In February 2018, we planted 3 lines of nursery sword ferns, 12 plants per line, hypothesizing that those planted into Ground Zero (GZN, GZS) would survive, but that those planted into (actually just ahead of) the active die-off zone (ADZ) zone would not do well. All 36 plants have been watered through three summers. The prediction continues to hold:
GZS: 1/12 ferns dead, 11 healthy
GZN: all 12 ferns are healthy
t.test pvalue, likelihood of this difference occurring by chance: 8.7e-4
We surmise that the presumed pathogen no longer resides at Ground Zero - but could possibly return. A continuous dense population of affected sword ferns may be needed for reinfection: the GZ sword ferns may be "socially distant" from current areas of active die-off.