Long-distance movement of New Zealand flower thrips (Thrips obscuratus Crawford) (Thysanoptera: Thripidae) into Central Otago orchards

Abstract

New Zealand fl ower thrips (NZFT) can damage nectarine fruits during the six weeks from fl owering. Cost-effective control strategies depend on the ability to predict when NZFT numbers will be high. Sampling carried out on gorse from July to November and on fruit trees between September and October established that few NZFT overwintered in Central Otago (CO), and hence that most of the thrips infestations on fruit trees in spring originate elsewhere. The source and possible route of NZFT into CO in spring was investigated using wind speed, wind direction and temperature data collected at several meteorological stations in Canterbury and Otago. The probable trajectories for the period prior to the arrival of high numbers of NZFT at Clyde (CO) were calculated and the departure conditions characterised. Flights appear to have been initiated during higher than average temperatures and northeasterly or northwesterly winds in Canterbury. Transport by north or northeast winds through the Mackenzie Basin seemed likely. Origins from within Canterbury probably varied, as did routes between mountains, fl ight times varied from 12 to 28 hours. The diversity of possible source sites and wind patterns explains the poor performance of a previous predictive model.