Effectiveness of Aquatic Invasive Plant Control In Emerald Bay, Lake Tahoe Dan Shaw – CA State Parks Zach Hymanson – CA Tahoe Conservancy Kim Boyd – Tahoe RCD Tamara Sasaki – CA State Parks
1995 2000 13 milfoil sites Milfoil filled in many of which south shore and were small and spread along sparse west shore and for 4 miles down Truckee River Slide Credit: Lars Anderson 2003 P. crispus Curly-leaf 2006 Pondweed 14 curly-leaf sites Detected- milfoil spreading Roughly 1 sparse rapidly acre in Emerald Bay
Eurasian watermilfoil ( Myriophyllum spicatum ) 1995 – First Discovered in Emerald Bay 2000 – Few Plants 2003 – Approximately 1 Acre 2010 – Well over 3 Acres of Milfoil Photo: Zach Hymanson
Emerald Bay milfoil infestation Photo :Doug Freeland A.C.E
Floating fragments colonize unvegetated substrate
Challenges to working in Emerald Bay
Recreation Project Area
Vikingsholm Parson’s Rock Avalanche Approximate infestation area boundaries 100 meters
Underwater transects to measure treatment effectiveness
Benthic Barriers
Swimming Barriers into place Photo: Jim Brockett
Barriers don’t work in hard to reach places, but suction removal does Photo: Jim Brockett
Laying out 10X40 Barriers for Installation
Milfoil Sandy Bottom After Barrier Removal
EWM Densities at Parsons Rock Site 70 No Barrier 60 After Barrier Bottom barriers in place Mean No. of Shoots per 0.25m 2 50 40 30 20 No Data 10 0 Spring 08 Spring 09 Fall 08 Fall 09 Spring 10 Fall 10
100 Avalanche VIKINGSHOLM VIKINGSHOLM 90 Vikingsholm MAINTENANCE COMPREHENSIVE TREATMENT TREATMENT- Parson's Rock 80 PARSON’S PARSON’S LIMITED COMPREHENSIVE TREATMENT PERCENT COVER – EURASIAN WATERMILFOIL 70 AVALANCHE AVALANCHE NONE LIMITED 60 50 40 30 20 10 0 0 0 2008 2009 2010 2011 spr 2011 fall
140 Avalanche 120 Vikingsholm Parsons Rock DENSITY – MEAN NO. PLANTS PER 0.25 M 2 100 80 60 40 20 0 0 2008 2009 2010 2011
Comprehensive treatment of all Invasive Aquatic Weeds in Emerald Bay is within our reach in 2012
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