Efficacy of an extract of the medulla of Juncus effusus on grapevine and apple plants against Plasmopara viticola and Venturia inaequalis, and identification of the main active compound

BACKGROUND
There is growing demand to replace chemical pesticides with alternatives owing to concerns related to impacts on human health and the environment. Plant-derived plant protection products could provide sustainable and environmentally friendly alternatives to chemical products. The aim of this study was to identify plant and fungal extracts with so far unknown activity against important plant pathogens by in vitro screening of a library of more than 3000 extracts.
RESULTS
Several plant extracts with promising in vitro fungicidal activity (MIC100 ≤ 50 µg mL−1) towards one or several of the investigated pathogens (Venturia ineaqualis, Phytophthora infestans, Plasmopara viticola) were identified by the screening. One of the hits, an ethyl acetate extract of Juncus effusus L. medulla, was further investigated, and dehydroeffusol (DHEF) was identified as its main active constituent. On susceptible grapevine and apple seedlings, efficacies of up to 100% were reached with the extract (EC50 123 or 156 µg mL−1) and with DHEF (EC50 18 or 21 µg mL−1) against P. viticola and V. inaequalis respectively.
CONCLUSIONS
Our results demonstrate that plants can provide promising alternatives for integrated and organic farming. J. effusus shows high efficacy at low concentrations and, as an abundant perennial species, is an interesting candidate for the development of a novel plant protection product. © 2015 Society of Chemical Industry