Invasive Species
FAQ's about Invasive Species in California
What are invasive species?
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Africanized Honey Bees
Africanized honey bees (AHB) are a hybrid between European and African bee subspecies which were inadvertently released in Brazil in the 1950s...
Argentine Ant
In addition to being a nuisance in urban settings, the Argentine ant is problematic in both natural and agricultural ecosystems. Argentine ants are also an economic threat because of their potential to tend plant pest insects, such as mealybugs, scales, and aphids...
Ash Whitefly
Ash whitefly represents an outstanding recent biological control success in California. Ash whitefly was first introduced into California in the late 1980s and was a significant pest of fruit and shade trees...
Asian Citrus Psyllid
Asian citrus psyllid is an efficient vector of the citrus disease huanglongbing (HLB), previously called citrus greening disease, which is one of the most destructive diseases of citrus worldwide. In North America, the psyllid vector...
Asian Long-Horned Beetle
A long-horned beetle has been discovered attacking ornamental trees in New York City and Chicago. Warehouse detections of this pest have been made in most states in the northeastern portion of the United States as...
Asian Tiger Mosquito
The Asian tiger mosquito entered the United States in shipments of used tires from northern Asia in the mid-1980s. Although the Asian tiger mosquito has not been found in California, it can survive in a broad...
Asian Wooly Hackberry Aphid
The Asian woolly hackberry aphid was first detected in North America on native hackberry trees in Georgia in 1996 and has been subsequently found throughout the southeastern states. In 2002 the aphid was detected...
Asiatic Citrus Canker
Asiatic citrus canker is a widespread bacterial disease in Asia and in certain other citrus-growing regions of the world, but it was eradicated from the U.S. after its introduction in the early part of this century. New infestations...
Australian Gum Tree Weevil
Eucalyptus is a ubiquitous landscape and windbreak tree throughout southern and central California. The trees are valued for their fast growth and tolerance of poor soils and drought. Eucalyptus is now threatened...
Avocado Lace Bugs
The common name "lace bug", is derived from the highly reticulate "lace-like-patterning" of the thorax and wings of adults. There are around 1,820 species of lace bug and 154 species are found in North America. Some lace bug....
Avocado Thrips
Avocados are subtropical perennial fruit trees 6-10 meters in height. California produces 95% of the nation's crop, and 85% of this harvest is from one cultivar, the black fruit Hass avocado. Annually, 6,000 growers in California...
Bagrada Bug
Feeding results in large stippled or wilted areas on leaves. Often the growth of newly formed central shoots or heads of plants become stunted. Populations can build up quickly reaching damaging densities that require control....
Black Scale
In California, black scale is a periodic pest of citrus in southern California and a consistent pest of olives in the San Joaquin Valley. It was introduced into the United States and California sometime before 1880. It now...
Blue Gum Galling Wasp
Beginning in the 1980s, a series of eucalyptus-feeding insects invaded the California region, beginning with the borer Phoracantha semipunctata (Coleoptera: Cerambycidae), which was first detected in...
Brown Citrus Aphid
The brown citrus aphid is an insect pest of all citrus varieties. The brown citrus aphid infests the stems and new leaves of citrus trees and in addition to feeding damage, it is a highly efficient vector of citrus tristeza virus...
Brown Widow Spider
The two major symptoms of a brown widow bite were that the bite hurt when it was inflicted and it left a red mark. These two symptoms are not much different from the bite of normal household spiders. However, there is one recent report of a verified brown widow bite manifesting in more...
California Red Scale
California red scale was introduced into California between 1868 and 1875, apparently on citrus seedlings from Australia. The scale insect is native to Southeast Asia but has been transported on citrus seedlings to all...
Caulerpa taxifolia or Killer Alga
Caluerpa is capable of rapid growth and reproduction of the invasive strain is asexual and dispersal occurs through fragmentation. Fragments as small as 1 cm give raise to viable plants. Long distance spread occurs...
