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Changes in distribution and frequency of fungi associated with a foliar disease complex of pyrethrum in Australia

Citation

Hay, FS and Gent, DH and Pilkington, SJ and Pearce, TL and Scott, JB and Pethybridge, SJ, Changes in distribution and frequency of fungi associated with a foliar disease complex of pyrethrum in Australia, Plant Disease, 99, (9) pp. 1227-1235. ISSN 0191-2917 (2015) [Refereed Article]

Copyright Statement

2015 American Phytopathological Society

DOI: doi:10.1094/PDIS-12-14-1357-RE

Abstract

In Australia, pyrethrum (Tanacetum cinerariifolium) is affected by a foliar disease complex that can substantially reduce green leaf area and yield. Historically, the most important foliar disease of pyrethrum in Australia has been ray blight, caused by Stagonosporopsis tanaceti, and other fungi generally of minor importance. Temporal fluctuations in the frequency of fungi associated with foliar disease were quantified in each of 83 fields in northern Tasmania, Australia, during 2012 and 2013. Sampling was conducted throughout winter (April to July), spring (August to September), and summer (November) representing different phenological stages. Microsphaeropsis tanaceti, the cause of tan spot, was the pathogen most prevalent and isolated at the highest frequency, irrespective of sampling period. The next most common species was S. tanaceti, whose isolation frequency was low in winter and increased in spring and summer. Known pathogens of pyrethrum, Alternaria tenuissima, Colletotrichum tanaceti, and Stemphylium botryosum were recovered sporadically and at low frequency. Two species of potential importance, Paraphoma chrysanthemicola and Itersonilia perplexans, were also found at low frequency. This finding suggests a substantial shift in the dominant pathogen associated with foliar disease, from S. tanaceti to M. tanaceti, and coincides with an increase in defoliation severity in winter, and control failures of the spring fungicide program. Factors associated with this finding were also investigated. Sensitivity of M. tanaceti and S. tanaceti populations to the fungicides boscalid and cyprodinil collected prior to and following disease control failures in the field were tested under in vitro conditions. A high proportion (60%) of the M. tanaceti isolates obtained from fields in which no response to the spring fungicide program was found were insensitive to 50 g a.i./ml boscalid. This represented a 4.2-fold increase in the frequency of this phenotype within the M. tanaceti population over 2 years. No shifts in sensitivities to cyprodinil of M. tanaceti and S. tanaceti, or S. tanaceti to boscalid, were observed. Considering the increase in defoliation severity over winter, the benefits of applying fungicides in autumn, in addition to the commercial standard (spring only), were quantified in 14 individual field trials conducted in 2011 and 2012. Mixed-model analysis suggested fungicide application in autumn may improve pyrethrum growth during late winter and early spring, although effects on defoliation and yield were minimal. The increasing prevalence and isolation frequency of M. tanaceti and boscalid resistance within the population is of concern and highlights the urgent need for adoption of nonchemical methods for disease management in Australian pyrethrum fields.

Item Details

Item Type:Refereed Article
Keywords:pyrethrum, disease complex, fungal pathogens
Research Division:Biological Sciences
Research Group:Plant Biology
Research Field:Plant Pathology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Horticultural Crops
Objective Field:Horticultural Crops not elsewhere classified
Author:Hay, FS (Dr Frank Hay)
Author:Pilkington, SJ (Mrs Stacey Pilkington)
Author:Pearce, TL (Dr Tamieka Pearce)
Author:Scott, JB (Dr Jason Scott)
ID Code:102636
Year Published:2015
Web of Science® Times Cited:12
Deposited By:Tasmanian Institute of Agriculture
Deposited On:2015-09-01
Last Modified:2017-11-03
Downloads:0

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