Development and evaluation of a warning model for the optimal use of copper in organic viticulture.
Downy mildew caused by Plasmopara viticola is one of the most serious diseases affecting grapevine worldwide, and can significantly affect crop quality and quantity. In organic viticulture, downy mildew control is mainly based on copper compounds, which are toxic to organisms in the soil. For this reason, restrictions concerning the maximum amount of copper that organic growers can apply per hectare have been enacted in several countries. We have developed a warning model and a decision-making procedure to help organic grapevine growers optimize their use of copper against downy mildew. This system is based on treating vines with a variable rate of copper when there is an immediate risk of infection and the vegetation is not sufficiently protected by previous treatments. In 2007, the warning model and the decision-making procedure were tested in two vineyards in northern Italy and compared with the local common practice and an untreated control. The treatment timings and copper application rates recommended by the system resulted in control of downy mildew equivalent to that associated with the common practice, but with a considerable reduction in the total amount of copper applied.
Modelling leaf wetness duration and downy mildew simulation on grapevine in Italy
Abstract Leaf wetness duration (LWD) is one of the most critical variables involved in the development of plant diseases. Many pathogens require the presence of free water on plant organs to move and to start their infective processes. For this reason LWD is extremely significant in the management of crop protection activities and in particular, the successful use of weather-related disease forecasting models. Their operational application is a very important tool for reducing fungicide applications, for environmental safeguarding in high quality production systems, and for reducing the waste of resources and financial losses. Despite the relevance of LWD, no standard has yet been accepted for its measurement. For this reason the use of simulation models, based on agrometeorological variables, represents a valuable alternative to field monitoring. In this work a physical model based on the energy balance was applied for the simulation of LWD on a grapevine ( Vitis vinifera ). The model, developed in the United States on the cultivars Chardonnay and Concord, and in Australia on Cabernet Franc, was applied for the Sangiovese variety and was adapted for use with agrometeorological data easily available from standard weather stations. The model outputs were compared both with data measured by sensors in the 1995–2003 period and with visual inspections of LWD conducted on vines during 2003. Following, simulated and recorded LWD data were used as input by a model for the simulation of grapevine downy mildew ( Plasmopara viticola ) and the results were compared with observed data in order to establish the impact of different LWD data on the quality of model simulations.
Net radiation model evaluation at an hourly time step for mediterranean conditions
A study was performed to evaluate a model for computing net radiation over grass canopies located in Talca (Chile) and Avignon (France). In both locations, an automatic meteorological station was installed over a grass main- tained in reference conditions to measure net radiation, solar radiation, air temperature and air vapour pressure on a hourly basis. Results indicated that there was a good correlation between measured (Rno) and estimated (Rne) values of net radiation, with a correlation coefficient greater than 0.95 for both locations. Major disagreements were observed during the night time, but they did not affect the final calculation of net radiation. This analysis suggest that the model could be used in the Penman-Monteith equation to compute crop water requirement in Avignon and Talca, using net- work measurements for the evaluation of net radiation.