2008 Milfoil Weevil Project at Eagle Landing

                  

                                      Eurasian Water Milfoil                                          Milfoil Weevil

Eagle Landing lake residents have experienced a increasing problem with a non-native invasive aquatic species of plant called Eurasian Water Milfoil (Myriophyllum spicatum L.) . This plant forms thick mats of weeds which entangle boat props and shades out other native plants. Eurasian Water Milfoil is usually introduced into a lake from plant matter not properly cleaned off boats coming from other infested lakes. As little as 1/4" of stem will grow a new plant.

The plants go dormant in the fall, and regrow each spring. A contact herbicide which is non-toxic to fish and wildlife has been repeatedly applied, but this herbicide is short acting and requires respraying several times a season making it expensive to apply.

Various other means of eradication have been considered. After much research it was decided not to use sterlized grass carp because milfoil is the least favored plant of these fish. The carp will eat all the other lake plants before eating the milfoil. Additionally, a representative from Texas A&M University states that carp can undermine the stability of an earthen dam by pulling out vegetation by the roots. Harvesting by a machine is ineffective and too expensive. One lake resident proposed trying a natural solution in the form of a specific weevil.

The Eurasian Water Milfoil Weevil (E. leconlei), native to the US, feeds upon Eurasian Water Milfoil exclusively. The 1/8" weevils bore into the stems, deposit their eggs, and the larva riddle the plants with holes interrupting the plants nourishment transport system which causes the plant to wither and die. The weevils do not bite, sting, swim, or fly. They simply crawl from one plant to another.

Weevil eyesite is excellent. When a fish is spotted they quickly crawl around to the backside of the stem to hide, much like a squirrel does on a tree. A study done in New York for the Lake Boneaparte Conservation Club, where there was a large blue gill population in the lake showed that within a given sample of 90 fish there were less than 2% of weevils in the stomachs of the fish. There were also sprigs of milfoil in the fish stomach contents which could indicate the weevils were accidently injested along with the plant. It was concluded the weevils are not a major food source for fish.

Once the weevils have the milfoil under control in a lake, usually between 3-5 years, the weevil population dwindles to a count that is proporationate to the remaining milfoil. The weevils will not remove all the milfoil but they will keep it under control and eliminate the need to spray a herbicide for milfoil. The adults overwinter in the lake mud. The life cycle of adult weevils is about 2-3 years.

EnviroScience, Inc.(www.enviroscienceinc.com), an environmental company from Ohio, has been stocking northern lakes with weevils with much success for 20 years, under their Midfoil Project. When contacted, Marty Hilovosky, President, agreed to stock a test area in Eagle Landing to see if the weevils would survive in the warmer waters of the south. He mentioned that the Army Corp of Engineers has 7 test ponds near Dallas where they have been monitoring the weevils for the past 8 years. It was formerly thought that the weevils needed cold waters to overwinter, but lately native weevils have been found near San Francisco, CA, where the water does not freeze in the winter, so it is hopeful they will thrive here.

       

   Eggs attached to milfoil     Planting the weevil eggs & larva

On June 18, 2008, Marty Hilovosky personally brought 3800 weevil eggs and larvae to Eagle Landing for planting. A protected site was chosen at the far north end of the lake in a cove that has several underground streams feeding the lake and a large mat of milfoil. He carefully planted the eggs and larvae into the Eagle Landing milfoil by tying bunches of dying milfoil stems containing the weevil eggs and larvae onto the lake milfoil. He then placed an orange marker showing the seeded location. He said the eggs will hatch in about 3 weeks. Since the weevils reproduce a generation about every 25 days he expects 5 generations to grow during this season. One resident will monitor the results and report to him. He will return at the end of the year for an observation, and will bring additional weevils in the spring of 2009 to add to the existing weevil population. Since the weevils are sensitive to herbicides and need healthy milfoil to feed upon, and time to build up a sustainable population, there will be no spraying in the north end of the lake for several seasons. The south end of the lake will receive a standard treatment as needed.

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8-15-08: Due to the success rate from the initial weevil seeding we decided to transplant several buckets of dying milfoil in other areas at the north end of the lake where there still are large mats of milfoil to see if we have the same success. We will continue to monitor and report here.

Please stay clear of the marked cove northeast of the island this year so as not to disturb the weevil area.  Thank you!

Please check your boat and equipment and hose them off every time before you bring your craft

back to the Eagle Landing lake water to keep invasive plants from contaminating our lake.

Watch this page for additional photos and status reports on the weevil project progress.

Call Jan Kenyan at 903-562-1549; with any questions related to aquatic plants, flora, fauna, insects or area wildlife and fish. She will research and assist you.