Henrys Fork CWMA

Biological Controls

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 Biological weed control involves the deliberate introduction and

 establishment of natural enemies to reduce the target plant's

 competitive or reproductive capacities. Insects are the most

 common agent released against noxious weeds.  However,

 plant pathogens, such as fungi, are increasing in use. Sheep and

 goats have been effective in reducing densities and limiting

 spread of specific weed species. Biological control can be a slow

 process, often requiring 5 to 20 years to be effective.  Its purpose

 is not eradication but a reduction in densities and rate of weed

 spread to an acceptable level. It is most effective on dense weed

 infestations over large areas.

 

 

   The 2009 Chester Wetlands Project was initiated to target thistle species that border riparian corridors.  Before Idaho

   Fish and Game purchased the Chester Wetlands, heavy grazing resulted in the release of several noxious weed species

   throughout the 1500 acre complex. With the discovery of Ute Ladies Tresses, a

   threatened orchid, weed management has been difficult at times.  No herbicide can be

   used in these orchid sites which are in close proximity to water and thistles.  

   Therefore, an ongoing effort to place bio control in these orchid sites took place in the

   spring of 2009.  Two colonies of Urophora carduii were donated by Nez Perce bio

   control and were placed in March.  Sixteen colonies of Urophora carduii were placed in

   late spring and eight colonies of Ceutorhynchus litura were placed in late summer. 

   Milestone and 2-4-D were applied on the 1500 acre complex with the help of Idaho

   Fish and Game, Fremont County, Madison County, and BLM.  Approximately 430 acres were treated.  Plans for 2010 are

   to continue bio control and herbicide applications.

 

  The Fremont County Bio project  received 11 colonies of Cyphocleonus achates during 2009.  They were released on a

  large infestation of Spotted knapweed above St. Anthony.   

 

The Sheridan Creek Riparian Project involved both herbicide treatment and bio-control

releases on Harriman State Park.  The main target weed in 2009 was Canada thistle, but

plumeless thistle and spotted knapweed were also treated with herbicide.  Bio-

control releases were started in the riparian areas along the Henry’s Fork.  At seven

different sites, a total of 2,300 Urophora cardui were released, and 1,300 Ceutrhynchus  litura were released.  The bio-control project was not completed as planned due to

problems encountered with the bio-control supplier.  Revisiting release sites in August

revealed the gall flies rapidly established at the release sites.  Both the herbicide

  treatments and bio-control releases are anticipated to continue in 2010. 

 

   HFCWMA is also involved in the "Holding the Line" Bio Saturation Project to protect Yellowstone National Park.  For more

   information on this Project visit: http://www.helpholdtheline.com/

 

   For more information on biological controls of Noxious weeds click on the following links: