SURVIVAL AND MULTIPLICATION OF STORED-PRODUCT BEETLES AT SIMULATED AND ACTUAL WINTER TEMPERATURES

Abstract

AbstractCryptolestes ferrugineus (Stephens), Cryptolestes pusillus (Schönherr), Tribolium castaneum (Herbst), and Rhyzopertha dominica (Fabricius) were gradually exposed to falling temperatures in the laboratory, simulating conditions in the centre of a 12- or 6-m-diameter granary containing wheat. Two years of overwintering mortality for C. ferrugineus and R. dominica were obtained from 11–13 farm granaries (40–100 t wheat). Cryptolestes ferrugineus (adults) was the most cold hardy species among the beetles tested. In the laboratory, survival was 40% at 25 °C declining to 10 °C over10 months, whereas at 25 °C declining to 0 °C over 10 months survival was 7%. Cryptolestes pusillus and T. castaneum did not survive once temperatures were below 10 °C, and R. dominica adults did not survive temperatures below 3 °C. In the field, there was no survival of C. ferrugineus in granaries that had February temperatures of −6.7 °C or lower. Six-week exposure to −10 °C killed most C. ferrugineus adults taken from granaries in February. Cryptolestes ferrugineus caught in granaries were more cold hardy than laboratory-reared strains. No T. castaneum or R. dominica survived an entire winter in granaries in the 2 years tested. Although C. pusillus was not tested in the granaries, it is unlikely it could survive the winter, as it had the same level of cold tolerance as T. castaneum in the laboratory. The implications for the population dynamics of these pest species in prairie grain are discussed.