Working Groups: Invasive Weeds

Be On the Lookout for Invasive Weeds
As invasive weeds continue to proliferate at alarming rates in the Basin, it is essential that we undertake a Basin-wide effort to stop the spread. Developing community partnerships and coordinating management efforts will allow us to tackle the economic and ecological problems associated with noxious weed infestations more effectively.

Interested agencies, biologists, and community groups have recently joined to form an invasive weed coordinating group that is committed to sharing information on the management and control of invasive weeds within the Lake Tahoe Basin. To join the effort, call Sue Donaldson, University of Nevada Cooperative Extension, (775) 784-4848.

last modified: April 29 2002

Toadflax: It’s Not Just a Funny Name!
The sun is shining, the ground is warm, and weeds are growing, especially the toadflaxes. Nope, no relation to amphibians! These two yellow-flowering weeds are spreading fast within the basin. Dalmatian toadflax (Linaria genistifolia spp. dalmatica), an attractive plant that grows to 3 feet tall, has heart-shaped leaves that clasp the stems. The yellow flowers resemble those of snapdragons, and have an orange-bearded throat. Yellow toadflax (Linaria vulgaris) tends to be shorter and has long narrow leaves that are lance-shaped. The flowers are similar to those of Dalmatian toadflax, and the color has led to the common name “butter-and-eggs.” Both species are aggressive perennials with extensive, deep root systems. They reproduce both by horizontal or creeping rootstocks, and by seed. As a mature Dalmatian toadflax plant can produce up to 500,000 seeds per year, infestations may spread rapidly. To make the matter worse, the two species can hybridize to create an intermediate species. Control is difficult, but hand-pulling, removing as much of the root as possible, can be used on young plants in small infestations before they go to seed. Bag the plants securely and dispose of them in the trash. Chemical control is complicated by genetic variability of the plants. If you spot these weeds, please call Sue Donaldson, (775) 784-4848, to report a location and receive additional control recommendations.

The California Invasive Weed Awareness Coalition (CALIWAC) is sponsoring a "decision makers" Invasive Weed Tour originating from the State Capitol on July 25 as part of California Invasive Weed Awareness Week. The target audience is legislators (or their capitol legislative staffers); water districts (in Sacramento region and statewide water associations); and state agency leaders who may need additional education on invasive weed issues. Sacramento Weed Warriors, CALIWAC Educational Committee, California Exotic Pest Plant Council, and Lake Tahoe Basin Weed Management Association are organizing the tour.

last modified: August 30 2004

Lake Tahoe is Losing Water Clarity
Lake Tahoe waters have been losing transparency at an average of about one foot each year since the late 1960s.

Lake Tahoe’s exceptional clarity is a result of the absence of suspended sediment and free-floating, single-celled algae in the water. Given undisturbed conditions, the lake’s water quality would change so slowly the changes would be undetectable over a human lifetime. Human settlements and logging activities that began in the late 1880s have contributed to the rapidly declining clarity. Lake Tahoe’s clarity has decreased by more than 33 percent since the 1960s and is steadily declining at the rate of one foot a year. Scientists say that the rate of water quality deterioration at Lake Tahoe has been steady for so long it may become irreversible in 10 years.

Lake Tahoe’s water quality problems are not caused by industry or by wastewater treatment plants. The causes of water pollution are the daily activities of the thousands of residents and visitors in the Lake Tahoe watershed. We all need to learn to reduce our impact on the environment—impacts like erosion, over-fertilization, spills, leaks, and disturbances of soils and stream environment zones.

last modified: December 27 2005

Fish Species of the Lake Tahoe Basin
Lake Tahoe Report #151
January 9, 2006
By John Cobourn and Heather Segale

In terms of lakes, Tahoe is a relatively harsh environment for fish. It was cutoff from other bodies of water many thousands of years ago, so as it evolved, only seven species of fish evolved in it. However, since the introduction of humans and human intervention at Lake Tahoe, that number has changed.

According to Brant Allen, fisheries biologist with the UC Davis Tahoe Environmental Research Center, “The original native game fish was the Lahontan cutthroat trout, which is no longer in the lake. But, there are still six native species of fish swimming in Tahoe.” The Lahontan cutthroat trout, named for the distinctive red streak under its chin, once topped Lake Tahoe’s food chain and weighed as much as 40 pounds. This fish thrived in the Tahoe Basin and migrated the length of the Truckee River between Tahoe and Pyramid Lake.

The native fish that still survive in Lake Tahoe include:

· The mountain whitefish (Prosopium willaimsoni) is Lake Tahoe’s only native game fish. It lives near the bottom to a depth of about 100 feet.

