- 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.
![A long, speckled brown insect with a pointed head on a green leaf. A long, speckled brown insect with a pointed head on a green leaf.](http://ucanr.edu/blogs/UCIPMurbanpests/blogfiles/107885.jpg)
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]
/h2>/h2>If you have eucalyptus trees, you might have noticed white, crusty growth on the leaves. Or maybe you saw a sticky, blackened mess of fallen leaves under a eucalyptus tree. These are signs of the redgum lerp psyllid, one of the most common psyllid pests that damages eucalyptus trees in California.
The adult psyllid is very small and as nymphs, they are concealed under a waxy cap, or lerp. As they feed, they excrete honeydew which can lead to the growth of black sooty mold, the source of those sticky leaves under the tree.
Although under biological control in coastal areas, this pest is still a problem under some growing conditions and on specific Eucalyptus species. Cultural practices to manage lerp psyllids, such as avoiding fertilization of eucalyptus trees and pruning only when and where needed, can help reduce lerp psyllid problems.
The newly revised and expanded Pest Notes: Eucalyptus Redgum Lerp Psyllid, authored by entomologists Timothy D. Paine, UC Riverside; Kent M. Daane, UC Berkeley and UC ANR Kearney Agricultural Research and Education Center; Steve H. Dreistadt, UC IPM Program; and Raymond J. Gill, California Department of Food and Agriculture, contains detailed information about the identification, biology, and management of this pest.
This revision has more information about the lerp psyllid's biology and damage they cause on eucalyptus, a list of eucalyptus trees resistant to this pest, and an expanded section on biocontrol, with detailed information about the imported parasitic wasp that only attacks redgum lerp psyllid.
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- Author: Karey Windbiel-Rojas
Invasive pests threaten California's natural environments, agricultural production, structures, landscapes and gardens, causing billions of dollars of damage to our agricultural systems and natural areas each year.
Throughout history, humans have moved plants and animals around the globe, bringing them from their native lands to new settlements. In California, some introductions did unexpected damage while others, such as food crops, had positive outcomes. New species are often intentionally introduced, although numerous exotic species arrive in products brought into California accidentally by travelers or shipped in commercial trade. Many invasive plant problems began as ornamental plants for sale by nurseries and garden centers. Exotic and invasive plants are still available in commercial nurseries.
What can you do about invasive pests?
Here are tips and resources that you can use to help stop or slow the spread and introduction of invasive pests.
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Don't plant or release invasive plants into the environment. Also, avoid dumping aquatic plants or aquarium water into local waters, since many aquarium plants are highly invasive.
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Use plants native to your area for landscaping.
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Don't bring foreign plant or animal material into California.
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Be careful when moving firewood.
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Learn to identify invasive species new to California.
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Report invasive species in your area! Contact your local UC Cooperative Extension office or Agricultural Commissioner to report invasives and to get information on controlling invasive species on your property.
For more information and resources on invasive pests, visit the UC IPM Invasive and Exotic Pests page.
[Original article published in the Summer 2020 issue of the Retail Newsletter]
- Author: Belinda J. Messenger-Sikes
- Author: Karey Windbiel-Rojas
Weeds are usually thought of as native plants we don't want in areas such as landscapes, fields, or vegetable gardens either because they reduce economic output or they are considered aesthetically displeasing. Invasive plants are generally non-natives that infest natural ecosystems and can become problems.
There are four distinctions between a weed and an invasive plant. The first is how they are introduced to an area. Weedy plants in gardens, landscapes, or in agricultural fields are usually accidentally introduced. While that is sometimes true for invasive plants, they are more often intentionally introduced as ornamental plants, for aquarium use, or for food or fiber purposes.
Next, weeds require human disturbance, such as tilling, to establish and flourish in an area. Invasive plants do not require any human assistance to grow and spread.
Invasive plants tend to be more persistent in an area once established and don't require irrigation or fertilization so are capable of growing and flourishing in areas without human assistance.
Finally, most weedy plants grow on land as annuals or herbaceous perennials, but invasive plants can be aquatic, parasitic, vining, woody, or herbaceous. Their life cycles range from annual to perennial.
For more information about invasive plants, see the UC IPM Pest Notes on Invasive Plants and Woody Weed Invaders.
[Original article published in the Summer 2020 issue of the Green Bulletin]
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- Author: Donald R. Hodel
- Posted by: Elaine Lander
Damage and Signs
Identification and Biology
The shell of this snail is unusually variable in appearance, especially in the dark bands and other markings. The adult has a medium-sized shell about the size of a nickel or dime. The non-glossy shell is typically ivory white (rarely pink), but can be light beige with narrow, dark brown bands. A similar looking but much less damaging snail, the milk snail (Otala lactea), sometimes occurs with the white garden snail and can be confused with it. The milk snail tends to be larger, up to 1.2 inches in diameter, and the inside of the thick opening is dark.
Unlike most snails and slugs, the white garden snail climbs and rests in a dormant state (estivates) on the cooler and least wind-exposed sides of vertical surfaces like trees, shrubs, fences, posts, and walls during the hot, dry season (Figure 3). They can survive for long periods by forming a wall of dry mucus to seal the shell opening and reduce water loss. They typically congregate in great numbers in an exposed, conspicuous manner to “ride out” the hot, dry season until the return of more suitable conditions in the fall.
Management
Control of the white garden snail can be time-consuming, difficult, and costly because they have a high reproductive rate, they climb high on objects, and they estivate for long periods. Effective management of this snail must rely on a combination of methods, including exclusion, early detection, and a variety of treatments.
Like most land snails, they move slowly so in order to reach new areas, they must be aided by people. To exclude the white garden snail from your area carefully check crates, boxes, and plants shipped from infested areas. To detect this snail, search plants, fences, posts, walls, and other vertical surfaces.
Measures used to manage other snails, such as sprays, baits, traps, and barriers, are only effective when the white garden snail is active and foraging on or near the ground. However, unlike other snails, this snail estivates in the open where they are visible and conspicuous, perhaps offering the best opportunity for their control; thus, hand-picking, knocking down, and then sweeping or vacuuming might be the best option, especially with limited infestations or in small landscapes. Because it can estivate in vacant fields or untended areas adjacent to landscape sites, these untended areas should be carefully checked and mowed.
For extensive details on the various management methods for the white garden snail, including habitat modification, biological control, hand-picking, and chemical control, see the full article at https://ucanr.edu/sites/HodelPalmsTrees/files/294710.pdf.
Word of Caution
Use rubber or latex gloves when picking or handling snails and vegetation with their slime trails, and wash hands thoroughly afterwards. Snails and slugs are intermediate hosts of rat lungworm disease, which is likely present but not yet officially detected in California. Rat lungworm disease is caused by a parasitic nematode that can attack the human brain and spinal cord if ingested.
[Original article published in the Summer 2020 issue of the Retail Newsletter]
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