- Author: Belinda Messenger-Sikes
Exotic and invasive pests threaten California's natural environments, agricultural production, structures, landscapes and gardens. Exotic pests are organisms introduced into an area beyond their natural range and become pests in the new environment. Most introductions have been unintentional and accidental, but some invasive plant problems began as ornamental plants for sale.
Invasive species prevention is the most economical and desirable approach to invasive species management. However, when prevention isn't successful, pesticides may be needed to eradicate or control invasive species.
What are some problematic invasive species?
Aedes mosquitoes can transmit some of the most debilitating and deadly mosquito-borne pathogens to humans, such as Zika virus, dengue virus, chikungunya virus, and yellow fever virus. One Aedes species is also capable of transmitting heartworm to dogs. These invasive mosquitoes are now present in many regions of California, from Shasta County to San Diego County.
The glassy-winged sharpshooter is a large leafhopper that can transmit several important, often fatal, plant diseases in California. This includes Pierce's disease of grape, alfalfa dwarf, almond leaf scorch, and mulberry leaf scorch. Pierce's disease is of most concern in California since the state produces 94% of U.S. grapes.
Pampasgrass is a common ornamental landscape plant that readily naturalizes throughout California's coastal areas and some interior regions. Historically, pampasgrass was planted for erosion control, but it has since escaped cultivation and spread along sandy, moist ditch banks throughout coastal regions of southern California. Pampagrass can also grow in the hot, dry climate of inland areas of California.
Hydrilla is an invasive, aquatic weed that can be found in many slow-moving freshwater bodies in California. The plant forms large mats that can crowd out native plants, restrict water flow, and interfere with boating and fishing. These mats can reduce habitat for fish and other wildlife, degrade water quality, and increase the risk of flooding
What can you do?
- Learn to identify invasive species new to California. See the UC IPM Invasive and Exotic pests pages.
- Use plants native to your area for landscaping. Native plants can require less water, provide habitat for native butterflies and pollinators, and usually have fewer pest problems, too.
- Don't release exotic or invasive plants into the environment. Never dump your aquatic plants or aquarium water into streams or creeks, since many aquarium plants are highly invasive.
- Be careful what you bring back when you travel. Don't bring foreign plant or animal material into California.
- Don't move firewood. Buy it where you burn it.
- Report invasive species in your area! Contact your local UC Cooperative Extension office or Agricultural Commissioner.
- Cooperate with authorities during invasive species control activities.
[Originally featured in the Summer 2024 edition of the Home and Garden Pest Newsletter]
- Author: Lauren Fordyce
Pampasgrass (Cortaderia selloana) is a common ornamental landscape plant that readily naturalizes throughout California's coastal areas and some interior regions. Historically, pampasgrass was planted for erosion control, but it has since escaped cultivation and spread along sandy, moist ditch banks throughout coastal regions of southern California. Pampagrass can also grow in the hot, dry climate of inland areas of California.
A similar-looking invasive grass, jubatagrass (Cortaderia jubata), is more widespread, aggressive, and is a major pest in coastal redwood forest areas. Jubatagrass thrives in cool, foggy environments and does not tolerate temperature extremes or drought.
Both pampasgrass and jubatagrass outcompete native plants; a single floral plume can make 100,000 seeds in a year. They create fire hazards with excessive build-up of dry leaves, leaf bases, and flowering stalks. In addition, their tough leaves have serrated edges that can easily cut skin.
What can you do?
Choose non-invasive ornamental grasses to plant in your garden or landscape. Many species, including native grasses, can resemble pampasgrass or jubatagrass. This includes several species of Muhlenbergia: deer grass, white awn muhly, and Lindheimer's muhly. California native Pacific reedgrass grows well on the coast and is deer resistant. For a large, tough bunchgrass, try giant sacaton, a native of the Southwest. Giant wildrye, another California native, will grow into dense stands that attract birds.
To learn more about these invasive species and alternatives to plant, visit https://plantright.org/invasive/cortaderia-selloana/ or https://plantright.org/invasive/cortaderia-jubata/.
For more information on their management, visit https://wric.ucdavis.edu/information/natural%20areas/wr_c/cortaderia_jubata-selloana.pdf.
- Author: Lauren Fordyce
The glassy-winged sharpshooter is a large leafhopper that can transmit several important, often fatal, plant diseases in California. This includes Pierce's disease of grape, alfalfa dwarf, almond leaf scorch, and mulberry leaf scorch. Pierce's disease is of most concern in California since the state accounts for about 94% of U.S. grape production.
Pierce's disease of grape has been reported in many counties throughout California. View a map of the current distribution of the pathogen. Glassy-winged sharpshooter adults are ½ inch long and dark brown to black with light-colored spots on their heads. Eggs are laid in masses under the leaf surface, resembling a greenish blister. Once the eggs hatch, the egg mass turns brown and remains as a scar on the leaf.
