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Use of survival analysis to assess management options for ray blight in Australian pyrethrum fields
Author(s) -
Pethybridge S. J.,
Ngugi H. K.,
Hay F. S.
Publication year - 2010
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.2010.02256.x
Subject(s) - pyrethrum , biology , fungicide , cultivar , sowing , blight , confidence interval , toxicology , horticulture , agronomy , pesticide , mathematics , statistics
The effects of fungicide, cultivar and plant density on the time‐to‐death of pyrethrum flowers affected by ray blight (caused by Phoma ligulicola var. inoxydablis ) in Australia were analysed using nonparametric Kaplan–Meier (KM) estimates and accelerated failure time (AFT) models with a Weibull probability distribution. Analyses using KM estimates and AFT models yielded similar results. The median survival time ( T ) for all flowers in the fungicide trial was estimated at 53 days [95% confidence interval (CI) = 43–53] in 2000 and 60 days (CI = 51–60) in 2001. In both years, all fungicides tested except copper oxychloride significantly ( P ≤ 0·0495) increased the duration of flower survival compared with nontreated plots. Significant variation ( P < 0·0001) was noted between years and among four cultivars in terms of flower survival, with T values for different cultivars ranging from 41 to 81 days, and averaging 69 days (CI = 60–69) in 2005 and 64 days (CI = 56–64) in 2006 for all cultivars. Planting at a quarter the density currently recommended increased flower survival by 41·8% (χ 2 = 29·19; P < 0·0001), but did not increase yield. Linear regression indicated that defoliation severity accounted for at least 94% of variation in median survival time. Improved management may be achieved via an integrated strategy incorporating these factors.