By Georgina Smith
OXFORD, England (AlertNet) - A surge in diseases and pests believed linked to climate change is expected to slash Thailand's cassava production this season and could spread across the region, researchers warn.
Small-scale cassava farmers across southeast Asia have been put on red alert following the outbreak in Thailand, which accounts for three-quarters of the world's cassava exports.
In Thailand, where cassava is a $1.5 billion annual industry, some farmers face losses as high as 80 percent of their crop, while others have abandoned heavily infested fields, according to experts at the International Centre for Tropical Agriculture, a non-profit organization that has issued guidelines to help farmers deal with the outbreak.
The country as a whole faces a drop in cassava production by at least 30 percent this season, the experts said. They predicted widespread economic and social consequences among southeast Asia's estimated 5 million growers.
Cassava, a starchy root crop, is a widely used food staple not only in parts of Asia but across regions of Africa and Latin America.
Increased numbers of mealybugs, which are normally rare in the region, as well as tropical whitefly and red mites are responsible for much of Thailand's problem, as is widespread cassava bacterial blight and brown leaf spot disease, according to centre experts.
Researchers are investigating possible causes for the outbreaks, but higher-than-usual rainfall in the region, believed linked to climate change, may be driving the problem.
The centre is investigating reports that the unusual pest and disease plague has already spread to fields in Cambodia, Laos and the Philippines.
"These pests and diseases will place a huge strain on Thailand's cassava production. Not only will the incomes of smallholder farmers be greatly affected, but so will those of the many labourers employed in the cassava industry. There will be widespread economic and social implications," predicted Tin Maung Aye, a cassava specialist at the centre's Asia office.
Tony Bellotti, an entomologist at the centre who is among those investigating the cassava plague, said it took only a quick look at the plants to realize how big a crisis farmers were facing.
"Straight away I realized we've got real problems. The disease was oozing from the stems. I've worked with cassava for 35 years and I'd never seen anything like it," he said.
The problems are likely to spread around the Mekong region and beyond, Bellotti said. Already, farmers in Vietnam have reported mealybugs, tropical whitefly and red mites in their fields, as well as a separate disease that drastically reduces the starch content of the crop.
Experts said that the cause of the spread is most likely to be movement of infected plants, prompting a call for authorities in affected countries to impose strict quarantine regulations on the movement of cassava - especially stems used for planting - and on movement of related species such as jatropha, an oil plant used to create biofuel.
Other recommended precautions include avoiding the use of certain pesticides and selecting only disease-free stems for planting. Researchers stressed that farmers will need training in pest and disease identification and management.
In the long term, breeding pest- and disease-resistant cassava varieties will need to become a priority, experts said.
"Cassava production in southeast Asia has enjoyed an extended honeymoon period. That period is now over," Bellotti said.
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