I fight pests with 36 Strategems
Originally a talk given at TEDxXiguan in 2016
Between 2014-2016, I spent nearly three years as a managing partner in a social enterprise engaged in rural development. From this I had the opportunity to be in charge of some ecological rice paddies. When friends from TEDxXiguan ask me to speak on its annual conference, I knew I had to marry science and culture and have a little fun.
Hi. I have been a smallholder farmer of 1.6 acre of paddy rice field (pause), for the past 4 months.
Being a rice farmer is really hard work. And my biggest concern is to get a good yield by the end of the season and my hard work will get paid off. And as a rice farmer, one of my worst nightmares is to have my precious plants damaged by insects pests in the before the end of the season.
To address the problem of insect pests, I have the obvious choice of using pesticides. But an FAO study suggested that over 20% of rice farmers in China suffer liver and kidney damage due to pesticide handling. And that is a little scary to me.
So I started to think about how I can control insect pests on my paddy, but at the minimal use of harmful pesticides.And I also thought whatever my findings might be, they can be useful to other small holder farmers, so we all can be safe while producing safe food.
Throughout human history, we became really good at manipulating parts of the world to produce concentrated amount of food. But some insects share our appetite. And for as long as agriculture has existed, human and these insects have been at war, both sides aiming to claim supremacy，and both sides have won and lost battles.
Each year, before men and insect pests face off in the rice paddy, there are several measurements we can take to get a head start. We can choose rice varieties that are most resistant to the pests that are prevalent in this area; we can make sure not to add to much nitrogen to the soil since nitrogen rich plants to pests is like candy to kids; we can also increase the distance between each hill to reduce shelter for the pests; even increasing the flow of air and water through the plants can help. But even if all above integrated pests management strategies are put in place, our enemies, who have co-evolved with these strategies, may still thrive. And we would have to face them in the battlefield.
On my rice paddy, there are three pests in particular that are highly problematic, and they also have evolved really effective strategies to avoid pesticides.
In the “Art of War”, Sun Tzu has said “Know your enemy and know yourself, and you can fight a hundred battles without defeat.” (知己知彼，百战百胜) So now we need to take a closer look at our enemies.
The rice planthoppers is probably public enemy number 1 in my village. They are tiny aphid-like insects that like to land near the base of the rice place and feed by sucking fluid from the plant. Rice leafhoppers multiply very fast and they move long distances in huge groups. And they can form huge numbers, kill a patch of rice very quickly between pesticide applications, before moving onto the next patch. Fast moving and huge numbers is leafhoppers’ strategy.
Public enemy number 2 is known as the rice leaffolder. In adult form, it’s a small moth. Adults lay eggs on rice leaves, and the larvae feeds on the vegetative parts of the rice plant, and it has evolved the very successful strategy of the folding the rice leaves and hiding inside, where the pesticides can hardly get into.
The last one is the rice borer, also called the rice stem borer. This is also a small moth that feeds on rice in the larval stage. After the borer hatches, it moves down to the base of the stem, chew a hole through it, move inside and spend the rest of its larval stage eating and killing a till from the inside, and sheltering itself from pesticides. It’s always a little heartbreaking for me to discover these borer-damaged tills, and when I pull one out, there’s always an awkward moment of me and a borer discovering each other.
All of these pests go through multiple lifecycles each year, and if their populations are left unchecked, farmers can suffer from a 10-100% of reduction in yield.
So since I declared war on these three insects, I thought some well tested war strategy could help.
The 36 stratagems is a list of 36 ancient Chinese war strategies that are now in the form of a book.
Now some historians believe that the book was first started by a general Tan Daoji from the Southern Song dynasty, some time in 400 AD, and additional content was added by different people later on.
Now the modern version of the 36 stratagems are organized in groups of 6, each group containing 6 proverbs that refer to a battle scenarios in Chinese history and folklore, predominantly of the Warring States period and the Three Kingdoms Period.
Stratagem #3
So now lets look at Stratagem number 3: Kill with a borrowed sword
(借刀殺人／借刀杀人, Jiè dāo shā rén)
The idea here is to cause damage to the enemy by getting a third party to do the deed. In the rice paddy, there are many ways in which we can use this stratagem.
First, we can introduce ducks to eat the insects. Ducks are probably the least picky eaters I’ve know, they can forage in the paddy from dusk to dawn. Duck-rice symbiosis is an effective and economical traditional strategy to keep the number of pests in the paddy in check. You just need to remember to bring the ducks back when the rice gains ripen, otherwise the ducks will eat them too.
Now, the rice leaf folder and rice borer spend the majority of their larval stage hiding inside the plant and they may be difficult for ducks to get to. But they lay their eggs on the leaf surface. Here we need to “borrow a smaller sword”. The trichogrammatid is family of really tiny parasitic wasps. They lay their eggs inside the eggs of larger insects, and when they hatch, the host eggs would not survive. These are particularly effective in controlling the rice leaffolder. There are commercially available trichogrammatids that we can simply introduce to the rice paddy at times when we predict the pests to lay their eggs.
Research has shown that properly introducing these wasps can suppress the number of rice leaf folders and rice borers by (insert data here)%, comparable to using pesticides.
