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The influence of acclimation, endosymbionts and diet on the supercooling capacity of the predatory bug Macrolophus pygmaeus

Maes, Sara, Machtelinckx, Thijs, Moens, Maurice, Grégoire, Jean-Claude, De Clercq, Patrick
BioControl 2012 v.57 no.5 pp. 643-651
Ephestia kuehniella, Hemiptera, Macrolophus, Rickettsia bellii, Wolbachia pipientis, acclimation, antibiotics, artificial diets, bacteria, biological control, biological control agents, body fluids, body temperature, cold tolerance, egg yolk, eggs, endosymbionts, freezing point, greenhouses, insects, predators, risk assessment, supercooling, supercooling point
The generalist predator Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a key biological control agent in European greenhouses. The influence of acclimation, infection with endosymbiotic bacteria and diet on the cold tolerance of the Mediterranean biocontrol population was assessed by determining the supercooling point, i.e. the temperature at which the insect’s body fluids freeze. This parameter provides a first indication of an insect’s establishment potential in a new region and of its possible geographical range. Allowing the predatory bugs to adapt to lower temperatures resulted in an increase in supercooling ability. Macrolophus pygmaeus bugs exposed to antibiotics in their artificial diet and hence cured from their infection with the endosymbiotic bacteria Wolbachia pipientis, Rickettsia bellii and R. limoniae were more tolerant to freezing than infected bugs. The diet of the predators also affected the freezing temperature of the body fluids. Predators fed an artificial diet based on egg yolk were less resistant to freezing than those fed Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. These findings illustrate that several factors may affect the cold hardiness of a biocontrol agent and may thus complicate the evaluation of its establishment potential in the framework of an environmental risk assessment.