have the most sterile hermaphroditic flowers, the total bracts are 5 ~ 12, and the base is United; The female head has only 1 female flower, and there are tumors or thorns on the back of the involucre. Achene obovate, hidden in a hard involucre. This genus is about 10 species, mainly produced in America. Artemisinin has alternate leaves and divided feathers. Trifoliate wood has opposite leaves, palmately 3-5-lobed. Both species are native to North America. In recent years, weeds that are easy to escape have been found in northeast, north and central China of China. Both species are classified as quarantine weeds in China, and their pollen is the main allergen of pollen allergy.
1, the occurrence and distribution of ragweed.
Ambrosia trifida L. is a weed in Compositae, which originated in North America and has spread to most parts of the world, mainly in the northeast of China. In the middle and late 1980s, there were sporadic occurrences in Haidian District, Tongxian County, Changping County, Chaoyang District and Fengtai District of Beijing, with an area of 8hm2 in Tongxian County and 13.3hm2 in Changping County. 1In July, 990, a large area of ragweed was found in Ma Po Township, Shunyi County, Beijing. The county government allocated special funds for continuous treatment for three years, but due to insufficient funds, the epidemic has not been controlled and spread. According to the investigation of1May, 1993, there are 10 natural villages, roads, canals, wasteland beside villages and individual farmers in Mapo Township. Xiaosungezhuang to Xifengle, on both sides of Ma Po-Xiangyang Highway, and in some sections of Jingcheng Railway, the occurrence area is 320hm2, of which the occurrence area of grain fields is 133.3hm2.
2. The harm of ragweed
Ambrosia trifoliata is a dangerous weed that harms human health and crop production. It is listed as a quarantine object by many countries. Because its pollen contains water-soluble protein, it can be released quickly after contact with people, causing allergic reactions. It is the main pathogen of autumn pollen allergy (hay fever). From August to September every year, a large number of ragweed pollen flies in the air. When the pollen density reaches 40 ~ 50 /m3, people will be infected after inhalation. In the United States, Canada and Europe, tens of millions of people are sick, and the incidence rate in some places is as high as 30%. The annual pollen output of ragweed in the United States is about 6.5438+0 million tons, and there are 6.5438+0.46 million people with pollen allergy, and the annual treatment cost is as high as 600 million dollars. In Osaka, Japan, when ragweed pollinosis was prevalent in autumn, a large number of residents left home. Shenyang is one of the serious producing areas of ragweed in China. The pollen content of Ambrosia trifoliata in Shenyang 1987 is 38 times that of 1983, and the population incidence rate is 1.52%.
Ambrosia trifoliata was introduced to China in 1930s. After a long adaptation period, it spread rapidly under the abnormal situation of nearly 10 years, invading farmland, orchards, towns, green belts, roads and railways and hillside wilderness, showing tenacious vitality and competitiveness. Ambrosia trifoliata has become the dominant weed population in some areas. With the spread of ragweed in some areas, the air pollution caused by its pollen is becoming more and more serious. Ma Po Township, Shunyi County is a tourist development zone. Since 1980s, golf courses, country racetracks and country parks have been built here. Tourism income is also the main source of economic income in Mapo Township. If ragweed is allowed to spread, it will affect the development of tourism in Mapo Township. The potential seriousness of the harm of ragweed has attracted the attention of the government, agriculture, medicine and environmental protection departments.
Ambrosia trifoliata is mixed in the fields of hemp, kenaf, corn, soybean, sunflower and other crops. After the farmland was invaded, the yield per hectare decreased by 300 ~ 495 kg, and even the corn had no female ear, which led to no harvest. After the introduction of Ambrosia trifoliata in the former Soviet Union, a large area of farmland grass shortage was caused. In order to control this kind of grass, the former Soviet Union invested huge manpower and material resources to organize the investigation and eradication of ragweed. Although efforts have been made for many years, ragweed is still one of their key control targets.
3, prevention and control of ragweed.
(1) Ambrosia trifoliata is the object of plant quarantine in our city. From 65438 to 0993, the occurrence range of Ambrosia trifoliata in Ma Po township was found out, and Ma Po township was designated as the epidemic area of Ambrosia trifoliata, and measures were taken to block and eliminate it to prevent the spread of Ambrosia trifoliata. In order to master the biological characteristics of Ambrosia trifoliata and the best control methods, the municipal and county plant protection stations and Mapo Township Agricultural Company set up a cooperative group to study the biological characteristics of Ambrosia trifoliata and carry out chemical control experiments. Through four years' research, the growth and development law of Ambrosia trifoliata in Beijing was basically found out, the ecological characteristics were mastered, safe and effective herbicides were screened out, and the best application time was determined. After four years of continuous control, Ambrosia trifoliata has been reduced from 65438+306 plants /m2 in 0993 to 0 plants /m2 in 1996. Now there is basically no Ambrosia trifoliata in the original serious plot, which has achieved the goal of blocking control.