The above are examples of killing with a borrowed knife, or in scientific terms, using biological control.
Stratagem #15
A very popular Stratagems is this one: #15 Lure the tiger away from the mountain (調虎離山／调虎离山, Diào hǔ lí shān)
In this case, the tiger is the enemy, and we want to lure him away from his position of strength or our position of weakness.
This is vetiver, it’s a tall perennial grass that’s common to the southern part of Asia. Nowadays they are commercially available and are often used to protect soil against erosion. We can grow the vetiver on the paddy ridge and successfully attract the stem borer away from our paddy.
The stem borer preferentially lay their eggs on the vetiver, but due to the vetiver’s physical properties, larvae cannot move onto the leaves and they fall and die. And this is how we lure the tiger away from the mountain.
Stratagem #10
I also really like Stratagem 10, probably because of its strong element of deception: # 10 Hide a knife behind a smile.
(笑裏藏刀／笑里藏刀, Xiào lǐ cáng dāo) This Stratagem tells you charm your enemy and you have gained his trust, move against him.
Nitrogen is a very important nutrient for rice, when there’s higher nitrogen, we get higher rice yield. But we already know that pests also like nitrogen, therefore when the nitrogen content is too high, we face the risk of causing pest outbreaks, and farmers offset this risk by using a more pesticides. As the pests gain resistance to the pesticides, this cycle starts to breakdown in favour of the pests. So what can do is to limit the nitrogen content for most of the paddy, but pick just one spot to add a lot of fertilizers. This is called a nitrogen trap.
It attracts the pests from other parts of the paddy to this concentrated area, and this allows us to only worry about this small area, which can be much more economical. We can for example use a light trap here to reduce adult moths, or we can use biological pesticides to control planthoppers.
Here we can also add the next Stratagem:
#31 The beauty trap (美人計／美人计, Měi rén jì)
It tells you to “send your enemy beautiful women to cause discord within his camp. “
The stem borer goes through 4-5 lifecycles in Southern China, and mating is the top priority for the adults. Here we can use sticky traps that sends out a chemical that mimic the sex pheromone of female stem borers. So while the males believe they are flying toward a hotspot of females…well, they are not. The biggest advantage of this strategy is that sex pheromones are highly specific so this costs no collateral damage to other species.
#35 Chain Stratagems
And if you have been wonderings, yes, we can use these Stratagems in tandem. In fact, combining Stratagems is a Stratagem in itself: #35 Chain Stratagems
(連環計／连环计, Lián huán jì)
For example, we can first start a nitrogen trap, and move in for the kill in may ways.
#36 If all else fails, retreat
And let’s not forget the most well known Stratagems of them all: #36 If all else fails, retreat (走為上策／走为上策, Zǒu wéi shàng ce) This formed a Chinese idiom: "Of the Thirty-Six Stratagems, fleeing is best". How is this actually the best Stratagem?
This Stratagem means that if it becomes obvious that your current course of action will lead to defeat, then retreat and regroup. Now to retreat is not defeat, because it means you are saving the chance for comeback.
In the case of rice cultivation, there are times when the pest problems are so big that all strategies to control them may fail. And the yield can be so low that the cost of labor and inputs simply do not add up. In this case, the best strategy is to skip a year. You can do this by fallowing, which means to leave it uncultivated, or rotate crop something unrelated. This is effective because many pests are host specific and they lay their eggs in the soil over the winter. When we skip a year of rice, the pests have a really starving year and their numbers are greatly reduced the year after.
I can’t take credit for the originality of any of these pest control strategies. But what inspired me to make the connection with the ancient 36 Stratagems?
A couple of month ago I was standing in my paddy and planning to install my new rice borer sex pheromone sticky trap, and a farmer from my village walked by and asked me what was in my hands. And I said: oh look at my sticky trap, it’s got sex pheromone trap for adult rice borers. And the farmer looked at me like “sex what?”. And I said, “adult rice borers are attracted to the green part on this and they can get stuck”. And the farmer looked like he really wanted to believe me. And I said, “so this tricks the male rice borers to believe the females are here, they fly in and get stuck.” And he immediately said, “Oohhh!!!”, like this is so cool! And he said “you should have just said that it’s a beauty trap.”
And this is how I realized that by using well-known folklore or proverbs can be really helpful communicational tools. First because they can make new idea easy to remember. And also they can provide mechanisms behind how something works without getting into too much scientific jargon. Both of these advantages are very important for smallholder farmers in China, who are overwhelmingly eldersly and without systemic background in science.
And along with my colleagues, we went through our small database of scientific papers, and came up with portions of the 36 Stratagems that can be used as a communicational tool to explain pest control strategies.
When I was a biology student at the University of Toronto many years ago, I was really interested in how scientific knowledge can move beyond academia and benefit the rest of the world. In terms of safer and more effective agricultural practices, I now understand that we are not just facing technical challenges, but also communicational challenges. So I challenge scientists, businesses and anyone else who may play a role in agriculture, to join me in a farmer-centered approach. And together we will make “last mile deliveries” of technologies and ideas fun and effective and really get to those who need them the most.
Thank you.