Posts Tagged: scotch broom

Scotch Broom Gall Mite: A New Partner in Broom Management for California

[From the July 2015 issue of the UC IPM Retail Nursery and Garden Center IPM News] A recent find...

New book helps pros manage invasive weeds in California forests

Beautiful but unwelcome in California wildlands, brooms are shrubs introduced into North America from Europe in the mid-1800s. Common species include Scotch broom (Cytisus scoparius) and Portuguese broom (Cytisus striatus). Brooms were introduced as ornamentals, but also were used extensively for erosion control along roadsides and in mined areas.

Now growing profusely in California forests, on roadsides, and wildlands, brooms:

• Crowd out out desirable vegetation
• Form impenetrable thickets that limit access to some areas
• Shade out tree seedlings, and make reforestation difficult
• Burn readily, increasing the intensity of fire, and carry fire to the tree canopy
• Are toxic to cattle and horses and unpalatable to most wildlife
• Produce abundant, long-lived seed
• Are able to fix atmospheric nitrogen, giving broom a competitive advantage over native plants

Management of these and other weeds are presented in the recently published second edition of Forest and Right-of-Way Pest Control. Invasive species that create a dangerous wildfire hazard and crowd out desirable vegetation and wildlife are examples of why this book emphasizes vegetation management and pesticide handling, including correct equipment calibration and effective herbicide application. The second edition also provides broader coverage of insects, plant pathogens, vertebrate pests, and the various practices to manage them, recognizing that lands commonly have multiple uses and when and how pests are managed depends on many considerations with sometimes conflicting goals.

One of many new features in this edition is a section with expectations and review questions, which will help professionals pass DPR's tough applicator certification examinations. The book may be used as a guide to safe and effective pest management on public and private forests, tree plantations and nurseries, and along roads, railways, utility corridors, biking and hiking trails, and other rights-of-way. Nearly 200 photos and illustrations, 56 tables and sidebars, and 11 main chapters aid in pest identification and problem diagnosis and provide users with pesticide and nonpesticide solutions.

Experts with Cal-Fire, Caltrans, PG&E, USDA Forest Service, private industry, the University of California (UC) Berkeley and Davis campuses, UC County Cooperative Extension offices, and the California Department of Pesticide Regulation (DPR) contributed to Forest and Right-of-Way Pest Control, prepared by UC ANR's Statewide Integrated Pest Management Program.

Forest and Right-of-Way Pest Control is available for $35 online in the UC ANR Catalog. The table of contents and more information about the book are available on the UC IPM website. You can also preview and electronically search the contents on Google Books.

Beautiful but ecologically harmful shrubs get a foothold in California forests

A glorious foothill display of yellow flowers and their spicy-sweet fragrance may delight the senses, but they pose a serious problem for California.

Scotch, Spanish and French broom were introduced from Europe in the mid-1800s as lovely, easy-to-grow garden accents and land stabilizers, but they have become aggressive invaders threatening native plants and increasing fire hazards.

“These brooms crowd out our native flora and form large, dense stands of just broom,” said Scott Oneto, UC Cooperative Extension advisor in the Central Sierra. “It’s also displacing the birds and animals that would live in this environment with native plants.”

The characteristics of invasive brooms cause several problems. The plants grow large and upright, developing thick trunks at the base. After its relatively short life span - typically 7 to 8 years, 15 at the most – they die and become tinder-dry woody skeletons that can burn high and hot.

The brooms are also a member of the legume family. Legumes are unique in the plant world. They have evolved a symbiotic relationship with bacteria that live on their roots. The bacteria are able to pull nitrogen from the atmosphere and deposit it into the soil, where it feeds the plant.

“These soils are naturally very low in nitrogen,” Oneto said. “Our native plants thrive in low-nitrogen soils. Large populations of broom are changing the soil chemistry so even after they are removed, the area is no longer ideal for our native vegetation.”

Large stands of broom are also a significant concern for rangeland managers. Cows don’t like the taste; only goats will eat it. When the plant is grazed off or cut back, it readily re-sprouts from the crown. The plant’s spread is bolstered by its intriguing ability to scatter seeds widely. Brooms grow seed pods that are naturally spring loaded. When the seeds are ready for dispersal, they fling from the pod with the force of a tiny explosion.

In collaboration with the non-profit California Invasive Plant Council, which received a grant from the Sierra Nevada Conservancy, Oneto is working to eradicate broom from a particularly sensitive location. Highway 120, for many the “gateway to Yosemite,” has populations of French and Spanish broom.

“We’ve started by mapping the broom along Highway 120 and plan to eliminate the population to prevent it from moving further into the forest and eventually into Yosemite National Park,” Oneto said.

The grant is providing the funding for environmental and regulatory compliance so that control measures can be implemented.

“Once the regulatory compliance is complete, the project will be shovel-ready and we can begin treatment,” Oneto said.

Despite French and Spanish broom’s invasive nature, the heat-tolerant greenery and pea-like spring floral display still inspire people to plant them in landscapes and even parks. Brooms are occasionally found in retail nurseries along with a cousin, called “sweet broom,” that is touted as a sterile, non-invasive substitute. However, DNA research conducted by scientists in the Department of Plant Sciences at UC Davis found that sweet broom hybridizes with French broom, potentially contributing to the invasive weed problem.

“If broom is growing wild or as an ornamental on your property, we suggest you remove it and replace it with a non-invasive plant,” said Rebecca Miller-Cripps, natural resources program representative with UCCE Central Sierra. For example, forsythia produces yellow flowers and a shrub of about the same size and shape as brooms, but isn’t invasive, she said.

For more about invasive broom, see the video below:

UCCE Central Sierra Plans for Broom Removal Project

Seeing yellow these days? As in…those brightly-blooming yellow-flowering shrubs along roads...

Scotch broom in flower

Cytisus scoparius flowers from UC Repository.

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