Evaluation of adjuvants for enhanced management of Podosphaera xanthii using potassium silicate and biocontrol agents |
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| Affiliation: | 1. Department of Geography, Environmental Management & Energy Studies, University of Johannesburg, P. O. Box 425, Auckland Park 2006, South Africa;2. Discipline of Plant Pathology, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa;1. CNRS, UMR 6553 Ecobio, Université Rennes 1, Campus de Beaulieu, 35042 Rennes, France;2. CNRS, UMR 6554 LETG, Université Rennes 2, Campus de Villejean, 35043 Rennes, France;1. Mycological Department, National Museum, Cirkusová 1740, Praha 9, Czech Republic;2. Department of Ecosystems Biology, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, Czech Republic;1. Department of Geography, University Toulouse II, GEODE UMR 5602 CNRS, France;2. Institut d''Etudes Politiques (IEP), Toulouse, France;3. Institut de Recherche pour le Développement (IRD), Vientiane, Lao People''s Democratic Republic;4. National Agriculture and Forestry Research Institute (NAFRI), Vientiane, Lao People''s Democratic Republic;5. Géosciences Environnement Toulouse (GET), UMR 5563 CNRS, France |
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| Abstract: | Three adjuvants [polyether-polymethylsiloxane-copolymer (Break-Thru®), alkoxylated fatty alkylamine polymer/ethoxylated sorbitane ester (Partner 650®) and polyoxyethylene 20 sorbitan monooleate (Tween-80®)] were compared for their ability to improve the efficacy of potassium silicate and biocontrol agents (BCAs) against powdery mildew of zucchini caused by Podosphaera xanthii (Castagne) U. Braun & Shishkoff. The most effective adjuvant was investigated for its direct impact on the pathogen and deposition of BCAs using electron microscopy and its compatibility with the BCAs and zucchini plant was evaluated to establish an integrated management of powdery mildew. Furthermore, effects of Si spray in accumulation of Si and K in the leaves were measured. Break-Thru® and Partner 650® improved the efficacy of silicate by 18–35%. The best adjuvant, Break-Thru®, caused a collapse and degeneration of the conidia and hyphae of the pathogen, restricted growth and spread of the powdery mildew colonies by binding its propagative structures, and improved deposition of BCAs on the leaf surface and the fungus. Break-Thru® was compatible with the plant and the BCAs at concentrations <0.4 ml l−1, and can be used with selected BCAs and SiO2 for an integrated management of powdery mildew. SiO2 applied as a foliar spray increased the level of Si in zucchini leaves, which may contribute to systemic resistance of the plant against the disease. |
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