- Author: Mackenzie Patton
- Posted by: Gale Perez
The Invasive Pest Spotlight focuses on relevant or emerging invasive species in California. In this issue we are covering brooms, a group of invasive shrubs.
Brooms are upright shrubs in the legume family that typically produce small, yellow, pea-shaped flowers. Shrubs range from 3 to 10 feet tall. They produce flowers from mid spring to summer and produce seed pods in late summer. All brooms are prolific seed producers, with a single shrub producing as many as 2,000 to 3,500 pods containing up to 20,000 seeds.
While brooms are attractive plants, they grow in dense stands that outcompete many native plants. These dense stands are highly flammable and increase the risk of wildfires. The most common species found in California are Scotch broom, French broom, Spanish broom, and Portuguese broom. Scotch broom is often found on interior mountains and on lower slopes in Northern California and is very prevalent in the Sierra Nevada foothills. Without management, these plants can survive for about 12 to 17 years, producing thousands of seeds.
Actions You Can Take
First, avoid planting any broom species. While most retailers do not sell the most common invasive brooms, many do sell hybrids that could become highly invasive in the natural landscape. There are similar-looking alternatives to brooms, such as forsythia and golden currant. Contact your local UC Master Gardeners or visit PlantRight.org for a list of other alternatives.
If you have brooms on your property and want to remove them, there are many different nonchemical and chemical methods that are effective in controlling these plants. These options are extensively detailed in the UC IPM publication Pest Notes: Brooms.
Original source: UC IPM's Home & Garden Pest Newsletter Summer 2023 issue
- Author: Mackenzie Patton
The Invasive Pest Spotlight focuses on relevant or emerging invasive species in California. In this issue we are covering brooms, a group of invasive shrubs.
Invasive Broom facts
Brooms are upright shrubs in the legume family that typically produce small, yellow, pea-shaped flowers. Shrubs range from 3 to 10 feet tall. They produce flowers from mid spring to summer and produce seed pods in late summer. All brooms are prolific seed producers, with a single shrub producing as many as 2,000 to 3,500 pods containing up to 20,000 seeds.
While brooms are attractive plants, they grow in dense stands that outcompete many native plants. These dense stands are highly flammable and increase the risk of wildfires. The most common species found in California are Scotch broom, French broom, Spanish broom, and Portuguese broom. Scotch broom is often found on interior mountains and on lower slopes in Northern California and is very prevalent in the Sierra Nevada foothills. Without management, these plants can survive for about 12 to 17 years, producing thousands of seeds.
Actions you Can Take
First, avoid planting any broom species. While most retailers do not sell the most common invasive brooms, many do sell hybrids that could become highly invasive in the natural landscape. There are similar-looking alternatives to brooms, such as forsythia and golden currant. Contact your local UC Master Gardeners or visit PlantRight.org for a list of other alternatives.
If you have brooms on your property and want to remove them, there are many different nonchemical and chemical methods that are effective in controlling these plants. These options are extensively detailed in the UC IPM publication Pest Notes: Brooms.
[Originally featured in the Summer 2023 issue of UC IPM's Home & Garden Pest Newsletter]
- Author: Elaine Lander
In the newly revised Pest Notes: Brooms, UCCE advisor Scott Oneto and UC Davis weed scientists Joe DiTomaso and Guy Kyser explain the issues with planting these invasive species. The publication includes expanded sections on biology and management and updated herbicide information. Effective application techniques with new photographs are also in this new version.
Read more in the full Pest Notes: Brooms on the UC IPM website.
/div>- Author: Scott Oneto
A recent find in El Dorado County has weed scientists, land managers, foresters, botanists, and plant conservationists throughout Northern California very excited over a tiny mite.
The broom gall mite has recently been observed attacking the invasive plant Scotch broom (Cytisus scoparius) in California's natural landscapes. Scotch broom, desired for its bright yellow flowers and rapid growth, was first introduced into North America as an ornamental and for erosion control. However, its ability to outcompete native plants and form dense stands has also made it one of California's worst wildland weeds (Figure 1).
The mites cause galls, small abnormal growths on the plant's buds, to form during feeding, greatly reducing Scotch broom's ability to grow and reproduce (Figure 2). This mite is considered to be an ideal biological control agent due to its specialized feeding habits and the debilitating damage it can cause to invasive weeds. In some areas, the gall mite has already killed large stands of broom (Figure 3).
The Scotch broom gall mite, more closely related to spiders and ticks than insects, is a type of eriophyid mite that is nearly invisible to the naked eye, measuring roughly the width of a human hair (Figure 4). Although the mite is tiny, the galls formed by plants in response to the mite's feeding are quite noticeable. The small fuzzy masses occur along the length of the stem and can be quite numerous.
Native to Europe, the mite was first found on Scotch broom in the Tacoma, Washington, and Portland, Oregon, regions in 2005. Since that time the mite has become established throughout western Washington and Oregon and even into parts of British Columbia. Up until 2013, the mite had only been found as far south as Ashland, Oregon, with no occurrences in California.
However in March 2014, a landowner in El Dorado County brought a sickly
Since the first detection in El Dorado County, USFS, UCCE, and the California Department of Food and Agriculture have been on the lookout for other occurrences of the gall mite on Scotch broom. Surprisingly, the mite has since been found in many areas throughout El Dorado, Placer, and Nevada counties; but how it got there is a mystery. Mites are known to travel long distances using wind currents and by hitching rides on animals, humans and equipment. It is likely that many more finds will be forthcoming.
Since the mite is a beneficial biological control agent and not a pest, do not apply pesticides to kill it! The broom gall mite can help greatly in the fight to control Scotch broom plants that have invaded wildlands throughout California. If you or your neighbors see evidence of Scotch broom gall mites, please report it on the University of California Cooperative Extension website: ucanr.edu/broomgallmite.
Alternatives to Scotch broom
Although some retail nurseries still sell a variety of broom species, homeowners should avoid planting them. Depending on your climate, a number of alternate plant species with similar attributes that are are not invasive weeds may be available. See the PlantRight article from our April 2015 Retail IPM Newsletter about alternative plants to recommend to your customers or contact your county UC Master Gardener program or UC Cooperative Extension office for a list of local recommendations.
Scotch broom currently infests millions of acres throughout California, causing loss of native plant biodiversity and an increased fire risk. The USFS and other agencies spend a considerable amount of time and taxpayer money each year treating Scotch broom plants either by applying herbicides or prying them up by the root. With the mites' help, we'll make much greater progress toward reducing Scotch broom infestations.
For more information about Scotch broom and other brooms, read UC IPM's Pest Note: Brooms. For plant alternatives, see PlantRight's list.
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