Scientists turn to math to protect cassava from pests


Whiteflies Are the biggest impediment to growth of hardy tuber

Monday April 17 2017

Two researchers are using math to protect cassava in Kenya from the crop’s biggest destroyer: whiteflies.

Professor Aminda Ateka from Jomo Kenyatta University of Agriculture and Technology(JKUAT) and Laura Boykin from School of Molecular Sciences in the University of Australia use phylogeny to isolate the insects that are predominant in Kenya.

Phylogeny is a branch in biology that studies evolutionary relationships among individuals, plants and other organisms. They then analyse the data using supercomputers that use complex mathematical programmes.

The whitefly, a tiny nearly invisible insect, has been the biggest impediment to the exploitation of cassava for nutritional and economic value in Kenya. It causes the viral diseases cassava mosaic disease and cassava brown streak virus which completely destroy the crop making it unsuitable for consumption.

Likening the manner in which the mosquito bites man to infect him with malaria, Prof Boykin said that the whitefly has a modified mouth that feeds on the leaves of the cassava and transmits the virus to the plant. Once infected with the virus, the stem wilts and the leaves yellow as its food making property(photosynthesis) is thwarted causing the plant to stunt.


They studied the presence of whiteflies in western Kenya in Bungoma, Busia and Kakamega as well as in Migori, Homa Bay, Nyamira and Kisumu and Siaya in Nyanza. Their work also included research in Machakos, Kilifi and Kwale. It is worth noting that these are generally wet and humid areas—except Machakos— that support other crops such as sweet potatoes and tomatoes.

Given the polyphagous nature of the insect which makes it able to feed on many plants, it makes the insect more dangerous because it spreads the virus further.

Cassava is increasingly being recommended by researchers, with support from nutritionists, as a crop that could bail Africa out of its hunger and malnutrition. The continent produces more cassava than any other part of the world, coming only third after rice and maize, according to the Food and Agriculture Organisation; In 2011 for instance, the continent produced 140 million metric tonnes against the world’s 65 million.

According to Prof Ateka, cassava is adaptable to most soils and climates, and is a staple food for more than 80 per cent of the population. “It is also easy to grow with little input” he said, “and apart from food security it could be used for making starch for making products like sweets in Kenya; currently the starch is imported. The Kenyan economic survey reported that in 2014 Kenya produced 1.2 million metric tonnes of cassava.

In a presentation that Prof Boykin made at a Ted Talk, the whitefly is a headache to farmers and researchers because there are so many species—more than 1,500— and they all look alike.

Speaking to HealthyNation, Prof Ateka said that their two-year study isolated the specific whiteflies that wreak havoc in Kenya: the Sub-Saharan 1 and Sub-Saharan 2, which are named according to the eight regional blocks in which the whiteflies  are scattered all over the world.

The data collected looks like a chain of arrows and lines on his screen, which is the computer linking one species to another and establishing a relationship.

Prof Ateka said that the data once analysed will be shared with breeders to help them know which plant samples should be used in specific regions. “This information is helpful for having more resilient crops”, he said. This study also involved Uganda which has also lost millions of cassava to whiteflies. However, there are several stumbling blocks before Professors Boykin and Ateka’s work could be used to achieve food security and poverty eradication.


Presently, there are no computers to analyse that kind of data in Kenya or East Africa. Prof Ateka sent his samples to Australia for analysis in Prof Boykin’s lab . Regionally there are labs—albeit smaller— such as Biosciences Eastern and Central Africa (BECA-ILRI) where scientists can take their samples for analysis at a fee.

Moreover, the switch from maize as a staple food will need massive attitude change.

In a previous interview, Gladys Mugambi the head of nutrition at the ministry of Health said that Kenyans shun food crops such as cassava because of a misguided notion that they are for the poor. Ms Mugambi also cautioned that cyanide, a compound found on the roots of certain types of cassava, can kill when consumed. “We need education on preparation as well as change of attitude”, she said.

Cassava originated from South America and was brought to Kenya  by the Portuguese in the 17th century. Nutritionally, the food may need to be taken alongside other crops.

In a high level meeting of FAO in  May 2009, the organisation raised concerns that cassava is much lower in proteins than other foods hence would need to be taken in combination with other foods.


 At a glance

  •   Cassava originated from South America and was brought to Kenya by the Portuguese in the 17th century.

  •   Kenya produced 1.2 million metric tonnes of cassava, according to the Economic Survey published in 2014.

  •   Africa produced 140 million metric tonnes of cassava in 2011, against the rest of the world’s 65 million metric tonnes.

  •   Cassava comes third after rice and maize in the list of Africa’s staple foods and is a staple for 80 per cent of the population, according to the Food and Agriculture Organisation.

  •   There are more than 1,500 species of whiteflies and two of them wreak havoc in cassava plantations in Kenya.