Emergency taskforce to tackle cassava curse in Cambodia

8 December, 2014 by (comments)
Sophearith Sok, checking cassava stakes, Kampong Cham, Cambodia

CIAT cassava researcher Sophearith Sok, checking cassava stakes, Kampong Cham, Cambodia. Photo credit: Georgina Smith / CIAT

Efforts to contain and control a devastating threat facing cassava farmers and industry in Cambodia will be ramped up this week. A regional taskforce brings together local and international cassava researchers, local government officials and extension officers to hammer out an emergency action plan to tackle a deadly cassava disease and stamp it out.

Cassava, cultivated by many poor farmers in Cambodia, is threatened by cassava witches’ broom, a systemic disease that results in 10-15% yield loss and 20-30% loss in starch content, spelling disaster for farmers. In some key cassava cropping areas of Cambodia, virtually all cassava fields are affected by this disease, with in-field incidence at worryingly high levels, say experts.

In Cambodia, cassava provides feedstock for the processing sectors in Vietnam and Thailand. The value of cassava products traded from Cambodia is estimated to be over US$250 million.

Dr. Keith Fahrney, CIAT’s agronomist in Asia, said: “In Cambodia, most cassava is processed by large-scale starch factories. Fresh roots and dried chips are also exported to factories in Vietnam and Thailand.” Wet starch used locally for making noodles now comes from medium-scale factories.

As starch is one of the primary final products, reduced starch content of diseased roots means processors need to buy more cassava roots, and farmers are paid a lower price for their product. The disease also causes roots to become sticky, taking longer to dry and turning starch a yellow-brown tinge instead of the industry-required white, he added.

A farmer shows his diseased cassava harvest.

A farmer shows his diseased cassava harvest. Photo credit: Georgina Smith / CIAT

Reduced starch content of diseased roots means processors need to buy more cassava roots, and farmers are paid a lower price for their product. The disease also causes roots to become sticky, taking longer to dry and turning starch a yellow-brown tinge instead of the industry-required white.

Deputy Director General at The General Directorate of Agriculture under the Ministry of Agriculture Forestry and Fisheries (MAFF) in Kampong Cham, Ms. Chan Phaloeun, said: “This situation can seriously impact Cambodian cassava farmers and bring down the national starch industry. Several cassava factories are particularly concerned about the disease impact on the profitability of their business, and fear an ultimate shut-down of their operations,” she added.

Dr. Men Sarom, vice-rector at the Royal University of Agriculture in Phnom Penh, said: “It’s vital we act now to safeguard the livelihoods of our cassava growers and the local cassava industry. Today we bring together some of the top researchers in the region to address concerns and find a way to fight these threats together.”

While active prevention carries some potential to manage the disease, there are currently no control options. Once the disease has struck, farmers are doomed – there is very little they can do to tackle cassava witches broom and save their crop, say experts. As cassava is propagated vegetatively, stakes cut from infected plants will fuel the spread of pests and diseases.

Farmers are also often entirely oblivious to symptoms in infected planting material and only become aware when they find their crop it’s time to sell the roots. It’s vital to find ways to disinfect stakes or ensure completely healthy materials, and put systems in place to actively distribute and promote certified disease-free seed to Cambodian farmers, researchers say.

Symptoms of cassava witches' broom include a proliferation of leaves at the top of the stem in the shape of a witches' broom.

Leaf proliferation and yellowing of leaves are key symptoms of cassava witches’ broom disease. Photo credit: Georgina Smith / CIAT

In Vietnam, state-of-the-art technology is being used to pin-point insects suspected to spread the disease and the feasibility of a pregnancy-like diagnostic kit is being evaluated. A research alliance is committed to developing stake disinfection protocols and actively preventing disease spread.

Researchers at CIAT and regional partner institutions are fine-tuning cassava tissue culture protocols and exploring options for demand-driven clean seed systems in the region, as well as training local farmers on symptom recognition and disease management – vital for sustainable disease control efforts.

The jury is out on what exactly is accelerating and aggravating Southeast Asian cassava pest and disease problems. Researchers say that although climate change is often blamed, movement via cross-border trade in non-certified planting materials is a much bigger driver. The rapid arrival of these threats only bolsters the likelihood that others are on the way, they warn.

These efforts are part of a wider program addressing cassava threats and diseases in the region, funded by the European Union through the International Fund for Agricultural Development (IFAD).

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