An insect that scientists have termed a “super fly” is decimating cassava crops in Africa. The super fly, a species of white fly called Bemisia tabaci, carries viruses that cause cassava brown streak disease (CBSD) and cassava mosaic disease (CMD).
Cassava is a crucial food source for millions of the world’s poor. Throughout the global south, it follows only rice and maize in percentage of calories that it provides, and in many places is the cheapest source of starch available. According to the UN Food and Agriculture Organization (FAO), cassava is the staple food for a billion people living in over 100 countries. The crop can be grown easily on marginal land. All of these factors make cassava vital to food and income security, health, and even survival for much of the world’s population.
But diseases carried by the super fly, including CBSD and CMD, are a threat to the important cassava crop. In Africa’s major cassava-growing region, which extends across the center of the continent, over four million square kilometers of cassava were destroyed by CMD between 1980 and the mid 2000s. Scientists worked to develop cassava strains resistant to CMD, and were successful.
Then CBSD hit Uganda, and spread to neighboring Kenya and Tanzania. CBSD now threatens Nigeria, Africa’s largest cassava producer and consumer. Millions of Nigerian farmers and cassava processors depend on the crop for both income and sustenance. It wasn’t until 2005 that scientists verified that both CBSD and CMD were transmitted by the same whitefly – Bemisia tabaci, the super fly.
The tiny super fly is a powerful creature. The insect appears to have a mutually beneficial relationship with the viruses that it transmits. Thus, the more plants that become infected with CBSD and CMD, the faster the fly reproduces and spreads.
Cassava’s high cyanide content protects it from almost all pests, but the super fly is not deterred by the poisonous chemical. (The cyanide in cassava also means that the root can cause serious illness in humans when not properly prepared.)
Increasing temperatures have further contributed to the super fly’s success. High altitude growing regions that were formerly too cold for the fly to survive have now warmed enough that it can live there.
The super fly does not affect only cassava. It is a worldwide agricultural pest that damages many types of fruit and vegetable crops in tropical, subtropical, and temperate climates. In Texas and California, the fly has caused over $100 million in damages to the agricultural industries. While it thrives in warm temperatures, cold weather kills both adults and larvae.
Fortunately, solutions to the global super fly epidemic are within sight. This week, experts will meet at the Conference of the Global Cassava Partnership for the 21st Century (GCP21), to be held at the Rockefeller Foundation Bellagio Center in Italy. Scientists and global leaders will gather to figure out how to stop the super fly, and “declare war on cassava viruses in Africa.”
Meanwhile, scientists have begun developing means to combat the super fly. These include addressing and researching the impact of climate change on the white fly, introducing control insects that may curb its spread, and producing cassava species that are resistant to whiteflies, viruses, or both.
– Kat Henrichs
Source: IRIN News
Photo: IRIN News