Cold tolerance of stored product beetles; implications on low temperature-based commodity disinfestation

Abstract: Safe and efficacious grain disinfestation techniques have become more important in
the wake of production constrains and uncertainties, disruption of global supply chains,
insecticide resistance, increasing consumer consciousness and associated changes in global
trade policies. The use of extreme low temperature remains one of the most relevant techniques in meeting most of these changing sets of demands and standards, however, it remains unclear whether previously set ‘blanket’ low lethal temperature thresholds are applicable to other strains and different thermal acclimation contexts. We used, supercooling points (SCP), chill comma recovery time (CCRT) and exposure to extreme low temperature to re-assess the lowtemperature responses of four stored product beetle pests. Based on CCRT responses, Rhyzopertha dominica and Tribolium castaneum were significantly more cold tolerant than Oryzaephilus surinamensis and Cryptolestes ferrugineus. None of the species survived extreme low temperature exposure, however, SCP responses showed that C. ferrugineus was the most cold tolerant species with T. castaneum as the least. Our results show that stored beetles had depressed SCPs and thus more cold tolerant than reported in literature. This has implications on choice of low temperature lethal limits to improve the efficacy of grain disinfestation using cold treatments.