Chytrid Fungus
Upwards of 40% of amphibian species are in decline worldwide, owing to several factors such as habitat loss, environmental degradation, pollutants, and disease. Recently the fungal pathogen Batrachochytrium dendrobatidis has emerged as a major threat to amphibians. Amphibians infected with B. dendrobatidis develop chytridiomycosis, which causes eventually death...
Citricola Scale
In California, citricola scale is a serious pest in San Joaquin Valley citrus when broad-spectrum pesticide use is reduced. It was also a serious pest in the inland areas of southern California until 1935, when an...
Citrus Greening (Huanglongbing)
huanglongbing (HLB), previously called citrus greening disease, is one of the most destructive diseases of citrus worldwide. Originally thought to be caused by a virus, it is now known to be caused by unculturable...
Citrus Leafminer
Citrus Leaf Miner rapidly became a significant pest, with infestation rates of up to 90% in some areas in Florida being observed within the year of introduction. By 1995, the citrus leafminer was discovered in...
Diaprepes Root Weevil
Diaprepes is originally from the Caribbean and was introduced into Florida in the 1960s. The larval stage feeds on roots and causes serious damage to ornamentals, citrus and a number of important agricultural crops...
Didymo or Rock Snot
is a highly invasive species of freshwater diatom that can form large and extensive mats in rivers, streams, and lakes. Didymo is native to cool temperate areas of the northern Hemisphere including Europe, North America, and Asia. In 2004, didymo was discovered...
Elm Leaf Beetle
Elms are a common shade tree planted throughout the U.S. and are valued for their large, high canopies and the shade they provide. The elm leaf beetle was accidentally introduced into the U.S. in the 1830s and is...
Eucalyptus Leaf Beetle
Eucalyptus leaf beetle is a new pest of ornamental eucalyptus and was introduced from Australia into southern California around 2003. It is not easily controlled by native parasites or predators. In Australia it is commonly known as...
Eucalyptus Longhorned Beetle
Eucalyptus that were grown in California from seeds were relatively free of insect pests until the 1980’s, when the eucalyptus longhorned borer, Phoracantha semipunctata, was discovered in Orange County in 1984...
German Yellowjacket
Accidentally introduced years ago from Europe into New England, the German yellowjacket recently became firmly established in California. As do most yellowjackets, this species aggressively defends its colony...
Giant Whitefly
The giant whitefly, a pest of over 50 common ornamental plants, was discovered in southern San Diego County in the early 1990s. It continues to extend its range northward into California and poses a serious threat to the...
Giant Reed, or Arundo
Arundo is an exceptionally fast growing plant, growing about 4 inches per day and reaching a mature height of 25 feet in about 12 months. An acre of arundo can produce about 25 tons of biomass per acre for each of two annual harvests. The plant is very tolerant of a variety ...
Glassy-Winged Sharpshooter
The Glassy-winged Sharpshooter (GWSS), likely introduced from the southeastern U.S. as eggs on nursery stock, was first observed in Orange and Ventura counties in 1989. It has a large plant-host range and is especially...
Goldspotted Oak Borer
The goldspotted oak borer (GSOB) was first detected in 2004 in San Diego Co., California by the California Department of Food and Agriculture during a survey for exotic woodborers...
Light Brown Apple Moth
Light Brown Apple Moth larvae feed on leaves and buds reducing photosynthetic rate, deforming growth patterns, which leads to general plant weakness and disfigurement. ...
Myoporum Thrips
This thrips causes considerable leaf deformation through the feeding activity of larvae and adults. This pest is likely native to Australia or New Zealand where it is probably a specialist...
New Zealand Mud Snail
As the common name indicates, this invasive pest is native to New Zealand. New Zealand mud snail has had a long invasion history. It was first found in the United Kingdom in 1859 ...
Pea Leafminer
In California, a new biotype of the pea leafminer was introduced in Northern California and is expanding rapidly into Central and Southern California. Already this insect has become a major pest of vegetable crops...
