Earlier this Spring I noticed some scale insects on my Victoria Red grapevines. It was on only 3 of 12 vines. I suspect they came in on the shipment of vines from Texas, but can’t be sure of it. I am no scale identification expert, but to my eye they look like Grape-Cottony Maple Scale (see image below).
Grape-Cottony Maple Scale (Pulvinaria vitis), overwinters as a small, brown scale on grape canes. The “cottony” part is an egg sac that comes out in the Spring. The scale can reduce the vigor of the vine as it feeds. They may also carry and transmit viruses. What to do about them? Well, they can be pruned out (which is what I did) or sprayed with a horticultural oil during the dormant season or with approved insecticides.
The vines I had were severely infested with these scale insects, so I decided to cut off the infested parts. In one case I took out the entire vine. In the other two I cut it back close to the graft union. It was not the most desirable thing to do, but these were observational plants and I had 9 more plants to look at. I was really concerned that they would get into my experimental vines and didn’t want that to happen.
The Pacific Northwest Insect Management Handbook has a great description of this insect (http://pnwhandbooks.org/insect/small-fruit/grape/grape-cottony-maple-scale) for more information.