(2) Observation on the growth period of ragweed. During the period of 1993, the growth of ragweed in the field and at different sowing dates was observed. The results show that the earliest emergence is usually in April1~ April 10. Due to the spring drought and dry soil in Beijing, there is little precipitation in the first half of the year, and the summer precipitation is concentrated in June-August. According to our observation, the occurrence of Ambrosia trifoliata in Beijing is positively correlated with rainfall. Generally, after every rain, ragweed will appear, which can last until the beginning of August and bear fruit. Ambrosia trifoliata, which emerged in early August, can bear 8 ~ 30 seeds. Ambrosia trifoliata in Beijing first appeared in July 15, with a flowering period of about 40 days. Each plant can bear up to 6652 seeds, generally 2300 ~ 3200 seeds per plant, and the seeds will mature on September 20 ~ 10. Seed viability can be maintained for at least 5 years.
The seedling rate of Ambrosia trifoliata collected in that year can reach 25% in the second year, and the seedling rate sown before June 1 accounts for 85% of the whole Ambrosia trifoliata seedling rate. Therefore, the key point of blocking and controlling Ambrosia trifoliata should also be the Ambrosia trifoliata unearthed before June 1 year.
(3) Screening test of chemicals for controlling Ambrosia trifoliata. In order to find the best medicament and dosage for controlling Ambrosia trifoliata, we have conducted medicament screening tests for two consecutive years. In the first year, we conducted experiments on different chemicals to control Ambrosia trifoliata in the yard of Mapo Rural Agricultural Company. The sowing date is April 9, the sowing depth is 2-3 cm, and the row spacing is 2-3 cm. Five treatments were set up in the experiment, that is, 20% 2,4-butyl ester 60 was dropped. 4-D butyl ester 2 100ml/hm2, 10% glyphosate 15000ml/hm2, 20% paraquat 4500ml/hm2, control plot area 15 m2, repeated three times, with water consumption of 450kg per hectare. Spray it evenly with the hand sprayer of Gongnong-16, and the application date is 1 1 July. According to the test results, when 2,4-D was used at 1050ml and 2 100ml per hectare, symptoms appeared five days after application, and the tip was bent and deformed. The leaves at the growing point turned yellow on 10 day after application, and appeared black and dry on 15 day after application. On the 25th day after application, symptoms were investigated per hectare. When glyphosate was used at the dosage of 0/5000 ml per hectare/kloc-0, the top growth point of the plant began to turn yellow and the bottom leaves turned green 5 days after application. 65,438+00 days after application, the growing point turned yellow and brown spots appeared on the stem. 65,438+05 days after application, the growing point became black and dry, the leaves turned yellow, and the brown spot on the stem expanded. After 25 days of application, the growth point died, the upper leaves appeared yellow filamentous deformity, and most of the stems were dark brown. The dosage of paraquat was 4500ml per hectare, and the leaves and upper stems were black rot 5 days after application, and the control effect was 95.6% 10 day after application. 35 days after application, the control effects of 2,4-d1050ml, 2 100ml, glyphosate and paraquat were 95%, 96.4%, 100% and 98% respectively. It can be seen from this experiment that the two treatments of 2,4-butyl ester have good control effects on Ambrosia trifoliata. Because the plants are relatively high (the average plant height is 80cm), it takes a long time (35 days) for all plants to die, and the number of plants can be reduced in practical application. The application of 1050 ~ 1500 ml, glyphosate and paraquat per hectare can achieve ideal control effect. When the plant height is less than 80cm, the dosage of 10% glyphosate is 1 1250ml per hectare, and the dosage of 20% paraquat is 3750ml per hectare.
(4) The best time to control ragweed. Experiments were carried out in the same place to control Ambrosia trifoliata with different chemicals at different growth stages. The experiment was divided into three stages: seedling stage (6 leaves, 1 heart) and before and after germination, and artificial sowing was used in the experimental site. March sowing date 18, sowing depth 2 ~ 3 cm. Before sowing, soak the land with water to ensure the soil moisture. On April 7, the seedlings began to emerge. There were 4 true leaves on May 2, and 6 true leaves on May 9, with a plant height of 4-6.5 cm. The first application was on May 9th, and the water consumption per hectare was 450kg. The second application before germination in July 16, the plant height was 70- 150~250cm, and the water consumption per hectare was 600kg. The third application was after germination on August 4th. In the experiment *** 10, the plot area is 15m2, and there is no duplication. The results showed that the control effect could reach 99% ~ 100 ml by applying 2 100ml per hectare before germination. The control effect is 97%, but it is difficult to popularize in production because the plants grow tall and die. The control effect of 20% paraquat was 3000ml/hm2 at seedling stage, 4500ml/hm2 before germination and 6000ml/hm2 after germination, and the control effect was 88% ~ 100% on the fourth day after application, but the plants that were not dead grew new buds and blossomed, so it should be at seedling stage15000. After budding, 30000ml of 10% glyphosate was used, and the control effect of 6000ml/ha of 4 1% roundup was even worse, only 70%.
