The first line of defence when bugs attack plants is often synthetic pesticides or insecticides.
But an international team conducting research in Thailand and other southeast Asian countries has documented an alternative way to counter-attack killer bugs: unleashing wasps.
Brock University biologist Liette Vasseur was part of the research team, led by Kris Wyckhuys, an agro-ecologist at Australia’s University of Queensland and the China Academy of Agricultural Sciences.
The team examined the impacts of Phenacoccus manihoti, a type of mealybug that attacks cassava plants, on Southeast Asia’s crop production of the root vegetable.
After invading Thailand in 2008, the pest quickly spread and destroyed the cassava plants, resulting in an almost 30 per cent decrease in Thailand’s cassava crops and a 162 per cent increase in the price of starches like cassava.
The same happened gradually in Cambodia, Vietnam and Myanmar. To solve the problem, farmers in all these countries cut down forests to make room for more cassava fields, leading to high levels of deforestation.
The study examined the impact of introducing a type of wasp called Anagyrus lopezi (Hymenoptera).
“The introduction of the wasp really helped control the population of the mealybug,” says Vasseur. “Having better yields reduced the pressure on farmers to clear forests to add more land for cassava production.”
Once the cassava crops were reinstated, deforestation rates in Thailand, Cambodia, Vietnam and Myanmar dropped anywhere from 31 to 95 per cent, because farmers no longer needed to clear the land for the cassava crops.
“With reduced damage, prices increased again making agriculture more sustainable,” says Vasseur.
This case study, she says, illustrates a successful biological control program.
“This is a great example of how, by using nature, we can help enhance agroecosystem sustainability,” says Vasseur.
“It is very often cheaper and more effective in the long term since most pests become resistant to synthetic pesticides.”
The researchers’ findings are in their recently published paper, Biological control of an agricultural pest protects tropical forests.