Lee T. Aalders

Transportation of nonindigenous species via soil on international aircraft passengers’ footwear

The potential for transported soil to harbour and spread nonindigenous species (NIS) is widely recognised and many National Plant Protection Organisations (NPPOs) restrict or prohibit its movement. However, surprisingly few studies have surveyed soil while it is in transit to provide direct support for its role in accidental introductions of NIS. Moreover, there are few border interception records for soil organisms because they are neither easily detected nor routinely isolated and identified. Better data would improve evaluations of risks from soil transported via different pathways, enable targeting of management resources at the riskiest pathways, and support development of new risk management methods. We surveyed organisms present in soil that had been removed from footwear being carried in the baggage of international aircraft passengers arriving in New Zealand and recorded high incidences, counts and diversities of viable bacteria, fungi, nematodes and seeds, as well as several live arthropods. These included taxa that have not been recorded in New Zealand and were therefore almost certainly nonindigenous to this country. In each gram of soil, there was an estimated 52–84% incidence of genera that contain species regulated by New Zealand’s NPPO, which suggests many were potentially harmful. Variation in the incidences and counts of soil organisms with sample weight, footwear type and season at the port of departure indicated it may be possible to develop methods for targeting management resources at the riskiest footwear. Comparisons with previously published data supported the hypothesis that survival of soil organisms is greater when they are transported in protected (e.g. in luggage) rather than unprotected environments (e.g. external surfaces of sea containers); this offers opportunities to develop methods for targeting management resources at the most hazardous soil pathways.

Botanical survey of perennial ryegrass-based dairy pastures in three regions of New Zealand: implications for ryegrass persistence

A botanical survey of 24 commercial dairy pastures ranging in post-sowing age and perennial ryegrass type (mid-season diploid, late-season diploid, tetraploid) was undertaken in each of Waikato-Bay of Plenty (BoP), Taranaki and Canterbury during autumn/winter. The mean perennial ryegrass proportion (85% of total DM) and tiller density (3252 m−2) was greatest in Canterbury and the broadleaved weed proportion lowest (2%). Conversely, Waikato–BoP had the lowest ryegrass proportion (59%), tiller density (1817 m−2) and greatest proportion of broadleaved weeds (15%), with Taranaki intermediate. Tiller density was greater in pastures sown with diploid rather than tetraploids (averaging 3033 vs. 1784 m−2). Grass grub (Costelytra zealandica, 11 m−2) populations were lowest in the youngest age category pastures where nematode populations were highest (80 g−1 dry soil). The soil seedbank was dominated by unsown species (with total species emergence averaging 4594 seeds m−2), with negligible ryegrass emergence.

Testing a new low-labour method for detecting the presence of Phasmarhabditis spp. in slugs in New Zealand

Most studies on distribution of Phasmarhabditis spp. in slugs use dissection of individual slugs, which is time-consuming. Here we use a technique modified from that used to collect Pristionchus spp. nematodes from their beetle hosts. Slugs are decapitated and cadavers incubated for 1 week prior to examining for presence of adult nematodes. We compared the new technique with traditional dissection using field-collected untreated slugs, and slugs infected with Phasmarhabditis hermaphrodita in the laboratory. There was no difference in the efficacy of the two techniques. We also used the new technique to study prevalence of P. hermaphrodita at 22 New Zealand sites. We found P. hermaphrodita present at three sites and P. californica at two other sites suggesting Phasmarhabditis spp. are relatively common in New Zealand.

Implications of grass–clover interactions in dairy pastures for forage value indexing systems. 5. Southland

ABSTRACT The implementation and monitoring of the treatments in the core experiment (eight perennial ryegrass cultivars grown under four combinations of plus/minus clover and high/low nitrogen (N)) at a dryland Waikato site is described. The N x clover interaction was significant in 10 of the 17 seasonal or total annual herbage accumulation (HA) data sets available, caused by substantially lower annual HA in the low N minus clover treatment compared with all other treatments. Five significant scaling-type clover × cultivar interactions in HA were evident. In all cases, HA was greater in plus clover than minus clover treatments, but more so for some cultivars than others. However, the interactions were not consistent across seasons, and different cultivars or phenotypic contrast groups were involved in many cases. The hypothesis that relative HA rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture versus mixtures with white clover is supported.

Implications of grass–clover interactions in dairy pastures for forage indexing systems. 3. Manawatu

ABSTRACT The implementation and monitoring of the treatments in the core experiment (eight perennial ryegrass cultivars grown under four combinations of plus/minus clover and high/low nitrogen (N)) at a dryland Manawatu site are described. Herbage accumulation (HA) was significantly greater for high N than for low N in 14 out of 21 annual and seasonal totals. There were no significant main effects of clover and there were no interactions between clover and N level. With the exception of autumn 2016, there were significant differences among ryegrass cultivars in all seasons, but no clover × cultivar or N × cultivar interactions for HA or nutritive value (NV). With the caveat that successive droughts reduced the proportion of white clover to low levels, the hypothesis that relative HA or NV rankings of ryegrass cultivars do not differ when ryegrass is grown in monoculture or in mixtures with white clover is supported.

Pasture renewal on Bay of Plenty and Waikato dairy farms: impacts on pasture performance post-establishment

To determine the impact of pasture renewal on dairy pasture performance, a total of 24 renewed and unrenewed pastures were monitored in Bay of Plenty and Waikato for 5 years. Renewed pastures produced an additional 1.5, 1.8 and 1.9 t dry matter (DM) ha−1 in the first, second and third years of monitoring, respectively, compared with unrenewed pastures. There was a greater contribution of clover, sown grasses and unsown grasses and a smaller contribution of broadleaf weeds in renewed than unrenewed pastures in some years (% of total DM). The sown grass DM content (kg DM ha−1), perennial ryegrass tiller densities and endophyte infection frequencies were similar in renewed and unrenewed pastures. The abundance of invertebrate pests and total nematodes was lower in renewed than unrenewed pastures in some years. The greater clover content, fewer weeds and fewer insect pests, contributed to the greater herbage production of renewed pastures.

First record of the root knot nematode, Meloidogyne minor in New Zealand with description, sequencing information and key to known species of Meloidogyne in New Zealand

Meloidogyne minor Karssen et al. 2004 was collected from perennial ryegrass (Lolium perenne L.) growing in a sports ground in Christchurch, New Zealand. This is a new record for M. minor, the first report of this nematode occurring in New Zealand, and the second report from the southern hemisphere (after Chile). In general, the New Zealand isolate of M. minor corresponds well to the descriptions of M. minor given by Karssen et al. (2004). The New Zealand isolate is characterized by having a female with dorsally curved stylet, 13-14 μm long, with transversely ovoid knobs slightly sloping backwards from shaft; rounded perineal pattern; and male with stylet 16-19 μm long, large transversely ovoid knobs sloping slightly backwards from shaft; head region not set off, labial disc elevated, lateral lips prominent; and second stage juvenile 370-390 μm long, with hemizonid posterior but adjacent to excretory pore; tail 53-63 μm long; and a distinct hyaline tail terminus 14-18 μm long. In addition, molecular phylogeny using near full length small subunit (SSU), D2/D3 expansion segments of the large subunit (LSU), the internal transcribed spacer region (ITS1 and 2), and the intergenic spacer (IGS2) of the ribosomal rDNA supports the identification.