Two-year experiments have proved that the best time to control Ambrosia trifoliata is 50 ~ 70 cm in plant height (July 8 ~ June 438+06), and 2,4-d butyl ester 1500 ~ 2250 ml/hm2 or 20% paraquat 3000~3750ml, which is not only convenient to control Ambrosia trifoliata.
(5) The benefit of controlling Ambrosia trifoliata was increased from 1993 to 1996. On the basis of mastering the biological characteristics of Ambrosia trifoliata, 199 1 ~ 1996 was used to control Ambrosia trifoliata in the best control period (plant height 50 ~ 70 cm) for three consecutive years, and the control effect was 1500ml/hm2. The blockade and control of Ambrosia trifoliata in Ma Po Township has effectively promoted the development of tourism in Ma Po Township and even Shunyi County. According to statistics, the income of golf courses, country racetracks and country parks in Mapo Township has increased year by year, with a total income of 49.809 million yuan in the first half of 1993, 1994, 1995 and 1996. In four years, * * * has eliminated 533.3hm2 of ragweed in grain fields. Based on the restored output of 450kg per hectare, * * * has lost 240,000kg of restored output, equivalent to RMB240,000, and the investment benefit ratio is 1: 178.
There are more than 380 invasive plants.
On August 8, the reporter saw a batch of soybeans doped with fake sorghum seeds in Chiwan Port, Shekou, Shenzhen. These soybeans came from Argentina and were purchased by Shantou Zhongxing Oil Factory from a German futures company. The reporter saw that soybeans were mixed with something similar to black sesame seeds. Mr. Jiang Yunbing from Shekou Entry-Exit Inspection and Quarantine Bureau told the reporter that this kind of thing similar to "black sesame" is the seed of "fake sorghum" with strong vitality.
The so-called invasive plants refer to plants that enter another environment from the original place of growth due to man-made or natural reasons, causing losses to the organisms, agriculture, forestry, animal husbandry and fishery production in this environment, damaging human health and destroying ecological balance.
For example, fake sorghum looks like sorghum, but its stems and seeds contain a small amount of cyanide. This plant has a strong vitality. If there is fake sorghum in the crop field, the crop yield will be reduced by about 20%. Not only that, the root penetration of fake sorghum is very strong. The root system of a false sorghum can add up to more than 1 km long. If it grows on the dam, it will also pose a great threat to the safety of the dam. Therefore, once the fake sorghum grows on the ground, it is difficult to eliminate it.
According to relevant literature, there are many invasive plants like fake sorghum. At present, there are more than 380 invasive plants in China, among which water hyacinth, Alternanthera philoxeroides, ragweed, Eupatorium adenophorum, Eupatorium odoratum, Spartina, Mikania micrantha and Chrysanthemum have brought serious harm to China's agriculture. These exotic plants threaten the agro-ecosystem of China, the habitat of livestock and fish, and affect our health.
Seize the local plant space and bring unexpected diseases.
One of the biggest characteristics of invasive plants is that after entering the new environment, their viability is very strong, robbing the living space and nutrients of other creatures around them. Li Jingming, director of the Energy and Ecological Construction Division of the Science and Technology Development Center of the Ministry of Agriculture, told reporters that water peanuts can reduce rice production by 45%.
In Guangdong, Mikania micrantha often covers bananas, lychees, longan, wild oranges and some shrubs and trees, which makes it difficult for these plants to carry out normal photosynthesis and die. In Caohai Lake, Kunming City, Yunnan Province, there used to be 16 kinds of local higher plants, but with the rampant growth of water hyacinth, most local aquatic plants such as seaweed lost their living space and died. At present, there are only three local higher plants in Caohai Lake.
In addition, invasive plants themselves may carry toxins, which will bring unexpected diseases to local animals and plants. For example, Eupatorium adenophorum contains toxins that can cause asthma in horses and sheep. Liangshan Yi Autonomous Prefecture in Sichuan Province once lost more than 60,000 sheep a year due to the invasion of Eupatorium adenophorum, and the loss of animal husbandry reached 2 1 more than 10,000 yuan. Eupatorium adenophorum has a strong ability to absorb soil fertility, which can greatly exhaust soil nutrients and destroy soil fertility.
The cost of eradication is very high, which threatens the traditional way of life of human beings.
