INSECT PESTS ASSOCIATED WITH RURAL MAIZE STORES IN MEXICO WITH PARTICULAR REFERENCE TO PROSTEPHANUS-TRUNCATUS (COLEOPTERA, BOSTRICHIDAE)

A survey was carried out into the occurrence of insect pests infesting rural stores in five regions of Mexico. Stores were sampled using pheromone-baited crevice traps, bait-bags and maize samples every 28 d for an entire storage season. Maize and store temperatures, and grain moisture content were measured. The most numerous primary pests were Sitophilus zeamais Motsch., Sitotroga cerealella (Olivier) and Prostephanus truncatus (Horn). P. truncatus was more abundant in stores in the drier, temperate regions of Guanajuato, La Laguna and Jalisco than in the more tropical regions, Veracruz or Chiapas. In La Laguna (and to some extent in Jalisco), many more P. truncatus were detected in the store using the crevice trap than were counted in the maize samples, perhaps because crevice traps may attract beetles from outside the store. La Laguna and Chiapas had significantly fewer larvae of P. truncatus in the samples than other regions, probably a result of the lower grain moisture content. Grain damage levels were very low in La Laguna and they occurred later in Guanajuato than elsewhere. The three pest species causing most damage were S. zeamais, S. cerealella and P. truncatus. It is suggested that P. truncatus was important in causing damage primarily in Guanajuato, whereas S. zeamais and S. cerealella caused more damage elsewhere, particularly in more humid areas.