I'm seeing an unusual orange slime on my Frontenac Wine Grapes. I recently pruned the grape vines and I'm getting the usual bleeding of clear liquid from the cuts. Now I have a Orange colored slime forming on the vines from the cut areas. It is on 2 of my Frontenac Wine Grapes. I have not seen any similar problem on other wine grapes or Concord grapes in my vineyard. Only spraying has been Daconil about 2 weeks ago. Question is what to do; nothing, wash it off with a soft brush and mild soap, spray with a different fungicide, or? Thanks for the help, Harry.
Cecil County Maryland
Hi - What you are seeing here is the result of yeast colonizing the sap flow. The yeast is feeding on the sugar. This article from Ohio State University describes this phenomena and shows several examples that look similar to yours. https://bygl.osu.edu/node/1233
There is really nothing you need to do about it. It is not pathogenic to the plant. No fungicide is needed. It can look alarming, but there is nothing you need to do.
Pruning of grapes is recommended in March. The heavy sap flow from fresh pruning cuts will not weaken or damage your canes.