[APWG] Plants Alien Biocontrol Spontaneous Re: Microstegium health questions update [01/10]

Thu Sep 3 16:13:21 CDT 2009

APWG:

Might dogs or other animals be vectors? Would it be a useful field experiment to harvest some infected Microstegium, toss it into the middle of a healthy stand, and observe the "results?" Crude, but perhaps not entirely without usefulness? Have the affected and unaffected stands been mapped? What other kinds of studies have been done? Links/references? 

WT

PS: Could it be possible that the longer a species is present and the more "successful" it is, the greater are the chances that organisms that use it in some way will tend to evolve? 

  ----- Original Message ----- 
  From: ForestRuss at aol.com 
  To: APWG at lists.plantconservation.org 
  Sent: Thursday, September 03, 2009 6:04 AM
  Subject: [APWG] Microstegium health questions update

  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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