Monday, December 7, 2015

Overview

A mixed lay/scientific group here in Seattle (Seattle Parks ecologists, UW researchers, the Friends of Seward Park) is trying to figure out an unprecedented and alarming sword fern die-off in one hundred acres of old-growth forest in Seward Park.  The affected area is spreading radially; lush understory of two years ago is now bare ground.  Drought, pollution and mountain beaver activity may be contributing factors, but deeper and as yet unknown causes appear to be at play.


Survey: October  2014



Fronds in Detail: October 2015



This blog serves to document and  present our work.  Please contact paul.thurmond.shannon@gmail.com for further information.

Candidate Sword Fern Pests 

Provided by Jenny Glass, from the USDA-APHIS Fungal-Host Database


I am not sure that I ever sent you the list of possibilities that I went through during your DEC 2014 submission:
The literature generally suggests the species Polystichum munitum is relatively disease and pest free and an investigation of other Polystichum species revealed more or less the same information.  As discussed, the laboratory investigated a similar concern about dying sword fern in the Jefferson County area in 2013.  We were also unable to pinpoint the origin of that damage beyond the impression that the sample contained no apparent disease or pest origins of damage.  

The USDA-APHIS Fungal-Host Database had these fungi listed as being observed on sword fern but none of the described fungi are likely to be associated as the cause of this patch of dying plants.

Chaetasbolisia falcata:  Polystichum munitum: California 

Helotium polystichi:  (Basidiomycete):
     Polystichum munitum (On stems.): California 

Herpobasidium abnorme:  (reported to cause distortion):
     Polystichum munitum: Idaho - 

Milesia polystichi - (Milesina winelandi):   (rust- obligate parasite unlikely to kill host)
     Polystichum munitum: California, Canada, Idaho, Montana, Oregon, Washington 

Milesia vogesiaca - (Milesina vogesiaca): (rust- obligate parasite unlikely to kill host)
    Polystichum munitum Canada, Oregon  

Milesina vogesiaca:  (rust- obligate parasite unlikely to kill host): 
    Polystichum munitum California

Milesina winelandi:  (rust- obligate parasite unlikely to kill host):
    Polystichum munitum: California, Idaho, Montana, Oregon, Washington  

Mycena fragillima:  (small saprophytic mushrooms): 
    Polystichum munitum: California, Oregon, Washington  

Phoma adianticola - (Didymella adianticola):  Phomopsis sp.: 
    Polystichum munitum (On fronds.): Oregon 

Phyllosticta sp.: Polystichum munitum (On fronds.): Oregon 

Phytophthora cinnamomi:  (thrives in saturated soils/poor drainage):
     Polystichum munitum (Root rot.): California 

Pythium sp.:  (thrives in saturated soils/poor drainage):
    Polystichum munitum California  

Rhizoctonia solani: (frond blight is a common symptom): 
    Polystichum sp.: California 

Taphrina faulliana: (leaf blister): 
    Polystichum munitum: Canada, Idaho, Oregon, Washington  

Valdensia heterodoxa: (apparent leaf spot/leaf blight pathogen):
    Polystichum munitum: Canada 

Xenasma filicinum - (Phlebiella filicina): 
     Polystichum munitum: Canada



Lab Report from Jenny Glass (12/04/15)


Dr. Marianne Elliott's Report (12/3/2015)

I have attached the sampling procedure and list of samples we collected. We did not find any Phytophthora, but I am not ready to rule it out as the cause of the die-off. It could be a species that is slow growing and difficult to culture, so we missed it. Or it was replaced by something else in dead material. Or this was the wrong time of the year to sample. I think the students who are working on this should keep an eye out for it.

There were a few Pythiums and other similar organisms that we see commonly in soil and roots. We didn't find anything associated with the dying sites vs the healthy sites, or with the dead cedar transplants. I have been asking various people I know and nobody has seen it in their travels, but now they are aware of the situation. I will let you know if anything turns up.


--Marianne

Sample Processing Protocol (Sword fern dieoff samples collected at Seward Park 11/10/15)


Sample #
Description
Treatment
1
5 x 5 plot, healthy, symptomatic fern foliage
Surface sterilize, plate 5 segments on PARPHV8 (3 plates)
2
5 x 5 plot, healthy, crown from healthy fern plant
Surface sterilize 10 necrotic root segments per plate (PARPHV8), dissect crown and look for brown staining symptoms (3 plates). If present, surface sterilize and plate 5 segments on PARPHV8 (1 plate).
3
5 x 5 plot, healthy, soil from base of 3 healthy ferns, upper 5 cm depth + litter & roots
Bait in 1 L bottles. Use rhododendron leaves and healthy sword fern leaves. Place one intact rhody leaf and one sword fern frond in each of 3 bottles containing 100 g soil and 500 ml water.
4
Ground zero, foliage and fronds from dying ferns
Surface sterilize, plate 5 segments on PARPHV8 (3 plates)
5
Ground zero, crown and roots from dead ferns
Surface sterilize 10 necrotic root segments per plate (PARPHV8), dissect crown and look for brown staining symptoms (3 plates). If present, surface sterilize and plate 5 segments on PARPHV8 (1 plate).
6
Ground zero, soil from base of 3 dead ferns, upper 5 cm depth + litter & roots
Bait in 1 L bottles. Use rhododendron leaves and healthy sword fern leaves. Place one intact rhody leaf and one sword fern frond in each of 3 bottles containing 100 g soil and 500 ml water.
7
Ground zero, soil from base of 3 dead, planted cedars
Bait in 1 L bottles. Use rhododendron leaves and healthy sword fern leaves. Place one intact rhody leaf and one sword fern frond in each of 3 bottles containing 100 g soil and 500 ml water.
8
Symptomatic foliage from other hosts along trail by Ground zero and road
Surface sterilize, plate 5 segments on PARPHV8 (3 plates).

Baiting protocol for soils
Label 1L bottles with sample and rep numbers. Use rhododendron leaves and healthy sword fern leaves. Place one intact rhody leaf and one sword fern frond in each of 3 bottles containing 100 g soil and 500 ml water. Cap tightly and incubate bottles on their sides for 48-72h.
After incubation, remove baits from bottles and rinse with water, then blot dry. If asymptomatic incubate an additional 3-7 days in ziplock bags containing moist paper towels. Plate symptomatic areas of foliage (5 per plate) on PARPHV8. Use two plates for each bait type per bottle.
All samples
Check for Phytophthora colonies on all plates after 2-5 days and isolate onto small PARP plates for identification.