Confessions of a Fall Armyworm

Confessions of a Fall Armyworm

I never thought that I was lying on the corn core leaves with my friends and enjoying the meal yesterday, but today, after a "war between humans and insects", I became a prisoner of humans.

Now that I'm a prisoner, I might as well confess everything.

Crossing the oceans to conquer the world

That's right, we are the fall armyworms that you are fighting against. Because we are used to long-distance raids, some people call us "marching insects". We belong to the genus Spodoptera of the family Noctuidae in the order Lepidoptera. We are native to America and live in tropical and subtropical areas. In the adult stage, we are not much different from common moths. In the larval stage, we have "eight"-shaped patterns on our heads, and there are four large black spots arranged in a square on the back of the eighth abdominal segment. You call it "eighty thousand on the head and four tubes on the tail". There is no need to hide it, that is the unique mark of our fall armyworm group.

In fact, we, the fall armyworm, have long been unwilling to be confined to America. In 2016, we invaded Africa in large numbers and quickly settled in 44 countries south of the Sahara. Later, we began to invade many countries in Asia.

In January 2019, we crossed the border from Myanmar into Yunnan, China. In just 4 months, we took root in 112 of Yunnan's 129 counties. In just 8 months, we invaded from Yunnan to 25 other provinces across the country. In 2019, our fall armyworm affected an area of ​​about 16 million mu nationwide. In 2021, the area affected was about 20 million mu nationwide.

When we hatch, we gather in groups to cause harm and eat young leaves; after the third instar, we kill each other and disperse to eat. The older larvae have a particularly large appetite, and it is normal for them to reduce corn production by 20% to 72%. If they get angry, they can even cause a total corn crop failure. Because of this, you regard us, the fall armyworm, as a huge threat to corn production and even food security.

In 2017, the International Center for Agriculture and Bioscience ranked us among the "Top Ten Plant Pests in the World". According to the United Nations Food and Agriculture Organization, based on estimates of 12 African countries in 2018, our record is to cause an annual loss of 17.7 million tons of corn, successfully making tens of millions of people lose their food. In August 2018, the organization issued a global warning in response to our destructiveness.

In 2020, we were included in China's "Class I List of Crop Diseases and Insect Pests" and ranked first.

Excellent skills and abilities

In recent years, you humans have been studying us more and more deeply, so we have started to suffer defeats one after another. It is said that you have summarized our characteristics as "very good at eating, very good at reproduction, very good at flying, and very difficult to defend against." Haha! We can dominate the world, of course, not by luck, and the title of "one of the top ten plant pests in the world" is not in vain.

Big eaters! Our staple food is corn, and our larvae feed on young leaves or young tassels of corn. Young larvae feed on the young mesophyll, leaving the epidermis of the leaves, forming translucent film-like "window holes". Older larvae feed on the leaves, forming holes of varying sizes. We have good combat capabilities, and one head can destroy an entire corn plant. We are not picky eaters, and we eat anything we see, including sugarcane, sorghum, rice, wheat, and peanuts. We eat whatever is available. More than 80 species of plants around the world have been on our plates.

Super fertility!

At 28℃, we can complete a generation in about 30 days. Female moths can lay 100-200 eggs each time, and can lay 900-1000 eggs in their lifetime. They reproduce all year round in tropical areas, and the number of generations decreases with increasing latitude in temperate areas. In Yuanmou County, Yunnan, they can reproduce 7 generations per year. In Hebei, they can reproduce 4-5 generations per year. If all the eggs laid by a female moth and its offspring in a year survive and grow into adults, their number can reach tens of billions.

Fly fast!

Adults can use the wind to migrate long distances at an altitude of several hundred meters. They can fly 100 kilometers every night, and 500 kilometers before laying eggs. You know, flies only fly 8 to 18 kilometers a day. Compared with us, flies are simply weak!

Difficult to control! Previously, humans believed that chemical pesticides were a magic weapon to fight us, but the use of chemical pesticides has made us more resistant. Not only did it not stop us from spreading further, it also promoted our evolution, making us stronger and stronger. When attacking corn, we hide in the body and leaves as larvae, so farmers must aim at the bell mouth when spraying pesticides, otherwise it will have little effect on us. In addition, we reproduce quickly, and there is a serious phenomenon of overlapping generations. There are different ages in the field, so it is not so easy to fight a war of annihilation against us.

The “Human vs. Insect” War is Hard to Resolve

In China, we currently adopt the combat mode of "migrating north and returning south, a year-round cycle". That is, we migrate northward from southwest or southern China from May to August every year, and spread to North China, Northwest China and Northeast China in mid-to-late August, trying to eat crops that are growing vigorously. When the weather turns cold in September and October, we return south. This goes on year after year.

In the first three years after entering China, we expanded our territory rapidly and were almost unstoppable. Now, with strict monitoring, blockade and early removal in all parts of China, it is becoming increasingly difficult for us to make any progress.

The strategies and tactics currently implemented by China are extremely harmful to us.

First, you use physical and chemical control measures such as high-altitude insect-attracting lights, sex traps, and food baits to kill our adult insects, interfere with the mating of males and females, and make our young warriors fewer and fewer.

Secondly, you breed and release a large number of beneficial bugs, parasitic wasps and other insects, which are our powerful enemies. Under the biological attack mode you adopt, our soldiers have suffered serious casualties.

Thirdly, you have developed more and more new weapons and methods to deal with us. When you first entered China three years ago, you did not have any weapons specifically for us. A few days ago, I secretly logged into your weapons development website, China Pesticide Information Network. I was shocked! In the past three years, you have developed 25 kinds of weapons specifically for us, including chlorantraniliprole, cyantraniliprole, lufenuron, azadirachtin, Bacillus thuringiensis, Metarhizium anisopliae, Beauveria bassiana, Spodoptera exigua nuclear polyhedrosis virus, and spinetoram. You have so many weapons that can be used alternately and in rotation, and you also implement unified prevention and control and joint prevention and control tactics at the same time, which has caused us heavy losses.

Finally, a very important point is that the monitoring and forecasting network you have established is becoming more and more rigorous. Many times, you have accurately predicted our attacks before they even started, and not only did we fail, but we also often lost a large number of soldiers.

Of course, we, the fall armyworm, will not give up easily. Our goal has always been to dominate the earth. The fight with humans is destined to be a protracted war.

Author: Liu Linming

Source: Guangxi Science and Technology Popularization and Communication Center

This article was scientifically reviewed by Chen Hongsong, a researcher at the Institute of Plant Protection, Guangxi Academy of Agricultural Sciences