ICE-NUCLEATING ACTIVE BACTERIA DECREASE THE COLD-HARDINESS OF STORED GRAIN INSECTS

This report provides further evidence that a freeze-dried, concentrate d form of Pseudomonas syringae, an ice-nucleating active bacteria, red uces the cold tolerance of stored grain insect pests. Application of i ce-nucleating bacteria to wheat or corn that contained insect pests de creased the insects' supercooling capacity: after treatment with 100 p pm of P. syringae the mean supercooling points of five insect species increased from 4.7 to 11.9-degrees-C above untreated controls. Treatme nt with P. syringae also decreased the capacity of insects to survive a 24-h exposure to subzero temperatures. Decreases in cold tolerance w ere observed in eight species of stored grain pests: Indianmeal moth l arvae, Plodia interpunctella (Hubner); red flour beetle adults, Tribol ium castaneum (Herbst); flat grain beetle adults, Cryptolestes pusillu s (Schonherr); rusty grain beetle adults, Cryptolestes ferrugineus (St ephens); Gibbium psylloides (Czenpinski); lesser grain borer adults, R hyzopertha dominica (F.); yellow mealworm larvae, Tenebrio molitor (L. ); and granary weevil adults, Sitophilus granarius (L.). Results of th is study provide further support for the use of ice-nucleating active bacteria as biological insecticides to kill overwintering insects by d ecreasing their low temperature tolerance. The approach may be particu larly appropriate for the control of a variety of insect pests in rest ricted areas such as grain bins.