Confirmation of ray blight disease of pyrethrum in Australia

Pethybridge, SJ; Wilson, C. R.

doi:10.1071/ap98004

Cited by 33 publications

(22 citation statements)

References 3 publications

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“…2 and 3) has been reported to negatively impact pyrethrum production in Tasmania (60,68,71,75), Kenya (59,81), and Papua New Guinea (85), although the disease generally causes minimal damage in the latter two countries. The name of this disease reflects necrosis of the ray florets of the flowers caused by the disease, and its similarity to a disease of the same common name caused by P. ligulicola var.…”

Section: Ray Blightmentioning

confidence: 99%

“…Tomato spotted wilt virus (TSWV) is also prevalent, although infected plants generally are asymptomatic (76). Ray blight is the most prevalent disease in early spring and is the primary target of spring fungicide programs (60,62,68,71,75). Sclerotinia and Botrytis flower blights can be observed when the crops are flowering from early November until harvest in December, and are managed using a fungicide program during summer flowering.…”

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confidence: 99%

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Diseases of Pyrethrum in Tasmania: Challenges and Prospects for Management

et al. 2008

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Section: Ray Blightmentioning

confidence: 99%

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confidence: 99%

Diseases of Pyrethrum in Tasmania: Challenges and Prospects for Management

et al. 2008

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“…The spectrum of diseases affecting pyrethrum production in Tasmania has been well characterized (20,23), with the prevalence of fungal foliar diseases varying temporally (19,22). To date, the most significant foliar disease of pyrethrum is caused by Phoma ligulicola Baker, Dimock & Davis v. Arx (19), which is most evident during spring when flowering stems are produced.…”

Section: Quantifying Loss Caused By Ray Blight Disease In Tasmanian Pmentioning

confidence: 99%

“…To date, the most significant foliar disease of pyrethrum is caused by Phoma ligulicola Baker, Dimock & Davis v. Arx (19), which is most evident during spring when flowering stems are produced. Disease due to P. ligulicola was first reported in Tasmania in 1995 (22), and is referred to as "ray blight" due to the necrosis of ray florets of the flower and its similarity to ray blight disease of chrysanthemum (Chrysanthemum morifolium Ram. ), which is caused by the same pathogen (2,24).…”

Section: Quantifying Loss Caused By Ray Blight Disease In Tasmanian Pmentioning

confidence: 99%

Quantifying Loss Caused by Ray Blight Disease in Tasmanian Pyrethrum Fields

et al. 2007

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The efficacy of newly implemented fungicide recommendations on reducing the intensity of ray blight disease caused by Phoma ligulicola to achieve site-specific attainable yield potentials in Tasmanian pyrethrum fields was quantified over two seasons in 46 and 51 fields during the 2003 and 2004 growing seasons, respectively. Disease intensity and yield in two plots (10 × 24 m), one following the commercial fungicide protocol recommendations and the second receiving no fungicide, were assessed in each pyrethrum field. The commercial fungicide protocol consisted of one application of azoxystrobin at 150 g a.i./ha, followed by two applications of a tank mixture of difenoconazole at 125 g a.i./ha and chlorothalonil at 1,008 liters a.i./ha at 14- to 21-day intervals. This program resulted in significant decreases in defoliation severity and the incidence of stems and flowers with ray blight, and increases in the height of stems and number of flowers produced per stem in October and November. In plots receiving the commercial fungicide protocol, the dry weight of flowers was increased by 76 and 68% in 2003 and 2004, respectively. Moreover, pyrethrin yield increased by 81 and 78% when the commercial fungicide protocol was used compared with the nontreated plots. Tobit regression was used to examine the relationships and thresholds among disease intensity measures (defoliation severity, stem severity, and incidence of flowers with ray blight) assessed just prior to harvest. This regression utilized a left-censored regression model to define subminimal thresholds, as none of the disease intensity measures could be less than 0. Defoliation severity had a threshold of 35.3% before stem severity linearly increased and a threshold of 38.2% before the incidence of flowers with ray blight linearly increased. Finally, the threshold for stem severity was 13.7% before the incidence of flowers with ray blight linearly increased. These thresholds can be used to assist growers in making disease management decisions with the objective of minimizing loss of flowers by maintaining defoliation severity below the critical point at which the incidence of flowers with ray blight begins to linearly increase.