What can you do?
Glassy-winged sharpshooter feeds on many woody plants as well as annual and perennial herbaceous plants. It is common to find this invasive insect on acacia, avocado, eucalyptus, citrus, crepe myrtle, heavenly bamboo, grape, photinia, pittosporum, hibiscus, periwinkle, xylosma, some roses, and many others. Inspect plants for this pest, especially new shoots or growth. Use yellow-sticky card traps to monitor their populations.
If you find glassy-winged sharpshooter in an area not currently known to have this pest, immediately call the California Department of Food & Agriculture Pest Hotline at 1-800-491-1899, or contact your local agricultural commissioner's office.
To learn more about this pest and the diseases is transmits, visit Pest Notes: Glassy-winged Sharpshooter.
- Author: Lauren Fordyce
Hydrilla is easily spread since it often breaks apart into tiny pieces that can each produce new plants. It also produces special survival structures on the stems (turions) and in the sediment (tubers). Each tuber can produce a new plant. The tubers can survive up to seven years in the sediment before sprouting, even if no water is present.
What can you do?
Hydrilla can be introduced to new areas on boats, trailers, fishing tackle, and sometimes even waterfowl. Inspect these items and remove any plant material from them before leaving the water. Hydrilla is also commonly sold for use in aquariums. Never dump your aquarium water into waterways or down the drain.
The California Department of Food and Agriculture (CDFA) conducts eradication efforts in multiple counties throughout California. The largest eradication effort is the infestation in Clear Lake which began in 1994. The program has successfully eradicated hydrilla from 15 counties since 1976.
If you find hydrilla, contact your local agricultural commissioner's office or the California Department of Food and Agriculture (CDFA) Pest Hotline: 1-800-491-1899.
Learn more about this invasive aquatic weed by visiting the links below:
- California Invasive Plant Council https://www.cal-ipc.org/plants/profile/hydrilla-verticillata-profile/
- Educational pamphlet on hydrilla https://www.cdfa.ca.gov/plant/npdes/docs/aquatic-weeds/HydrillaPamphlet.pdf
- Hydrilla Eradication Program https://www.cdfa.ca.gov/plant/ipc/hydrilla/hydrilla_hp.html
- Author: Lauren Fordyce
Aedes mosquitoes can transmit some of the most debilitating and deadly mosquito-borne pathogens to humans, such as Zika virus, dengue virus, chikungunya virus, and yellow fever virus. One Aedes species is also capable of transmitting heartworm to dogs. These invasive mosquitoes are now present in many regions of California, from Shasta County to San Diego County. View a map of Aedes distribution by county.
The yellow fever mosquito (Aedes aegypti), the Asian tiger mosquito (Aedes albopictus), and the Australian backyard mosquito (Aedes notoscriptus) are unlike most native mosquitoes. They prefer to bite during the day, especially around your legs and ankles. Adults are black with white stripes on their legs and back.
Many Aedes mosquitoes live in close contact with people and can breed in backyards and even inside homes. They are known as “container breeding mosquitoes” because they lay eggs in small containers, such as flowerpots or old tires. Eggs are laid in moist areas just above the water surface, can overwinter, and are resistant to drying so may remain viable for months or longer. Their entire life cycle can occur in as little as 7–8 days.
What can you do?
In many areas of California, public Mosquito and Vector Control Districts work to keep mosquito numbers down to tolerable levels. Since these mosquitoes primarily breed on residential properties, you can help by eliminating mosquito breeding sources around your home. This includes draining standing water in rain gutters, buckets, and watering cans. Change the water in pet dishes and bird baths weekly. Clean up clutter in the yard since these mosquitoes can lay their eggs in anything that can hold water. Standing water or ponds can be treated with Bacillus thuringiensis subspecies israelensis (Bti) or mosquito fish. Wear mosquito repellents and protective clothing outdoors. Keep mosquitoes out of your home by keeping fine mesh screens on windows and doors in good condition.
Learn more about invasive Aedes mosquitoes and how to protect yourself by visiting the following resources:
- UC IPM Pest Notes: Mosquitoes: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
- Mosquito repellent information from the California Department of Public Health: https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/Mosquito-Repellent.aspx
- Interactive map of Aedes distribution in California: https://cdphdata.maps.arcgis.com/apps/webappviewer/index.html?id=57367199287a4d18a2cecf107854255b
- Invasive Aedes fact sheet from the Mosquito and Vector Control Association of California: https://acrobat.adobe.com/id/urn:aaid:sc:US:908f4b9e-8266-47b3-9e3d-ec165913fc7f?viewer%21megaVerb=group-discover
[Featured in the Summer 2024 edition of the Home and Garden Pest Newsletter]
