Second, prevention and control methods
Third, the plague of locusts in the history of China.
Four. Introduction of locusts
Verb (abbreviation of verb) locust plague in Israel
[Edit this paragraph] I. Reasons
People have long noticed that serious locust plagues are often accompanied by serious droughts. There is a record of "drought locust" in ancient books in China. In recent years, several major locust plagues in Africa are also related to the severe drought in the region. The main reason for this phenomenon is that locusts are warm and dry insects, and the arid environment has many benefits for their reproduction, growth and survival. Because locusts lay eggs in the soil, the soil is relatively solid, and the water content is 10% ~ 20%, which is most suitable for them to lay eggs.
Drought makes locusts multiply and grow rapidly, and there are two reasons for the disaster. On the one hand, in dry years, due to the drop of water level, the soil becomes more solid, the water content decreases, the ground vegetation is sparse, and the number of eggs laid by locusts increases greatly, reaching 4000-5000 eggs per square meter of soil in many cases, with 500-80 eggs in each egg block, that is, 200,000-400,000 eggs per square meter. At the same time, in dry years, the water surface of rivers and lakes shrinks and the low-lying land is exposed, which also provides more suitable places for locusts to lay eggs. On the other hand, plants that grow in arid environment have low water content, and locusts feed on it, which makes them grow faster and have higher fertility.
On the contrary, the rainy and humid environment has many adverse effects on the reproduction of locusts. The plants eaten by locusts have high water content, which will delay the growth of locusts and reduce their fertility. Rainy and humid environment will also make locusts epidemic diseases, and rain and snow can directly kill locust eggs. In addition, the increase of natural enemies such as frogs will also increase the mortality rate of locusts.
When a certain part of the locust's hind leg is touched, it will change its habit of living alone and become fond of living in groups. Locusts are usually timid and like to live alone, with limited harm. However, they sometimes change their habits, like to live in groups, and eventually gather in large numbers and migrate collectively, forming a formidable locust plague, which has caused great damage to agriculture. Scientists at Oxford University say that they have experimented with desert locusts living alone and repeatedly touched many parts of their bodies to see if there are some tactile factors that make them change their habits. It was found that when a certain part of the locust's hind legs was stimulated, they would suddenly live in groups, but touching other parts of the body, such as tentacles, mouth or abdomen, would not have this effect.
Scientists believe that the occasional gathering of locusts in the natural environment may lead them to change their habits and start to live in groups, and their members will increase in large numbers in the same way, thus forming a locust plague. If we can find out which chemical signals stimulate the nervous system of locusts to change their behavior, it is possible to develop new pesticides to prevent locusts from gathering.
To sum up, why can locusts break out and cause disasters?
1. From the environmental point of view, it is mainly caused by drought.
2, from the point of their living habits, mainly:
(1) is very gregarious.
(2) Strong fertility.
(3) It is omnivorous, that is, it can eat a variety of plants.
(4) Its flying ability is very strong and difficult to control.
(5) Its eggs are buried deep underground and are not easy to be destroyed.
After the warm winter, locusts flooded.
Global warming, especially the rising temperature in winter, is conducive to the increase of locusts' overwintering eggs and provides "eggs" for the outbreak of locust plague in the following year; In addition, the combined effects of climate warming, intensified drought, grassland degradation and other factors will provide suitable places for locusts to lay eggs. Locusts have strong adaptability to drought, because other insects and birds can't survive in this situation, and a filamentous fungus that can cause locust diseases is suppressed, so its number is greatly increased. Therefore, experts predict that with the trend of global warming, the scale of locust plague will become larger and larger in the future, which will have a serious impact on grain production in China.
4. Excessive population density will cause locust plague.
In a paper published in the journal Science on June 2nd, James Bull and his colleagues proved that the key factor is specific population density. When the locust swarm reaches this density, the locusts will line up and start moving in the same direction.
Locusts are isolated wingless nymphs in the early life history, and they tend to avoid each other. But if resources become scarce, they are forced to influence each other. Then, they can form an orderly local locust swarm. This locust swarm has the ability to act in unison, enter the neighbor's habitat, let more and more locusts join in, and finally become a huge locust swarm. Therefore, it is very important to predict the beginning of group action for controlling the outbreak of locust plague.
This group of scientists put more and more locusts in a round field, recorded their behaviors and tracked their movements with computer software.
At medium density (25 to 62 locusts per square meter), locusts will line up and start moving in the same direction, or even suddenly change direction.
In the experiment, when the number of locusts per square meter exceeds 74, the locusts arranged in sequence stop changing direction and keep moving in the same direction for 8 hours.
These observations confirm the results predicted by a computer model called self-propelled particle model. Boolean and his colleagues believe that using such a model may help to design a method to control the outbreak of locust plague.
Their research results also support FAO's definition of locust nymph population. Under this defined density, locusts can easily cross the "critical point", thus causing locust plague.
[Edit this paragraph] 2. Prevention and control methods
1, the method of environmental protection and radical cure.
Natural factors are the main factors of locust plague, but there are undeniable human factors.
