Circulation

Using ice nucleating bacteria to reduce winter survival of Colorado potato beetles: Developing a novel strategy for biological control

Copyright

R. E. Lee, Jr.1 , L. A. Castrillo 1 , M. R. Lee 2 , J. A. Wyman 3 & J. P. Costanzo 1

Dept. of 1 Zoology and 2 Microbiology, Miami Univ., Oxford, OH 45056, USA, 3 Dept. of Entomology, Univ. of Wisconsin, Madison, WI 53706, USA

A key factor in the overwintering survival of Colorado potato beetle, Leptinotarsa decemlineata, populations is the regulation of the temperature at which the insect freezes. Like most overwintering insects, Colorado potato beetles are unable to survive internal ice formation. Winter survival is enhanced by burrowing in the soil and by lowering their supercooling point, the temperature at which ice formation spontaneously occurs in their body fluids. We have shown that the supercooling capacity, a major factor in winter cold hardening of these beetles, can be regulated by exposure to ice-nucleating active bacteria. These bacteria are potent biological nucleators capable of initiating freezing of aqueous suspensions at temperatures above –10°C. When fed to Colorado potato beetles, ice nucleating bacteria immediately elevate the beetle’s supercooling point. Furthermore, recent field and laboratory studies demonstrated that two strains of Pseudomonas fluorescens persisted and maintained their ice nucleating activity in the beetle’s digestive tract through winter. Beetles recovered from the field seven months after overwintering in the soil had significantly elevated supercooling point values versus control beetles. By exposing Colorado potato beetles to ice nucleating bacteria in late summer to early autumn, prior to their burrowing into the ground, it is possible to reduce beetle survival in winter and, thereby, delay their population build up and reduce crop damage the following summer.

Index terms: Leptinotarsa decemlineata, Pseudomonas fluorescens, insect cold-hardiness, overwintering insect pests

Copyright: The copyrights of this original work belong to the authors (see right-most box in title table). This abstract appeared in Session 18 – REPRODUCTION AND DEVELOPMENT Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000.