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Pests and diseases threatening cassava in Southeast Asia

Mealybugs weaken plants and lower root yields (Neil Palmer/CIAT)
Mealybugs weaken plants and lower root yields
Neil Palmer/CIAT

An outbreak of pests and diseases, predicted to cut cassava output in Thailand by at least 30 per cent this season, is spreading rapidly across Southeast Asia, the International Centre for Tropical Agriculture (CIAT) has warned. In Thailand, CIAT investigations revealed a large number of mealybugs, tropical whitefly and red mites, as well as Cassava Bacterial Blight (CBB) and Brown Leaf Spot disease. "These pests and diseases will place a huge strain on Thailand's cassava production," explains Dr Tin Maung Aya, a cassava specialist at CIAT. "Not only will the incomes of smallholder farmers be greatly affected, but so will those of many labourers employed in the cassava industry. There will be widespread economic and social implications."

In addition to mealy bugs, tropical whitefly, red mites, and CCB, the disease known as Witches Broom was also discovered in neighbouring Vietnam. CIAT is investigating reports that cassava fields in Cambodia, Laos and the Philippines have also been affected. "It's no surprise if these problems are spreading quickly," said Dr Tony Bellotti, CIAT entomologist. "If the mealybug, for example, can find its way from its native Latin America, across the Atlantic to Africa, and then to Asia, it can find its way around the Mekong region and beyond. We can be fairly sure that China and Myanmar will be hit soon, and in time, Indonesia too," he warns.

In response, CIAT has issued preliminary management guidelines to help tackle the outbreaks and contain the spread. "The spread is almost certainly caused by the movement of infected planting material," Tin added. "One of the first responses is for the authorities in affected countries to impose strict quarantine regulations on the movement of cassava, especially the stems used as planting material." Other recommendations include training farmers to be able to select clean planting material and identify pests and diseases, developing an Integrated Pest and Disease Management strategy, and in the long-term, breeding varieties that are resistant to pests and diseases.

Date published: March 2010

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