A locust plague refers to a catastrophe caused by locusts. In the event of a locust plague, a large number of locusts will swallow up the grass fields, completely destroying the agricultural products, causing serious economic losses and causing famine due to food shortages.
Locust plagues are a worldwide catastrophe, and they have a long history. It is mentioned in the Book of Verses that "to remove their borers (moths are locusts) and their cockroaches are harmless to me." Tian Zu has a god, and he is on fire." The first plague of locusts in Japan was seen in the book "The Later Chronicles of Japan".
In the history of China, locust plagues have occurred repeatedly, and the affected areas are mostly concentrated in Hebei, Henan, Shandong provinces, Jiangsu, Anhui, Hubei and other provinces are also distributed, and when they are serious, they may spread throughout the loess plateau, Deng Yunte's "History of China's Disaster Relief" statistics, the Qin and Han dynasties averaged 8.8 years, the two Song Dynasties were 3.5 years, the Yuan Dynasty was 1.6 years, and the Ming and Qing dynasties were 2.8 years.
In ancient China, there was not much understanding of locusts, so there was the saying of "locust god", and there was also the saying of "mutualization of locusts (shrimps)", such as: Lu Tong's "Pi ya" of the Song Dynasty: "Or locusts are the embodiment of fish eggs". Pan Zimu's "Remembering the Yuanhai": "There are locusts turned into fish and shrimp". Li Fang's "Taiping Imperial Records" (Shrimp Gate) records: "Locusts fly into the sea and turn into fish and shrimp"
The main species caused by locust plagues are locusts. Locusts belong to the arthropod phylum, insect class, orthoptera, locust family, the body is generally green or yellow-brown, chewing mouthparts, hindzu is large, suitable for jumping, not completely metamorphosed, its larvae are called "grasses", mainly based on grass plants as food, there are many species, there are about 10,000 species in the world, there are more than 300 species in China, such as flying locusts, rice locusts, bamboo locusts, Italian locusts, cane locusts, cotton locusts, etc. are the main pests of agriculture and forestry.
When a locust is touched in a certain part of the hind leg, the locust will change its original habit of being alone and become a group. Locusts usually prefer to live alone and have limited harm. But they sometimes change their habits, prefer to live in groups, and eventually gather in large numbers and migrate en masse, forming a formidable locust plague that causes great damage to agriculture. Scientists at oxford university say they experimented with desert locusts that were living alone, repeatedly touching multiple parts of the locust's body to see if there were certain tactile factors that caused the locusts to change their habits. It was found that when a certain part of the locust's hind legs is stimulated, they suddenly become gregarious, and touching other parts of the body such as antennae, mouth or abdomen does not have this effect.
Scientists believe that the occasional gathering of locusts in a natural environment when their hind legs touch each other, which may cause them to change their habits and begin to live in groups, and their members will increase in the same way, thus forming a locust plague. If it is possible to discover exactly which chemical signals stimulate the locust's nervous system to cause its behavior to change, it is possible to develop new pesticides to prevent locust swarms.
Cause
drought
From an environmental point of view, it is mainly caused by drought. The main reason for this phenomenon is that arid environments have many benefits for locust reproduction, growth and survival. Because locusts lay their eggs in the soil. The soil is relatively solid, and the moisture content is 10% to 20% when they are most suitable for spawning.
Drought causes locusts to multiply and grow rapidly, and there are two reasons for disasters. On the one hand, in dry years, due to the decline in water level, the soil becomes relatively solid, the water content decreases, and the ground vegetation is sparse, and the number of eggs laid by locusts is greatly increased, and most of the time it can lay 4,000 to 5,000 eggs per square meter of soil, and there are 50 to 80 eggs in each egg block, that is, 200,000 to 400,000 eggs per square meter.
In dry years, the shrinking water surfaces of rivers and lakes and the exposed low-lying areas also provide more suitable places for locusts to lay eggs. On the other hand, plants growing in arid environments have a lower water content, and locusts feed on them, grow faster, and have higher fertility.
At the same time, droughts have caused explosive migrations from arid areas to low-lying flood-prone areas.
Habits of life
Judging from its life habits, the main ones are:
(1) It has the habit of living in groups.
(2) It has strong fecundity.
(3) It has a lot of food, that is, it can eat many kinds of plants.
(4) Its flight ability is very strong and difficult to control.
(5) Its eggs are hidden deep in the ground and are difficult to destroy.
