Evaluation of biofungicides for management of powdery and downy mildew in grape production

Project Code BPI09-080

Project Lead

Dr. Peter Sholberg - Agriculture and Agri-Food Canada

Objective

To compare the efficacy of stand-alone applications of Regalia SC (5% active ingredient) and Regalia Max (20% active ingredient) for the control of fungal diseases, Powdery mildew (Uncinula necator) and Downy mildew (Plasmopara viticola) on grapes

Summary of Results

Grapevines belong to the genus,Vitis (Vitacaea) with V. vinifera being the most economically important of about 60 species. Numerous fungal pathogens including Downy mildew (Plasmopara viticola) and Powdery mildew (Uncinula necator) impact the yield and quality of berries. Powdery mildew attacks all aerial plant parts making whitish or greenish-white powdery patches on leaves which become mottled or distorted, as well as curled and withered. Infected blossoms dry up and/or fail to set fruit, while berries develop a netlike pattern of russet, may crack open, dry up, or drop from the cluster. Downy mildew attacks canes, leaf petioles and tendrils where it causes discoloration and depression of the tissues. Powdery mildew, grey mold and other post-harvest rots are the main diseases associated with the production of wine grapes in British Colombia. In 2009, six different reduced risk materials were tested in a mature vineyard for their efficacy in managing these diseases. Results were assessed in comparison with a conventional standard treatment regimen involving Nova, Flint, Sorvan, Elevate, and Vanguard.

This trial identified MilStop and MilStop/PureSpray as effective materials for the control of grape powdery mildew and Regalia SC as effective for the control of post-harvest rots.

Regalia Max and Regalia SC were not effective on foliar powdery mildew but reduced its severity on fruit. Regalia Max reduced severity of grey mold and blue mold. Regalia SC reduced the severity of grey mold and there was a significantly lower incidence and severity of "raisining". It was also effective at controlling the severity of blue mold to a level comparable to the standard program. In addition, the Regalia SC-treated clusters had a significantly lesser amount of mold on the rachis. This indicates that applications of Regalia SC and Regalia Max should target grey mold and rots more so than powdery mildew.

MilStop and MilStop/PureSpray effectively controlled powdery mildew on foliage early in the growing season. The addition of 0.5% PureSpray oil was necessary to improve the effectiveness of MilStop to a level comparable to the one obtained with the standard program in September for foliar powdery mildew. There was a reduction in the incidence of fruit powdery mildew in September for MilStop/PureSpray and both MilStop and MilStop/PureSpray were effective at controlling symptoms by harvest. Both were effective at reducing the severity of powdery mildew on fruit over the growing season.

MilStop and MilStop/PureSpray Oil effectively reduced severity of grey mold and incidence of blue mold. Even though both MilStop and MilStop/PureSpray were effective on powdery mildew, the berries were significantly lower in weight than the ones treated with the standard program. This may be associated with the damage from the phytotoxicity effect which impaired berry growth. MilStop and MilStop with 0.5% PureSpray Oil are effective for the control of grape powdery mildew.Testing to prevent damage to the surface of the fruit with rates lowered post-bloom, as well as alternation with other materials should be undertaken to address this observation.

There was no significant difference in any of the juice quality parameters of the materials tested compared to the standard program indicating that none of the materials tested are likely to be detrimental to wine making.

The information developed in this project has been shared with the registrants of the tested products and the Pesticide Risk Reduction Program will be able to take advantage of any label expansion opportunities through the program's biopesticides regulatory support. Priorities for this biopesticides regulatory support are selected by Canadian growers during the annual Biopesticides Priority Setting workshop.

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