Is my country using chickens and ducks to control locust plagues? The real scientific control of locusts is actually like this

Produced by: Science Popularization China

Author: Insect Intern (PhD in Biology)

Producer: China Science Expo

I believe that all of you have heard of locust plagues. But what you may not know is that locust plagues are one of the most serious insect plagues in Chinese history. They were once listed as one of the three major natural disasters along with floods and droughts, and have plagued the Chinese people for three to four thousand years.

Today, large-scale locust plagues have almost disappeared in China. Do you want to know why? The story behind this is full of twists and turns. Let me tell you one by one.

Locust swarm

(Photo source: Veer Gallery)

The old method of locust control is inefficient and destructive

In ancient times, when faced with a locust plague, people could only kill them continuously, which was inefficient and not very effective.

With the advancement of science and technology in modern times, there are more and more ways to kill locusts. The most effective way to kill locust swarms is to spray pesticides from airplanes. The scene shown in the picture below is a scene using this method - in 1953, in Ethiopia, as part of international technical cooperation, American airplanes and pilots sprayed pesticides on locusts that were devouring crops in the Ogaden Desert.

(Photo source: Visual China)

In the last century, many areas used chemical drugs to kill locusts on a large scale. Although it achieved good results in the short term, it also caused environmental pollution and damaged the surrounding ecological environment. Therefore, this method of killing locusts with chemical pesticides alone is not highly regarded by Chinese scientists.

The key link to eradicate locust infestation

Looking back at the thousands of years of locust control in my country, in the 40 years since the founding of the People's Republic of my country, Chinese scientists have learned from history, exerted their own wisdom, summed up experience, carried out scientific prevention and control, and proposed a forward-looking strategy of ecological prevention and control. The damage of locusts has finally been brought under control. This is the victory achieved by the working people of the Chinese nation in their thousand-year battle with locusts.

So how did scientists solve the locust plague problem that has plagued the country for thousands of years? They found the key to eradicating the locust plague: destroying the locust breeding bases.

(Photo source: Veer Gallery)

Since locusts have the habit of migrating, gathering and choosing where to lay their eggs , it is crucial to destroy the "hotbed" where locusts breed. Therefore, it is impossible to eradicate their harm by only using pesticides and other control methods. To truly solve the problem of locust pests, we must treat both the symptoms and the root causes. First, we must transform the ecological environment of the "hotbed" where locusts breed, that is, to make this environment less suitable for the reproduction of locusts. Only in this way can we fundamentally eliminate the locust plague.

After a generation of governance, my country has successfully transformed the birthplace of large-scale locust plagues, making it impossible for large-scale locust gatherings to form in China. However, in some local areas, it is inevitable that too many locusts will destroy crops. Large-scale spraying of chemical drugs will damage the natural environment, so what should we do?

New ideas for environmentally friendly pesticides

Fortunately, we have a new approach - using fungi to develop environmentally friendly pesticides.

Since the 21st century, people have discovered that fungi, as organisms that are widely distributed in nature, are toxic to many insects. As people pay more and more attention to biological control, in the process of locust control, we can consider using more natural fungal insecticides to replace chemical insecticides to control pests and protect the environment.

However, the control effect of fungal insecticides is not stable, which may be because the gregarious locusts that form locust plagues have a higher resistance to fungi. Based on this problem, many studies have been carried out.

The team led by Academician Kang Le of the Chinese Academy of Sciences conducted research on green muscardine and migratory locusts. Green muscardine is a commonly used insecticidal fungus. Kang Le's team found that after being infected with green muscardine, gregarious migratory locusts can block pathogen molecules, thereby shielding the pathogens from contact with body fluids, thereby protecting themselves.

Further research also found that gregarious locusts are more tolerant to fungi, while solitary migratory locusts resist fungal infection through phagocytosis. These findings also provide scientists with ideas for developing more effective fungal insecticides - if we can find a fungus that specifically targets migratory locusts, we may be able to solve the problem of locust infestations in a targeted manner, which is both environmentally friendly and efficient!

In nature, there is a specific green muscardine that only infects migratory locusts . Compared with the broad-spectrum green muscardine, it lacks the tryptamine metabolism gene. Studies have found that tryptamine can induce the production of reactive oxygen species by activating the locust aromatic hydrocarbon receptor LmAhR and can inhibit the locust immune system, producing toxic effects.

Therefore, after the researchers deleted the monoamine oxidase gene (tryptamine metabolism gene) in the broad-spectrum Metarhizium, the tryptamine content in its body was higher than that of the original broad-spectrum Metarhizium, which significantly improved the insecticidal efficiency and shortened the half-lethal time (the number of deaths accounts for half of the total number) of locusts infected by ordinary broad-spectrum Metarhizium from 7.33 days to 5.92 days. This is a huge breakthrough in the use of fungi to eliminate pests!

This genetic modification of the broad-spectrum green muscardine does not affect the host range, is harmless to the environment and humans, and has good biosafety. It provides a new idea for the design of new fungal insecticides and is expected to play a role in controlling locust plagues in the future.

Schematic diagram of transformation of Metarhizium anisopliae

(Image source: Reference 1)

A variety of new scientific and technological means to control locust infestation

To date, based on my country's many years of locust prevention and control practices in agricultural and grassland areas, we have adopted ecological management measures that combine plant protection, biological protection, resource protection, and environmental protection, and established a sustainable prevention and control technology system with biological control as the main and ecological regulation as the supplement.

At the same time, we are also vigorously developing new, efficient and green biological pesticides, using new and efficient spraying technologies such as airplanes, drones or large machinery, and combining natural enemy prevention and control with ecological regulation measures to achieve sustainable control of locusts and sustainable development of grassland ecosystems.

On the other hand, we need to further improve the medium- and long-term prediction and early warning technology of locust plagues to prevent them from happening. In addition, scientists have found that the extent of locust plagues is negatively correlated with temperature, which provides an important theoretical basis for long-term prediction.

Since 2000, my country has combined manual field surveys of locusts with insect radar, geographic information system (GIS), global positioning system (GPS) and remote sensing system (RS) (referred to as "3S") technology to conduct real-time early warning monitoring of dynamic changes in locust populations.

In the future, my country will continue to use modern information technologies such as "3S" technology, drone monitoring technology, and locust AI intelligent identification technology to establish a multi-level, comprehensive "sky-air-ground integrated" locust intelligent monitoring system and locust occurrence database management system, to achieve long-, medium- and short-term real-time monitoring and early warning, and form a more complete locust disaster indicator system to ensure that scientific governance strategies are adopted when locust disasters occur, and to be timely and efficient.

We believe that with the continuous advancement of human science and technology, people will be able to solve the locust plague problem more effectively and environmentally friendly, and the scene of locust plagues ravaging China will eventually become history!

Editor: Guo Yaxin

References:

【1】Tong.et al, Tryptamine accumulation caused by deletion of MrMao-1 in Metarhizium genome significantly enhances insecticidal virulence. PLoS Genet 16(4): e1008675(2020)

https://doi.org/10.1371/journal.pgen.1008675