The climate is warming
Global warming, especially the rise in winter temperatures, is conducive to the increase of locust overwintering eggs, providing "worm eggs" for the outbreak of locusts in the second year; in addition, the superposition of various factors such as warming, intensification of drought, and grassland degradation will provide a suitable place for locust eggs to lay eggs, and locusts have a strong ability to adapt to drought, this is because other insects and birds can not survive in this situation, and a filamentous fungus that can cause locust disease is suppressed, so its number increases greatly. Therefore, experts predict that with the trend of global warming, the scale of locust plagues will become larger and larger in the future, which will have a serious impact on food production in China and the world.
The insect density is too large
In a 2006 research paper published in the journal Science, J. Buhl and other scientists demonstrated that excessive locust density is also an important factor in locust plagues. [5] When the swarm is at this density, the locusts will line up and begin to move in the same direction. Locusts were isolated, wingless "nymphs" early in their life history, and they tended to avoid each other. But if resources become scarce, they are forced to influence each other. They can then form orderly local swarms of locusts. This swarm of locusts has the ability to act in unison, enter the habitat of neighbors, and allow more and more locusts to join in, eventually becoming a huge swarm of locusts. Predicting the start of group action is therefore crucial to controlling locust outbreaks. The scientists placed the growing swarms of locusts in a circular field, recorded their behavior, and used computer software to track their movements. At medium densities (25 to 62 locusts per square meter), the locusts will line up and begin to move in the same direction, even abruptly changing direction uniformly. In the experiment, when the number of locusts per square meter exceeded 74, the orderly swarm of locusts stopped changing direction and instead continued to advance in the same direction for 8 hours. These observations confirm the results predicted by computer models called self-propelled particle models. Buhl and his colleagues believe that using such a model could help devise ways to control locust outbreaks. Their findings also support the FAO's definition of locust nymph populations. In this definition of density, locust swarms tend to cross the "tipping point", triggering locust plagues.
Prevention and control methods
environmental protection
Natural factors are the main factors in the occurrence of locust plagues, but it is undeniable that there are a considerable number of human factors. Locusts must lay their eggs on land with less than 50% vegetation coverage, and if a place is beautiful and has no bare land, locusts cannot reproduce. At present, the ecological awareness of some places is not strong, and some simply believe that pollution control is to protect the environment, and for improving the vegetation, soil and microclimate of the locust suitable area, they do not pay attention to it because they cannot see benefits in the short term.
Therefore, in order to fundamentally prevent and control locust plagues, great attention should be paid to the protection of the ecological environment.
Pharmaceutical control
It is recommended to choose high-efficiency, low-toxicity, low-residue counterpart pesticides, such as 5% Ruijin Special Suspension Agent, and spray 50-60 kg per mu with 20-30 ml of water.
It can also be sprinkled on small bamboo and weeds with enemy insect powder within 10 days of the emergence of locusts (locust nymphs), or smoked with enemy tobacco. After application, it is also necessary to strengthen monitoring, quickly check the prevention and treatment effect within one week, and re-administer the drug once in time for the missed treatment and poor prevention effect.
You can also use the booby trap method: cut the straw into four or five inches long, put in 50 kg of human urine, and add 50% wettable enemy insect 0. 05－0． l kg of prepared liquid medicine, immersed for 8 hours, scattered in many places on a sunny morning.
At present, the most effective way to kill locusts is to spray pesticides by aircraft, which has a high rate of insecticidalization and a wide range of killing, but the cost is high, and the prevention and control method based on chemical control can only respond to the needs of the moment and cannot guarantee long-term peace and stability.
Natural enemy prevention
In the long run, in order to effectively prevent and control locust plagues, we must focus on ecological construction and implement the four combinations of plant protection, biological protection, resource protection, and environmental protection. In particular, it is necessary to ensure biological diversity and protect the natural enemies of locusts. According to statistics, There are currently 68 species of natural enemies of locusts in China, including birds, amphibians, reptiles, etc., which play an important role in controlling the number of locusts.
The relevant departments of Shandong Province once conducted experiments in Dongying to cultivate the natural enemy of locusts, the Chinese chick bee fly, and achieved certain results.
Xinjiang and other places have adopted methods such as duck herding and chicken herding to eliminate locusts, and the effect is also more obvious.
The Guangdong Institute of Entomology once conducted an experiment in the Pearl River Delta region to introduce a large number of ducks into the farmland to hunt rice locusts, and it only took 2,000 ducks to eat the locusts in 4,000 acres of land cleanly. In addition, garden spiders, tarantulas, cat spiders and other wandering spiders in the fields can also quickly find small locusts in the fields and swallow them.
Farmers should try to protect farmland spiders to prevent locust infestation. The specific method is: do not burn the straw casually after harvesting, but put it in the field to create a good "living environment" for the spider; another practice is to concentrate the found spider egg sac in a safe place and protect it before and after harvesting.