Population structure of Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) in the United States

The potato tuberworm (PTW) Phthorimaea operculella is one of the most prominent pests of potatoes world wide. PTW was first reported in California in 1856. In 2002 it was first reported in damaging numbers in Oregon and Washington. Due to increased PTW population densities, economic losses increased substantially in the Columbia Basin in 2004 and 2005. Without baseline information on the population structure of this pest it was difficult to pinpoint the origin of the PTW individuals observed in Oregon and Washington. Thus, the objective of this study was to determine the population structure of PTW in the US. Individual adult male moths were collected from potato fields in major production regions including Oregon, Washington, Oregon, California, Idaho, Texas, Virginia and Georgia. AFLP markers, and a Bayesian based model (Structure 2.2) were used to determine the geographic population structure of the PTW. Medina’s SESim method was used to statistically determine individual and marker sampling adequacy. Whitlock’s AFLP Score was used as a locus selection and allele calling method.