Development and evaluation of a model for management of brown rot in organic apple orchards

Abstract

Temporal development of brown rot (Monilinia fructigena) on fruits was analysed in two organic apple orchards on three apple cultivars in Eastern Hungary from 2002 to 2006. The threeparameter logistic function gave the best fit to brown rot over four non-linear growth functions in all cultivars, years and orchards. Depending on location, year and cultivar, disease increased continuously from 6 to 8 weeks before harvest up to harvest, reaching 19-37% of disease incidence. Disease variables of Y f , the final disease incidence; β, relative rate of disease progress; AUDPC S , standardized area under disease progress curve; T 1.5 , the time when disease incidence reaches 1.5% (day), and M, the inflection point were derived from the three-parameter logistic function. The disease variables of Y f , β, and AUDPC S were used in a computer simulation for predicting temporal brown rot development, and the disease variables of T 1.5 , M, and Y f were used to determine threshold values for epidemic intensity. Afterwards these were used to construct a fundamental model for developing a brown rot forecasting and management strategy (BRFMS). The fundamental model contained four parts: i) data insertion and analyses by computer simulation of pathogen submodels, ii) calculation of yield loss threshold levels based on disease incidence, iii) determination of epidemic intensity levels and iv) a decision module with suggestions for disease management practices for each epidemic intensity level. The fundamental model was supplemented with the prediction of occurrence of the first fruit rot symptoms and with the insect injury prediction related to brown rot development in order to complete a BRFMS for organic apple orchards. In a 3-year field evaluation from 2006 to 2008, season-long application of BRFMS treatments reduced the number of sprays against brown rot by 22-33% compared with the treatments of general spray schedules against brown rot.

Fruit injury in organic fruit production and its relationship to brown rot caused by Monilinia spp.

“…Seeing high brown rot incidence level at harvest, an improtant task is to further improve both insect and frungal disease managements in organic fruit production. A succesful example of this was a development of brown rot management strategy in organic apple production by Holb et al (2011).…”

Disease warning models for brown rot fungi of fruit crops

“…• check reference of historical weather to decide if fungicide application is needed; • and spray fungicide immediately. In a more recent study Holb et al (2011) prepared a brown rot forecasting disease management strategy for M. fructigena for organic apple orchard. In this five-year-study, temporal development of brown rot on fruits was analysed in two organic apple orchards.…”

Spore dispersal, diurnal pattern and viability of Monilinia spp. conidia and the relationship with weather components in an organic apple orchard

“…Insect dispersal of conidia has also been an importamt factor from one fruit to another (Croxall et al, 1951;Lack, 1989). Studies demonstrated a low aerial concentration of M. fructigena in integrated apple orchards (Van Leeuwen et al, 2000;Xu et al, 2001;Holb, 2008b) while in organic apple orchards high conidial concentration were recorded (Holb, 2008b;Holb et al, 2011). Previous studies showed that viability of trapped conidia was 60 % (Holb, 2008b).…”