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]