New Zealand Plant Protection 2020-09-25T22:07:45+12:00 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> Symptom expression of Phytophthora colocasiae in inoculated taro corms 2020-01-27T06:00:51+13:00 Amy Maslen-Miller Robert A. Fullerton Angelika Tugaga Faalelei Tunupopo Seeseei Molimau-Samasoni Joanna K. Bowen Robin M. MacDiarmid Joy L. Tyson <p>Taro leaf blight (TLB), caused by <em>Phytophthora colocasiae</em>, is normally characterised by leaf lesions. There are isolated reports of <em>P. colocasiae</em> causing a corm rot but the symptoms are not well defined and have not been recorded in Samoa. Here we report on an inoculation method and describe the symptoms of corm rot caused by <em>P. colocasiae</em>. In this study, a corm inoculation method was developed in physical containment laboratories in New Zealand and subsequent symptom development studies were undertaken on TLB-tolerant taro cultivars in Apia, Samoa. The Samoan TLB-tolerant taro cultivars were able to be wound-infected with <em>P. colocasiae</em> and the results confirm previous descriptions of <em>P. colocasiae</em> infection giving rise to light brown firm rots in corms. This work has allowed the pictorial record of corm rots to be updated, potentially providing for better distinction between corm rots caused by <em>P. colocasiae</em> and those caused by other pathogens, such as <em>Fusarium</em> spp.</p> 2020-01-27T00:00:00+13:00 Copyright (c) 2020 New Zealand Plant Protection Pathogenicity of Ceratocystis fimbriata from New Zealand kumara on kiwifruit cultivars 2020-06-03T21:42:31+12:00 Joy L. Tyson Michael A. Manning Peter J. Wright <p><strong>Abstract</strong> <em>Ceratocystis fimbriata</em> was reported in 2010 causing wilt and death of kiwifruit (<em>Actinidia</em> spp.) vines in Brazil, with losses of up to 50% of vines on some orchards. New Zealand is one of the largest producers of kiwifruit in the world, but <em>C. fimbriata</em> has been recorded only on kumara (<em>Ipomoea batatas</em>) in this country. In this study the pathogenicity of New Zealand isolates of <em>C. fimbriata</em> from kumara was examined using potted vines of four kiwifruit cultivars. During the trial, none of the vines became visibly diseased, growth rates were not restricted, and discolouration at the inoculation sites on the stem was minimal. In comparison, tests by researchers in Brazil using <em>C. fimbriata</em> isolated from symptomatic kiwifruit resulted in lengthy lesions and death of susceptible kiwifruit seedlings. Sequences of the internal transcribed spacer (ITS) region of rRNA from the New Zealand <em>C. fimbriata</em> isolates were 100% identical to those sequences from <em>C. fimbriata</em> isolates from Ipomoea batatas in GenBank. This study has shown that the New Zealand isolates of <em>C. fimbriata</em> from kumara are not pathogenic to the kiwifruit cultivars tested, and are a different pathotype to those found on kiwifruit in Brazil.</p> 2020-07-27T00:00:00+12:00 Copyright (c) 2020 New Zealand Plant Protection Meeting droplet size specifications for aerial herbicide application to control wilding conifers 2020-06-26T23:20:04+12:00 Brian Richardson Carol Rolando Andrew Hewitt Mark Kimberley <p>Large areas of New Zealand are being aerially sprayed with herbicides to manage ‘wilding’ conifer spread. The purpose of the study was to obtain and analyse droplet spectra produced by nozzles commonly used for wilding conifer spraying to determine whether or not operational recommendations for a target droplet size class (~350 µm) are being met. Droplet spectra were measured in a wind tunnel for 27 nozzle x 3 operating condition (nozzle angle, air speed and pressure) combinations tested for each of three spray mixes. AGDISP, an aerial spray application simulation model, was used to quantify the field performance implications of changes to droplet spectra parameters. Only one nozzle, the CP-09, 0.078, 30°, met the target droplet size specification when used at 45° but not at 0°. However, under these conditions, this nozzle produced a large driftable fraction. All but one of the other scenarios tested produced much larger droplet sizes. Operational spray mixes tended to slightly increase the potential for spray drift compared with the water control. The CP-09, 0.078, 30° nozzle used at 45° met the operational droplet size specification but is more sensitive to changes to nozzle angle (0° versus 45°) than the other nozzles tested. None of the three Accu-Flo<sup>TM</sup> nozzles tested met the target droplet size specification. However, the Accu-Flo<sup>TM</sup> nozzles produced very few fine droplets making them good choices for reducing spray drift potential.