Invasive plants are not easy to eradicate, and the cost of eradication is also high. For example, Guangdong, Yunnan, Jiangsu, Zhejiang, Fujian, Shanghai and other provinces and cities have to salvage water hyacinth manually every year. The annual cost of salvaging water hyacinth in Shanghai exceeds 60 million yuan, and the economic losses caused by water hyacinth in agricultural irrigation, grain transportation, aquaculture and tourism are even greater.
The harm of invasive plants does not stop there. There are special animal and plant resources and unique ecosystems around the Dai, Miao and Buyi communities in China. These natural resources play an important role in the formation of local national culture and lifestyle. However, due to the continuous expansion of invasive plants such as Eupatorium odoratum and gradually replacing local plant resources, many traditional crops have gradually disappeared, and the ancient lifestyle is being forced to change.
In addition, alien invasive organisms will also pose a direct threat to human health. Whenever ragweed blooms,
People with allergic constitution will have asthma, sneezing, runny nose and other symptoms, and people with weak constitution may have other complications, leading to death. The "hay fever" caused by ragweed has brought trouble to people in many countries in the world.
Blind introduction of species is the easiest way to "lure the wolf into the room"
Dr Wan, director of the Biological Invasion and Biosafety Research Office of China Academy of Agricultural Sciences, told the reporter that there are three main ways of invasive alien harmful plants. First, it is introduced through the diffusion force of plants themselves or with the help of natural forces. The second is to bring some harmful plants into China through trade and transportation. This is how the fake sorghum seeds that the reporter saw at Chiwan Port in Shekou, Shenzhen entered the country. In addition, some domestic institutions and individuals have consciously introduced some plants to develop agricultural production and beautify the landscape without knowing the harm. There are similar harmful plants among these plants. In this regard, our country has had a painful lesson.
From 1960s to 1980s, China introduced Spartina to protect beaches from British and American aggression. In recent years, this plant has spread wildly in coastal areas, covering an increasing area. The wanton spread of Spartina not only destroyed the habitat of coastal organisms, but also suffocated many coastal cultured species. In addition, this plant also blocks the waterway and affects the ship's departure from the port; Obstructing the flow of seawater, leading to the decline of water quality and causing red tides; Competing with coastal plants for growth space, leading to the death of local plants and so on. Therefore, it is necessary to block the invasion channels of harmful plants from the source.
Keep harmful plants out of the country.
The dangers of invasive plants are constantly emerging, which makes people realize that "ecological security" is as worthy of attention as environmental protection. In order to maintain ecological security, on the one hand, we should keep harmful plants out of the country, on the other hand, we should control harmful plants in China.
First of all, put an end to the invasion of harmful plants from the source and intensify the inspection of harmful plants by inspection and quarantine departments. At present, the staff of relevant inspection and quarantine departments have received strict professional training and higher education in related fields. Coupled with the inspection and quarantine experience accumulated in their work, under normal circumstances, known harmful plants can hardly escape their eyes.
In addition, in order to better prevent the invasion of harmful plants from inspection and quarantine, China often sends relevant quarantine personnel to inspect the origin of imported plants, so as to know what pollution there is in the local soil, what diseases and pests are in the process of plant growth, and what harmful weeds are easily mixed with products in the field. According to their understanding, there are fake sorghum in the fields of South American countries. It is estimated that the fake sorghum seeds mixed in soybeans were brought in together when the machine was harvested.
In China, biological control is the best way to control harmful plants.
For the harmful plants that have invaded our country, the most common method is to pull them out manually and use chemicals. Miyun County, Beijing has accumulated some experience in this respect. In Miyun County, Beijing, the alien invasive plant Ambrosia trifoliata is threatening the local ecological environment.
This plant is "burly" and can reach more than 4 meters in height. The three-leaf ragweed grows very densely here. Comrades of Beijing Agriculture Bureau said that this kind of grass has strong vitality and can survive for five years in harsh environment. Its seeds go with the wind, and once it takes root, it is difficult to eradicate it, and it is difficult to grow other plants around it. The reporter pulled out a plant by hand and found that the grass grew very solid and it was very difficult to pull it up by hand.
It is said that the stems of some finless porpoises are as thick as wrists, and it is difficult to pull them out by manpower. To deal with them, you have to cut them with a knife and wear protective gloves, which is a lot of work. In addition, the use of chemical agents is very limited, because some ragweed is scattered in other crops, and large-scale drug use is not only costly, but also may cause harm to other plants.
Dr. Wan is studying biological methods to deal with invasive plants. To this end, he visited the origin of many harmful plants. Because the country of origin often has natural enemies of these harmful plants. If natural enemies of harmful plants are introduced into China, the spread of harmful plants in China may be limited.
Dr. Wan said that the natural enemy of Ambrosia trifoliata has been found to be an American moth. After experiments, these moths only bite ragweed and will not bite other plants. Therefore, the disaster of ragweed in Miyun, Beijing is expected to be solved.