I just spent an extremely interesting two days at the Lake Tahoe Invasive Species Symposium. This two day event was organized with a couple of different focuses. The first day was organized for technical experts from around the Country and local units of government that are charged with management of this priceless resource. The second day was organized for stakeholders around the lake, those that live on the water or earn their living from the resource.
I was especially interested to see where the lake was with respect to invasive aquatic plants. In 1984, the Tahoe Keys property owners on the south end of the lake asked us to give them some ideas on aquatic weed management.
Upon our review of the system, we noted that these waters had a problem infestations of native aquatic plants at densities that were impacting their use of the waterway, but we also noted the presence of Eurasian Milfoil at pioneering levels. We recommended immediate treatment of that problem. In those days, treatment technologies were fairly limited, chemicals or mechanical options were about it. The regulatory agencies at that point would not allow us to use an aquatic herbicide to target this weed so they bought a number of aquatic weed harvesters and moved on from there. 20 or so years later, Eurasian Milfoil has spread beyond the keys and is now impacting larger areas of the lake.
A couple of key observations in this regard.
Time after time over the past 30 years we have been involved in Eurasian Milfoil control, there are been regulatory constraints that would not allow us (or anyone else) to kill the first infestations. Left unchecked, this weed will expand and in Lake Tahoe that is currently the case, it is moving around the lake and setting up shop. Hopefully this meeting organizes the troops around the lake to get on top of this and I think the energy generated by the meeting will help get going on this mission.
Lake Tahoe is also threatened by a number of other invasive species. We learned about the shift in the fishery in the lake as a result of introduced species over time. At this point in the life of the lake, warmwater species like Bass and Sunfish pose a huge threat to the resource and teams are mobilizing to fight this introduction. Other problem species like the Quaggla Mussel are not far away and we learned boats come from those waters on a regular basis. One of the smaller local lakes took on the mission of installing a boat wash system to protect their lake and awareness in the basin seems to be growing.
In the absence of the ability to use aquatic herbicides because of the permitting and regulatory environment in the basin, a number of tools have been attempted to impact Eurasian Milfoil. We learned that the Solar Bees installed in the Tahoe Keys did not deliver any observable weed control. We learned that demonstration diver dredging had had some success.
We will remain involved with the community there and will attempt to pass on some of our knowledge in the management of Eurasian Milfoil in similar systems. Lake Pend Oreille in northern Idaho is a similar water body to Tahoe, an extremely large lake system that is very deep. We successfully targeted over 4,000 acres of milfoil in that water body last year. We have developed a number of techniques that limit the impact of herbicides in the environment, we will be forwarding information on our Shoecraft Lake Barrier Curtain project where we isolated milfoil infested waters and targeted them with herbicides. We will pass on our herbicide tent methodologies to target small patches and eradicate them from lake systems, and we will pass on our DGPS aerial digital camera technologies we have used to successfully detect probable milfoil infestations from the air.
Best wishes to the resource managers at Tahoe. Thanks for the opportunity to attend and learn from your experiences and offer some ideas.