In order to avoid chemical pesticide treatments, we are working hard to avoid copper, and even sulphur. This is very important in order to achieve healthy grapes without harmful products that can affect to the correct development of native saccharomyces cerevisiae yeast (and weird collateral fermentations done by other yeast, like dekkera).
Oidium is usually explained as a fungal spore, which is the offspring body of a fungus, or as a fungi itself of the Ascomycota family. It is more commonly known as powdery mildew due to its parasitic nature that exists as a soft film on the surface of host plants such as grape vines. Mildew odium can have a devastating effect on wine crops, and it is known to have contributed to the near collapse of the wine industry in Europe in the mid 19th century.
It starts with this oil like stains, when temperature and humidity are relatively high.
In order to have no aggressive treatments, but looking for maintain our vines healthy and odium free, we are working with biodinamyc and using raw milk instead of copper and sulfur. Just milk diluted at 10% and mineral water sprayed on levees, grapes and wood at the afternoon (to avoid young leaves burning). It works.
Is usual in order to increase protection effects, mix it with biodynamic preparations like Horsetail, or others mix with liquid manures. But we have started to work just with milk to see the especific effects. By spraying every 15 days since 4th leaf to verasion we see perfectly healthy vines, extra green leafs (because milk protein) and a vineyard in equilibrium, with insects living its wars in peace.
Milk is working nicely!