Researchers have confirmed that a type of hopper transmits the virus associated with red blotch disease. Experts believed spread was happening as symptoms were popping up sporadically, and now researchers know why.
Researchers out of University of California (UC) Davis have successfully transferred the red blotch disease virus through a three-cornered alfalfa hopper. “We were able to confirm that a membracidae, called three-cornered alfalfa hopper, is able to transfer the virus to grapevines,” University of California, Davis professor of entomology Frank Zalom said.
Signs of transmission
This is the first and only insect they have found to transfer the disease. Zalom says experts in the field were certain that spread was occurring based on what they were seeing. “There were a number of our UC farm advisors and growers that believed spread was occurring because they had situations where they had no symptoms of the the red blotch virus and then they would start seeing an increase in symptoms,” Zalom says. “It didn’t match the pattern of something that had been planted uniformly from a nursery type of situation. We were able to start mapping some of those vineyards and recognized that indeed the infections were increasing.”
Finding the culprit
Confirming the increase in infections is what started the researchers investigation. Zalom says they looked at over a 100 insects in their trial. “We started looking at a number of different sucking insects that could potentially transmit a virus,” Zalom says. “We probably screened over a hundred different species of insects. We would collect them in the field, bring them back to the lab and try to start colonies or at minimum feed on infected plants. We would then put those in clean grapevines and basically waited for any evidence that the virus was replicating in the plants and increasing.”
Zalom says they tested the plants monthly and identified the three-cornered alfalfa hopper as an insect that can transmit the virus.