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Efficacy of a Magnolia officinalis bark extract against grapevine downy mildew and apple scab under controlled and field conditions

Thuerig, Barbara; Ramseyer, Justine; Hamburger, Matthias; Ludwig, Mathias; Oberhänsli, Thomas; Potterat, Olivier; Schärer, Hans-Jakob and Tamm, Lucius (2018) Efficacy of a Magnolia officinalis bark extract against grapevine downy mildew and apple scab under controlled and field conditions. Crop Protection, 114, pp. 97-105.

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Online at: https://www.sciencedirect.com/science/article/pii/S0261219418302151

Summary

In organic agriculture, the control of several diseases is largely depending on copper fungicides. Yet, copper can accumulate in the soil if the annual input exceeds annual uptake by plants, which can have a negative impact on soil fertility. Its use should thus be avoided or reduced. The aim of the present study was to evaluate the efficacy of a bark extract of Magnolia officinalis Rehder and Wilson to control three pathogens including Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni (causing grapevine downy mildew), Venturia inaequalis (Cooke) G. Winter (causing apple scab), and Phytophthora infestans (Mont.) De Bary (causing potato and tomato late blight) under controlled and field conditions, and to identify compounds responsible for the antifungal activity of the extract. Under controlled conditions, M. officinalis bark extract showed a mean efficacy of 97% (P. viticola) and 93% (V. inaequalis) at 1 mg mL−1, and EC50 between 0.14 and 0.20 mg mL−1. Efficacy against P. infestans was comparatively low (52% at 1 mg mL−1). Magnolol and honokiol were identified as the main active compounds, both with EC50 ≤ 0.08 mg mL−1 against P. viticola and V. inaequalis. Under field conditions, preliminary formulations reached efficacies up to 71% at 1–2 mg plant extract mL−1 against grapevine downy mildew, whereas activity against apple scab could not be confirmed. Magnolia officinalis is a promising candidate for the development of a sustainable plant protection product against grapevine downy mildew due to a combination of good efficacy, high availability of the raw material at affordable prices, reasonable extraction efficiency, and expected low human toxicity due to its longstanding use in traditional Chinese medicine.


EPrint Type:Journal paper
Keywords:Plant extract, Fungicide, Botanical plant protection product, Honokiol, Magnolol, Magnolia officinalis, Department of Crop Sciences, Crop Protection, pathology
Subjects: Crop husbandry > Crop health, quality, protection
Crop husbandry > Production systems > Fruit and berries > Viticulture
Research affiliation: Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Plant Protection and Biodiversity
Deposited By: Thürig, Dr. Barbara
ID Code:33740
Deposited On:05 Sep 2018 13:26
Last Modified:05 Sep 2018 13:26
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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