Abstract
RAPD‐PCR was used to determine the genetic variation of Metopolophium dirhodum collected in a winter wheat field and in a nearby 2.5‐m‐high suction trap at Lincoln, New Zealand. Over three collection dates, five distinct genotypes were identified, using two primers (OPK16 and OPC09) independently. There was a significant temporal effect on the ratio of genotypes in populations collected in the field. There was no significant spatial aggregation or association of these genotypes in the field. Two of the genotypes present in the field were also detected in the suction trap sample. Using a higher resolution method of RAPD‐PCR (with the Stoffel fragment of Taq polymerase), a total of 124 genotypes were distinguished from 142 individuals collected from Scotland and New Zealand. The Jaccard similarity index ( S ) was used to measure similarity between individual aphids within and between populations from both hemispheres. All populations were very diverse ( S M. dirhodum was significantly more diverse in Scotland than in New Zealand. The results are discussed in relation to the value of monitoring aphid flights for pest forecasting, and in terms of the most appropriate RAPD‐PCR techniques.