An article in the New York Times (Sept 27, 2011) describes efforts in a lab to use small postage size paper bits to diagnose mold and bacteria.  One impact of a low cost test for mold is diagnosis of aflatoxin, a mold produced poison that grows on corn, peanuts etc.   A disease free crop can enable the farmer to earn higher prices.  Similarly testing milk from individual farmers whose mixed output if collected by cooperatives can enable diseased cows to be identified and treated instead of spoiling the entire batch.  Will improvement of crop yields in developing countries require a focus on low cost detection methods ? Does  the method used in this case, a $ 10 million grant from the Gates foundation, suggest a role for developed country governments to act as externalities in the poverty elimination and supply chain improvement ? Given the large benefit to such methods, what prevents the for-profit companies from devising such low cost solutions ?