Herbicides are a vital tool to reducing weed competition during the establishment phase of revegetation plantings. However, there is limited information on herbicide tolerances of native species, hindering the ability to develop effective weed-management plans. In a pilot study, tolerances of five New Zealand native species (Coprosma propinqua, Griselinia littoralis, Hoheria angustifolia, Prumnopitys taxifolia, and Cyperus ustulatus) were tested against the herbicides clopyralid, haloxyfop-P-methyl, triclopyr, glufosinate-ammonium and glyphosate at label rates, and to a dilute glyphosate treatment used to simulate drift from spraying around native plants. Treatments were sprayed directly onto plants, with survival and growth over four months compared to a control group. Clopyralid caused significant damage to H. angustifolia and G. littoralis, but increased growth in Cyperus ustulatus. Haloxyfop-P-methyl did not damage any species. While glyphosate and glufosinate-ammonium at label rates caused significant mortality, a low dose of glyphosate did not damage any species except Coprosma propinqua. Triclopyr also caused significant mortality or damage even in non-dicotyledonous plants, possibly due to small plant sizes. These results identify broader than expected susceptibility to triclopyr and clopyralid, suggesting additional caution with these herbicides may be required. The findings from this study also indicate that spraying glyphosate carefully around these species is unlikely to cause harm, except to Coprosma propinqua.

Species of root-lesion nematode (Pratylenchus spp.) are associated with significant reductions in wheat yield in wheat-growing regions around the world. Of these, Pratylenchus thornei and P. neglectus are known to cause the highest damage to the Australasian wheat industry. New Zealand is known to produce high wheat yields on a per-hectare basis yet little research has been conducted to date to determine the effects of Pratylenchus spp. on the production of wheat in New Zealand. Therefore, as the first step towards filling this knowledge gap, the current research focused on conducting surveys to determine the population densities and distribution of Pratylenchus spp. in wheat-growing regions in Canterbury, South Island, New Zealand. Surveys were conducted at ten selected sites that were geographically distinct from each other. At six of the ten sites, lesion nematode populations were reported to be above the recorded Australian threshold of 2000 nematodes per kg of soil. In Australia, it’s been recorded that around 50% yield reductions can occur in intolerant wheat varieties when population densities reaches this number. Differences in population density within each location was also observed indicating the uneven distribution of lesion nematodes within a field. Morphological measurements of the nematodes collected from multiple sites during this study confirmed the presence of P. thornei and P. neglectus in Canterbury wheat-producing areas indicating a potential threat to the New Zealand wheat industry by root-lesion nematodes. Further studies need to be conducted to fully understand the situation and to develop management strategies to mitigate threats from nematodes.

Neonectria ditissima causes a debilitating apple tree canker disease. We determined the efficacy of polymerase chain reaction primers, originally designed for European strains, by sequencing New Zealand strains. The concatenated ribosomal inter-transcribed spacer and β-tubulin gene regions of 17 New Zealand isolates were compared with those of two European strains by phylogenetic analysis. New Zealand and European isolates of N. ditissima were in the same clade, suggesting that there has been little change in these gene regions following introduction to New Zealand. There was 100% homology with Bt-FW135 and Bt-RW284 primers. Based on sequencing 17 New Zealand isolates from several locations, these polymerase chain reaction primers can be relied upon to amplify New Zealand isolates of N. ditissima.

The greenhouse thrips, Heliothrips haemorrhoidalis is a quarantine pest of kiwifruit. There is a need for reliable information on its phenology in kiwifruit orchards to inform the development of new management options. Numbers of larval, pupal and adult greenhouse thrips were counted on leaves of the two main kiwifruit cultivars Actinidia chinensis var. deliciosa (‘Hayward’) at two sites at different times and A. chinensis var. chinensis ‘Zesy002’ at one site. Greenhouse thrips were also counted on leaves of shelter tree species Cryptomeria japonica, and other plants present on kiwifruit orchards, blackberry (Rubus fruticosus s.l.), barberry (Berberis glaucocarpa), and wineberry (Aristotelia serrata) across a number of sites at different times. There was a strong seasonal pattern to the phenology of greenhouse thrips and it was relatively synchronous for all the host plants surveyed. In general, number of greenhouse thrips on foliage increased from January to peak in April or May before declining in late autumn or winter and remaining low until the following January or February. The phenology of greenhouse thrips followed the same seasonal pattern for a variety of host plants found on kiwifruit orchards at sites in the Bay of Plenty across two two-year time periods. Therefore, host species does not appear to be a factor affecting the phenology of thrips. Other, non-host factors such as microclimate may be important drivers of phenology but they require further study. The consistency of the seasonal pattern of relative abundance means that there is a well-defined window to target for thrips management.