Persea Mite
Persea mite, was first described in 1975 from specimens collected from avocado foliage intercepted from Mexico at an El Paso, Texas, quarantine facility. Persea mite is native to Mexico and damages avocados in arid regions...
Potato Psyllid
Potato psyllid causes yield loss by directly feeding on crop plants causing a significant reduction in quality and crop longevity. Yield losses of greater than 85% have been reported in potatoes and tomatoes....
Quagga Mussels
Quagga and zebra mussels are freshwater bivalves that are native to eastern Europe. The quagga mussel originated from Dnieper River drainage of Ukraine. The zebra mussel was first described from the lakes of southeast Russia....
Redbay Ambrosia Beetle and Laural Wilt
In 2002, a non-native insect, the redbay ambrosia beetle, Xyleborus glabratus (Coleoptera: Scolytidae), was first detected in the United States near Port Wentworth, Georgia. The beetle was likely introduced in untreated wooden packing material, such as crates and pallets, imported through the shipment of goods from its native range in southeast Asiar....
Red Bug
Several species of brightly colored, ground dwelling bugs are familiar to California residents who observe the insects running over dry ground, feeding and migrating among urban vacant lots and weedy fields. Most familiar are those species with contrasting red and black coloration which feed upon developing or mature seeds and seed pods.....
Red Gum Lerp Psyllid
High density red gum lerp psyllid populations secrete copious amounts of honeydew and excessive feeding pressure causes premature leaf drop. Heavily infested leaves are readily noticeable because of the large...
Red Imported Fire Ant
These ants pose an immediate threat to the California's economy because they require a quarantine of nursery products because ants maybe accidentally shipped in potting soil to new areas....
Russian Thistle
Russian thistle, commonly known as tumbleweed, is a profusely branched annual herb. Its efficient taproot, abundant seed production and reduced leaf surface adapt this weed well to disturbed semiarid...
Saltcedar / Chinese Tamarisk
Native to Eurasia, several species of saltcedar were introduced to Southern California and Arizona in the early 1800s for ornamental use, bank stabilization, and as windbreaks. Since that time, saltcedar has...
Silverleaf Whitefly
When the silverleaf whitefly struck southern California's desert valleys in fall 1991, clouds of the tiny insects could be seen moving across the region, which produces 90 percent of the fall and winter vegetables grown in the...
Spotted Wing Drosophila or Cherry Vinegar Fly
This fly causes economic damage berry crops, in particular fresh cherries, strawberries, raspberries, blackberries, and blueberries. It may also attach grapes, and perhaps some stone fruits, however this is not certain. Damage to berries is caused by white legless maggots...
Sting Nematode
The sting nematode is an important pest on most agricultural and horticultural crops, including turf, citrus and grapes. This ectoparasite is native to sandy soils in the Southeastern and Midwestern United States...
Sudden Oak Death
Phytophthora ramorum is one of several species of related fungus-like water molds (oomycetes) that are pathogenic to plants. Another member of this group, P. infestans, is notable as the cause of the potato blight epidemics in Europe in the mid-1800s. More recently, P. ramorum has emerged as a major threat to California woodlands...
Tipu Psyllid
Tipu psyllid nymphs and adults nymphs are tiny insects that feed on phloem. Extensive feeding causes the leaves on host plants to curl and drop prematurely. Nymphs produce pelletized wax-like residue and nymphs and adults...
Vine Mealybug
Vine mealybug, even more so than other mealybugs, produces copious amounts of honeydew that causes sooty mold damage. High densities of the insect lead to decreased plant vigor, defoliation, and the insects themselves may be contaminants of grape clusters...
Western Flower Thrips
In Southern California, western flower thrips is the most common vector responsible for transmission of Tomato Spotted Wilt Virus (TSWV). The pathogen was discovered on tomatoes in 1915 in Australia, and has been...
Zebra Mussels
Quagga and zebra mussels are freshwater bivalves that are native to eastern Europe. The quagga mussel originated from Dnieper River drainage of Ukraine. The zebra mussel was first described from the lakes of southeast Russia....