Global grassland moth spread path
Grass nocturnal moth larvae
Courtesy of the Chinese Academy of Agricultural Sciences
■ Han Yangmei, intern of this newspaper, Liu Runan, reporter, Li Chen
Hainan, as the national scientific research and breeding base for southern breeding, shoulders the heavy responsibility of breeding and breeding major food crops in the country.
On June 16, more than 40 days after the discovery of the grassland moth, one of the "world's top ten plant pests", in Hainan, this pest has been endangered in 18 cities and counties in Hainan.
Lu Baoqian, a researcher at the Institute of Environment and Plant Protection of the Chinese Academy of Tropical Agricultural Sciences, who is responsible for monitoring insect conditions in Hainan, told China Science Daily that the grassland moth mainly harms grass crops such as corn and rice, which is the main crop in Nanfang. The effective prevention and control of the grassland night moth in Hainan is of great significance to ensuring China's food security. Especially in the next southern season, it is necessary to do a good job in adequate prevention and control technology and prevention and control material reserves.
At the same time, Hainan is located in the tropics, and the grassland night moth can occur every anniversary and become one of the sources of northern migration insects.
Since the invasion of Yunnan in January this year, it has spread in 18 provinces and municipalities across the country, and has shown a trend of continued northward migration, which seriously threatens China's grain production.
Han Changfu, minister of agriculture and rural affairs, clearly pointed out that "the prevention and control of grassland night moths should be grasped as a major, important and urgent matter in the current agricultural and rural work." ”
A battle of insects for food is unfolding in a race against the clock.
Go north with the "wind"
In 2018, the grassland moth was listed by the Food and Agriculture Organization of the United Nations as a major migratory agricultural pest for global alert.
At that time, Wu Kongming, an academician of the Chinese Academy of Engineering and vice president of the Chinese Academy of Agricultural Sciences, was keenly aware that the pest was likely to invade China, and quickly set up a monitoring point in Jiangcheng, Yunnan.
At the same time, they systematically carried out research on the grassland moth, its characteristics, and prevention and control techniques, and bought time for the battle of "insect rations for food". The results were published in a recent issue in the journal Plant Protection.
Wu Qiulin, a member of the Wu Kongming team and a postdoctoral fellow at the Institute of Plant Protection of the Chinese Academy of Agricultural Sciences, has conducted in-depth research on the "migratory nature" of the grassland night moth. She told China Science Daily that the grassland night moth is characterized by only migrating at night, and has the ability to migrate multiple consecutive nights. Relying on the transport carrying effect of the wind, the distance of the flight is more than 100 kilometers per night. It has been recorded that the grassland moth has completed a 1600-kilometer migration flight in 30 hours.
Professor Hu Gao's team at Nanjing Agricultural University analyzed and predicted the migration path of the pest based on the meteorological data provided by the NOAA database in the United States for the past 5 years. Hu Gao said that since the grassland nightcrawler entered India in May 2018, it has gone all the way to the east, and soon entered Southeast Asian countries such as Bangladesh, Thailand, Myanmar and so on, as far as Yunnan, China. In China, the grassland night moth enters the main corn-producing areas in northern China through two paths, east and west, threatening China's corn production.
On the reasons for the formation of the insect's domestic migration pattern, Wu Kongming said, "The migration of the grassland night moth is mainly driven by air currents, and in the summer, most of China is affected by the East Asian monsoon, and the East Asian monsoon circulation accelerates the migration of the insect." ”
Wu Kongming pointed out that in tropical China and tropical South Asia, a source base for the grassland nightcrawler has been formed, and its anniversary with neighboring countries such as Thailand and Myanmar is a pest breeding area. Every May, the grassland moth will migrate to China with the monsoon, which may be a long-term pest law, so it is necessary not only to do a good job in domestic prevention and control, but also to cooperate with neighboring countries to establish a joint prevention and control system.
Tenen fly, tenac eat, tenen raw
The grassland moth not only has a strong ability to migrate, but also has the characteristics of high fertility, wide suitable growth area, strong resistance and overeating. Scientists vividly describe it as "particularly capable of flying", "particularly able to eat", and "particularly capable of giving birth to babies".
According to the data, the grassland night moth can breed a generation in about 30 days under the condition of 28 °C. Each spawn can be 100 to 200 eggs, a lifetime can lay 900 to 1000 eggs; the host plant up to 180 kinds, can harm more than 80 kinds of crops, has caused tens of billions of dollars in losses around the world.
In the Americas, the grassland moth has differentiated into two ecological types, "corn type" and "rice type". The former prefers maize and sorghum; the latter feeds mainly on rice and pasture.
The latest research by Xiao Yutao, a researcher at the Shenzhen Institute of Agricultural Genomics of the Chinese Academy of Agricultural Sciences, found that there are two genotypes of the grassland moth that invaded China, about 10% of which are pure "corn type" and about 90% of which are "corn type" carrying a small number of "rice type" genomes, and the sequence characteristics of Chinese samples are strongly consistent with the Florida population and African samples.
Therefore, they deduced that the population of grassland moths that invaded our country was a geographical population of Florida, USA.
Wu Qiulin explained that in tropical China and tropical South Asia, the annual planting of corn, sugarcane and other crops provides superior conditions for the colonization and anniversary of the grassland night moth, forming a domestic insect source of the grassland night moth, which helps it to spread or migrate in various seasons. The National Agricultural Technology Extension Service Center has found that it is harmful to sugarcane in Yunnan.
The reason why the grassland moth is harmful is mainly due to the entire reproductive period of its larvae that can harm corn at all ages. Wu Qiulin introduced that in the young larval stage, most of them gather as the heart leaves of corn at the seedling stage, nibble on the young leaves, and form translucent "window holes" on the leaves; they also have the habit of "spitting silk", under the action of the wind, the spitting silk droops and transfers to the surrounding plants.
