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

Abstract

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.

Occurrence of Venturia inaequalis races in Poland able to overcome specific apple scab resistance genes

“…This may be associated with the various efficacy of fungicides recommended for both systems. In general, copper and sulphur products are less effective against apple scab than synthetic products used in IPM systems (Holb et al 2005). Holb (2007) confirmed that the same cultivar can show different reactions depending on the performance of the orchard system.…”

Management of Apple Scab and Powdery Mildew Using Bicarbonate Salts and Other Alternative Organic Products with Fungicide Effect in Apple Cultivars

“…The number of annual necessary treatments against these diseases is depending on weather conditions, disease pressure and cultivar susceptibility (Holb et al, 2005). The monthly and annual mean values of temperature during 2014-2016 presented in the Fig.…”

“…Most commercial apple grown cultivars are very sensitive to scab, so that in an commercial apple orchard, very frequent fungicide applications (15-22 annually) are applied in order to control apple scab, depending on weather conditions, disease pressure and cultivar susceptibility (Holb et al, 2005).…”

Disease Decision Support Systems: Their Impact on Disease Management and Durability of Fungicide Effectiveness

“…Much less attention has been paid to secondary infections, mainly because they are often assumed to depend largely on primary infections (Carisse et al, 2009;Holb et al, 2005). In the absence of management tools for summer scab, however, risk-averse growers may apply fungicides regularly, potentially resulting in an additional 6 to 8 sprays, whereas growers who are convinced that they have achieved adequate primary infection control may not spray enough during the summer, potentially resulting in yield losses (Holb et al, 2003;Holb et al, 2005;MacHardy, 1996). Nevertheless, despite the large amount of research that has been done on apple scab, the disease is still one of the most destructive and economically important disease in several apple production areas.…”

“…Nevertheless, despite the large amount of research that has been done on apple scab, the disease is still one of the most destructive and economically important disease in several apple production areas. Scab management may require 6 to 16 sprays annually depending on disease pressure, cultivar susceptibility, weather conditions, and marketing objectives (Reardon et al, 2005, Van der Sheer, 1992, Holb et al, 2005. Intensive use of fungicide in apple production has led to unstable control as fungicide resistance arose.…”