The causes of locust disaster are very complex, which can be summed up as internal and external causes.
One is its own high reproduction rate and strong ability to adapt to the environment. The high reproduction rate of locust and its strong adaptability to environment are the essential factors of locust outbreak. According to statistics, a female locust can lay 50-125 eggs at a time and reproduce 2-3 generations a year. In addition, locusts also have the characteristics of migration and diffusion. When plants in one place cannot meet their needs, they will move to another place and continue to do harm. In addition, there are many kinds of locusts, the difference between species is great, and the period of centralized damage is also different, all of these bring great difficulties to the work of locust control.
The second is the habit mutation of Mantis. The mutation of locust habit is also one of the factors leading to locust disaster, but it is often ignored in the work. One example is the desert,one of them is slow and timid, often staying in one place and motionless. When encountering other locusts, they tend to avoid and fly at night, which will not bring disaster to people. However, the other kind of desert locust has the same temperament as this kind originally, but because of the change of the desert environment on which they live , resulting in changes in their habits, forming swarms of locusts in the daytime, with a number of billions, which can eat tons of vegetation in an instant, bringing people devastating disasters.
Figure 8-1 since the early April of 2010, a large number of locusts have swept through four states in southeast Australia, covering an area of about 500000 km2. The local million mu of wheat, grass and other plants have been eaten by locusts, which has a serious impact on the production and life of local residents.
Although locusts have strong survival instinct, their outbreak depends on external environmental factors.
① Climatic and meteorological factors. Climate and meteorological factors that affect locust disaster mainly include temperature, light, precipitation, drought and flood, global warming and so on.
Temperature and temperature can affect the occurrence of locust disaster from three aspects: the development of locust, the amount of occurrence and the amount of feeding. Locusts are variable temperature animals. Their body temperature changes with the change of the ambient temperature. With the increase of the daily average temperature, locusts absorb and transform the heat. When they accumulate to a certain amount, they enter into different stages of development, and then affect the development of locusts. In addition, the number of locusts is closely related to the temperature. Low and high temperature are not conducive to the occurrence of locusts.
The influence of precipitation on locusts is very complex, and there are some differences due to different regions and different species.
The relationship between locust disaster and drought and flood: drought and praying disaster often occur in a chain. In dry and rainless years, the water level of rivers and lakes decreases, and the recession area is particularly suitable for female locusts to lay eggs, which makes the number of locusts surge. If there is less rain and drought in the early stage, the female locust will lay eggs, and more rain in the later stage is conducive to the growth of locust larvae, the locust disaster will break out.
② Ecological factors
Topography includes altitude, geomorphic type, slope and aspect, which mainly affect the distribution and density of locusts. This kind of influence is manifested through its redistribution of temperature, light and precipitation, which belongs to indirect influence.
The coverage and height of vegetation can directly affect the reproduction and survival of locusts.
The influence of soil on locusts mainly depends on soil temperature, soil texture and water statlocust control
The prevention and control methods are also various, which are summarized as follows.
(1) Mechanical prevention and control. That is to use physical factors and mechanical control methods. At present, the grassland locust suction and catching machine is the most widely used in the mechanical control. The machine is easy to operate, reliable in action, and widely used. It can control the harm of locusts to the grassland under different species and population density, and it is not affected by the grassland climate, does not pollute the environment, almost does not destroy the natural enemies of locusts, and maintains the benign cycle of grassland ecology.
(2) Chemical control law. It is a traditional and effective control method. Chemical insecticides are mainly used for locust control, such as aircraft spraying chemicals.
(3) Biological control. At present, a variety of biological control technologies have been used in locust control practice, including fungi, bacteria and protozoa.
Chemical control and biological control have advantages and disadvantages. Chemical control cost is low, but it will kill a lot of natural enemies of locusts: biological control cost is too high, and the effect is slow. On the basis of these two measures, the comprehensive management of grassland ecological environment is also urgent.
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