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“…inoxydablis, can reduce plant growth and pyrethrin yield in Tasmania (31,34,36,40). Ray blight was first observed causing minor losses on pyrethrum flowers in Tasmania in 1995 (41). Since 1999, considerable losses have been reported in Tasmania from foliar dieback on developing stems in early spring caused by a severe form of ray blight (33,37).…”

Section: Pyrethrum (Tanacetum Cinerariifolium)mentioning

confidence: 99%

Site-Specific Risk Factors for Ray Blight in Tasmanian Pyrethrum Fields

et al. 2009

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Ray blight of pyrethrum (Tanacetum cinerariifolium), caused by Phoma ligulicola var. inoxydablis, can cause defoliation and reductions of crop growth and pyrethrin yield. Logistic regression was used to model relationships among edaphic factors and interpolated weather variables associated with severe disease outbreaks (i.e., defoliation severity ≥40%). A model for September defoliation severity included a variable for the product of number of days with rain of at least 0.1 mm and a moving average of maximum temperatures in the last 14 days, which correctly classified (accuracy) the disease severity class for 64.8% of data sets. The percentage of data sets where disease severity was correctly classified as at least 40% defoliation severity (sensitivity) or below 40% defoliation severity (specificity) were 55.8 and 71%, respectively. A model for October defoliation severity included the number of days with at least 1 mm of rain in the past 14 days, stem height in September, and the product of the number of days with at least 10 mm of rain in the last 30 days and September defoliation severity. Accuracy, sensitivity, and specificity were 72.6, 73.6, and 71.4%, respectively. Youden's index identified predictive thresholds of 0.25 and 0.57 for the September and October models, respectively. When economic considerations of the costs of false positive and false negative decisions and disease prevalence were integrated into receiver operating characteristic (ROC) curves for the October model, the optimal predictive threshold to minimize average management costs was 0 for values of disease prevalence greater than 0.2 due to the high cost of false negative predictions. ROC curve analysis indicated that management of the disease should be routine when disease prevalence is greater than 0.2. The models developed in this research are the first steps toward identifying and weighting site and weather disease risk variables to develop a decision-support aid for the management of ray blight of pyrethrum. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Pyrethrum (Tanacetum cinerariifolium) is a perennial plant in the family Asteraceae that is cultivated for the production of six closely related esters called pyrethrins, which possess insecticidal properties (7,10,48). Pyrethrum is an integral component of the cropping system rotation used in the northwest coast of Tasmania, contributing approximately 30% of the world's supply of pyrethrins. The crop is planted by seed from July to September, and harvests are conducted annually for the duration of the crop (typically 4 to 5 years) (34). AuthorsIn the absence of fungicide applications in spring, ray blight, a fungal disease caused by Phoma ligulicola var. inoxydablis, can reduce plant growth and pyrethrin yield in Tasmania (31,34,36,40). Ray blight was first observed causing minor losses on pyrethrum flowers in Tasmania in 1995 (41). Since 1999, c...

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Confirmation of ray blight disease of pyrethrum in Australia

Cited by 33 publications

References 3 publications

Diseases of Pyrethrum in Tasmania: Challenges and Prospects for Management

Diseases of Pyrethrum in Tasmania: Challenges and Prospects for Management

Quantifying Loss Caused by Ray Blight Disease in Tasmanian Pyrethrum Fields

Site-Specific Risk Factors for Ray Blight in Tasmanian Pyrethrum Fields

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