LOW-TEMPERATURE MORTALITY AND OVERWINTERING OF THE WESTERN FLOWER THRIPS FRANKLINIELLA-OCCIDENTALIS (THYSANOPTERA, THRIPIDAE)

The UK glasshouses in which the western flower thrips Frankliniella oc cidentalis (Pergande) is prevalent offer protection from adverse winte r conditions. As such, F. occidentalis may not have been exposed to se lection for cold tolerance that would allow successful overwintering i n the field. In this study, the cold tolerance of larval and adult F. occidentalis has been assessed in the laboratory. Both age groups show pre-freeze mortality in chronic and acute cold exposures though adult s are more cold hardy. Larvae and adults are both able to increase the ir cold tolerance in response to a combination of lower temperatures a nd decreased photoperiod. Field experimentation confirmed that F. occi dentalis is unlikely to survive for the duration of a harsh UK winter, but a level of cold tolerance that would be adequate for survival in mild winters or for short exposures at sub-zero temperatures was obser ved.