Locusts must lay eggs on land with vegetation coverage below 50%. If a place is beautiful and there is no bare land, locusts cannot reproduce. At present, the ecological awareness in some places is not strong, and some simply think that pollution control is to protect the environment, without paying attention to improving the vegetation, soil and microclimate in locust-suitable areas, because no benefits can be seen in the short term.
Therefore, we must attach great importance to the protection of the ecological environment in order to fundamentally prevent and control the locust plague.
2, chemical control, the most important means.
It is suggested to choose a counterpart pesticide with high efficiency, low toxicity and low residue, such as 5% Ruijinte suspension, 20-30ml water per mu and 50-60kg spray.
You can also spread trichlorfon powder on bamboo and weeds or kill them with dichlorvos within 10 days after the locust (locust nymph) is unearthed. After application, it is necessary to strengthen monitoring, quickly check the prevention and control effect within one week, and timely supplement the application in areas with poor prevention and control effect.
You can also use the trapping method: cut the straw into four or five inches long, put it into 50 kg of human urine, add 0.05-0. 1 kg of 50% wettable trichlorfon, soak it for 8 hours, and scatter it in places with many locusts in sunny mornings.
At present, the most effective way to kill locusts is to spray pesticides by plane. This method has high killing rate and wide killing range, but the cost is high. Moreover, chemical control can only meet temporary needs and cannot guarantee long-term stability.
3, natural enemy control, the effect is obvious.
In the long run, in order to effectively prevent and control locust plague, we must focus on ecological construction and implement four combinations of plant protection, biological protection, resource protection and environmental protection. In particular, it is necessary to ensure biodiversity and protect natural enemies of locusts. According to statistics, there are 68 natural enemies of locusts in China, including birds, amphibians and reptiles, which play an important role in controlling the number of locusts.
The relevant departments of Shandong Province once conducted an experiment in Dongying to cultivate the natural enemy of locusts, the Chinese wasp scale insect, and achieved certain results.
In Xinjiang and other places, the method of grazing ducks and chickens is used to eliminate locusts, and the effect is also obvious.
Guangdong Insect Research Institute once conducted an experiment in the Pearl River Delta region, introducing a large number of ducks into farmland to prey on rice locusts. As a result, only 2000 ducks can eat all the locusts in 4000 mu of land. In addition, stray spiders such as tarantulas, tarantulas and cat spiders can also quickly find small locusts in the field and swallow them.
Farmers should try their best to protect spiders in farmland to prevent locust plague. The specific methods are: don't burn straw casually after harvesting, but put it in the ground to create a good "living environment" for spiders; Another method is to concentrate the discovered spider oocysts in a safe place before and after harvest and protect them.
[Edit this paragraph] III. The plague of locusts in the history of China
There have been many locust plagues in the history of our country, and their geographical distribution is mainly concentrated in Hebei, Henan, Shandong and other provinces, and there are also many in Shaanxi, Shanxi, Jiangsu, Anhui and Hubei provinces. These locust plagues not only caused great harm to agricultural production in past dynasties, but also caused many famines, diseases and even social unrest. In the prevention and control of locust plague, there has always been a struggle between science and superstition in ancient China; With the progress of the times and the popularization of scientific knowledge, science has gradually defeated superstition.
[Edit this paragraph] 4. Introduction of locusts
Locust belongs to Arthropoda, Insecta, Orthoptera and Acridoidea. Its body is generally green or yellow-brown, with chewing mouthparts and large hind feet, which is suitable for jumping and incomplete metamorphosis. Its larvae are called "cockroaches" and mainly feed on Gramineae. There are about 654.38 million+species in the world, and there are more than 300 species in China, such as flying.
[Edit this paragraph] V. The Great Locust Disaster in Israel
On June 5438+065438+1October 2 1 day, 2004, millions of locusts flocked to the red sea coastal city of Eilat, Israel, destroying a large number of crops and flowers in this southern Israeli city. The Israeli government used airplanes to spray pesticides to kill locusts.
According to Reuters, this is the first time since 1959 that Israel has suffered such a serious locust plague. Local residents said that swarms of locusts covered the sky, eating not only palm leaves, but also all the flowers in the whole garden. It is said that they eat everything, even the green grass on the roadside.
These locusts come from North Africa, and some are as long as 10 cm. One resident said it was like a disaster in Egypt. According to the Bible, the plague of locusts is the eighth disaster in 10. The Egyptian Pharaoh refused to let the Jews leave and was punished by God.
However, this locust plague is not necessarily a bad thing for some Israelis. Locust is the only edible insect in Jewish law. Some Israelis seized the opportunity to catch many locusts and take them home for cooking. An Israeli even picked up a locust from the ground, stuffed it into his mouth, and praised it while smacking his lips: "It's delicious!" A website also lists a variety of locust menus, including locust strings, locust strips, fried locusts and so on.
Later, the locusts moved eastward to Jordan and Saudi Arabia, without passing through northern Israel, Gaza and fertile areas in the West Bank.