POPULATION FLUCTUATIONS OF THE RUSTY GRAIN BEETLE, CRYPTOLESTES FERRUGINEUS (COLEOPTERA: CUCUJIDAE), MONITORED WITH INSECT TRAPS IN WHEAT STORED IN A STEEL GRANARY

Abstract Population fluctuations of adults of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), in wheat stored in a steel granary were monitored using insect detection traps 35 cm below the surface of the grain during the fall of 1983, and the spring, summer, and fall of 1984. In both years, the peak population occurred from the beginning of September to the third week in October. In 1984, no beetles were found in the traps until early June. The number of beetles in each trap increased slowly until late August (range 0 to 315), and then rapidly until late October (range 91 to 1212), and then decreased rapidly thereafter until mid-November (range 236 to 2). No beetles were caught during the winters after 30 November 1983 and 19 November 1984. The absence of beetles in the traps before June or after November and the small catches before July or in early November were attributed to the combined effects of low population levels and reduced movement of adults at low grain temperatures. A few beetles were caught at a grain temperature of 8°C but none at temperatures lower than 4°C. Approximately 65% of adults found in samples of grain at −7°C in February 1985 were alive and became active in the laboratory. Practical recommendations for monitoring insect pests of stored grain are given, based on the results.