Light brown apple moth, Epiphyas postvittana, is a significant horticultural pest native to Australia, and currently with a limited global distribution. However it can tolerate very heterogeneous climatic and vegetation conditions and has recently invaded California with considerable consequences for US international and domestic trade. A genetic factor that may contribute to its environmental adaptability, and consequently invasive capability, is the phosphoglucose isomerase gene (pgi). This gene codes for a key enzyme in the second step of glycolysis and for which the isozyme composition has been associated with the fitness and dispersal capacity of other moths. As a first step, to determine if this locus is variable within E. postvittana, novel primers were designed enabling access to 957 bp of the coding region across exons 4 to 11 of pgi. Exon-primed intron-crossing (EPIC) primers were then designed to compare sequences of 17 specimens across one laboratory and three wild New Zealand populations from a laditudinal range of ~39-45°S. A total of 70 segregating sites in the exons were found, including 61 synonymous and nine nonsynonymous. Introns 3 to 11 (excluding intron 10) were also sequenced for 13 individuals revealing significant length variation within and between introns and populations. The level of variation revealed here indicates that this could be a useful target gene to assess fitness factors associated with invasibility of E. postvittana.