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

Abstract

Most insects are not able to survive internal ice formation. Thus, a key factor in their winter survival is the regulation of the temperature at which they freeze. This temperature is termed the supercooling point (SCP) or the temperature of crystallization. A major factor in the overwintering survival of insect pests is their ability to seasonally enhance their cold tolerance by increasing their capacity to supercool and, thus, avoid the lethal effects of internal ice formation. Any agent that limits the supercooling capacity of a freeze-intolerant insect will increase the likelihood of injury or death following exposure to subzero temperatures. In the 1970s, a unique class of biological nucleators, icenucleating active (INA) bacteria, was discovered. These bacteria are remarkable for their ability to catalyze ice nucleation at temperatures as high as -1 to -2°C. Ice-nucleating activity is conferred by the presence of ina genes, which code for ice nucleating proteins localized on the bacterium's outer membrane. This chapter reviews a paper that uses Colorado potato beetle, Leptinotarsa decemlineata, (Coleoptera: Chrysomelidae) as a model system to address basic questions regarding the seasonal regulation of cold tolerance and insect–microbial interactions. These studies provide a foundation for novel approaches in biological control by manipulating insect cold-hardiness and overwintering survival using INA microorganisms.