New Zealand Plant Protection 2021-02-07T00:00:00+13:00 Dr Ruth Falshaw Open Journal Systems <p>ISSN 1175-9003 (print), ISSN 1179-352X (online)</p> <p><strong>2019 CiteScore</strong>: 1.2</p> <p><strong>Scope:</strong> Research on all aspects of biology, ecology and control of weeds, vertebrate and invertebrate pests, and pathogens and beneficial micro-organisms in agriculture, horticulture, forestry and natural ecosystems.</p> New Zealand indigenous Myrtaceae in foreign botanic gardens: testing the sentinel plant concept for biosecurity risk assessment 2020-11-26T14:49:20+13:00 Kirsty S.H. Boyd-Wilson M. Virginia Marroni Mark R. McNeill David A.J. Teulon <p>The use of sentinel or expatriate plants is a growing concept for risk assessment in plant biosecurity. This approach involves ascertaining the presence and impact of pests and pathogens on plants foreign to a given location but planted in international botanic gardens or arboreta. The data obtained provide information on the potential pest status of these pests and pathogens, as invasive alien species (IAS), to plant species in their native or indigenous range. Assessment of the biosecurity threat from IAS for indigenous plants not found within the geographic distribution of these pests and pathogens is challenging, however, as they may be relatively taxonomically distinct from plants found in the distribution of the IAS and can be in different climates and environments. We examine the sentinel/expatriate concept in relation to risk assessment for myrtle rust (Austropuccinia psidii) on New Zealand Myrtaceae on these plants found in botanic gardens and arboreta outside New Zealand. Between September 2017 and September 2018, we identified and then contacted 65 botanic gardens or arboreta that putatively had New Zealand Myrtaceae and were within the known distribution of myrtle rust. We asked for information on the presence of New Zealand Myrtaceae species in their collections and whether these plants were infected by myrtle rust. Sixteen gardens/arboreta responded; most were in Australia or the United States. Only one of these gardens provided information that was useful for biosecurity risk assessment for myrtle rust on New Zealand Myrtaceae. The results are discussed in the context of plant biosecurity risk assessment and the broader sentinel/expatriate plant concept.</p> 2021-02-07T00:00:00+13:00 Copyright (c) 2021 New Zealand Plant Protection Factors affecting sporulation and infection of Peronospora sparsa in New Zealand boysenberry gardens 2020-12-03T23:32:09+13:00 Anusara M.H. Mudiyanselage Hayley J. Ridgway Monika Walter Jason Smith Marlene V. Jaspers E. Eirian Jones <p>Downy mildew, caused by <em>Peronospora sparsa, </em>is an economically important disease of boysenberries. Sporangia produced on infected tissue initiate berry infections; however the timing of sporangial release under New Zealand environmental conditions is unknown. The number of <em>P. sparsa </em>sporangia trapped on Vaseline®-coated slides placed weekly in three boysenberry gardens in the Nelson region from October to December in 2010 and September to December in 2011 was determined. Climate data were used to determine environmental factors that promoted sporangia production/release. Incidence of dryberry symptoms and sporulation on tissue samples incubated at 15 or 20°C under high relative humidity (RH) were assessed. <em>Peronospora sparsa </em>sporangia were observed on slides from all three sites, with peak sporangial numbers in mid-November in both years. Sites with the highest numbers of sporangia trapped in November had higher dryberry incidence in December. Data indicated that sporangial release was triggered by percentage of rainy days, RH and warm temperatures (16–23°C) in early spring, where high moisture periods promoted sporulation and a subsequent dry period allowed sporangial release. This study improves understanding of the timing of sporangial release to inform management practices.</p> 2021-02-16T00:00:00+13:00 Copyright (c) 2021 New Zealand Plant Protection Determining the presence of host specific toxin genes, ToxA and ToxB, in New Zealand Pyrenophora tritici-repentis isolates, and susceptibility of wheat cultivars 2020-12-03T23:31:02+13:00 Sean Weith Hayley J. Ridgway E. Eirian Jones <p>Tan spot, caused by <em>Pyrenophora tritici-repentis </em>(Ptr), is an important disease of wheat worldwide, and an emerging issue in New Zealand. The pathogen produces host-specific toxins which interact with the wheat host sensitivity loci. Identification of the prevalence of the toxin encoding genes in the local population, and the susceptibility of commonly grown wheat cultivars to Ptr will aid selection of wheat cultivars to reduce disease risk. Twelve single spore isolates collected from wheat-growing areas of the South Island of New Zealand representing the <em>P. tritici-repentis </em>population were characterised for the Ptr ToxA and ToxB genes, <em>ToxA </em>and <em>ToxB</em>, respectively, using two gene specific primers. The susceptibility of 10 wheat cultivars to <em>P. tritici-repentis </em>was determined in a glasshouse experiment by inoculating young plants with a mixed-isolate spore inoculum. All 12 New Zealand <em>P. tritici-repentis </em>isolates were positive for the <em>ToxA </em>gene but none were positive for the <em>ToxB </em>gene. Tan spot lesions developed on all inoculated 10 wheat cultivars, with cultivars ‘Empress’ and ‘Duchess’ being the least susceptible and ‘Discovery’, ‘Reliance’ and ‘Saracen’ the most susceptible cultivars to infection by the mixed-isolate spore inoculum used. The results indicated that the cultivars ‘Empress’ and ‘Duchess’ may possess a level of tolerance to <em>P. tritici-repentis </em>and would, therefore, be recommended for cultivation in regions with high tan spot incidence.</p> 2021-04-15T00:00:00+12:00 Copyright (c) 2021 New Zealand Plant Protection