The issues surrounding the use of pesticides in food production prior to harvesting, are widely covered in the literature. Those relating to post-harvest practices are much less so, even though they are essential for food security and for the health of agricultural workers. In this study, we analyze the practices of small-scale farmers in Southeastern Mexico when storing maize grain, and examine their use of a reference insecticide, aluminum phosphide. We assess the reasons why farmers choose this technology, their sources of information, and their perceptions of the associated risks. The results show that practices vary in terms of doses used, application methods, exposure time, combination with other products, and grain cleaning after application. This variability results from a drastic lack of information available in rural communities regarding the correct use of pesticides. This lack is a consequence of a marketing system that is largely based on retail sales, with no instructions for use on packaging, and on village grocery sellers who are unaware of good practices and potential risks. Farmers systematically minimize the risks associated with pesticides, and believe they are protected from toxic side effects. These results suggest that rural development policies should focus on training farmers and input retailers, and on promoting alternative grain storage technologies.