I test our oca varieties annually and whenever suspicious symptoms are observed. Plants that produce our parent tubers are tested and field grown plants are randomly tested for the common viruses. All varieties listed in the catalog have passed this testing regimen. The tolerance is zero. Any variety with a confirmed positive result will not be offered. This testing program began in 2018.

Virus Method Schedule Rationale
Arracacha Virus B Not tested Not tested There has been at least one oca variety in the USA that previously tested positive for AVB-O in the early 2000s.  I would like to test for this virus, but, unfortunately, there is no affordable way to test for it currently.
Cucumber Mosaic Virus Immunostrip Once at introduction and when suspected I have only seen CMV in oca once, but it is easy to test for.
Nepovirus genus PCR (sometimes ELISA for PBRSV) Once at introduction Cautionary against Arracacha Virus A and Potato Black Ringspot Virus, but I have never seen a positive result for either one.
Papaya Mosaic Virus (PapMV) Immunostrip & ELISA Annually A few heirloom ocas have been positive for PapMV. I have not seen a positive result for years, but it is the most widespread virus in Andean root crops and it is easy to test for, so better safe than sorry.
Potato Virus T (PVT) ELISA Once at introduction PVT is present in many Andean root crops in the Andes, but I have never seen a positive result. I will probably stop testing for this virus in seed-grown ocas after 2020.
Potyvirus genus Immunostrip & ELISA Annually Heirloom ocas have occasionally tested positive for Potyvirus, but I don’t know which one. Because potyvirus is a group that widely infects Andean tubers, I test everything annually.
Tobamovirus genus PCR Once at introduction An unidentified Tobamovirus was twice detected in heirloom ullucos, which I would guess was most likely Ulluco Mild Mosaic Virus.  It is known to also infect oca, but I have not seen a positive result yet. I will probably stop testing for this virus in oca after 2020, with the exception of any new heirloom varieties that might turn up.
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