Epidemiology of potatoes infected with "Candidatus Liberibacter": movement of potato psyllids, Bactericera cockerelli Sulc., and spatial patterns of disease

An emerging disease of potato in the US called “Zebra Chip” or “Zebra Complex” (ZC), vectored by the potato psyllid, Bactericera cockerelli Sulc., results in tuber defects that render them unmarketable. The putative causal pathogen is a fastidious bacterium “Candidatus Liberibacter”, similar to that which causes citrus greening, or HLB. Although it is well-known that potato psyllids migrate over considerable distances from overwintering areas to breeding areas, very little information is available concerning psyllid movement when they ultimately arrive in potato fields. Such information is crucial to understanding disease pattern formation and how insect movement contributes to these patterns. Consequently, it is imperative that psyllid movement be quantified. Initial trials designed to evaluate local movement of potato psyllids and studies of disease patterns in commercial potato fields indicate that psyllid adults move substantial distances within a potato field, thereby exacerbating disease distribution. It is suspected that individual psyllids move frequently while in potato fields and infect multiple plants, resulting in the formation of discrete patches of diseased plants. Moreover, psyllids will move from early planted fields that are heavily infested with psyllids and/or from plants that are in decline into later plantings that are in close proximity. Therefore, we need to determine how far psyllids can disperse so that effective buffer zones can be established between potato fields and/or fields of different planting dates.