Effect of temperature and wetness duration on infection by Plasmopara viticola and on post-inoculation efficacy of copper
2016
Caffi, Tito | Legler, Sara Elisabetta | González-Domínguez, Elisa | Rossi, Vittorio
A weather-driven model was developed to predict P. viticola population dynamics on grape leaf surfaces during a discrete wet period. To develop this model, the relationships between temperature, wetness duration, zoospore release, and infection were investigated with environmentally controlled experiments, and equations were developed that fitted the experimental data. Release of P. viticola zoospores from sporangia and infection occurred over a wide range of temperatures, but were highest at 15–20 °C. At these temperatures, zoospore began to be released within 1 h after inoculation, and most infections had already occurred by 3 h after inoculation. β-Gompertz and Weibull equations were used to describe zoospore release and infection, respectively. The post-inoculation efficacy (PIE) of two cooper fungicides was also evaluated. For both fungicides PIE decreased rapidly as application time after inoculation increased, and was < 20 % after 6 h at the optimal temperature for P. viticola development (20 °C). The model proposed here can be used to improve the weather-based models that have been developed for simulating secondary cycles of downy mildew. The model can also be used to predict whether a fungicide application during a discrete infection period will be effective. PIE values for the two copper fungicides were positively correlated with the proportion of P. viticola sporangia on a leaf that had not yet caused infection. Model simulations suggested that the efficacy of a copper treatment increased when these scenarios were less conductive for disease development.
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