Topical application of ice-nucleating-active bacteria decreases insect cold tolerance

Area of Science:

• Insect physiology
• Cryobiology
• Biological pest control

Background:

• Overwintering insects survive cold by avoiding lethal freezing through supercooling.
• Supercooling involves lowering the body fluid's spontaneous ice nucleation temperature.
• Ice-nucleating-active bacteria can trigger ice formation at warmer temperatures.

Purpose of the Study:

• To investigate the impact of ice-nucleating-active bacteria on the cold-hardiness of freeze-intolerant insects.
• To assess the efficacy of Pseudomonas syringae in altering the supercooling point of the lady beetle, Hippodamia convergens.
• To compare different application methods and doses of bacteria for their effect on insect cold tolerance.

Main Methods:

• Topical application and ingestion of Pseudomonas syringae were used to treat Hippodamia convergens.
• Supercooling points of treated and control beetles were measured.
• The effect of various bacterial concentrations and application routes was evaluated.

Main Results:

• Topical application of P. syringae significantly increased the supercooling point of H. convergens to approximately -3°C.
• This reduced cold tolerance persisted for at least 3 days post-treatment.
• Different doses and application methods (topical vs. ingestion) showed varying degrees of supercooling point elevation.

Conclusions:

• Ice-nucleating-active bacteria effectively reduce insect cold tolerance by elevating their supercooling points.
• P. syringae demonstrated a significant impact on the cold-hardiness of H. convergens and four other insect species.
• These findings support the use of ice-nucleating-active bacteria as a potential biological insecticide for winter pest control.