Apple and Pear Scab in East Anglia

Weston, W. A. R. Dillon; Petherbridge, F. R.

doi:10.1080/03683621.1933.11513417

Cited by 5 publications

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“…In such cases, primary infection could occur from other sources, such as diseased wood, shoots, or buds infected by scab conidia or mycelia (16). Many older studies reported that conidia could overwinter as scab lesions of wood and young shoots (9)(10)(11)(12)15,16,18,(25)(26)(27)33,37). Some of these studies also warned that conidia could cause symptoms in early spring before the period of ascospore release and infection (10,11,16,33).…”

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“…Many older studies reported that conidia could overwinter as scab lesions of wood and young shoots (9)(10)(11)(12)15,16,18,(25)(26)(27)33,37). Some of these studies also warned that conidia could cause symptoms in early spring before the period of ascospore release and infection (10,11,16,33). Recent investigations demonstrated that scab conidia could overwinter mainly in two ways: on the tips of shoots (21,(29)(30)(31) and associated with bud tissues (4)(5)(6).…”

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Overwintering of Conidia of Venturia inaequalis and the Contribution to Early Epidemics of Apple Scab

2004

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Overwintering of conidia of Venturia inaequalis associated with shoots and buds was determined, and the contribution to early spring epidemics of apple scab was evaluated during three consecutive seasons (1999 to 2001) in the Netherlands. Examinations of shoot samples collected before bud break showed that the percentage of shoots with superficial black fungal mycelia or conidia was above 65%, and the mean number of conidia on a 1-cm piece of shoot length ranged from 581 to 1,033. However, germination tests showed that the viability of conidia on shoots was less than 1.5%. No macroscopic scab lesions were detected on the scales of dormant buds. However, microscopic examinations of individual bud tissues demonstrated that the number of conidia was >3,000 per 100 buds in each year. The mean viability of conidia associated with buds ranged from 0.7 to 1.9% and from 3.7 to 10.5% for the outer and inner bud tissues, respectively. Results of field assessments at tight-cluster phenological stage showed that the percentage of infection caused by the viable overwintered conidia ranged from 0.3 to 3.8% in the various treatments. Our results indicated that conidia were unlikely to overwinter on the surface of shoots or outer bud tissues, where they were exposed to fluctuating environmental conditions, and, consequently, were unlikely to play a role in initiating an early epidemic of apple scab in the spring. However, our results indicated a risk from overwintered conidia in the inner bud tissues arising from a high level of scab the previous autumn. Therefore, orchards with high levels of apple scab, where ascosporic inoculum is much reduced, e.g., by sanitation, should be protected in early spring by means of fungicide treatment at green tip.

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Overwintering of Conidia of Venturia inaequalis and the Contribution to Early Epidemics of Apple Scab

2004

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“…On the other hand, although variously orientated sticky microscope slides erected as spore traps caught some conidia among the branches of apple trees, ascospores were rarely caught unless the slides were very close to perithecia in dead leaves lying on the ground. Dillon Weston and Petherbridge (1933) found mature perithecia in February 1932 but did not catch ascospores until April 12, when the trees already had scab lesions, which they presumed to have originated from conidia. They considered that ascospores had not been important in causing the earliest infections in 1932.…”

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The Origin of Apple Scab Epidemics in the Wisbech Area in 1953 and 1954

et al. 1955

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“…France Griffen and Maublanc, 1908;Saccas, 1944Germany Sorauer, 1890Aderhold, 1900;Voges, 1907;Sorauer, 1908;Voges, 1910;Kennel, 1981a;Kennel, 1981b;Ahrens, 1985;Moosherr and Kennel, 1986;Moosherr and Kennel, 1995;Portz, 2002India Gupta and Lele, 1980Ireland McKay, 1938Italy Cuboni, 1892 The Netherlands Goossens, 1934;Van der Scheer and Grabowski, 1991;Holb et al, 2004;Holb et al, 2005New Zealand Cunningham, 1925Norway Schøyen, 1907Gjaerum, 1962;Stensvand et al, 1996Poland Rogaśand Grabowski, 2005Sweden Eriksson, 1911Olsson, 1960South Africa Louw, 1951Switzerland Müller-Thurgau, 1902Wiesmann, 1932;Wiesmann, 1935;Siegfried et al, 1989UK Salmon (1906; Massee, 1910;Morse and Darrow, 1913;Bagenal et al, 1925;Moore, 1930;Marsh and Walker, 1932;Dillon Weston and Petherbridge, 1933;Preece, 1961;Swinburne, 1965;Cook, 1974;Hill, ...…”

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Primary inoculum of Venturia inaequalis (Cooke) Wint. in its asexual form in apple – a review

2023

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This review summarizes and discusses the geographical distribution, overwintering, dissemination, and management of the asexual stage of Venturia inaequalis, the fungal pathogen causing apple scab. The asexual overwintering of V. inaequalis has primarily been described as wood scab, superficial scab, or bud scab, and more rarely, it is mentioned as overwintering on infected leaves and fruits still attached to the trees. Wood scab is fungal pustules found on new and 1-year-old shoots, but it is also found on 2-year-old wood. It has been reported in many apple-growing countries throughout the world; however, most reports of wood scab being an important source of primary inoculum, as well as the most in-depth studies, are from the UK. Reports from some countries describe what is named superficial scab, which are symptomless infections of the pathogen on shoot surfaces. Overwintering of V. inaequalis on the inner or outer bud scales has also been reported in some countries. Infections may appear as small lesions on the bud scales, but numerous conidia have also been found in buds without symptomatic fungal tissue. The incidence and quantity of overwintering in the asexual stage are dependent on the amount of scab in the previous season, growth characteristics, and cultivar susceptibility. In orchards with limited options for fungicide control and/or in orchards with loss of scab control in the preceding season, conidia of V. inaequalis should not be underestimated as a source of primary inoculum.

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Apple and Pear Scab in East Anglia

Cited by 5 publications

References 3 publications

Overwintering of Conidia of Venturia inaequalis and the Contribution to Early Epidemics of Apple Scab

Overwintering of Conidia of Venturia inaequalis and the Contribution to Early Epidemics of Apple Scab

The Origin of Apple Scab Epidemics in the Wisbech Area in 1953 and 1954

Primary inoculum of Venturia inaequalis (Cooke) Wint. in its asexual form in apple – a review

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