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# Thermal biology and establishment potential of two non-native candidate biological control agents, Nesidiocoris tenuis Reuter (Hemiptera: Miridae) and Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae), in the U.K.

Hughes, Gwennan Elen (2010)
Ph.D. thesis, University of Birmingham.

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## Abstract

$$Nesidiocoris$$ $$tenuis$$ Reuter (Hemiptera: Miridae) and $$Lysiphlebus$$ $$testaceipes$$ (Cresson) (Hymenoptera: Braconidae, Aphidiinae) are candidate biological control agents known to play an important role in the management of agricultural and horticultural pests in southern Europe. Through a series of laboratory and field assessments, this study investigates the establishment potential of these two species in cool temperate climates typical of northern Europe. Laboratory results demonstrated a low level of cold tolerance in $$N.$$ $$tenuis$$ with a developmental threshold of 12.9°C and no indication of ability to diapause. Field trials supported these findings with 100% mortality occurring after less than 4 weeks of winter field exposure. Collectively, these data suggest that $$N.$$ $$tenuis$$ is unlikely to establish outdoors in northern Europe and would therefore have little or no non-target effects on native species in such regions, thereby constituting a ‘safe’ candidate for release. Additionally, investigations into temperature-related thresholds indicated that $$N.$$$$tenuis$$ would be an effective control agent against species with a similar activity profile to the two-spotted spider mite $$Tetranychus$$ $$urticae$$ Koch (Acari: Tetranychidae). $$Lysiphlebus$$ $$testaceipes$$demonstrated a greater ability to tolerate cold than $$N.$$ $$tenuis$$ but there was no indication of ability to diapause. With a developmental threshold of 5.8°C, parasitoid larvae and pupae continued to develop during the 70 d of winter field trials yielding reproductively viable adults. With this level of cold tolerance and a host range in excess of 100 aphid species, including some known to overwinter in the UK and other temperate regions, it seems reasonable to predict that $$L.$$ $$testaceipes$$ would be able to establish in northern Europe. Thermal activity threshold investigations also indicated that $$L.$$ $$testaceipes$$ would constitute an effective control agent for pest species with similar activity profiles to $$Aphis$$ $$fabae$$ Scop. (Hemiptera: Aphididae) under a range of climatic conditions. These data are discussed in relation to current debate on the environmental risk assessment and regulatory system in Europe for the release of non-native biological control agents.

Type of Work: Ph.D. thesis. Bale, Jeffrey S Colleges (2008 onwards) > College of Life & Environmental Sciences School of Biosciences QR Microbiology University of Birmingham 1071
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