Overwintering of Conidia of<i>Venturia inaequalis</i>in Apple Buds in New York Orchards

Becker, C. M.; Burr, Tom; Smith, Cheryl A.

doi:10.1094/pd-76-0121

Cited by 34 publications

(28 citation statements)

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“…In this study, leaf collection treatments (Collect-L, Collect-L + Mulch-C, Collect-L + Plastic-F) showed great reduction on ascosporic inoculum sources (Tables 4 and 5). However, as earlier studies (Becker et al, 1992;Holb et al, 2004a) demonstrated, conidia could overwinter within the buds of an apple tree twig in orchards with large inoculum sources. Consequently, if most overwintered pseudothecia are eliminated from the ground of an organic orchard by sanitation, then it might be hypothesized that overwintered conida may assume a greater importance in early spring than ascospores.…”

Section: Discussionmentioning

confidence: 81%

Effect of six sanitation treatments on leaf litter density, ascospore production of Venturia inaequalis and scab incidence in integrated and organic apple orchards

Holb

2006

Eur J Plant Pathol

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A two-year study was conducted to determine the effect of six sanitation treatments on leaf litter density (LLD), relative ascospore production of Venturia inaequalis and scab incidence on spur-leaf clusters, leaves and harvested fruits, on two cultivars with low and high scab susceptibilities, in Hungarian integrated and organic apple orchards. The following sanitation treatments were used: sprays of lime sulphur in autumn, collecting fallen leaves in autumn, straw mulch cover in late winter, sprays of lime sulphur followed by mulch cover, collecting fallen leaves followed by mulch cover, collecting fallen leaves followed by covering the orchard floor with plastic foil, and non-sanitized control. LLD decreased continuously in all treatment plots by 0-23% by mid-May in both orchards and years; however, LLD reduction was 1.4-4.2 times higher in the organic orchard compared to the integrated one. All treatments, except for the lime sulphur treatment, resulted in significant (P < 0.05) reduction of LLD and ascospore production in both the integrated and organic apple orchards compared to non-sanitized plots. The most efficient treatment was leaf collection combined with plastic foil cover, followed by leaf collection combined with mulch cover, leaf collection alone, mulch cover alone, and lime sulphur spray combined with mulch cover, with a reduction in the ascospore production of >95, 72-92, 56-79, 24-38, and 27-46%, respectively, in the mean of both orchards and years. However, only treatments of leaf collection applied alone, or in combination with mulch or with plastic foil cover reduced significantly (P < 0.05) leaf and/or fruit scab incidence by 18-57% compared to non-sanitized plots. These three leaf collection treatments are recommended in both integrated and organic orchards and the possibilities of successfully incorporating these methods into orchard management practices are interpreted.

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Section: Discussionmentioning

confidence: 81%

Effect of six sanitation treatments on leaf litter density, ascospore production of Venturia inaequalis and scab incidence in integrated and organic apple orchards

Holb

2006

Eur J Plant Pathol

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“…Most bud scales in a bud are open until the end of the shoot growth. If the levels of scab in the previous year were high, large numbers of conidia would remain on the surfaces of the developing buds during the summer (10,11,31,32). These conidia could become entrapped between the bud scales through the effects of wind or rainfall water and could infect the inner bud tissues.…”

Section: Discussionmentioning

confidence: 99%

“…In some instances, however, summer development of apple scab can be severe even if spring disease pressure is relatively low (47). In addition, severe scab on foliage during summer may lead to greater overwintering of the asexual form of the fungus on the shoot surfaces (31,44,52) on the outer or inner bud tissues (11,31,32) or as wood lesions (40,63,65). Moreover, environmental considerations are becoming increasingly important and, as a consequence, interest has turned from conventional to integrated and organic apple production, where management practices differ from those in conventional production.…”

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confidence: 99%

Analysis of Summer Epidemic Progress of Apple Scab at Different Apple Production Systems in the Netherlands and Hungary

