Leaf stamp spells control of aflatoxins for shillings

International scientists are close to launching a groundbreaking technology that equips plants to warn farmers of the presence of specific diseases or toxic fungi – through a simple colour change on a stamp on their leaves, in a system that offers the hope of a trasnformation in plant disease control. 

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The technology, being developed by a University of California researchers through funding from the Bill and Melinda Gates Foundation, develops an early warning system for crop diseases by stamping unique colour changing bio sensors directly onto maize leaves to detect pathogens such as aflatoxins which have cost Kenyan farmers thousands in crop losses and claimed lives.

If contamination shows up, farmers will be able to isolate a plant to prevent its spread.

"The long-term goal is to detect multiple plant pathogens or their markers by chemical reactions that turn areas of leaves different colors," Hideaki Tsutsui the researcher of the technology says.

He likened the basic mechanism to home pregnancy tests, which have areas that turn blue to indicate a positive result.

Fungi such as Aspergillus and Fusarium produce toxins such as aflatoxin which are responsible for stunted children's growth, liver cancer and suppression of the immune system. Death from aflatoxin infection can occur within 48 hours. The UN Food and Agriculture Organization estimates that toxins like aflatoxin infect around a quarter of the world's crops every year, wasting one billion metric tons of food.

According to Tsutsui, paper-based color metric tests already exist, but they can only be used once. His new technology, however, will develop a self-inking stamp that delivers the chemicals that detect the toxins directly into plant leaf veins, possibly through fine needles incorporated into the stamp to ensure the reagents get inside. The stamps, which Bill and Melinda Foundation are funding, will be made available first to Sub Saharan African farmers who are struggling with toxins from the early stages of planting to post harvest. The researchers estimate that the technology, which should be widely distributed by early next year, will cost about Sh1000 for 200 tests.

Kenyan scientists have hailed the leaf stamp as a revolution in the fight against aflatoxin a threat that has had a devastating effect on farmlands and livelihoods.

In 2010, Aflatoxin was widely reported in Eastern Province, and also in Western Kenya in the maize basket of Rift Valley. The Ministry of Agriculture destroyed over 200,000 90kg bags of maize that were infested with Aflatoxin. About 10 Kenyans died of aflatoxin poisoning the same year, while some 130 died in 2004.

Other moves to fight aflatoxins, which can be caused by harvesting too early, include a moisture meter that measures the grains moisture. But such options are often beyond the reach of small scale farmers at a cost of between Sh30,000 to Sh70,000.

By contrast, says Dorothy Ndegwa, a scientist from Tegemeo Institute of Agriculture, the leaf stamp technology is one of the most problem oriented ever since “it is very scientific, and if this is detected early enough, it can be prevented early. With post harvest the harm is already done.”

Initially, Tsutsui plans to focus on maize, which is one of the most widely grown staple crops in Sub Saharan Africa and the only one that suffered from aflatoxin in 2010 and 2011 in Kenya. The veins in its leaves run in parallel, and it is therefore especially suitable for simultaneous monitoring of different pathogens in adjacent veins.

Written by Bob Koigi for African Laughter

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