· The Lahontan redside shiner (Richardsonius egregious) is a native minnow that is abundant in the shallow shorezone and can usually be seen in large numbers around marinas and rock crib piers. It grows to 3 to 4 inches long.

· The Lahontan speckled dace (Rhinichthys osculus) is another native minnow that grows to about 2 to 3 inches long. It is difficult to find, as it seeks the cover of rocky substrate on the bottom of the lake.

· The tui chub (Gila bicolor) is a bottom-oriented chub that feeds on zooplankton or sediments on the bottom of the lake.

· The Tahoe sucker (Catostomus tahoensis) is a bottom feeder that grows to about 16 inches long.

· The Paiute sculpin (Cottus beldingi) grows to about 3 inches long. It lives under rocks and is rarely observed in less than 10 feet of water.

The native Lahontan cutthroat trout went extinct in Lake Tahoe in 1939, due in part to overfishing, competition with nonnative species, and the development of dams. In particular, Derby Dam below Reno and Sparks and the Tahoe Outlet Dam in Tahoe City isolated the Tahoe population of cutthroat trout from other populations within the historic range.

Beginning in the late 1800s, when the effects of human environmental changes had reduced the numbers of Lahontan cutthroat in the lake, humans began introducing nonnative fish species in hopes of increasing Tahoe’s yield of game fish. These introductions included lake trout from the Great Lakes, Chinook salmon, Atlantic salmon, golden trout, Arctic grayling, Great Lakes whitefish, brook trout, brown trout, and rainbow trout. Of these fish species, the lake trout, brown trout, brook trout, and rainbow trout were able to establish self-supporting populations in the Tahoe Basin.

In the 20th century, additional introductions of nonnative invertebrates and fish further altered the Tahoe Basin ecosystem. Using the best available science at the time, exotic species were introduced with the intention of adding a recreational component or supporting an existing fishery. Unfortunately, not all of the species behaved as expected in the clear, cold waters of the Tahoe Basin.

After 70 years of alteration, the aquatic ecosystem now supports nonnative lake trout (Mackinaw) as the top predator. They are accompanied by rainbow trout, brown trout and kokanee salmon, providing multiple recreational fishing opportunities for shallow and deep-line anglers. The native Lahontan cutthroat trout is now among the most endangered western salmonids. Fortunately, as noted above, the other six native Tahoe fish species have survived the planned exotic introductions and continue to thrive within the Tahoe Basin.

In recent years, new threats to Tahoe’s remaining native fish have arisen. A number of warm-water fish species have been illegally introduced to Lake Tahoe, including largemouth and smallmouth bass, crappie, and sunfish. While these fish are typically associated with warm-water environments, their populations are able to grow and spread within the Tahoe Basin. Taking advantage of seasonally warm water in bays and marinas, the fish feed on native minnows and successfully spawn.

Scientists from University of California Davis and University of Nevada Reno plan to study the potential expansion of these species, and with help from the USDA Forest Service Lake Tahoe Basin Management Unit, implement a plan for their control. “The warm-water invasive species appear to pose a great risk to Tahoe’s remaining native species,” states Brant Allen a research biologist for UC Davis. “Their ability to consume large numbers of fish and the apparent overlap with native minnow spawning areas is a big concern.”

Warm-water fish invasions are not new to California. Nearby Lake Davis continues to experience problems resulting from the illegal introduction of northern pike, a voracious predator. Controlling the spread of similar species in the Tahoe Basin could go a long way to preserving native fish and assist the recovery of Tahoe’s once great Lahontan cutthroat trout.

The Lake Tahoe Report is a collaboration between John Cobourn, Water Resource Specialist with University of Nevada Cooperative Extension, and Heather Segale, Education and Outreach Coordinator for the University of California, Davis. For more information, contact Heather Segale, (530) 583-3279, or logon to www.lteec.org, www.tahoe.unr.edu, or terc.ucdavis.edu.

last modified: January 10 2006

Bald Eagle Viewing More Likely During the Winter
Lake Tahoe Report #153
January 23, 2006
By Heather Segale and John Cobourn

Sighting a bald eagle is a magnificent experience, especially after the bald eagle’s near extinction in the not-so-distant past. The bald eagle population fell to endangered levels of less than 500 pairs in the early 1960s due to hunting, habitat loss and contamination of waterways and food sources by various pollutants and pesticides, most notably DDT.

