The Fall River Resource Conservation District (RCD), the Fall River Conservancy (FRC), and California Trout, are joining forces to implement a pilot program that will help restore wild trout populations and critical habitat conditions in the Fall River by reducing the spread of Eurasian Watermilfoil (EWM), Myriophyllum spicatum.
Please find below, answers to key questions regarding the proposed project:
What is the purpose of this program?
The purpose of this project is to restore Fall River habitat and wild trout populations by reducing the spread of invasive Eurasian watermilfoil (EWM) Myriophyllum spicatum. First discovered 1999, EWM has spread rapidly in the lower river, overtaking native aquatic plants and destroying sensitive habitat for fish and macro-invertebrates. EWM also degrades the Fall River levee system, which causes flooding and threatens the valley’s agricultural commodities.
Why is this project necessary?
EWM poses a considerable long-term threat to the economic and ecological health of the Fall River Valley. Although Fall River stakeholders differ significantly in demographics, we share a common interest in the general economic, cultural, and ecological well-being of the valley. EWM threatens this common interest. EWM impacts recreation, hydropower, agriculture, water quality, and fish and wildlife.
Who will pay, how much will it cost, and how long will it take?
The Fall River Partnership mentioned above is working together to raise $125,000 to implement a two year pilot program for managing EWM in the Fall River. Money raised will go towards working with EnviroScience Inc. to propagate a biological control (weevils), distribute the weevils in strategic locations throughout the river, and then monitor the results to ensure that the intended impact occurs.
After two years, we’ll monitor the impact of the program to determine whether additional resources should be invested in the program. The California Department of Fish and Game, the U.S. Department of Agriculture, and the Regional Water Quality Control Board will provide regulatory oversight and guidance to ensure that all necessary permits and procedures are followed.
The Fall River Partnership is currently working with the USDA and PG&E to secure partial funding for this project. But we also need private support and individual donations to meet our funding needs.
What is Eurasian watermilfoil?
Eurasian watermilfoil (EWM), Myriophyllum spicatum L. is an invasive, submerged aquatic plant found in most of the United States and portions of Canada. Its native range is Europe, Asia, and Northern Africa but since its first introduction in the 1940’s, it has become one of the most noxious aquatic weeds in North America.
How does EWM affect the Fall River?
In 2003, broad areas of EWM in the lower river reached sufficient density and height to significantly impede flow, which caused water to back up in upstream areas. This culminated in the failure of large sections of levee along Horr pond and the flooding of approximately 4,000 acres of agricultural lands.
Beyond the destruction of field crops, EWM also impacts other important economic drivers of the regional economy including outdoor recreation. The Fall River is considered one of California’s most productive spring creek wild trout fisheries. EWM degrades the Fall River’s sensitive cold-water habitat and wild trout populations by reducing the diversity and abundance of native plants, as well as associated invertebrate populations.
What is a biological control?
A biological control is the practice of rearing and releasing natural enemies (predators and parasites) that seek out and destroy other species that are considered pests. In the case of EWM, control is defined as a condition where EWM is reduced to the point where it becomes a relatively small part of the overall plant community.
What is a milfoil weevil?
The milfoil weevil, Euhrychiopsis lecontei Dietz, is a small (think sesame seed), aquatic weevil native to North America that feeds on and lives in Eurasian watermilfoil: killing it in the process. Interestingly, milfoil weevils prefer invasive EWM over all other aquatic plants. Milfoil weevils have no known negative impact on desirable native aquatic vegetation, wild trout, macro-invertebrates, agricultural commodities or people.
How will milfoil weevils control the EWM problem?
The milfoil weevil damages EWM directly at the growing tip and the supporting stem. Damage to the stem by milfoil weevil larvae effectively reduces the plant’s ability to grow higher in the water column where it thrives by accessing more light to photosynthesize into energy.
The larval stage creates holes in the stem walls as it moves in and out, hollowing out the stem tissue. This internal damage disrupts the flow of nutrients throughout the plant and to the roots, where energy is stored for subsequent growth.