The elderly larvae have a gluttony, like to drill the heart leaves of corn moths, nibble on the growth points, affect the growth of males and fruit ears; it can also directly drill male spikes and fruit spikes, bite off male panicle branches, affect pollination, nibble on young seeds, and directly affect corn yield and quality. In addition, during the seedling stage of corn, it will also drill the rhizome of moth, causing the death of the entire corn plant, which is the most damaging.
"Combination Fist" comprehensively kills "Moths"
Experts admit that China's complex climate and terrain conditions, the gradual movement of crops from south to north, and the characteristics of the grassland moth itself have increased the difficulty of monitoring, early warning and prevention and control of the grassland moth.
On June 5, the Ministry of Agriculture and Rural Affairs and the Ministry of Finance urgently arranged a central financial agricultural production disaster relief fund of 500 million yuan to support the prevention and control of grassland night moth insect pests in the insect outbreak area and the migration and flight transition area.
Wu Kongming introduced that at present, the main prevention and control measures are physical and chemical enticing control, chemical control, biological control, etc., the basic prevention and control idea is to implement zoning treatment according to local conditions, early monitoring and booby-trapping of adult insects, to prevent large-scale migration, focus on the prevention and control of larvae, and avoid outbreaks of harm.
At present, the grassland night moth is still in the pre-colonization stage and the population growth period of invasive insects, and the chemical control based on the application of chemical pesticides is the most effective. This can quickly reduce the density of insect populations, recover crop losses to a certain extent, and prevent large-scale migration and diversion.
"'Spraying' is the most emergency prevention and control measure, which is the mainstream practice at present and is also necessary." Zhang Lisheng, a researcher at the Institute of Plant Protection of the Chinese Academy of Agricultural Sciences, said.
On June 4, the Ministry of Agriculture and Rural Affairs announced the list of emergency drugs for the prevention and control of grassland nightcrawler, including chemical pesticides such as methylaminoavermectin benzoate, tetrachlorospermamide, and chlorpyrifos benzamide, as well as biopesticides such as Thuringiensis, Anchovy aeruginosa, and Coccidioid albicans.
Zhao Shengyuan, a doctoral student in Wu Kongming's team, told China Science News, "The quick-acting properties of biopesticides are lower than those of chemical pesticides, but they are the main direction of green prevention and control, and they are more suitable for application on crops with high economic value such as melons, fruits, vegetables and so on." ”
In the long run, the use of natural enemies of insects to "treat insects with insects" is the core measure of biological control. At present, scientists are carrying out the investigation, collection and evaluation of natural enemy resources.
Zhang Lisheng has long been engaged in the research of natural enemy insects. He said that the grassland moth "settled" in the place of origin for thousands of years and has its own "natural enemies". However, once in a new habitat, the grassland moth will quickly erupt due to the lack of natural predator insects and some resistance to conventional microbial insecticides in the invading area.
In order to find a suitable "natural enemy", Zhang Lisheng's team and collaborators recently took the lead in China to carry out the use of natural enemies such as cockroaches and beneficial bugs to prevent and control the grassland night moth, and found that both the fly bug and the beneficial bug can actively search for the grassland night moth, which can lock the pest within 9 minutes, quickly launch an attack at a distance of 1 cm and cause its death.
The road to pest control is a long way off
There are still many scientific questions about the grassland moth that are not yet clear, and scientists feel that they cannot relax at all.
In terms of migration characteristics, Wu Qiulin believes that it is also necessary to clarify China's unique atmospheric environment and seasonal circulation background field, so as to elucidate the atmospheric dynamic mechanism of the continuous migration and invasion process in China, so as to construct its migration path, main migration and affected areas in China.
Hu Gao said that the meteorological data of 5 years can reflect the general migration trajectory of the grassland night moth, but the accuracy is not enough to be specific to a city and county, a certain day, which requires more accurate meteorological data and weather predictions, as well as the migration and flight behavior of the grassland night moth.
In terms of control strategies, Zhang Lisheng said that due to the large area of pest occurrence, the cost of large-scale application of artificially expanded natural enemy insects is too high, and the actual operation is not realistic, and the fundamental solution lies in the protection and utilization of indigenous natural enemy insects. At this stage, it is necessary to pay attention to the rational application of chemical pesticides so as not to kill predatory insects.
It is understood that in order to strengthen the monitoring and prediction of field populations, Wu Kongming's team is promoting the establishment of ovarian anatomy and grading standards for grassland nocturnal moths, developing identification apps for adults and larvae of grassland nocturnal moths, and establishing a life table of natural populations in the field of grassland nocturnal moths, exploring the influencing factors and regulatory mechanisms of their natural populations.
These control strategies are supported by scientists in the field of plant protection. Ma Zilong, secretary of the Institute of Environment and Plant Protection of the Chinese Academy of Tropical Sciences, told China Science Daily that they are looking for native natural enemies of insects in Hainan, and at the same time designing joint control measures for chemical pesticides and biopesticides, hoping to find a quick and effective way to control insect pests as soon as possible.
"The grassland moth is preventable and controllable in China, and the actual harm caused to production is not large at present." Wu Kongming pointed out, "But the time is tight, everyone shoulders the heavy responsibility, we must 'race' with the grass night moth to win the battle." ”
Related paper information:
doi:10.16688/.zwbh.2019207
doi:10.16688/j.zwbh.2019264
dol:10.16688/.zwbh.2019240
doi:10.16688/j.zwbh.2019296
China Science Daily (2019-06-18 5th Edition Agricultural Science and Technology)