Allen, Claire Marie (2010)
Ph.D. thesis, University of Birmingham.
Amblyseius swirskii and Phytoseiulus longipes are targeted as biological control agents for the horticultural pest Tetranychus urticae. This study applies a standardised protocol to evaluate the risk of establishment of introduced species and investigates temperature related behavioural thresholds for all three species. Laboratory results demonstrate a low level of cold tolerance in A. swirskii and no diapause. Field studies recorded 100% mortality within two weeks of outdoor winter exposure. Amblyseius swirskii has a higher activity threshold temperature than it’s target prey T. urticae. Amblyseius swirskii lacks cold tolerance and is unlikely to establish outdoors and thus can be considered a ‘safe candidate’ for release. Laboratory results demonstrate that P. longipes can not diapause yet is more cold tolerant than A. swirskii. Field studies report 100% mortality after 73 days of winter exposure. Phytoseiulus longipes demonstrates mid-range cold tolerance yet is unlikely to survive an entire winter outdoors. Phytoseiulus longipes has lower activity threshold temperatures than T. urticae. Further studies are required on other factors attributable to establishment potential before it can be classified a ‘safe candidate’. As a consequence of the findings of the present study A. swirskii was granted a license for release into the UK in 2006.
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