Holb¹,

Heijne²,

Withagen³

et al. 2005

Phytopathology®

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Holb, I. J., Heijne, B., Withagen, J. C. M., Gáll, J. M., and Jeger, M. J. 2005. Analysis of summer epidemic progress of apple scab at different apple production systems in the Netherlands and Hungary. Phytopathology 95:1001-1020. Two, 4-year studies on summer epidemic progress of apple scab were conducted at Randwijk, the Netherlands, from 1998 until 2001 and at Eperjeske, Hungary, from 2000 until 2003. Disease assessments were made on scab-susceptible cv. Jonagold. A range of nonlinear growth functions were fitted to a total of 96 disease progress curves (3 treatment classes × 2 plant parts × 2 disease measures × 4 years × 2 locations) of apple scab incidence and severity. The three-parameter logistic model gave the most consistent fit across three treatment classes in the experiment (integrated, organic-sprayed, and organic-unsprayed). Parameters estimated or calculated from the three-parameter logistic function were used to analyze disease progress. These were disease incidence and severity on the day of the first assessment (Y s ); final disease incidence or upper asymptote for incidence (Y if ) or severity (Y sf ); fruit incidence and severity on day 40, after which no new lesions on fruits appeared (Y 40 ); leaf incidence and severity on day 75, at which shoot growth stopped (Y 75 ); relative (β) and "absolute" (θ) rates of disease progress; inflection point (M); and area under the disease progress curve (AUDPC S ) standardized by the duration of the total epidemic. Comparisons among disease progress curves were made by correlation and factor analysis followed by Varimax rotation. There were large differences but high positive correlations among the parameters Y s , Y f , θ, and AUDPC S across the three treatment classes. In the factor analysis, two factors accounted for more than 85% of the total variance for both incidence and severity. Factor 1 gave an overall description of epidemic progress of both scab incidence and severity and included the parameters Y f , Y 40 , Y 75 , θ, and AUDPC S . Factor 2 identified a relationship between the relative rate parameter (β) and the inflection point (M) for severity and a relationship between disease incidence and severity. For an integrated or an organic orchard, θ, AUDPC S , and one of Y f or Y 75 (because of the link with host phenology) can characterize apple scab epidemics during summer. Based on these findings, improved scab management approaches were provided for integrated and organic apple production systems.Additional keywords: Akaike information criterion, disease management, disease warning model, epidemiology, fixed effect, nonlinear mixedeffect modeling, random effect, R language.

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“…Ascospore maturation models, usually based on degree-days, have been developed for apple scab (Gadoury and MacHardy 1982;Schwabe et al 1989;Gadoury et al 1992;Gadoury et al 2004) and European pear scab (Spotts and Cervantes 1994;Spotts et al 2000). In addition, the importance of overwintering conidia in apple scab as a primary inoculum has also received considerable attention (Becker et al 1992;Moosherr and Kennel 1995;Holb et al 2004;Holb et al 2005a). In contrast, the effects of weather conditions on overwintering of V. nashicola inoculum, whether it is as conidia or ascospores, have not been adequately studied so far and further research is needed in this area.…”

Section: Discussionmentioning

confidence: 99%

A dynamic model forecasting infection of pear leaves by conidia of Venturia nashicola and its evaluation in unsprayed orchards

Yang

Dong

et al. 2007

Eur J Plant Pathol

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A dynamic model, called VenInf, was developed to forecast infection of pear leaves by conidia of Venturia nashicola. By simulating conidial infection processes following a rain event, the model estimates % conidia that successfully infected leaves at the end of an infection period. The model is mainly derived from logistic models developed from recent laboratory and glasshouse experimental results on infection of pear seedlings to estimate the rates of infection and mortality. It simulates the conidial infection process at 5 min intervals using temperature, relative humidity (RH), surface wetness and rainfall as input. The model was evaluated against pear scab in four unsprayed orchards in China over a 4-year period. In all orchards, all significant disease increases were associated with infection periods predicted by the model. In one orchard, in 2004 the incidence of leaf infection remained very low (<3%) during the entire season despite the model forecasting several severe infection periods. Results of orchard evaluation suggest that the model is able to identify all important potential infection periods. Thus, further field studies should be carried out to determine whether and how the model can be used in practice to assist farmers in making decisions on fungicide applications.

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Overwintering of Conidia ofVenturia inaequalisin Apple Buds in New York Orchards

Cited by 34 publications

References 0 publications

Effect of six sanitation treatments on leaf litter density, ascospore production of Venturia inaequalis and scab incidence in integrated and organic apple orchards

Effect of six sanitation treatments on leaf litter density, ascospore production of Venturia inaequalis and scab incidence in integrated and organic apple orchards

Analysis of Summer Epidemic Progress of Apple Scab at Different Apple Production Systems in the Netherlands and Hungary

A dynamic model forecasting infection of pear leaves by conidia of Venturia nashicola and its evaluation in unsprayed orchards

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