On the previous post, I mentioned that “At this time of the season, what we typically recommend is either mancozeb or captan mixed with sulfur to protect young shoots and leaves.  The reason why I typically do not recommend a use of newer materials such as Revus or Phosphite for downy or Luna or Rally for powdery is because we want to keep it for the critical time for cluster infection, which is from bloom to 4-5 weeks after bloom.”

However, it looks like at out site, the downy mildew pathogen is taking advantage of the weather conditions.  Although our last application of mancozeb and sulfur was only 6 days ago, I noticed that some of older leaves show symptoms of downy mildew (i.e., the infection might have happened prior to the previous application).  At this point, many of leaves look like the first picture, and disease incidence is probably less than 0.5%, thus, it is difficult to find them; however, we came across with a few leaves with clear symptoms as in the second picture.

Thus, I will probably add a phosphite material (Prophyt, Phostrol, etc.) to next round of fungicide application in this week to stop further spread of the disease.  Based on the look on the clusters and warm weather in the forecast, we are speculating that bloom for our Chardonnay will happen in 10-14 days from now.