Invasive milfoil hand harvesting tecniques

[Soakedlontra]

I could not find a forum that specifically deals with fresh water habitats conservation so here I am with a post about invasive fresh water milfoil. You are welcome to move it somewhere else if you can find a better place on Scubaboard.

To cut a long story short I am looking for any info on how to harvest the invasive milfoil in a safe manner (without having to break the plant in pieces, for instance). This noxious weed is choking Cranberry Lake at Deception Pass State Park. The park manager is trying to figure out a way to control/eradicate this non native aquatic plant without releasing nasty chemicals. I have read on Wikipedia that:

"Since roughly 2000, invasive milfoils have been managed by hand-harvesting. Several organizations in the New England states have undertaken successful lake-wide hand-harvesting management programs. Periodic maintenance is necessary; the species cannot be completely eradicated once established, but it can be reduced to manageable levels. Well-trained divers with proper techniques have effectively controlled milfoil and maintained lakes, such as in the Adirondack Park in Northern New York where chemicals, mechanical harvesters, and other management techniques are banned as disruptive. The Adirondack Watershed Institute (AWI) of Paul Smiths College touts the effectiveness of hand-harvesting."

Nearly a month ago I contacted folks at the Paul Smiths College by phone and e-mail but I haven't received a reply yet. I am wondering if somebody here knows about these techniques or know somebody else who does.

Thank you very much

cheers
[h=2][edit][/h]

 

[drbill]

We are facing a similar dilemma here in SoCal with an invasive Asian seaweed (Sargassum horneri). So far our Fish & Wildlife service is unwilling to let us remove it by hand even though it is an invasive in a marine protected area. Sounds like the powers that be are more supportive in your case. Good luck with the project!

 

[Tool Belt]

I have been pulling milfoil in Northern WI for 10 years. Our lake originally (2001) had about 4 acres (out of 478) treated with Navigate. Since then we have controlled it with hand (SCUBA) pulling. Generally we find it growing in 5 - 11 feet in a silty area.The technique is to get your hands into the silt and loosen it as much as possible.Once that is done pull the plant out and roll it up onto itself. Try to keep fragmentation to a minimum as the weed can propagate from pieces. We then place it in a mesh (laundry) bag. When the bag is full we hand to someone in the boat or to a kayak handler. The water is drained and the the weeds placed into a garbage bag. In the silty conditions ZERO visibility happens pretty quick It is best to place a buoy to mark the area to make it easy to return to it. A second visit after the water has settled will reveal more weeds.

This works well, but does not totally remove the weed. The best one can hope for is to keep the weed to a minimum, but once it is there, it is there.

We have a had a very dry couple of years resulting in a 2 - 3 foot reduction in the level of the lake. That, together with a very hot summer caused an explosion of weed growth in general, and yes in milfoil too. We'll see how it looks next year but it appears we may have to chemically treat again as the hand pulling is not effective or practical over large areas.

 

[Soakedlontra]

I have been pulling milfoil in Northern WI for 10 years. Our lake originally (2001) had about 4 acres (out of 478) treated with Navigate. Since then we have controlled it with hand (SCUBA) pulling. Generally we find it growing in 5 - 11 feet in a silty area.The technique is to get your hands into the silt and loosen it as much as possible.Once that is done pull the plant out and roll it up onto itself. Try to keep fragmentation to a minimum as the weed can propagate from pieces. We then place it in a mesh (laundry) bag. When the bag is full we hand to someone in the boat or to a kayak handler. The water is drained and the the weeds placed into a garbage bag. In the silty conditions ZERO visibility happens pretty quick It is best to place a buoy to mark the area to make it easy to return to it. A second visit after the water has settled will reveal more weeds.

This works well, but does not totally remove the weed. The best one can hope for is to keep the weed to a minimum, but once it is there, it is there.

We have a had a very dry couple of years resulting in a 2 - 3 foot reduction in the level of the lake. That, together with a very hot summer caused an explosion of weed growth in general, and yes in milfoil too. We'll see how it looks next year but it appears we may have to chemically treat again as the hand pulling is not effective or practical over large areas.

Thank you very much for the info. I was able to track down a local diver who has experience in harvesting milfoil. Now it's up to the park manager to discuss the issue with him and figure out a plan of some sort. I have no idea whether he will end up using divers at all or not.

I am wonder how the chemicals effect the water quality. I mean, do they kill all the living organisms?

A nearby lake has the same problem but apparently another, more serious problem has taken over: toxic algae. It sounds like that the lake may be doomed...I snorkeled there once. Fortunately I was covered with neoprene from head to toes!

cheers

---------- Post added November 27th, 2012 at 09:23 AM ----------

We are facing a similar dilemma here in SoCal with an invasive Asian seaweed (Sargassum horneri). So far our Fish & Wildlife service is unwilling to let us remove it by hand even though it is an invasive in a marine protected area. Sounds like the powers that be are more supportive in your case. Good luck with the project!

Thanks!

Can the Sargassum horneri be harvested commercially to make fertilizer, for instance?

 

[Tool Belt]

The chemicals used to control the milfoil do have some collateral effect on other aquatic plants, but I was surprised it didn't seem to wipe out everything in the treated area, it seemed *somewhat* selective.

 

[Kharon]

Here is a link from the lake I volunteer at every summer. Eurasian milfoil (EM) has been virtually completely eliminated. EM beds were located, covered with mats which stayed in place 2-3 years, killing everything. Mats were then removed and the bed monitored for new EM growth. EM was hand harvested by divers as it appeared (leaving native plants) while volunteer kayakers with nets patrolled the surface and scooped up any fragments. We used pontoon boats equipped with double (home made) winches to lower & raise the mats. Divers unrolled and rolled them. Lift bags made the removal a lot easier because divers could position the rolled mat rather than having to position the pontoon. I found the work worthwhile and it gave me a great education in working UW blind in a cooperative team effort. My air consumption rate dropped considerably. An important factor in getting divers to volunteer was that the local VFD supplied tanks. They have their own compressor and a large number of tanks for their Search & Rescue squad.

Brant Lake Milfoil Control

 

[Soakedlontra]

Here is a link from the lake I volunteer at every summer. Eurasian milfoil (EM) has been virtually completely eliminated. EM beds were located, covered with mats which stayed in place 2-3 years, killing everything. Mats were then removed and the bed monitored for new EM growth. EM was hand harvested by divers as it appeared (leaving native plants) while volunteer kayakers with nets patrolled the surface and scooped up any fragments. We used pontoon boats equipped with double (home made) winches to lower & raise the mats. Divers unrolled and rolled them. Lift bags made the removal a lot easier because divers could position the rolled mat rather than having to position the pontoon. I found the work worthwhile and it gave me a great education in working UW blind in a cooperative team effort. My air consumption rate dropped considerably. An important factor in getting divers to volunteer was that the local VFD supplied tanks. They have their own compressor and a large number of tanks for their Search & Rescue squad.

Brant Lake Milfoil Control

Very interesting info thank you very much!

 

[smellzlikefish]

Oahu has a big-time problem with invasive seaweeds including Gracillaria salicornia, Kappaphycus and Avrainvillea. To combat this, some clever folks at UH came up with something they call the "Super Sucker." Basically, it is a boat that uses a trash pump to suck up the seaweeds that get sorted on deck by workers. Divers direct the suction end. It has proven highly efficient and I can image similar apparatus might be used with great efficiency to combat other seaweeds like your milfoil issue. See here for some more info:The Supersucker Project