I recently spotted virus symptoms of a sort that I haven’t seen before on an oca plant. Although oca is frequently infected with several different viruses, they are typically asymptomatic. This plant had some lower leaves with obvious yellowing and mosaic and some leaf tip browning. I ran it through a few ELISA tests for potato viruses without result and then sent off some leaves for further testing. They came up positive for Cucumber Mosaic Virus. CMV is a common plant virus with a very wide host range. I scanned the literature and found no previous reports of it infecting oca, but there is a report of it infecting Oxalis corymbosa (Sheikh 2013).
The plant did not appear to be severely affected by the virus, but I destroyed it before it would have been harvestable, so I can’t say how the tubers might be affected. As always, the best practice is to cull any plants that show obvious virus symptoms. Cucumber mosaic virus is principally spread by aphids. There are also reports of CMV being spread through seed in some species. I hope this will not turn out to be the case with oca, but I will add a CMV ELISA kit to our standard testing to see if it pops up anywhere else.