Adult numbers of the maize weevil,
Sitophilus zeamais Motschulsky, were investigated using pheromone traps in five low-temperature grain storage warehouses on the Kanto Plain, Japan, for two years. Pheromone traps were placed in the storage rooms and working areas of each warehouse and replaced with new ones monthly. The efficacy of mass trapping of
S. zeamais adults was tested in two of these warehouses. In each warehouse, 14 or 20 pheromone traps were also placed in the working areas from October to December and from March to May. In one warehouse, it seems that overwintering of
S. zeamais in the warehouse might have led to an increase in the number of adults caught by the traps starting in spring. In one of the warehouses in which the efficacy of mass trapping was tested, the number of adults caught by monitoring traps was low during the monitoring period, and the number of adults caught by traps for mass trapping was also low. In the other warehouse, more than 100 adults were caught between October and December 2018, and more than 10 adults were captured in the other periods. The conditions under which the mass trapping is effective are discussed.
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