In addition, holes in the stem allow gas to escape and cause the plant to lose buoyancy. As the stem begins to fall over it weighs down nearby stems, pulling them further from the water’s surface. All of these effects serve to reduce EWM growth, density, and expansion and allow native plants to fill in as EWM drops out of the water column.
Won’t milfoil weevils also destroy desired native aquatic plants?
According to information in the peer-reviewed literature on the milfoil weevil (Euhrychiopsis lecontei) the milfoil weevil can damage several native milfoils in addition to Eurasian watermilfoil (Myriophyllum spicatum).
Specifically, research presented by Dr. Raymond M. Newman (Arch. Hydrobiol. 159 pages 145 – 184) indicates that the water milfoil weevil will feeds upon and damage M. sibiricum (northern watermilfoil), whorl-leaf milfoil (M. verticillatum), alternateflower milfoil (M. alterniflorum),low watermilfoil (M. humile), and parrot’s feather (M. aquaticum).
The Newman article indicates that the native host plants of the milfoil weevil include northern watermilfoil (M. sibiricum) and other native watermilfoils such as whorl-leaf milfoil (M. verticillatum). This means that the weevil is capable of completing its life cycle and surviving in the presence of these plants even when no Eurasian watermilfoil is present in the water body.
Other than the research presented above, milfoil weevils have no known negative impact on other desirable native aquatic vegetation, wild trout, macro-invertebrates, agricultural commodities, or people. Weevils destroy EWM gradually. As the once dominant EWM begins to die, native aquatic plants can begin to grow again.
Will milfoil weevils affect agricultural commodities in any way?
Milfoil weevils have no known negative impact on desirable native aquatic vegetation, wild trout, macro-invertebrates, agricultural commodities or people. Milfoil weevils only affect Eurasian milfoil and hybrid milfoil species and will not impact other species in or out of the water. Weevils have been used regularly on lakes in the Midwest for over 10 years: no agricultural commodities or desirable aquatic vegeation have ever been negatively impacted.
Will milfoil weevils affect wild trout populations in anyway?
Milfoil weevils have no known negative impact on desirable native aquatic vegetation, wild trout, macro-invertebrates, agricultural commodities or people. Milfoil weevils will likely benefit wild trout populations by restoring the original diversity and abundance of the Fall River’s aquatic plant and macro-invertebrate communities.
What results do we hope to achieve with this approach?
Most biological control programs do not completely eradicate the pest, but manage it at reduced levels. This project will decrease EWM plant density, reduce the existing canopy at the river’s surface to a non-nuisance level, and in many cases, eliminate large outbreaks all together. The project will also restore native plant species and invertebrate abundance and diversity in areas once dominated by EWM.
How will we measure the impact of this program?
Baseline measurements on the size and severity of the milfoil problem will be taken prior to stocking and three additional follow-up surveys will be conducted over the next two years. Data collection will be performed by EnviroScience Inc. with oversight and guidance provided by USDA-NIFA researchers.
What unintended consequences may result from this program?
Based on more than two decades of research and twelve years of commercial stocking experience, the milfoil weevil has been well-documented to attack only EWM and does not damage any other aquatic or terrestrial plants. As EWM decreases in the treated system, the weevil population gradually declines to a self-sustaining level. They don’t swarm, bite, or get into your house!
Does the community support this approach?
The following agricultural and livestock stakeholders strongly support alternatives for managing EWM in the Fall River Valley:
- Intermountain Hay Growers
- Northeastern California Water Association
- Fall River Wild Rice Cooperation
- Prather Ranch Organic Beef
- Shasta County Agricultural Commission
- California Invasive Plant Council
- Fall River Big Valley Cattleman’s Association
The following resource agencies, conservation groups, and research entities are working together to develop long-term solutions for improving native aquatic vegetation and associated macro-invertebrate populations in the Fall River:
- The California Department of Fish and Game
- The California Regional Water Quality Control Board
- California Trout
- The Fall River Conservancy
- The Fall River Resource Conservation District
- UC Davis Center for Watershed Sciences