L.A. County Weed Management Area

The LA County WMA meets quarterly at the Los Angeles County Agricultural Commissioner/ Weights & Measures Department office, at 12300 Lower Azusa Road in Arcadia. The meetings start at 10:00 a.m., and generally last until noon. Future meetings are announced through E-mail. To be placed on the E-mail list, call Rose @ (626) 575-5462

The LA County WMA is currently undertaking several projects to begin the process of effectively managing some of the most invasive weeds in the County. Starting in 2001, we began conducting surveys of selected invasive plants based on the threat they posed to the environment and the ability to control them. Some of our specific control projects are:

First found by a beekeeper in the Angeles National Forest, we are in the third year of an eradication project that continues to show promising results. We have used a number of methods to eradicate this invasive weed such as hand removal, quarantine, and chemical treatments. With the outstanding cooperation of the US Forest Service, we estimate that we have achieved better than 90% reduction of plant biomass after the first year. Our eradication plan now centers around the prevention of seed production that will add to the already established "seed bank". A "seed bank" consists of seeds that already exist in the soil from previous years growing seasons. With each plant producing upwards of 40,000 seeds, and seeds being viable for 3-5 years, we have a lot of work ahead of us. A second, much smaller infestation has been found in Charmlee Park in Malibu, and a single plant was recently detected in Lancaster near the Kern County border. This last find was the result of a landowner recognizing the plant from an "invasive species alert" postcard developed by the Weed Management Area to help the public to help us identify new areas of infestation. To obtain copies of the post card, call Rose at (626) 575-5462.

With the last years' dry spring triggering an early fire season, we have seized the opportunity created by the Copper Hill Fire in Santa Clarita. Large areas of San Francisquito Canyon were burned including the Arundo along the creek. This unique situation removed the dead canes and last years' growth by fire, and the cost of removal is greatly reduced allowing us to treat just the re-sprouts. In the third season of suppression, we are encouraged that the only sprouting is coming from previously untreated rhizomes that did not sprout after the fire last year. There plants were treated in the spring to further control the infestation. There are several other Arundo suppression efforts being undertaken by WMA members. Members help each other out with expertise, materials, and moral support.

January 2004.

A regenerating stand of Arundo
in San Francisquito Canyon

Los Angeles County Agricultural Chemical Sprayer Chris Linardy treating resprouts in San Francisquito Canyon

We have been working with the National Park Service at their Paramount Ranch property located in the Santa Monica Mountains National Recreation Area. A portion of Medea Creek runs through this area, and it is infested with Perennial Pepperweed. Currently, a portion of the upper creek channel has been mowed to prevent flowering and subsequent seed production. We began herbicide treatments of re-sprouts enabling biodiversity to return to this unique riparian habitat. The Park has re-vegetated this portion of the creek to provide the necessary 'pressure' to begin the slow process of reclaiming this habitat.

Geraldton Carnation Spurge infests revegetaion efforts taking place at Soltice Canyon near Malibu.

This weed was first found in the late 1990's infesting the El Segundo Dunes near LAX and up in the Solstice Canyon area of the Santa Monica National Recreation Area. Surveying began in the summer of 2001 in the Malibu drainage to delimit the size of the infestation. We started in areas that were likely to be favorable to the weed, and moved out to areas that were less favorable. Concluding our surveys in early winter of 2001, we found that the infestation is considerably more widespread than earlier believed, making eradication only possible in small areas. During our survey, a satellite infestation was found in Monterey Park on property owned by the Metropolitan Water District (MWD). Permission was secured to treat the MWD infestation, and about 3 acres of spurge were treated. Surveys of this same property during the spring of 2002 showed excellent control was achieved. In cooperation with the National Park Service, we plan to eradicate Geraldton Carnation Spurge in Zuma Creek and Solstice Creek using a variety of control methods, and try to limit its spread elsewhere.

Tree Spurge Control

Tree Spurge (Euphorbia dendroides) was discovered in the late spring of 2002 infesting the area around the Chantry Flats Ranger Station. Not much is known about this plant, but it grows to be 8 feet tall and appears to be spreading down the hill into Santa Anita Canyon. We have entered into a cooperative agreement with the US Forest Service to continue to control this and several other invasive species in the area. Native plant species have begun to repopulate the areas.

Chantry Flats, USFS, north of Arcadia

Tree spurge is a hardy perennial that requires many treatments.

We have entered into a cooperative agreement with the US Forest Service to continue to control this and several other invasive species in the area. Native plant species have begun to repopulate the areas.

Arundo is cut then treated immediately.