The widespread occurrence of overwintered conidial inoculum of Venturia inaequalis on shoots and buds in organic and integrated apple orchards across the Netherlands

I. Holb, Bart Heijne, Michael J. Jeger

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

A 2-year study was conducted to determine the widespread occurrence of overwintered conidial inoculum of Venturia inaequalis and its impact on the apple scab control in 18 apple orchards (organic and integrated) with various levels of scab in the Netherlands. Autumn assessments of scab lesions showed that the integrated orchards had a significantly lower scab incidence (<20%) compared to that of the organic orchards (> 60%). At the bud-break phenological stage, the mean numbers of nonviable and viable conidia on 1 cm pieces of shoots ranged from 1 to about 90 and from 6 to more than 1000 in the integrated and the organic orchards, respectively, for both years. However, viable conidia on shoots were found only in 2 integrated and 6 organic orchards out of the 18 and the viability of conidia was below 2%. The mean numbers of viable and nonviable conidia per 100 buds ranged from 24 to more than 1000 and from 230 to almost 5000 in the integrated and the organic orchards, respectively, for both years. In both years, some 60-85% of the conidia was found on the outer bud scales. The percentage viability associated with the outer bud tissues was below 2% for all the orchards. However, the percentage of viable conidia within the inner bud tissues ranged from 0% to 6% in the integrated and from 2% to 11% in the organic orchards for both years. Differences between the organic and the integrated orchards were clearly demonstrated for overwintered conidia associated with both shoot and bud samples. The relationship between autumn scab incidence and numbers of overwintered conidia associated with shoots or buds was exponential. If the autumn scab incidence was above 40%, then the number of overwintered conidia markedly increased. We conclude that specific treatments for overwintering conidia of Venturia inaequalis may not be necessary in integrated orchards with a low scab incidence in the previous autumn. However, the risk of early scab epidemics initiated by overwintered conidia potentially is high in organic orchards. Preventative measures in early spring and also in the previous year must be established in these orchards.

Original languageEnglish
Pages (from-to)157-168
Number of pages12
JournalEuropean Journal of Plant Pathology
Volume111
Issue number2
DOIs
Publication statusPublished - Feb 2005

Fingerprint

Venturia inaequalis
conidia
Netherlands
inoculum
orchards
apples
buds
shoots
autumn
incidence
viability
lesions (plant)
budbreak
overwintering

Keywords

  • Apple scab
  • Epidemiology
  • Integrated production
  • Organic production
  • Overwintering of conidia
  • Scab control

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Horticulture
  • Plant Science

Cite this

@article{2e94e54b3dfb4be0ba7a90e7403270fc,
title = "The widespread occurrence of overwintered conidial inoculum of Venturia inaequalis on shoots and buds in organic and integrated apple orchards across the Netherlands",
abstract = "A 2-year study was conducted to determine the widespread occurrence of overwintered conidial inoculum of Venturia inaequalis and its impact on the apple scab control in 18 apple orchards (organic and integrated) with various levels of scab in the Netherlands. Autumn assessments of scab lesions showed that the integrated orchards had a significantly lower scab incidence (<20{\%}) compared to that of the organic orchards (> 60{\%}). At the bud-break phenological stage, the mean numbers of nonviable and viable conidia on 1 cm pieces of shoots ranged from 1 to about 90 and from 6 to more than 1000 in the integrated and the organic orchards, respectively, for both years. However, viable conidia on shoots were found only in 2 integrated and 6 organic orchards out of the 18 and the viability of conidia was below 2{\%}. The mean numbers of viable and nonviable conidia per 100 buds ranged from 24 to more than 1000 and from 230 to almost 5000 in the integrated and the organic orchards, respectively, for both years. In both years, some 60-85{\%} of the conidia was found on the outer bud scales. The percentage viability associated with the outer bud tissues was below 2{\%} for all the orchards. However, the percentage of viable conidia within the inner bud tissues ranged from 0{\%} to 6{\%} in the integrated and from 2{\%} to 11{\%} in the organic orchards for both years. Differences between the organic and the integrated orchards were clearly demonstrated for overwintered conidia associated with both shoot and bud samples. The relationship between autumn scab incidence and numbers of overwintered conidia associated with shoots or buds was exponential. If the autumn scab incidence was above 40{\%}, then the number of overwintered conidia markedly increased. We conclude that specific treatments for overwintering conidia of Venturia inaequalis may not be necessary in integrated orchards with a low scab incidence in the previous autumn. However, the risk of early scab epidemics initiated by overwintered conidia potentially is high in organic orchards. Preventative measures in early spring and also in the previous year must be established in these orchards.",
keywords = "Apple scab, Epidemiology, Integrated production, Organic production, Overwintering of conidia, Scab control",
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AU - Holb, I.

