Bright blue substance on vines?

On Jan. 19, I was a short way along the Overlook Trail at Welton's Gorge and noticed some cut branches (vines?) that had a very bright blue sap-like substance coming out of the cut ends. The blue certainly doesn’t look natural color-wise, so I wouldn't be surprised if it is some sort of treatment. Thanks for any information you can share!

Occasionally, Natural Resource Management controls grapevines that pose a threat to some of the park’s more mature and valuable wildlife trees (like oaks). Normally, we do not control these grapevines because they are valuable in their own ways; they provide nesting material for many songbirds, and of course food and habitat for wildlife. Once in a while, though, there are situations when they begin to damage our highly important mature trees. After discussion with me, the land stewards decided to remove some of them in this case . The vines are first cut, then carefully treated by our licensed pesticide applicators (land stewards) with an approved herbicide. The blue you see is simply a dye that helps them keep track of which vines have been treated.

Thank you for your interest in our parks.

-Park Biologist Paul Pira