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Petria - “Dosi ridotte di rame e prodotti alternativi per la difesa antiperonosporica”Observations on the effectiveness of reduced rates of copper and alternativecompounds against downy mildew on grapevine, and on the rain fastness ofcopper derivativesFive trials were conducted in 2007-2009 to evaluate the effectiveness of theuse of reduced rates of copper and alternative compounds against downy mildew ongrapevine, four under controlled conditions (Trials A, B, D and E) and one in the field(Trial C). The trials were also aimed at evaluating the residual effectiveness of copperderivatives and the copper concentrations in leaves and in run-off water after artificialrainfall (10, 20 and 40 mm).In Trial A, where a mean value of 56% infected leaves was recorded onuntreated plants, the highest protection levels (Abbott’s index ~94%) were obtainedwith a formulate of copper sulphate pentahydrate that although applied at its highestlabel rate, allowed the use of the lowest amount of copper (120 g/ha of metalliccopper). Similar effectiveness levels were reached with dicopper oxide (Abbott’s index~92%), but with metallic copper rates equivalent to 1125 and 787.5 g/ha. A significantreduction in infections was also achieved with two formulations of Bordeaux mixture,as compared to the untreated control, but only when applied at the highest rates (2000and 2400 g/ha of metallic copper). Infection values that were not statistically differentfrom the untreated control were seen with tribasic copper sulphate (304, 532 and 760g/ha of metallic copper) and with a mixture of rock powder and propolis. After anartificial rainfall equivalent to 10 mm (Trial B), the percentage reductions of coppercontent in the leaves ranged from 8% (tribasic copper sulphate, 200 g/ha of metalliccopper) to 52% (Bordeaux mixture, 2000 g/ha of metallic copper). The statisticalanalysis did not show any influence of the effects of the rate on the percentage reductionin copper in the leaves after the artificial rainfall of 10 mm. Copper concentrationsin the run-off water were always lower than 0.22 mg/kg, except with treatment withBordeaux mixture (2400 g/ha of metallic copper), where a concentration of 1.4 mg/kgwas recorded.In the field trial (Trial C), in untreated control plots, symptoms were observedon 49% of leaves, and almost all of the bunches showed brown rot symptoms. Copperhydroxide applied at either 587.5 or 375 g/ha of metallic copper provided a significantreduction in the infections, as compared to the untreated control, with no appreciabledifferences between the two rates tested. Orto-silicon acid and bentotamnio were noteffective. The high effectiveness of copper hydroxide observed in the field trials wasconfirmed under the controlled conditions (Trial D). With 29% infected leaves on theuntreated control vines, copper hydroxide yielded values of Abbott’s index of 92%,95% and 100% at the rates of 260, 455 and 650 g/ha of metallic copper, respectively.The effectiveness of copper sulphate pentahydrate and dicopper oxide (120 and 1125g/ha of metallic copper, respectively) was confirmed, with Abbott’s index values of83% and 95%, respectively. On the plants treated with copper hydroxide (455 and 650g/ha of metallic copper) or dicopper oxide (1125 g/ha metallic copper), the percentageof infected leaves was always significantly lower than in the untreated control, even15
Petria 20 (1), 1-72 (2010) – Atti Convegno - Ancona, 26 Febbraio/February 2010after an artificial rainfall equivalent to 40 mm. Copper hydroxide (260 g/ha metalliccopper), copper oxychloride (375 g/ha), Bordeaux mixture (2400 g/ha) and coppersulphate pentahydrate (120 g/ha) maintained their effectiveness even after 20 mm ofartificial rainfall. Residual copper concentrations in leaves and run-off water appearedto be directly related to amounts of copper applied. Significant percentage reductionsin copper concentrations in leaves were seen only after an artificial rainfall equivalentto 40 mm (Trial E).The trials showed that under controlled conditions, it was possible to obtainsatisfactory disease control even with rates of metallic copper equivalent to 120 g/ha(copper sulphate pentahydrate), 260 and 455 g/ha (copper hydroxide) and 1125 g/ha(dicopper oxide). Copper hydroxide proved to be effective also in the field trial, atrates of metallic copper of 375 and 587.5 g/ha. In Trial A, however, copper hydroxideat 269 and 455 g/ha (metallic copper) did not provide any significant reductions ininfections, confirming some of the inconstant results previously seen (Dongiovanni etal., 2006, 2008). All of the tested copper compounds provided significant reductionsin the percentage of infected leaves, even after artificial rainfalls equivalent to 10 and20 mm. In the trials discussed here, the compounds used as possible alternatives tocopper derivatives did not show any effectiveness against downy mildew.Key words: Copper, Downy mildew, Grapevine, Rain fastness.RingraziamentiSi ringrazia la Regione Marche per il progetto “Valutazione dell’efficacia contro Plasmoparaviticola di composti rameici utilizzati a dosi ridotte in viticoltura biologica e valutazione di prodottialternativi”.Lavori citati/ReferencesDongiovanni C., G. Tauro, C. Giampaolo, A. Santomauro, F. Faretra, 2006.Valutazioni su dosi ridotte di rame e nuovi fungicidi nella protezione dellavite dalla peronospora in Puglia. Atti Giornate Fitopatologiche, 2, 187-192.Dongiovanni C., C. Giampaolo, M. Di Carolo, A. Gasparre, N. Masiello, A.Santomauro, F. Faretra, 2008. Attività antiperonosporica di dosi ridotte dirame e di sostanze alternative in vigneti dell’Italia meridionale. Atti GiornateFitopatologiche, 2, 315-320.16
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