Ice-nucleating active bacteria decrease the cold-hardiness of stored grain insects

This report provides further evidence that a freeze-dried, concentrated form of Pseudomonas syringae, an ice-nucleating active bacteria, reduces the cold tolerance of stored grain insect pests. Application of ice-nucleating bacteria to wheat or corn that contained insect pests decreased the insects' supercooling capacity: after treatment with 100 ppm of P. syringae the mean supercooling points of five insect species increased from 4.7 to 11.9 degrees C above untreated controls. Treatment with P. syringae also decreased the capacity of insects to survive a 24-h exposure to subzero temperatures. Decreases in cold tolerance were observed in eight species of stored grain pests: Indianmeal moth larvae, Plodia interpunctella (Hubner); red flour beetle adults, Tribolium castaneum (Herbst); flat grain beetle adults, Cryptolestes pusillus (Schonherr); rusty grain beetle adults, Cryptolestes ferrugineus (Stephens); Gibbium psylloides (Czenpinski); lesser grain borer adults, Rhyzopertha dominica (F.); yellow mealworm larvae, Tenebrio molitor (L.); and granary weevil adults, Sitophilus granarius (L.). Results of this study provide further support for the use of ice-nucleating active bacteria as biological insecticides to kill over wintering insects by decreasing their low temperature tolerance. The approach may be particularly appropriate for the control of a variety of insect pests in restricted areas such as grain bins.