Southeast Asia responds to industry-threatening cassava mosaic disease

Government representatives, development partners and cassava researchers from Cambodia, Laos, Thailand and Vietnam gather this week to devise a regional plan to contain the potentially devastating Cassava Mosaic Disease (CMD) in Southeast Asia. They convene from September 18-20 in Phnom Penh, Cambodia.

Researchers from Zhejiang University and Holley Group Co. in China first reported CMD in northeast Cambodia in 2015 in the journal Plant Disease. Since then, authorities have reported CMD in seven provinces in Cambodia and ten provinces in Vietnam.

Previously, CMD was only found in India and Africa, where it was identified a century ago. CMD in sub-Saharan Africa is responsible for a 15-24 percent loss in annual yields, resulting in estimated losses of 12-23 million tons of cassava worth US$1.2-2.3 billion.

CMD in Southeast Asia could be devastating to the 55 million-ton cassava industry. The disease threatens the food security and livelihoods of several million subsistence-oriented households and smallholder producers. As a threat to global value chains, CMD in the region could put billions of dollars of investments at risk.

“CMD could be potentially disastrous for Southeast Asia,” said Dr. Claude Fauquet, the Adjunct Director of Global Cassava Partnerships for the 21st Century. “The international cassava community is willing to contribute to an effective response through numerous measures, including by providing CMD-resistant plant material that are suitable for the region.”

Experts agree that a coordinated, region-wide response is required to respond to the CMD breakout.

Together with the global research community, researchers at the International Center for Tropical Agriculture’s (CIAT) cassava program have identified a number of short-term actions to contain CMD’s spread. These include promoting the propagation and trade of virus-free stakes, testing CMD-resistant cassava varieties, and enabling cassava merchants and farmers to trade only virus-free planting materials, said CIAT cassava program lead Dr. Luis Augusto Becerra.

The third most produced crop in Southeast Asia after sugarcane and rice, cassava is a key ingredient in biofuel, animal feed, and starch, from which products including paper, textiles, alcohol, sweeteners and others are made.

Demand for cassava-based products is increasing as incomes in Asia rise and consumption patterns change. New global markets are developing with growing demand for ‘clean label’ and differentiated products such as gluten-free or GMO-free.

“Cassava starch (or tapioca) has always had superior functional properties in many applications sought after by food processors and manufacturers, with new breeding efforts enhancing these characteristics adding to the competitiveness of cassava in the starch market,” said Dr. Jonathan Newby, an agricultural economist at CIAT. “However, farm-level productivity remains critical to ensure competitiveness in the market.”

While the market outlook for cassava will depend on how quickly the disease is brought under control, there are already serious short-term livelihood impacts.

“Cassava has many great characteristics in terms of smallholder inclusion,” Newby said. “However, the poorest and most vulnerable households are highly exposed to the impacts of this disease. Crop failures associated with CMD will have deep and long-lasting impacts on many livelihoods in the region.”

CMD is caused by a member of the Geminiviridae virus family and spreads through the use of stakes from infected cassava mother plants. It is also transmitted by the whitefly Bemisia tabaci.

When infected, cassava plants can display stunted growth and mosaic patterns on deformed, twisted, and undersized leaves. Depending on a variety of factors, CMD-afflicted plants produce fewer or no roots. Infection through cuttings is more damaging than infection through whiteflies.

Large volumes of cassava stakes are traded across several hundred kilometers to meet farmer demand, according to a CIAT study of seed systems in cassava-growing regions of Cambodia and Vietnam.

CMD in Southeast Asia is caused by the Sri Lankan cassava mosaic virus (SLCMV) found in Sri Lanka and India. However, experts are not clear at this time as to where the disease in Southeast Asia originated from, nor as to its current real extent in the Southeast Asia region.

“Globalized commerce has made it easier for pathogens to transcend national boundaries,” said Dr. Wilmer Cuellar, lead virologist at CIAT. “Often, what happens is that before officials can verify the presence of a disease or pest, it has spread so wide across the country and threatens to cross borders.”

For more information, contact CIAT Communications: Madelline Romero, m.romero@cgiar.org, and Julio Mario Fernandez, j.m.fernadez@cgiar.org. Expert interviews may be facilitated upon request.