Fern Liquid Manure is a resinous-scented liquid manure made from fern (Polystichium filix-mas) which French consultant Michel Barbaud claims can discourage attacks from grape berry moths and the leaf hopper vector of the Flavescence Dorée (grapevine yellows) phytoplasma disease, especially when used in conjunction with essential oils. Barbaud’s method is to soak 15kg of dried fern in 1,000 litres of cold water which is left outside to warm under the sun for around 4 days if it is to be sprayed on the vines and up to 10 days if it is to be sprayed on the soil. For each hectolitre of fern liquid manure Barbaud says to add 50 ml of essential oil of fennel (a well-known insect repellent for home gardeners) if spraying before véraison, or 20 ml of essential oil of garlic if spraying after véraison, although this latter strategy may, depending on picking date, impart a negative taste to the wine. See plant-based sprays.