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New Zealand Plant Protection 67 (2014): 326

Low incidence of Liberibacter-positive psyllids (Bactericera cockerelli) in Pukekohe potato growing area

R. Gardner-Gee and A.J. Puketapu


In the Pukekohe region, potatoes grown over the summer season without insecticide protection typically have 40% of tubers with symptoms of zebra chip (ZC), a disease caused by the bacterium Candidatus Liberibacter solanacearum (Lso). The bacterium is vectored by the pest psyllid species Bactericera cockerelli, known in New Zealand as the tomato potato psyllid (TPP). Although TPP has been present in New Zealand since at least 2006, relatively little is known about the incidence of Lso or the Lso-titre levels in New Zealand TPP populations. Preliminary sampling work conducted near the Pukekohe Research Station over the summer of 2013/2014 is presented. One-hundred TPP adults were collected from sticky traps in potato fields over 4 months. Each insect was tested for the presence of Lso using established qPCR diagnostic protocols. For comparison, 100 TPP from laboratory colonies were also tested for Lso over the same time period. Although plants with ZC symptoms were widespread in the sampling area, only 2% of the TPP sampled from sticky traps had detectable levels of Lso, and Lsotitre in the Lso-positive TPP was extremely variable. In contrast, colony TPP (originally collected from potatoes and then maintained on tomato plants) tested 100% positive for Lso and had consistently high Lso-titre.

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