There was a similar drop in eagle populations at Lake Tahoe during the late 1980s, when the two nest sites in the basin were both inactive. There are usually only one or two pairs of bald eagles in the Tahoe Basin during the summer. However, during the winter, bald eagles migrate to Tahoe because it is more temperate than Alaska and Canada. According to wildlife biologist Stewart McMorrow, “as many as 20 eagles have been counted in the Tahoe Basin during the winter months.”

Bald eagles live near large bodies of open water, such as lakes, marshes, seacoasts and rivers, where there are plenty of fish to eat and tall trees for nesting and roosting. Bald eagles feed primarily on fish, but also eat small animals, such as ducks, coots, muskrats, turtles, rabbits, and snakes. Occasionally, they also eat dead animals. They are a kind of predator called raptors. They swoop down to seize fish in their powerful, long and sharp talons. They exert approximately 1,000 pounds of pressure per square inch in each foot. They can carry their food off in flight, but can only lift about half their weight. Bald eagles can fly at speeds of about 65 miles per hour in level flight, and up to 150 or 200 miles per hour in a dive.

Bald eagles are monogamous and mate for life. A Bald eagle will only select another mate if its faithful companion dies. They build large nests, called eyries, at the top of sturdy, tall trees. The nests become larger as the eagles return to breed and add new nesting materials year after year. Bald eagles make their new nests an average of 2 feet deep and 5 feet wide. Eventually, some nests become 10 feet wide and weigh several tons. When a nest is destroyed by natural causes, it is often rebuilt nearby. Bald eagles line their nests with twigs, soft mosses, grasses and feathers.

The female lays one to three eggs each spring, which hatch after about 35 days of incubation. Feathers of newly hatched bald eaglets are light grey, and turn dark brown before they leave the nest in about 12 weeks. When they are 3 or 4 years old, bald eagles have mottled brown and white feathers under their wings and on their heads, tails and breasts. The distinctive white head and tail feathers do not appear until they are about 4 to 5 years old. Their beaks and eyes also turn from dark brown to yellow during this time.

Bald eagles are about 29 to 42 inches long, can weigh 7 to 15 pounds, and have a wingspan of 6 to 8 feet. This makes them one of the largest birds in North America. Females are larger than males, but both have white heads and tail feathers and yellow beaks.

The bald eagle is our national symbol, so when it became threatened with extinction in the 1960s, people took notice. Strong endangered species and environmental protection laws, as well as active private, state and federal conservation efforts, have brought back the bald eagle population from the edge of extinction in the United States. The use of DDT pesticide is now outlawed in the United States, which has contributed greatly to the return of the bald eagle to America's skies. There are now over 5,000 nesting pairs and 20,000 total birds in the lower 48 states. There are over 35,000 bald eagles in Alaska.

There are several other common raptors living at least part of the year in the Lake Tahoe Basin. One of the most common is the osprey, which is somewhat similar in appearance to the bald eagle, having white markings on its head and throat and a dark brown back and tail. It also preys mostly on fish. Most nests that you see in the Tahoe Basin are osprey nests. Sometimes eagles will steal freshly caught fish from the slightly smaller ospreys.

Forest hawks, which do not fish for food, include the sharp-shinned hawk, the Cooper’s hawk, and the northern goshawk. Such raptors are called accipiters. Other raptors in the Basin include the merlin, the great horned owl, the western screech owl, the flammulated owl, the northern Pigmy owl, the northern Saw-whet owl, and the rare California spotted owl. Red tail hawks also frequent Tahoe, and peregrine falcons sometimes pass through the region.

For more information about the birds of the Tahoe Basin, visit http://www.fs.fed.us/r5/ltbmu/recreation/wildlife/birds.shtml.

The Lake Tahoe Report is a collaboration between John Cobourn, Water Resource Specialist with University of Nevada Cooperative Extension, and Heather Segale, Education and Outreach Coordinator for the University of California, Davis. For more information, contact Heather Segale, (530) 583-3279, or logon to www.lteec.org, www.tahoe.unr.edu, or terc.ucdavis.edu.

last modified: January 23 2006

Spot a Knapweed, Win a Prize
If you spot the dreaded Spotted Knapweed at Tahoe you may win a prize. Maybe it`s time for a day trip to the lake?

Spotted knapweed is at the top of the hit list of a local group out to control noxious weeds in the Tahoe Basin. Because it’s in full bloom now, they’re asking residents to report sightings and call them in for tracking and treatment advice. The noxious weed is also making a foothold in the Truckee Meadows.

The Tahoe Basin Weed Coordinating Group describes spotted knapweed as a purple, aster-like flower with flower bracts that are spotted, growing 1 foot to 3 feet tall and blooming in mid- to late-summer. It is distinguishable from some other noxious weeds by its thornless, stickerless stems.

