What is in this article?:
- California wine grape growers on red blotch virus alert
- Red blotch virus cases increasing?
- Insect vector a possibility
- Virus slows planting boom
- Grapevine red blotch associated virus, or GRBaV, is front and center on the California wine grape industry's radar screen.
- The virus has been found in a limited number of blocks statewide with more suspected.
Insect vector a possibility
In the world of plant viruses, many viruses are vectored by an insect which raises the question, is red blotch virus transmitted by insects? Maybe yes and maybe no.
The Geminiviridae family of plant viruses is vectored by whiteflies and leafhoppers. Yet the red blotch virus is unique and different from other viruses in the family. That said, some researchers are unsure if red blotch virus belongs in the Geminiviridae family, and if that is true, whether red blotch can be transmitted by these insects.
Researchers at Washington State University have reported that the Virginia creeper leafhopper can vector red blotch in a greenhouse setting. It is unknown if the same insect could vector red blotch in a vineyard.
Meanwhile, Smith says several growers made prophylactic applications of insecticides targeting leafhoppers.
What is known, Smith emphasizes, is red blotch virus can be spread through plant propagation –taking buds from one plant for grafting to another.
Smith warned, “Don’t collect buds from one block to field bud another block unless you are 100 percent certain the budwood is clean. Test the budwood for viruses.”
The top question wine grape growers ask Smith about red blotch disease is which farming practices can best minimize the impact of the virus on the vine and fruit.
Her response is to first verify through a commercial lab that a block is positive for red blotch virus, and acknowledge the vine will never be 100 percent healthy. Then, take measures to reduce stress on the vine which are under the grower’s control, and optimize vine nutrition and soil fertility; a practice already in place by many growers.
“Good vine health is about a good irrigation strategy and a good fertility program,” Smith said.