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Backyard battle

CIMMYT E-News, vol 4 no. 3, March 2007

CIMMYT leads fight against post-harvest pests close to home.

mar01Top officials in the state of Mexico, home of CIMMYT’s headquarters, have praised a project led by the Center to help the state’s maize farmers protect harvested grain from hungry storage pests.

“This is the most important agricultural project in the state,” says Ramón Cruz Altamirano, Director of the department that supports and promotes technological development in the state’s Council of Science and Technology, COMECYT-CONACYT. “It will produce important science and technology information to benefit the state’s farmers….Reducing post-harvest losses is a way of boosting farmers’ profitability and productivity.”

Begun in 2005, this multi-faceted project aims to limit damage to stored maize grain caused by two formidable pests, the maize weevil and the larger grain borer. “Initial work has included detailed assessments and mapping of losses,” says Silverio García Lara, CIMMYT experimental maize biologist who has worked in the project along with CIMMYT maize entomologist, David Bergvinson. “Farmers can lose as much as 70% of their grain to these pests, over 10 months of storage,” García explains. “As well as undermining household food security, the pests reduce grain quality, so farmers can’t keep maize to market it when prices are good.”

Sitting next to a huge, hungry city

The state of Mexico surrounds the national capital—Mexico City—on three sides. Mexico City is home to some 18 million persons and a voracious market for nearly anything. Most state of Mexico inhabitants depend on off-farm employment, but many still farm, either as a major economic activity or simply a sideline to have preferred grain types for making tortillas, Mexico’s maize flatbread, or to maintain tradition. “Maize farming accounts for 85% of the state’s agricultural activity but less than a third of total value from crop production,” says García.

Part of the issue is the widespread use of traditional varieties, whose grain is ideal for tasty and nutritious tortillas, but which yield considerably less than improved varieties or hybrids. Added to this, maize farming in the state is solely rainfed—the monstrous water demands of Mexico City take precedence over competing use for irrigation in nearby regions.

Despite these constraints, Garcia believes state farmers might access several potential markets. “For example, there are many cattle growers in the state of Mexico who produce meat for Mexico City,” he says. “They’re looking for alternate suppliers of high-quality grain, now that maize imports from the USA are costly and transport for grain from large-scale producers in northern Mexico expensive. Cutting pest damage in local farmers’ maize can help them link to cattle producers and other promising markets.”

Simple breeding adds useful genes to cherished varieties


Participants in the post-harvest project, which involves all the main agricultural research and extension agencies in the state, have already conducted trials for yield, pest resistance, and farmer preferences using a selection of 56 hybrids and open-pollinated varieties from seed research institutions, including CIMMYT. Using the results, work will now begin to generate seed of the best varieties and make it available.

As trials were conducted, Bergvinson pioneered a unique approach to improve pest resistance and other traits in traditional varieties, while conserving the grain quality and other characteristics that farmers value. He traveled throughout the state, collecting samples of farmer varieties from a dozen or so locations. Next he grew out the seed and crossed the plants with experimental varieties that were known sources of pest resistance and other improved traits—like the ability to stand firmly in strong winds—that traditional varieties normally lack. Seed increased from the best crosses was returned to participating farmers for further on-farm selection, together with a manual that outlines simple breeding techniques, so farmers themselves could continue improving the varieties for specific traits.

“The results have been encouraging,” says Bergvinson. “Farmers value the opportunity to learn more about the all-important maize plant and its genetics, while preserving the genetic diversity in their local varieties, which are important from a family history or cultural perspective.” Project participants will extend this “allele introgression” approach throughout the state of Mexico, working with diverse farmer groups to collect and improve selected local varieties.

Knowledge and silos to stifle pests

The project has also resulted in three manuals for extension workers and farmers that cover management practices for post-harvest pests, simple breeding methods for improving post-harvest pest resistance in improved and farmer maize varieties, and the construction and use of metal silos for medium- and small-scale farmers.

The low-cost metal silos seal hermetically, blocking entry of pests and suffocating those already in the grain, and have proven very successful in Palmar Chico, a village that adopted them. “The village, which is located in a relatively impoverished zone, benefited from a state program providing credit to obtain the silos,” says García. “Now Palmar Chico is known as a year-long source of high-quality maize grain and inhabitants have profited.” The project will seek to expand the use of silos, through a similar, revolving credit scheme.

For information: Silverio García Lara, Experimental Maize Biologist (s.garcia@cgiar.org)