Grapevine & Wine 02/04/2012

Natural extracts against downy mildew

The Institut Français de la Vigne et du Vin is testing the antigerminative, preventive and healing activities of some natural extracts such as artemisia, equisetum, willow cortex and absinthe

From 2010 the Institut Français de la Vigne et du Vin (Ifv) is testing the properties of some natural extracts from plants (pnpp) against downy mildew.

In the context of a more sustainable agriculture and a more eco-friendly approach to the phytosanitary problem, it is important to determine and understand different and natural approaches to these problems.

The research program is called “4P” and employs hydro-alcoholic solutions of compounds deriving from plants. Data from the Perignan University demonstrated the extraction of plant metabolites (in particular polyphenols and phytoalexins) by means of simple water solutions to be ineffective.

In 2011, Ifv research projects concentrated on the use of four essences: artemisia, equisetum, willow cortex and absinthe. Treatments were tested at 0.5 and 1 % concentrations.

By now all the testing were performed in vitro, i.e. on leaves or portion of leaves infected by downy mildew. In the case of precautionary treatment, leaves were exposed to these molecules for 12 hours before the downy mildew inoculation. In the germination test, the efficacy of the treatment was tested on zoospores and cysts; in healing tests they were tested on the sporeling, instead. All the leaves used were from a Merlot vine.

These tests showed the very limited efficacy of the healing approach, since the propagation of spores was not impaired by the treatment. Willow cortex and absinthe demonstrated some efficacy just with very minor infection cases.

On the other hand, preliminary results showed the strong efficiency of the precautionary treatment in preventing germination. This was especially true for absinthe, willow cortex and equisetum. However, according to the principal investigator Nicolas Aveline, the results are still ambiguous since they show very high standard deviations, i.e. they show a very high variability from trial to trial.

di Graziano Alderighi