The virus has the heart-breaking habit of waiting until late in the season to attack and not showing signs of illness above ground, but only in the large, edible, potato-like roots. A farmer thinks he has a health crop until harvest.
"The other thing that farmers can do if they suspect they have the disease is to harvest early. They will get smaller roots of cassava but they will be less affected by the disease – it shows up late in the production cycle," said Robson.
The International Institute of Tropical Agriculture is currently developing eight varieties of Cassava Brown Streak Disease resistant cassava, reports the BBC, but they won't be widely available for another two years.
A man walks through cassava fields near the Kopeyia drumming village in Ghana. (Jacob Silberberg, Getty Images)
Cassava roots (David Monniaux, Wikimedia Commons)