Some unusual orange-colored growths have been noticed recently on pruning wounds in local vineyards. These appear as oozing clumps that can cover an entire spur and stain the cordon with their bright orange residue.

Figure 1. Orange Slime growing on pruning wounds of Sauvignon Blanc in early April 2011 in Santa Barbara County.

These Orange Slime growths consist of one or more fungi that subsist on the sap that is exuding from the pruning wounds. The fungi are generally not thought to be harmful to the vine, as they are growing on the nutrients contained in the sap. The Orange Slime seems to be more prevalent here in wetter winters; it was also observed in March and April of 2011 on the tail end of that relatively wet winter. The combination of wet soil conditions and late pruning can lead to copious amounts of sap bleeding from the pruning wounds, which combined with warm weather creates the ideal conditions to support heavy Orange Slime growth. Similar fungal growths are observed on grape pruning wounds in the eastern USA as well, as well as on other trees and vines.

Figure 2. The Orange Slime can cover the entire spur and drip onto the ground leaving an orange puddle.