The cassava mealybug (Phenacoccus manihoti) thrives on the plant's starchy root—a staple of many diets worldwide. That's because the pest and the crop evolved together in South America, before Europeans transplanted the woody shrub across the world in Africa and Asia. In the absence of these pest insects the crop has thrived in countries ranging from Nigeria to Thailand.
Unfortunately, the mealybug is equally capable of traveling via a human vector—and it is now devastating the cassava (aka manioc or yucca) crop on some 200,000 hectares in Thailand, where some 60 percent of global exports (worth $1.5 billion) are grown, according to the International Center for Tropical Agriculture (CIAT), a Colombia-based research nonprofit focused on reducing hunger and poverty via sustainable agriculture. So Thailand's agriculture department has decided on a bold experiment—importing P. manihoti's own worst nightmare, a two-millimeter-long wasp from South America that uses the pest as a host for its larvae, thereby destroying the bugs.
Roughly 250,000 of the wasps (Anagyrus lopezi) landed in Thailand's northeastern province of Khon Kaen on July 17—after initial small-scale field trials proved effective.
View a slideshow on the wasp biocontrol effort
The wasps have also been successful in a similar effort in Africa, earning entomologist Hans Herren the World Food Prize in 1995 for his efforts to introduce it as a "biocontrol" there during the 1980s. Of course such efforts at biocontrol have backfired in the past in some cases, most famously with the introduction of the cane toad to Australia (although recent efforts to use carnivorous Australian ants as a biocontrol on the invasive toads are showing some success).
"Applying chemicals on such a large scale would be environmental vandalism," Tony Bellotti, an entomologist with CIAT, said in a press release. "Sending in the wasps is a proven way to kill the cassava mealybugs quickly and effectively. Think of them as a kind of ecofriendly SWAT team."
More like mealybug assassins. At the release event farmers could be spotted attempting to catch the wasps to bring them to their own farms, noted Rod Lefroy, CIAT's regional coordinator for Asia, in an e-mail. Here's hoping they don't set their sights on anything else in their new home.