[APWG] Microstegium health questions update

Thu Sep 3 08:04:14 CDT 2009

APWG:

Since sending out my initial e-mail about some sort of unknown disease  or 
pathogen killing Microstegium in West Virginia  I have  received an 
encouraging number of responses and I would like to pass on some  answers to 
questions that several people have asked.  I would also like to  pass on some 
updated information.

Does it appear that the disease or whatever it is shows similar or  related 
symptoms in native plants?  From what I have observed, the  answer would be 
yes.  I have seen similar lesions in a couple of local  woodland grasses 
but it seemed more to damage or kill individual leaves of  grass plants rather 
than the entire plant.  

There is still no word on the name or identity of the pathogen but a fresh  
sample of sick and dying stiltgrass was mailed to Indiana University to see 
 whether our pathogen matched something discovered in Microstegium patches 
there  recently.

The weather in central West Virginia has been pretty normal this  summer.  
It has not been anywhere as wet as parts of the northeast.   We had a very 
dry period during late June and early July but generally it has  not been a 
year of extremes.  

I have been in contact with people at the WV Department of Agriculture and  
the disease and they have identified a similar health issue with stiltgrass 
in  Lincoln County, West Virginia.

Several people have suggested a rust and some people suggested that it was  
a wind born virus.  Because I have found infected individual plants over  
100 feet from any other plants I would have to vote for wind dispersal.  I  
have found very small individual plants, the kind that are usually at the  
leading edge of an invasion with spots on their leaves...those plants are so  
small that all evidence of their existence is gone as soon as they die.

As the stiltgrass plants die it appears that they die from the bottom  
up....kind of like diseased tomatoes.   Some  of the plants  develop black spots 
on their stems and it seems that when the black spots show  up the 
likelihood of seed production drops.

At Crummies Creek there are several sites where the mortality has been  
occurring that will be easy to relocate next year to see what  happens. 

I am taking additional photos each day as things deconstruct and will post  
a follow up as soon as I hear anything on the identity of the disease  
organism.

One final observation.  It appears that whatever it is very  contagious.  
Woods roads that have been traveled since being infected  sport nothing but 
dead stiltgrass wherever wheel tracks have passed over.  

I hope the photos and comments below add some worthwhile information  to 
the discussion.

Russ Richardson, Certified Forester
Crummies Creek Tree Farm
PO Box 207
Arnoldsburg, WV 25234

304-655-8919
 c-304-3773231

Japanese stiltgrass at Crummies Creek.  The plants in this  photo were 
climbing the road bank and averaged close to six  feet tall as they went up the 
slope.  Nearly all plants on  the more gently sloping terrain above are very 
stunted and  average less than a foot tall and will produce no seed in 2009 
and  seed production in general should be off by more than 95%.   This is 
open woodland that receives several hours of sunshine each  morning.  

This is a close up of the remaining stiltgrass in the photo  above.

This is very sick Japanese stiltgrass growing in optimum  conditions for 
MV...very fertile woodland sites, northeastern  exposure with at least three 
hours of full sun a day.  For  forest management purposes the area has a site 
index of over 80 and  the understory vegetation of the site includes:  
American  ginseng, Goldenseal, black Cohosh and several other related forest  
plants.

This is my dog Roy for a comparison of what "healthy"  stiltgrass looks 
like. Roy is a very large dog and sits close to  three feet tall...the 
stiltgrass on the road behind him is over  four feet tall.  In healthy stiltgrass 
the only part of him you  can see walking through the woods is the tip of his 
tail.

   There will be no problem finding the dogs in this sick  patch of 
stiltgrass.

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