Reflecting on a Lesser-Known Disease Calamity of Spring 2020

March 08, 2021

Reflecting on a Lesser-Known Disease Calamity of Spring 2020. 

At the change of seasons, it is a very human thing to reflect back on what was happening a year ago…even when that year was as unpopular as 2020.   

Ahh,  early spring 2020…that memorable time marked by the detection of COVID-19 in the U.S.  During March, UMN experienced the beginning of travel restrictions, alternative instruction for classes, canceled conferences, collecting personal protective equipment (PPE) for donation, the first Stay at Home order, and emerging guidelines about how to keep people separate and safe.

As if that wasn’t enough…It was April 22, 2020.  A geranium sample arrived at the Plant Disease Clinic.  This was one day after the USDA confirmed Ralstonia solanacearum  race 3 biovar 2 (RSr3b2) in ‘Pink Flare’ geraniums plants in a Michigan greenhouse.  This Ralstonia is a select agent pathogen.  PDC staff was on alert.  We knew these ‘Pink Flare’ geraniums were shipped to 288 greenhouses in 39 States (including Minnesota).  Would this geranium-filled box be the PDC’s first real-life experience with a select agent...AND in the middle of a pandemic???  At least the variety was not ‘Pink Flare,’ but the sample did not look good.   Even if the plants did look good, there was still a reason for concern. Just as humans can be asymptomatic for COVID-19, geraniums and other ornamental host plants can have latent/asymptomatic Ralstonia solanacearum (Rs).  Fortunately, there are simple species-level serological tests for Rs.  These tests can detect asymptomatic infections (especially in crown tissue of geraniums).  As for our sample geranium, it turned out to be just a bad case of edema.  If it had tested positive for Rs, we would have contacted regulatory specialists.  The sample would have needed further testing (PCR to test for race and biovar) by USDA APHIS PPQ. 

Sometimes plants need physical distancing too…and testing, tracing (forward and backward), identifying which plants were co-mingled with infected plants, sanitation, etc.  Use your imagination between parallels that can be drawn regarding responses to disease outbreaks in people and plants…    

The End.  While there are always potential troubles, at least for RSr3b2 of 2020,  the last headline was “Ralstonia eradicated from Greenhouses.”