</p> 2020-09-19T00:00:00+12:00 Copyright (c) 2020 New Zealand Plant Protection Spill-over attack by the gall fly, Urophora stylata, on congeners of its target weed, Cirsium vulgare 2020-08-20T16:22:43+12:00 Michael Cripps Jovesa Navukula Benjamin Kaltenbach Chikako van Koten Seona Casonato Hugh Gourlay <p>The gall fly, <em>Urophora stylata</em>, was released in New Zealand in 1998 as a biocontrol agent for the thistle weed, <em>Cirsium vulgare</em> (Scotch thistle). In the summer of 2018, a survey was conducted to assess the field host range of the biocontrol agent in New Zealand.&nbsp; A random selection of 18 pasture populations under sheep and/or beef production, where <em>C.</em> <em>vulgare</em> was present, was surveyed to quantify the attack intensity (gall size relative to seedhead size) on <em>C. vulgare</em>, and the presence of attack on other thistle weeds within the same population. At each location, seedheads were collected from <em>C. vulgare</em> and all other thistle species (Cardueae) present, which included <em>Cirsium arvense </em>(Californian thistle)<em>, Cirsium palustre </em>(marsh thistle)<em>, Carduus nutans </em>(nodding thistle), and an <em>Arctium </em>species (burdock). In addition to attack on <em>C.</em> <em>vulgare</em>, the gall fly was recorded on <em>C. arvense</em> (at six locations) and <em>C. palustre</em> (at one location). The probability of the presence of attack on <em>C. arvense</em> was positively correlated with the attack intensity on <em>C. vulgare</em>, suggesting that attack on <em>C. arvense</em> is a ‘spill-over effect’ occurring where seedheads of <em>C. vulgare</em> are in limited supply.</p> 2020-10-27T00:00:00+13:00 Copyright (c) 2020 New Zealand Plant Protection An improved clearing and staining protocol for evaluation of arbuscular mycorrhizal colonisation in darkly pigmented woody roots 2020-04-02T17:13:21+13:00 Romy Moukarzel Hayley J. Ridgway Alexis Guerin-Laguette E. Eirian Jones <p>Arbuscular mycorrhizal fungi (AMF) establish symbiotic interactions with the roots of vascular plants, including grapevines. Verifying AMF colonisation routinely requires establishing the presence of hyphae, arbuscules and vesicles. Clearing roots with potassium hydroxide (KOH) followed by staining with trypan blue has been used previously to visualise fungal structures, however visualisation is difficult with darkly pigmented roots, such as those of grapevines so additional steps are required to ensure clear visualisation. Three fixing and clearing processes were evaluated prior to staining with trypan blue: 1) fixing grapevine roots in 70% v/v ethanol overnight; 2) clearing by heating the roots in either 2% or 10% w/v KOH; and 3) clearing the roots in 3% v/v hydrogen peroxide for 10 min. Roots were examined under a compound light microscope for the presence of AMF. A combination of fixing grapevine roots in 70% ethanol overnight and clearing by autoclaving in 10% KOH produced the greatest enhancement in subsequent staining of grapevine roots with trypan blue overnight. The best method tested enabled the discrimination of arbuscular mycorrhizal structures in fresh roots of grapevines without the use of toxic chemical fixatives.</p> 2020-11-15T00:00:00+13:00 Copyright (c) 2020 New Zealand Plant Protection Vapour-phase efficacy of selected essential oils individually and in combination against Aspergillus flavus, A. niger, Fusarium proliferatum, and Curvularia lunata 2020-08-05T14:22:04+12:00 Alex Ahebwa Rachsawan Mongkol Paranee Sawangsri Mana Kanjanamaneesathian <p>Grain storage plays a crucial role in ensuring food security to Thai farmers so sustainable protection methods against deleterious microorganisms, such as fungi, are necessary. Essential oils (EOs) have demonstrated broad-spectrum fumigant antifungal activity against most storage fungi that are problematic in Thailand. Four storage fungi (<em>Aspergillus flavus, A. niger, Curvularia lunata</em> and <em>Fusarium proliferatum</em>) were isolated from dried rice and corn grains (stored for at least six months). EOs were extracted by hydrodistillation from clove buds (<em>Syzygium aromaticum</em>), fruit peel and leaves of makrut lime (<em>Citrus hystrix</em>), eucalyptus leaves (<em>Eucalyptus</em> sp.) and lemongrass stems (<em>Cymbopogon citratus</em>). The fungi inoculated on PDA in plastic cups were exposed to each EO vapour originating from paper disc attached in the lids in an inverted position. The minimum inhibitory concentration (MIC) for each EO was determined. Selected MICs were combined