Abstract

                                Grapevine downy mildew caused by Plasmopara viticola is an explosivedisease that causes severe damage to leaf, flowers and fruits of the vine.In the present study, an epidemiological model was developed to supportthe vine-growers to reduce the number of fungicidal sprays and protect theenvironmental hazards besides saving the input cost. To record the weatherdata, an automatic weather station was installed at Mathampatti Village,Coimbatore, India and the weather parameters such as relative humidity,minimum, maximum and night temperatures, rainfall, leaf wetness, dew fall,solar radiation etc., were recorded at once in a 10 minutes interval during2014-17. A logistic equation was designed based on the biological data(disease incidence, weather parameter and crop age) and its mathematicalanalysis was shown in this paper. The critical weather parameters werestudied using logistic equation with the support of “Curve expert programme”.The mode described the development of the infection and infection ratethrough computation-based analysis. The Decision Support Systems (DSS)were arrived using the disease progress curve obtained from the logisticequation. The DSS indicates the first two sprays during the congenial phaseof the disease from 25 to 45 Days After Pruning (DAP). Then the secondphase, ie rapid growth stage was termed as ‘Exponential phase’, in which twosprays on 55 and 65 DAP (flowering and fruiting stage) were carried out. Inthe final plateau phase (66 DAP to till harvest), the management strategiesapplied would not be cost-effective and no spray was recommended. Thefield experiment was carried out using the findings of the logistic equationwith different management modules for validation. The number of spraysof fungicide was reduced from 15 to 5 times in the logistic equation-basedtreated plot.

Key words : Grapevine downy mildew, logistic model, weather index,azoxystrobin