“Super-fly” threatens cassava, food security

IRIN: A tiny, rapidly breeding cyanide-munching insect, dubbed a "super-fly" by scientists, is threatening the food security of millions of Africans.  The Bemisia tabaci - one of several whitefly species - carries lethal viruses that cause cassava brown streak disease (CBSD) and cassava mosaic disease (CMD), which have decimated the hardy cassava plant.

Cassava, a tropical root crop, is the third most important source of calories in the tropics, after rice and maize. According to the UN's Food and Agriculture Organization (FAO), it is the staple food for nearly a billion people in 105 countries, where it comprises as much as a third of daily calories consumed. The cheapest known source of starch, cassava is grown by poor farmers - many of them women - often on marginal land; for these people, the crop is vital for both food security and income generation.

The threat to cassava is particularly alarming as the plant is often called the "Rambo" root for its ability to withstand high temperatures and drought. With climate change expected to take a major toll on maize in the coming decades, many hope cassava will offer an alternative route to food security in Africa. Cassava may also prove to be an important source of biofuel.

Experts plan to take aim at the whitefly this week, at a conference of the Global Cassava Partnership for the 21st Century (GCP21), at the Rockefeller Foundation Bellagio Center in Italy. The conference is dedicated to "declaring war on cassava viruses in Africa."

From the 1980s to the mid-2000s, CMD ravaged more than 4 million square km in Africa's cassava-growing heartland, stretching from Kenya and Tanzania in the East to Cameroon and the Central African Republic in the West. But in recent years, the scientific community developed cassava varieties resistant to CMD.

James Legg, a leading cassava expert at the International Institute of Tropical Agriculture (IITA), who works out of Tanzania, told IRIN, "The premature celebrations for this apparent victory were very soon squashed, however, as sinister new reports were received of the occurrence and apparent spread of CBSD in southern Uganda."....

USDA photo of bemisia tabaci

Researchers demonstrate control of devastating cassava virus in Africa

Seed Daily: An international research collaboration recently demonstrated progress in protecting cassava against cassava brown streak disease (CBSD), a serious virus disease, in a confined field trial in Uganda using an RNA interference technology. The field trial was planted in November 2010 following approval by the National Biosafety Committee of Uganda.

The plants were harvested in November 2011 and results were published in the August 1, 2012 issue of the journal Molecular Plant Pathology . These results point researchers in the right direction as they develop virus-resistant cassava varieties preferred by farmers in Eastern Africa.

In Sub-Saharan Africa, more than 250 million people derive at least 25 percent of their daily calorie intake from the starchy cassava tuberous roots. In the East African countries of Uganda, Kenya, Tanzania, Mozambique, Rwanda, Burundi and Malawi, 63 percent of households also sell cassava products to earn income for their families. It is estimated that in the next 15 years, cassava will constitute the second most important source of income for more than 125 million people in East Africa.

Cassava brown streak disease is a major problem because it destroys the edible tuberous roots, but visual symptoms on leaves and stems are sometimes difficult to detect. This means unexpected losses for farmers at harvest, with potential devastating impact on families that depend on cassava for food security. Since farmers preserve cassava cuttings in the fields for the next crop, the disease is passed on to the next growing season....

Cassava roots, shot by David Monniaux, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license