Determination of the lethal high temperature for the Colorado potato beetle (Coleoptera : Chrysomelidae)

The susceptibility of insects to high temperatures has been used to develop control methods for pests in stored products and crops. Recently, microwav es and propane flamers were evaluated as control techniques for the Colorad o potato beetle, Leptinotarsa decemlineata (Say). These methods aim to incr ease the body temperature of the insect above its lethal threshold. The let hal high temperature for six stages of the Colorado potato beetle was evalu ated by exposing the insects to either warm water or hot air. The lethal te mperature obtained by immersing insects in warm water was up to 5.2 degrees C lower than with hot air. The difference in the LT95 between the warm wat er and hot air tests varied with the size of the insect, the larger stages showing a larger difference. When large stages of the insect were placed in an oven, it took 10 to 15 minutes for the body temperature to reach a valu e close to the air temperature. In hot air conditions, the body temperature remained several degrees below the air temperature indicating heat loss by evaporation. Reducing the exposure time to hot air from 20 to 10 minutes r esulted in an increase of up to 3.7 degrees C in the lethal temperature. Th e effect of the reduction of the exposure time was more pronounced with the larger stages. The value of the LT95 ranged from 50.1 to 56.2 degrees C de pending on the stage of the Colorado potato beetle. Implications for the de velopment of new physical control methods are also discussed.