A cocoa farmer in Vietnam has been using weaver ants rather than traditional pesticides to kill off pests and bugs on his land.
The curious story of Doan Van Le, of Tay Hoa Commune, Trang Bom District in Dong Nai Province, began in 2007 when Dr. Pham Hong Duc Phuoc, a friend of his and distinguished plant physiologist, paid a visit to Le’s cocoa plantation in the southern province.
“Why don’t you raise ants to kill off those mosquitoes?” Dr. Phuoc asked his farmer friend upon noticing a colony of weaver ants nesting inside a neighbor’s tree.
Le shrugged off the idea initially, thinking to himself that it wouldn’t work. Given pesticides had been used on his farms for so long, he doubted whether any ants would even come near it.
“Will they stay if I succeed in luring them here? Will they kill off the mosquitoes if they do?” These were the questions that remained unanswered.
“I was in two minds,” Le said. “I spent around VND10 million [US$446] a year on pesticides, which were both expensive and harmful to my health, so I gave it a shot in the end.”
To begin luring ants to nest in his cocoa trees, Le stopped using pesticides and set up wires between his trees and those of his neighbors where there were known to be colonies of weaver ants.
It was not until a few months later that ants began to arrive on his farm, though their numbers were too small to eliminate the mosquito problem.
Refusing to give up, Le discovered that the ants had been reluctant to use his wires as they did not like the smell of new plastic.
After replacing the new wires with old, weather-beaten telephone wires bought from thrift shops, the ants immediately began making new homes on his cocoa trees, though their numbers were still not enough to eradicate his mosquito infestation.
To further improve the appeal of his trees to the ants, Le experimented with various food types, which included fresh fish, dead mice and the intestines of chickens and ducks.
“I eventually realized they were most attracted to chicken and duck intestines, as long as they were cleaned of any fat,” Le said.
The 58-year-old farmer also had to calculate precise portions, as the ants would not be tempted if there was not enough food, while spoiling them with too much food would make them too docile to hunt mosquitoes.
All of Le’s hard work eventually paid off, as his entire cocoa plantation became free of pests two years after introducing the weaver ants.
“What was more surprising was that somehow the ants had also deactivated the citrus mealybugs that had previously been responsible for the premature withering of my cocoa fruits,” Le said.
Le’s farms now yield up to 15 metric tons of cocoa fruit per hectare, sold at a higher price than before thanks to the fact that they are pesticide-free.
“Now that the bugs have been taken care of by my 'ant workers’ who only need to be manually fed once every month, I have more free time to enjoy my old age,” Le said.
Weaver ants crawl onto a cocoa fruit at Doan Van Le’s farm in Dong Nai Province. Photo: Tuoi Tre