[RWG] Canada thistle tolerance thresholds

[Derek Ellis]

I was wondering if anyone had any information on response thresholds for
invasives in native plant communities, particularly Canada thistle.  Many of
our restoration clients have infestations of Canada thistle.  Often the
infestations are located in areas questionable for treatment with persistent
and mobile chemicals such as clopyralid and picloram, due to shallow water
tables.  I have read lots of statistics on the degradation of native plant
communities by leafy spurge and spotted knapweed, but am unclear on the
level of impact that Canada thistle has on plant communities and habitat,
especially in seasonally wet and riparian areas.  Also, I was wondering if
there was any information out there documenting how non-chemical control
methods affect different densities of invasive plant populations.  Thanks
for your time.

Derek Ellis

Intermountain Aquatics
P.O. Box 1115
Driggs, ID 83422
208-354-3690
fax 208-247-0941