Ice-nucleating-active bacteria,Pseudomonas syringae(strain 31a), applied as a freeze-dried powder on grain in laboratory tests, caused an increase in the ice-nucleating activity of the grain and an increase in the supercooling point ofCryptolestes ferrugineus(Stephens) adults.Sitophilus granarius(L.) andOryzaephilus surinamensis(L.) also had increased mortality when placed on grain treated with ice-nucleating-active bacteria and held at -lO°C. Cold-acclimatedC. ferrugineus,S.granarius, andO. surinamensiswere more cold hardy than noncold-acclimated insects, but when these insects were held on grain treated with ice-nucleating-active bacteria, their mortality at -1O°C was increased. These results were confirmed in a simulated granary application whenC. ferrugineusadults were placed in vials with 10 g of ice-nucleating-active bacteria-treated wheat before being placed in granaries containing 100 t of grain. Two of the three bins were aerated until the temperature had reached −9 or −15DC. Ice-nucleating-active bacteria increased insect mortality in the aerated bins at bacterial concentrations as low as 10 ppm. The potential of using ice-nucleating-active bacteria as a cold synergist that will make low temperature a more effective means to control stored-product and other insect pests is discussed.