Although it doesn’t have thorns or stickers, the weed has many other undesirable qualities. It is highly competitive and reduces desirable and native plant communities, producing a substance that inhibits growth of other plants. It can also irritate human skin. Perhaps most important to the Tahoe Basin, it decreases water quality. A recent study found stream sediment was 192% higher at spotted knapweed-dominated sites than it was at bunchgrass-dominated sites. Stream sediment is a significant factor in reducing the clarity and quality of water both at Lake Tahoe and in the Truckee River.

According to Sue Donaldson, chair of the weed group and water quality education specialist at University of Nevada Cooperative Extension, each spotted knapweed plant can produce up to 18,000 seeds in one year. “So, it’s important to identify early infestation so they can be controlled. In Montana, it has already invaded over 4.5 million acres,” she said. “We still have a chance to control it here in Nevada, before it gets out of hand – that’s why it’s at the top of our list,” she said. Although it is native to Eurasia, it thrives in our Western climate, especially in rangeland and forest settings.

About 140 infestations have been identified in the Tahoe Basin.

The weed group is asking residents to be on the lookout for the weed. If you think you have spotted it, get an accurate description of t! he location, do not pull or treat the weed, and call to report the location to the group. The weed group has prizes for those who help find the weed. In Nevada, call Donaldson, (775) 784-4848.

last modified: July 22 2003

Tahoe Homeowners: Watch Out for These Dangerous Garden Runaways
By Ellen Swensen, Lake Tahoe Basin Weed Coordinating Group

The Lake Tahoe basin is being invaded by non-native, invasive weeds. These weeds are prolific, highly competitive, and hard to control. They displace native plants and decrease wildlife habitat. One of their biggest threats to Tahoe is their tendency to increase soil erosion and stream sedimentation, which can damage the lake’s famed, clear water quality.

Many of these weeds have accidentally been brought to this country from other parts of the world. They have spread into the Tahoe basin via many sources including cars, erosion-control straw bales, and domestic stock animals. However, many invasive weeds in Tahoe actually started out harmlessly as ornamental plants in home gardens! These “escaped ornamentals” have invaded neighboring gardens and vacant lots, and have moved into surrounding native areas, where they continue to thrive and spread.

There are several escaped ornamentals that currently threaten native areas at Tahoe. These include Dalmation toadflax, yellow toadflax, oxeye daisy, and Scotch broom.

Work closely with your local plant nursery or landscaper to select ornamentals that are safe to plant at Tahoe. Avoid using seed mixes and plants from catalogs not local to the Sierra. Try to select native plants whenever possible. In addition to the many environmental benefits of natives, they are usually not invasive. Work with your nursery on safe alternatives.

last modified: June 20 2003

Group Targets “Triple Threat” Weeds
The Tahoe Basin Weed Coordinating Group, a multiagency coalition of invasive weed experts, is asking the public’s help in identifying and reporting sightings of three invasive weeds emerging in the Tahoe Basin.

Invasive weeds are nonnative plants that are prolific, highly competitive, and difficult to control. They displace native plants, decrease wildlife habitat, alter normal ecological processes, reduce recreational values, and cost us millions of dollars each year in treatment and production losses.

In the Tahoe Basin, one of the biggest threats from invasive weeds is their tendency to increase soil erosion and stream sedimentation, which can damage Tahoe’s famed water quality.

While the Weed Coordinating Group is working to control all invasive weeds in the Basin, it is especially interested in finding new infestations of three particularly dangerous weeds, which the group has dubbed “Tahoe’s Triple Threat.” These weeds are Spotted Knapweed (Centaurea maculosa), Yellow Starthistle (Centaurea solstitialis), and Diffuse Knapweed (Centaurea diffusa).

If you think you have found any of these weeds in or around the Tahoe Basin: 1) get an accurate description of the location, 2) do not pull or treat the weed, and 3) report the sighting to the appropriate county contact listed below.

Douglas Co., NV - Douglas Co. Weed District, (775) 782-9835
Washoe Co., NV- UNR Cooperative Extension, (775) 784-4848
Nevada Co., CA - Agricultural Commissioner, (530) 273-2648
Placer Co., CA - Agricultural Commissioner, (530) 889-7372
El Dorado Co., CA - Agricultural Commissioner, (530) 273-2648

View the Priority Invasive Weeds to Watch For in the Tahoe Basin for photos of these invasive weeds.

last modified: June 25 2002

Eurasian Watermilfoil
Eurasian Watermilfoil

Eurasian watermilfoil grows submerged in our lake, with vine-like stems from 6 feet to nine feet long. It has feather-like leaves up to 1 and one-half inches long, whorled around the stems in groups of four. Broken-off plant fragments are capable of growing roots and starting new plants.

