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Douglas-fir seed chalcid (DFSC) Megastigmus spermotrophus, a small (3 mm long) host-specific seedpredatory wasp, was accidentally introduced into New Zealand in the 1920s. Concern over DFSC reducing Douglas-fir seed production in New Zealand led to an attempt at biocontrol in 1955 with the release, but failed establishment, of the small (2.5 mm long) parasitoid wasp, Mesopolobus spermotrophus. We investigated why DFSC causes little destruction of Douglas-fir seed in New Zealand (usually <20%) despite the apparent absence of major natural enemies. Douglas-fir seed collections from 13 New Zealand sites yielded the seed predator (DFSC) but also potential parasitoids, which were identified using morphology and partial COI DNA sequencing. DFSC destroyed only 0.15% of Douglas-fir seed. All parasitoids were identified as the pteromalid wasp, Mes. spermotrophus, the host-specific biocontrol agent released in 1955. Total parasitism was 48.5%, but levels at some sites approached 90%, with some evidence of density-dependence. The discovery of the parasitoid Mes. spermotrophus could indicate that the biocontrol agent released in 1955 did establish after all. Alternatively, Mes. spermotrophus could have arrived accidentally in more recent importations of Douglas-fir seed. The high level of parasitism of DFSC by Mes. spermotrophus is consistent with DFSC being under successful biological control in New Zealand. Suppression of DFSC populations will benefit commercial Douglas-fir seed production in New Zealand, but it also represents the likely loss of a potential biological control agent for wilding Douglas-fir. [ABSTRACT FROM AUTHOR]

[Display omitted] • NZ surveys with new primers show Leu absence coincides with broom psyllid absence. • Leu likely entered NZ in 1993 with psyllids released for biocontrol of broom. • Other entry routes/maintenance mechanisms for Leu in NZ were improbable. • We advise molecular screening of biocontrol agents that may vector plant pathogens. The bacterium, Candidatus Liberibacter europaeus (Leu) was reported in New Zealand (NZ) in 2011 in Scotch broom, Cytisus scoparius Link, and its biocontrol agent, Arytainilla spartiophila Förster (Hemiptera: Psyllidae). The aim of the study was to investigate the pathway by which Leu arrived in NZ using a retrospective risk assessment of Leu being accidentally imported with the broom psyllids in the 1990s. We developed species-specific primers for Leu detection and carried out end-point and real-time PCR analyses for Leu in potential host plants and broom psyllids throughout NZ to test two hypotheses: 1) Leu was accidentally released in NZ in broom psyllids in 1993; or 2) Leu was present in NZ pre-1993, and maintained in cultivated plants via cuttings/grafting, or in wild Scotch broom populations via shared parasitic plants. There was strong evidence to support the arrival of Leu with broom psyllids in NZ. Firstly, methods used to import broom psyllids from the UK provided a likely pathway for inadvertent release of Leu, which at the time was unknown to science, into NZ. Secondly, Leu in NZ Scotch broom plants was significantly associated with the presence of broom psyllids, with Leu absent from plants at sites without psyllids. In contrast, there was no evidence suggesting Leu was present in NZ before the release of broom psyllids: Leu was not found in ornamental brooms or pears, Pyrus communis L. (a Leu host in Europe), and parasitic plants were too uncommon to maintain Leu in wild Scotch broom. In addition, Leu in UK Scotch broom and broom psyllids has a matching partial 16S sequence to NZ Leu. It remains uncertain whether Leu is pathogenic in Scotch broom, or symptomless as in pears. Unpredictable impacts of Ca. Liberibacter spp. in different plant species probably implies that psyllids considered as future weed biocontrol agents will need to be free of these potential plant pathogens. This accidental introduction of Candidatus Liberibacter europaeus into NZ via a weed biocontrol agent happened because detection methods for unculturable organisms were not developed at the time. Molecular characterisation of insect microbiomes could become an essential procedure for pre-release safety screening of biocontrol agents that are potential vectors of plant pathogens. [ABSTRACT FROM AUTHOR]

Premise of The Study: Simple sequence repeat (SSR) markers were developed for the study of genetic diversity of New Zealand Nassella trichotoma (Poaceae) and to support future studies in its native range. Methods and Results: Genomic DNA was extracted from N. trichotoma leaf material and subjected to Roche 454 sequencing. From a total of 745 putative SSRs, 48 with di‐ to pentanucleotide repeats were screened, 32 primer pairs were designed, and 15 polymorphic markers were optimized for multiplex PCR on 105 N. trichotoma samples from four New Zealand regions. Each locus resulted in two to six alleles per locus, and four of the loci cross‐amplified in N. tenuissima. The mean observed and expected heterozygosity ranged from 0.00 to 0.90 and 0.00 to 0.50 per locus, respectively. Conclusions: The novel SSR markers are valuable for the study of genetic diversity of N. trichotoma and might also be useful for closely related species. [ABSTRACT FROM AUTHOR]