FUNGICIDAS DE EFEITOS FISIOLÓGICOS NO CONTROLE DO MÍLDIO E NO DESENVOLVIMENTO DE MUDAS DE VIDEIRA

Abstract

This study objective was to evaluate downy mildew control and the physiological effects on vine cuttings cv. Isabel Precoce inoculated by a pathogen with distinct fungicides under protected environment. Such experiment was carried out in the period of 2014-15, at an experimental area at the Phytopathology laboratory of Agronomy Department at West Central State University, in the city of Guarapuava, PR. Treatments evaluations were as follow: 1 – control (H2O); 2 – control (H2O) and pathogen inoculation; 3 – Buscalid (75 g ha-1); 4 – pyraclostrobin) 100 g ha-1); 5 – Buscalid (100 g ha-1) plus kresoxim-methyl (50 g ha-1); 6 - metiram (1100 g ha-1) plus pyraclostrobine (100 g ha-1). The first application occurred 45 days after pruning seedlings and thereafter at 15 days interval totaling four applications. The experimental design was entirely causal with four repetition treatments. To evaluate disease control, measurements were carried out every two days for downy mildew incidence and control on vine cuttings cv. Isabel Precoce right after the first leaves symptoms surge under pathogen infections conditions. Eighteen evaluations were carried out for disease severity through a multivariate and discriminant statistical analyses. Progress curves for the incidence and severity of each treatment were plotted and compared through epidemiologic variables of time in order to get a maximum incidence value and disease severity as well as all areas below the progress curve (ABPC). Discriminant analysis allowed the selection of ten types of severity evaluations which allowed six types of treatments and formed three distinct groups. Use of distinct fungicides caused a reduction at the area under the progress curve for disease incidence (AUPCDI) as well at the area under the incidence curve for disease severity (AUICDS) at the inoculated control. Boscalid, boscalid + kresoxim-methyl, pyraclostrobin and metiram + pyraclostrobin values were reduced to 73.6%, 65.3%, 79.3% e 96.2% for AUPCDI and 43.5%, 60.0%, 39.5% e 86.7% for AUICDS, respectively, in relation to the inoculated control. Significant differences were found in relation to temporal epidemiological variables. Principal component analysis (PCA) identified and classified in three distinct groups whose treatments were used for Plasmopara viticola control on vine cuttings cv. Isabel Precoce. Fungicide metiram + pyraclostrobin was the best choice as a treatment to control downy mildew on vine cuttings cv. Isabel Precoce, followed by boscalid plus kresoxim-methyl. To evaluate physiological effects upon cv. Isabel Precoce vine cutting growth sixteen physical properties were measured and evaluated. Multivariate, hierarchical grouping (HG) and ACP were used for data analyzes. With only two principal components, it was possible to determine 89.72% of data variance, accordingly to the suggested model. Multivariate analyses, Cluster and PCA were able to identify and classify all used treatments, showing that vine cv. Isabel Precoce had better growth results after the use of metiram plus pyraclostrobin followed by boscalid, boscalid plus kresoxim-methyl and pyraclostrobin.