AU - Heijne, Bart

AU - Jeger, Michael J.

PY - 2005/2

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N2 - A 2-year study was conducted to determine the widespread occurrence of overwintered conidial inoculum of Venturia inaequalis and its impact on the apple scab control in 18 apple orchards (organic and integrated) with various levels of scab in the Netherlands. Autumn assessments of scab lesions showed that the integrated orchards had a significantly lower scab incidence (<20%) compared to that of the organic orchards (> 60%). At the bud-break phenological stage, the mean numbers of nonviable and viable conidia on 1 cm pieces of shoots ranged from 1 to about 90 and from 6 to more than 1000 in the integrated and the organic orchards, respectively, for both years. However, viable conidia on shoots were found only in 2 integrated and 6 organic orchards out of the 18 and the viability of conidia was below 2%. The mean numbers of viable and nonviable conidia per 100 buds ranged from 24 to more than 1000 and from 230 to almost 5000 in the integrated and the organic orchards, respectively, for both years. In both years, some 60-85% of the conidia was found on the outer bud scales. The percentage viability associated with the outer bud tissues was below 2% for all the orchards. However, the percentage of viable conidia within the inner bud tissues ranged from 0% to 6% in the integrated and from 2% to 11% in the organic orchards for both years. Differences between the organic and the integrated orchards were clearly demonstrated for overwintered conidia associated with both shoot and bud samples. The relationship between autumn scab incidence and numbers of overwintered conidia associated with shoots or buds was exponential. If the autumn scab incidence was above 40%, then the number of overwintered conidia markedly increased. We conclude that specific treatments for overwintering conidia of Venturia inaequalis may not be necessary in integrated orchards with a low scab incidence in the previous autumn. However, the risk of early scab epidemics initiated by overwintered conidia potentially is high in organic orchards. Preventative measures in early spring and also in the previous year must be established in these orchards.

AB - A 2-year study was conducted to determine the widespread occurrence of overwintered conidial inoculum of Venturia inaequalis and its impact on the apple scab control in 18 apple orchards (organic and integrated) with various levels of scab in the Netherlands. Autumn assessments of scab lesions showed that the integrated orchards had a significantly lower scab incidence (<20%) compared to that of the organic orchards (> 60%). At the bud-break phenological stage, the mean numbers of nonviable and viable conidia on 1 cm pieces of shoots ranged from 1 to about 90 and from 6 to more than 1000 in the integrated and the organic orchards, respectively, for both years. However, viable conidia on shoots were found only in 2 integrated and 6 organic orchards out of the 18 and the viability of conidia was below 2%. The mean numbers of viable and nonviable conidia per 100 buds ranged from 24 to more than 1000 and from 230 to almost 5000 in the integrated and the organic orchards, respectively, for both years. In both years, some 60-85% of the conidia was found on the outer bud scales. The percentage viability associated with the outer bud tissues was below 2% for all the orchards. However, the percentage of viable conidia within the inner bud tissues ranged from 0% to 6% in the integrated and from 2% to 11% in the organic orchards for both years. Differences between the organic and the integrated orchards were clearly demonstrated for overwintered conidia associated with both shoot and bud samples. The relationship between autumn scab incidence and numbers of overwintered conidia associated with shoots or buds was exponential. If the autumn scab incidence was above 40%, then the number of overwintered conidia markedly increased. We conclude that specific treatments for overwintering conidia of Venturia inaequalis may not be necessary in integrated orchards with a low scab incidence in the previous autumn. However, the risk of early scab epidemics initiated by overwintered conidia potentially is high in organic orchards. Preventative measures in early spring and also in the previous year must be established in these orchards.

KW - Apple scab

KW - Epidemiology

KW - Integrated production

KW - Organic production

KW - Overwintering of conidia

KW - Scab control

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U2 - 10.1007/s10658-004-1883-z

DO - 10.1007/s10658-004-1883-z

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