The green spruce aphid Elatobium abietinum (Walker) is an introduced pest in the United Kingdom and more recently in New Zealand. In outbreak years this aphid can cause severe defoliation and sometimes death of spruce trees ( Picea spp.). As chemical control is not financially viable, other options including host-plant resistance and biological control are currently being investigated. An understanding of the genetic variation of this pest is imperative in fully utilizing these control strategies. To examine this, E. abietinum was collected from Sitka spruce Picea sitchensis from four locations in the UK that were up to 240 km apart. Of these, 40 aphids were analysed via two alternative polymerase chain reaction (PCR) analyses using primer pairs. The first analysis used 10-mer random primers, whilst the second analysis used primers designed to amplify across the intergenic spacer region of rDNA. Combining results from the two analyses allowed the 40 UK aphids to be separated into 28 different genotypes. The genetic variation was also high within each UK site, with 77 to 89% of the aphids sampled being of a different genotype. The two PCR analyses were subsequently used to examine 40 aphids across six sites in New Zealand up to 1200 km apart. No genetic variation was identified. Further analysis of several of these New Zealand aphids with 87 individual 10-mer primers and two polymerase enzymes, still did not detect any genetic variation. The high degree of genotypic diversity in the UK populations was presumably due to a longer period of establishment, multiple introductions and/or sexual reproduction. The contrasting lack of genetic variation in New Zealand populations was probably due to a very limited founder population, continued isolation and lack of sexual reproduction. Reduced genetic diversity can seriously decrease the ability of a population to adapt to control strategies. Therefore the durability of certain control methods may be more readily maintained in such an isolated population in New Zealand.

New Zealand is currently the only major fruit producing country in the world that is free of economically important fruit flies. As part of the effort to maintain this status, there is a need to supplement quarantine decision-making procedures with a means of rapidly identifying immature life stage infestations to the species level. Here we describe a molecular method that achieves this, using simple restriction patterns of ribosomal DNA (rDNA) as diagnostic markers. The 18S and 18S plus internal transcribed spacer (ITS) regions were amplified from larval DNA by the polymerase chain reaction (PCR). Nineteen species, spanning four genera (including five subgenera of Bactrocera) were analysed. Restriction analysis of the 18S PCR product provided poor resolution, even at the generic level. Digestion of the 18S + ITS PCR product, however, generated thirteen diagnostic haplotypes as defined by the composite restriction patterns from RsaI, Sau3a HaeIII and AluI. No variation was detected at these restriction sites within or between populations. Twenty two restriction enzymes have been screened, but diagnostic RFLPs have yet to been found for six out of the ten Bactrocera (Bactrocera) species; B. passiflorae (Froggatt) cannot be distinguished from B. facialis (Coquillet), nor B. kirki (Froggatt) from B. trilineola (Froggatt) or B. neohumeralis (Hardy) from ti. tryoni (Froggatt). Geographic origin could assist in distinguishing the first four species, but the latter pair are very closely related with overlapping origins, hosts and adult morphology. All six species, however, are considered high risk with respect to their likely establishment in New Zealand. Therefore diagnosis based on this molecular technique would support the same quarantine decision. We consider this method could be useful as a diagnostic technique and discuss directions for further development.

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 < 0.33). However, at similar crop growth stages, 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.

Immature life stages of fruit flies (Diptera: Tephritidae) and leafroller moths (Lepidoptera: Tortricidae) can not be readily distinguished by phenotype. The need to identify these groups originated for different primary reasons but identification has been achieved using a common molecular approach. Restriction fragment length polymorphism (RFLP) detected in polymerase chain reaction (PCR) amplified ribosomal DNA (rDNA) provides a rapid diagnostic test for several of these species across a broad taxonomic range, irrespective of life stage or tissue quality. Application of this technique to identify fruit fly specimens intercepted at the border and parasitised leafroller cadavers in the field is presented.