New Zealand Plant Protection 2020-08-20T16:22:43+12:00 Dr Ruth Falshaw Open Journal Systems <p>ISSN 1175-9003 (print), ISSN 1179-352X (online)</p> <p><strong>2018 CiteScore</strong>: 0.68</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