Summer epidemics of apple scab: The relationship between measurements and their implications for the development of predictive models and threshold levels under different disease control regimes

I. Holb, B. Heijne, M. J. Jeger

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24 Citations (Scopus)

Abstract

A 2-year study on epidemic progress of apple scab was conducted at Randwijk, the Netherlands, in 1998 and 1999. The summer epidemic caused by conidia was studied instead of the well-described spring season epidemic originating from ascospores. The aim was to investigate relationships between disease measurements, i.e. disease incidence and severity measures of apple scab, and their implications for the development of predictive models and threshold levels. The study characterized good relationships between the measurements on cultivar Jonagold using regression analyses in three disease control regimes (untreated, organic and integrated). For fruit quality prediction, the relationship between fruit incidence (If) and leaf incidence (Il) in the organic control regime was given by I f = 1.966 + 0.402 × (Il) (R2 = 0.92). As a result of low level of disease in the integrated control regime, shoot incidence (Is), with higher values than leaf incidence, was better suited for prediction. The relationship was given by If = -0.162 + 0.028 × (Is) (R2 = 0.91). For the integrated control regime, disease threshold levels were constructed for timing of the final fungicide application. If an apple grower wants to keep fruit infection under 1% incidence (harvest scab threshold), the timing of the final fungicide application (action threshold) should correspond to 4% shoot scab incidence at the beginning of August. The results are compared with similar studies and their biological interpretation is discussed.

Original languageEnglish
Pages (from-to)335-343
Number of pages9
JournalJournal of Phytopathology
Volume151
Issue number6
DOIs
Publication statusPublished - Jun 2003

Fingerprint

Venturia inaequalis
Malus
disease control
incidence
summer
Incidence
Fruit
pesticide application
fruits
shoots
prediction
ascospores
Fungal Spores
disease incidence
disease severity
conidia
fruit quality
leaves
Netherlands
growers

Keywords

  • Apple scab (Venturia inaequalis)
  • Disease thresholds
  • Integrated and organic disease control
  • Predictive model
  • Relationship between measurements

ASJC Scopus subject areas

  • Plant Science

Cite this

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title = "Summer epidemics of apple scab: The relationship between measurements and their implications for the development of predictive models and threshold levels under different disease control regimes",
abstract = "A 2-year study on epidemic progress of apple scab was conducted at Randwijk, the Netherlands, in 1998 and 1999. The summer epidemic caused by conidia was studied instead of the well-described spring season epidemic originating from ascospores. The aim was to investigate relationships between disease measurements, i.e. disease incidence and severity measures of apple scab, and their implications for the development of predictive models and threshold levels. The study characterized good relationships between the measurements on cultivar Jonagold using regression analyses in three disease control regimes (untreated, organic and integrated). For fruit quality prediction, the relationship between fruit incidence (If) and leaf incidence (Il) in the organic control regime was given by I f = 1.966 + 0.402 × (Il) (R2 = 0.92). As a result of low level of disease in the integrated control regime, shoot incidence (Is), with higher values than leaf incidence, was better suited for prediction. The relationship was given by If = -0.162 + 0.028 × (Is) (R2 = 0.91). For the integrated control regime, disease threshold levels were constructed for timing of the final fungicide application. If an apple grower wants to keep fruit infection under 1{\%} incidence (harvest scab threshold), the timing of the final fungicide application (action threshold) should correspond to 4{\%} shoot scab incidence at the beginning of August. The results are compared with similar studies and their biological interpretation is discussed.",
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