Why Should I Care About Eurasian Watermilfoil?
Eurasian watermilfoil threatens our pristine lake. It quickly displaces native water plants. In New York’s Lake George, it cut native water plant species in half in just two years! Its rapid growth and eventual decay degrades water quality and uses up oxygen needed to support fish populations. For boaters, its dense matted growth restricts movement. Its vine-like stems wrap around propellers and may be sucked into water intakes. Most importantly, its decay releases phosphorous into the lake, supporting algae growth. Tahoe’s blue could become murky green very quickly if this weed is not stopped!

Efforts are underway to reduce the amount of Eurasian watermilfoil in Lake Tahoe. You can help prevent further spread. Here’s how:

• Remove all aquatic vegetation from your boat and trailer before launching at or leaving any boat ramp. Dispose of plant parts away from the lake or waterway.
  
• When leaving infested areas in Lake Tahoe, stop for a moment and run your boat in reverse. This helps knock off plant parts and leaves them in the infested areas, preventing spread.
  
• Pass the word among friends and neighbors so they’ll help control this weed.

last modified: June 25 2002

Why Should We Care About Noxious Weeds?
Noxious weeds:

• Displace native plants. It has been estimated that competition from noxious weeds has resulted in an 18% decline in endangered plant species. Lake Tahoe is home to several rare and endangered plant species that contribute to the uniqueness of this upper elevation ecosystem.
  
• Reduce biodiversity.
  
• Alter normal ecological processes (e.g., nutrient cycling, water cycling) that help maintain functioning ecosystems.
  
• Decrease wildlife habitat.
  
• Increase soil erosion and stream sediment, damaging water quality.
  
• Cost millions of dollars each year in weed control efforts and lost revenues.
  
• Reduce forage production for livestock and wildlife.
  
• Decrease property values.
  
• Reduce recreational values and uses and decrease tourism.
  

Noxious and invasive weeds are:

• Aggressive nonnative invaders
  
• Detrimental to crops and native plant communities
  
• Damaging to the environment
  
• Difficult to control
  

As invasive weeds continue to proliferate at alarming rates in the Basin, it is essential that we undertake a Basin-wide effort to effectively stop the spread. Developing community partnerships and coordinating management efforts will allow us to more efficiently tackle the economic and ecological problems associated with noxious weed infestations.
Interested agencies, biologists, and community groups have recently joined to form an invasive weed coordinating group that is committed to sharing information on the management and control of invasive weeds within the Lake Tahoe Basin. To join the effort, call Sue Donaldson, University of Nevada Cooperative Extension, (775) 784-4848.

last modified: May 9 2002

Center for Invasive Plant Management Website
The Center for Invasive Plant Management (housed in the Dept. of Land Resources and Environmental Sciences at Montana State University) maintains a website (www.weedcenter.org) designed to serve as an information clearinghouse for land managers in the west. Our site, completely redesigned and revised in May 2004, includes up-to-date noxious weed lists, databases and image galleries, educational resources, case studies of restoration projects, information on ecological management, and much more. CIPM offers several annual grants that can be applied for online, and we also maintain a current list of other funding opportunities. Invasive plant information can be found for each state and province in the west. We maintain a current calendar of weed events, as well as a "what's new" section on our home page. We hope that you will take a look at our site and find it useful. Any comments, additions, or corrections would be very much appreciated; please send them to the webmaster via the website at www.weedcenter.org.

last modified: November 8 2004

Review of TRPA Official Plant List
Jenny Leach has been hired as a vegetation technician by TRPA on a temporary basis ending in December. She has undertaken a review of TRPA’s official plant list, which can be found in the Home Landscaping Guide for Tahoe and online at >http://www.unce.unr.edu/publications/EBPubs/EB0201/Chapter07Table1.pdf and http://www.unce.unr.edu/publications/EBPubs/EB0201/Chapter07Table2.pdf (this is the accent plant list).

Jenny is particularly interested in comments on the accent plant list and the grasses. Please send her comments by October 20, including reasons for your objections to any listed plants (see contact info above). We have a real opportunity to decrease the use of invasive plants at Tahoe, as this list is considered the primary resource for selecting plant materials in the basin.

You can reach Jenny at jleach@trpa.org or (775) 588-4547, Ext. 307.

last modified: October 1 2004