During the inspection of imported sweet corn (Zea mays), a specimen with dry rot symptoms was detected by Ministry for Primary Industries quarantine officers. A sample was sent to the MPI Plant Health and Environment Laboratory for diagnostics, and initial examination found a layer of yeast cells on the surface of the symptomatic tissue. The fungus was cultured and identified based on DNA sequences as Ustilago maydis. While the corn-smut pathogen U. maydis is well known to cause tumour like galls on corn kernels, it is a less recognised fact that this fungus can also grow as a yeast. To determine if the yeast stage could have been associated with the dry-rot symptoms observed on the specimen, healthy material was inoculated with the isolated U. maydis strain. No symptoms developed on inoculated material, indicating that the yeast cells were likely multiplying on the surface of the cut corn ear as saprobes. To our knowledge, this is the first report of U. maydis yeast stage on corn ears and indicates a previously unconsidered pathway for the organism. For the yeast stage to cause disease, mating with a compatible mating type on the surface of a living host plant would be required.

The Mycology and Bacteriology team of the Ministry for Primary Industries’ Plant Health and Environment Laboratory is responsible for the identification and verification of all suspected exotic, new, and emerging pathogens affecting plants and the environment in New Zealand. We work in an applied diagnostic environment where results can have significant implications for biosecurity. Sample submissions often result in detection of new to New Zealand fungi and bacteria on plants for which information on fungal and bacterial associations is generally sparse. The complexity of testing required is quite varied with samples being submitted from post entry quarantine (looking for a known pathogen using specific tests), border or surveillance (unknown pathogens requiring multiple tests), or a biosecurity response (scaling up to test large numbers, identification resolution required to strain level). Applied test methods depend largely on the sample type and consist of morphological identification, biochemical testing, pathogenicity testing, serological and molecular techniques, including high throughput sequencing. A profile of our diagnostic work and the most commonly detected taxa and host associations are presented.

Recently, fruit drop in two green varieties of kiwifruit (Actinidia deliciosa; VarA and VarB) has increased towards the harvest date. The efficacy of two biofungicides, applied post-flowering, to ameliorate the effects of early fruit drop in VarA and VarB during the 2017–18 growing season was tested. Treatments were applied to a single bay, with buffer bays and rows adjacent. Treatments were two different Bacillus-based biofungicide products; Serenade® Max (a.i. B. subtilis QST713 strain) and Triple-X® (a.i. B. amyloliquefaciens BS 1b). There was an untreated control. All fruits in the canopy, within the treated bay, were counted and recorded at 4-weekly intervals, over 5 months until harvest. At the VarA site, there was no statistical difference (P>0.1) in the percentage of fruit drop between the control (7%), Triple-X® (5%) and Serenade® Max (10%) treated vines. At the VarB site, fruit drop differed statistically (P<0.1) between Triple-X® treated vines (5%) and the control (10.5%), with Serenade® Max treated vines (6.5%) having intermediate fruit drop. The use of Triple-X® may be an option to assist with reducing fruit drop in kiwifruit.