in a binary manner and similarly tested against the fungi. Fractional inhibitory concentration indices (FICI) were determined for each combination. Lemongrass and makrut lime leaf EOs were the most effective with MICs of 0.09 µL/mL against <em>Curvularia lunata</em> and 0.19-0.28 µL/mL against <em>A. flavus, A. niger</em> and <em>F. proliferatum</em>. Eucalyptus oil produced the least effective vapour (MIC 0.56-0.74 µL/mL) against all tested pathogens. A combination of lemongrass and makrut lime leaf EOs was partially synergistic against<em> A. niger</em> (FICI=0.75) but was fully synergistic against the other three fungi tested (FICI=0.5). The EOs from lemongrass and makrut lime leaf have potential to suppress the growth of the four grain-storage fungi tested.</p> 2020-11-19T00:00:00+13:00 Copyright (c) 2020 New Zealand Plant Protection The leaf-feeding beetle, Cassida rubiginosa, has no impact on Carduus pycnocephalus (slender winged thistle) regardless of physical constraints on plant growth 2020-09-25T22:07:45+12:00 Jonty Mills Sarah Jackman Chikako van Koten Michael Cripps <p>The leaf-feeding beetle, <em>Cassida rubiginosa</em>, is an oligophagous biocontrol agent capable of feeding on most species in the tribe Cardueae (thistles and knapweeds). The beetle was released in New Zealand in 2007, primarily to control <em>Cirsium arvense</em> (Californian thistle), with the recognition that it had potential to control multiple thistle weeds. The objective of this study was to test the impact of different densities of <em>Cassida rubiginosa</em> larvae (0, 50, 100, or 200 per plant) on the growth and reproductive performance of the annual thistle weed, <em>Carduus pycnocephalus</em> (slender winged thistle). Since the effectiveness of biocontrol agents is often enhanced when plants are stressed, different levels of growth constraint were imposed by growing the weed in different pot sizes (0.5, 1, 5, and 12 litres). We hypothesised that feeding damage by <em>Cassida rubiginosa</em> larvae would have a greater impact on the weed when grown in smaller pots, since root growth would be constrained, and the weed’s ability to compensate for feeding damage would be restricted. Contrary to our hypothesis, pot size had no effect on feeding damage by <em>Cassida rubiginosa</em> on <em>Carduus pycnocephalus</em>. As expected, most measures of plant performance increased with larger pot sizes, including plant height, biomass, and the number of seedheads per plant. The results of this study indicate that <em>Cassida rubiginosa</em> is unlikely to contribute to the control of <em>Carduus pycnocephalus</em>. Additional oligophagous biocontrol agents targeting the rosette stage and seed production should be considered for release in New Zealand.</p> 2020-11-19T00:00:00+13:00 Copyright (c) 2020 New Zealand Plant Protection Geodata collection and visualisation in orchards: interfacing science-grower data using a disease example (European canker in apple, Neonectria ditissima) 2020-08-18T10:52:36+12:00 Juliane Buhrdel Monika Walter Rebecca E. Campbell <p>The collection and visualisation of data in orchards are important for management of many orchard processes, including pests and diseases. We present methods combining visualising data with efficient, accurate, standardised data collection, using European canker in apple orchards as an exemplar. Using grower-collected current and historical disease data, we investigated Environmental Systems Research Institute (ESRI) ArcGIS tools to analyse and visualise data. Historical data were collected by growers on paper and current data, also collected by growers, using Survey123. ArcGIS Pro was the operating software for analysis, and ArcGIS Online, Web Maps and ArcGIS Dashboards, for visualisation. Data collection, summarising and visualisation were more efficient using Survey123, than paper collection and subsequent data entry. Higher quality data, including spatial location of the disease, informed disease patterns. A standardised geodatabase enabled efficient data querying and analytics to understand disease distribution and temporal dynamics. This study exemplars a standardised disease and pest database to benefit both scientific and industry data management. Geodata collection, combined with visualisation, facilitates the use of data to understand disease and pest dynamics. These techniques offer opportunity for a cohesive industry approach to area-wide disease and pest monitoring and management, integrating previously disparate datasets by using location.</p> 2020-12-11T00:00:00+13:00 Copyright (c) 2020 New Zealand Plant Protection