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Circular leaf spot (CLS), caused by Plurivorosphaerella nawae , is a serious disease affecting persimmon ( Diospyros kaki ) that is characterized by necrotic lesions on leaves, defoliation, and fruit drop. Under Mediterranean conditions, P. nawae forms pseudothecia in the leaf litter in winter, and ascospores are released in spring, infecting susceptible leaves. Persimmon growers are advised to apply fungicides for CLS control during the period of inoculum availability, which was previously defined based on ascospore counts under the microscope. A model of inoculum availability of P. nawae was developed and evaluated as an alternative to ascospore counts. Leaf litter samples were collected weekly in L'Alcúdia (Spain) from 2010 to 2015. Leaves were soaked and placed in a wind tunnel, and the released ascospores of P. nawae were counted. Hierarchical Bayesian beta regression methods were used to model the dynamics of ascospore production in the leaf litter. The selected model included accumulated degree-days (ADDs) and ADDs taking into account the vapor pressure deficit (ADDvpd) as fixed effects and year as random effect. This model had a mean absolute error of 0.042 and a root mean square error of 0.062. The beta regression model was evaluated in four orchards from 2010 to 2015. Higher accuracy was obtained at the beginning and the end of the ascospore production period, which are the events of interest to schedule fungicide sprays for CLS control in Spain. This same modeling framework can be extended to other fungal plant pathogens whose inoculum dynamics are expressed as proportion data.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Alternaria brown spot (ABS) is a serious fungal disease of mandarin in the Mediterranean Basin. Due to the rigorous fruit quality standards, models for ABS should avoid false negatives. Experiments were conducted with susceptible 'Fortune' and 'Nova' inoculated at different temperatures and leaf wetness durations, including interrupted periods. Effects of temperature and time elapsed after inoculation were also studied. Disease incidence data were fitted to generalized additive models and a generic infection model. Exposure of trap plants in affected orchards was used for model evaluation, including the Alter-Rater and a simple rule system (SRS). The predictive ability of the models was analyzed using the partial area under the receiver operating characteristic curve in the high-sensitivity range between 0.9 and 1. Postinoculation temperature had a significant effect on disease incidence, with maximum symptom expression after 30 h on Fortune and 60 h on Nova. ABS incidence did not increase after a leaf wetness interruption of 1 h on Nova and 2 h on Fortune. All the models evaluated had high false-positive rates on Fortune. Only the SRS showed a substantial strength of agreement in Nova, with a true-positive rate of 0.93 and false-positive rate of 0.16.