Black foot disease of grapevines is a major economic issue for the viticulture industry, with several Dactylonectria and Ilyonectria species identified as causal agents worldwide. This study aimed to confirm the pathogenicity of an Ilyonectria pseudodestructans isolate recovered from a symptomatic grapevine in a nationwide survey. An initial pot experiment inoculated callused and root-wounded grapevine propagation material of varieties ‘101- 14’ and ‘5C’ with I. pseudodestructans conidia. The second pot experiment compared the pathogenicity of I. pseudodestructans conidial, chlamydospore and mycelial inocula. Disease incidence, severity and root and shoot dry weights were determined after 4–5 months of growth. Ilyonectria pseudodestructans was recovered from inoculated plants resulting in higher disease incidence and severity compared with the uninoculated control. Disease severity and incidence was higher for callused compared to rooted propagation material, but did not differ between grapevine varieties. Conidial inoculum caused greater disease incidence and severity compared with chlamydospore and mycelial inocula. Ilyonectria pseudodestructans propagules infected grapevine plant material via the callused basal ends or wounded roots, indicating this species is a potentially important pathogen of grapevines both in nurseries and vineyards.

Neonectria ditissima is a serious pathogen of apple. Low-virulent cultures of this fungus have been isolated from cankers, but how and why low-virulent isolates can infect apple is unknown. Rasp wounds on ‘Royal Gala’ trees were inoculated with agar plugs from six low-virulent N. ditissima isolates in a glasshouse. Neonectria ditissima was re-isolated 10 weeks after inoculation. Agar plugs from the re-isolated cultures were used to inoculate ‘Royal Gala’ trees again. After the second re-isolation, conidial suspensions of the original cultures and the 2 x 6 re-isolates were used to determine the virulence on ‘Royal Gala’ compared with field-collected conidia. Three cultures did not cause any lesions; neither did their re-isolates. The re-isolates of two cultures did not differ in virulence compared with the originals. However, the virulence of one isolate increased with each re-isolation, with the second re-isolation causing significantly more lesions, lesion development occurring faster and the lesions being larger than those caused by the original isolate. Therefore, the virulence of N. ditissima isolates can change over time, with loss or gain possibly being attributed to epigenetic and/or genetic changes in the genome.

The brown marmorated stink bug (BMSB) Halyomorpha halys (Heteroptera: Pentatomidae) is an invasive pest in North America and Europe that damages many plant species and invades human dwellings. It is regularly intercepted at Aotearoa/New Zealand’s borders but is not yet known to have established. Māori are partners in New Zealand’s biosecurity community and an understanding of the potential impact of any invasive alien species to their interests is essential. The known impacts of BMSB in published literature were reviewed with a focus on Māori plant taonga (valued or treasured plant species) in: (1) Māori commercial enterprises; (2) mara kai (food gardens); and (3) the natural estate. Many fruit and some vegetable species are likely to be affected by BMSB in commercial and non-commercial Māori horticulture but the impact of BMSB on indigenous/native and other taonga plant species in mara kai and the native estate is difficult to evaluate. BMSB poses a serious economic threat to some crop species of commercial value to Māori, as well as threat to some native taonga species. A kaupapa Māori approach examining unpublished mātauranga (knowledge) would considerably broaden this understanding. He ngārara raupatu kaha nei i te tini o ngā tipu, te urutomo noa i te hunga tangata te ngārara nei. Ka kaha haukotingia te ngārara nei e te mana ārai o Aotearoa heoi anō, kāore anō kia whakawhenua i a ia. E mahi tahi ana a Māori rāua ko te hapori marukoiora, anō hoki e mārama ana i te mōrearea o ngā tipu tauiwi - e whai pānga kia rātou. Te Tukanga. I arotake i ngā tuhinga e hāngai ana ki ngā kopuratanga e mōhio nei - e Māori ai te titiro o roto: (1) ngā pākihi Māori (2) ngā māra kai (3) te taiao anō hoki. Te Whakautu. He maha hoki ngā huawhenua me ngā huarākau ka pāngia e te BMSB o roto i ngā pākihi, i ngā ahuone Māori heoi anō, te taea te whakatau i ngā pānga o te BMSB ki te iwi taketake me ōna taonga o roto i ngā māra kai. Te Whakakapinga. Kei tino raru ētahi tipu e whai pānga ki te Māori, ngā tipu taketake anō hoki i te BMSB. Mā te tirohanga Māori e whakawhānui i ngā mōhiotanga.