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The Situation: A large number of introduced Eucalyptus pests have invaded California over the last ten years, including boring beetles, psyllids, gall forming wasps, and leaf chewing beetles in the family Chrysomelidae. The blue gum psyllid was the first to become a pest of ornamental eucalyptus, silver-leaved mountain gum or baby blue gum, and Eucalyptus pulverulenta Sims. The blue gum psyllid was not a pest for long, however, due to the introduction of Australian parasitoids.

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 one of the eucalyptus tortoise beetle species. It is known as an outbreak pest of commercial E. globules, blue gum plantations in southeastern Australia.

Damage: Eucalyptus leaf beetle prefer to oviposit in batches of 30-60 eggs on younger foliage; whereas, adults will feed on older foliage. Hatchlings feed gregariously on the younger foliage causing damage to leaf edges that resembles caterpillar feeding damage, and it can be quite extensive. The immature stages of Eucalyptus leaf beetle are daytime feeders. In(…)

The Situation: Arundo donax, also known as giant reed or arundo, is native to Eastern Asia but has been widely planted around the world because this plant has a variety of practical uses. Arundo has been used for walking sticks, fishing poles, musical instruments, and recently it is being investigated as a biofuel source. Arundo was first planted in California in the 1820’s to provide roofing materials and for erosion control in the Los Angeles Basin area. Arundo has also been widely planted in parts of the USA, Mexico, Central and South America, the Mediterranean, the Caribbean, Australia, and New Zealand. In many of these areas it is now considered an invasive weed (e.g., California, Texas [especially the Rio Grande River Valley], Hawaii, Nevada, Utah, Missouri, Virginia, New Mexico, and Florida).

The Problem: 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 of environmental conditions and can be found growing in damp riparian areas, and it is tolerance(…)

The Situation: 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 infesting freshwater rivers in the South Island of New Zealand, the first record of this diatom in the Southern Hemisphere. Even in parts of what is presumed to be the native range of didymo, this pest is starting to expand its range aggressively. The reasons for this change in behavior are not known.

The Problem: Because of the extensive smothering of rocks and other underwater structures, habitat and food sources can be changed or eliminated to the detriment of other organisms living in infested waterways. Excessive biomass accumulations associated with didymo result from asexual reproduction. When the diatom divides, the stalk that was attaching the diatom to a rock or some other hard surface divides also. As this process repeats itself a mass of branched interconnected stalks results. It is the aggregation of these stalks, which are highly resistant to degradation, that causes the formation of large mats of didymo, or rock snot.(…)

The Situation: 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 Asia (e.g., India, Japan, Myanmar, and Taiwan). Adult beetles are small, 2 mm long, slender, cylindrical, and brown-black in color. The larvae are white, legless grubs with an amber colored head capsule and are found feeding in galleries in infected trees. These beetles can be difficult to identify, and a specialist should be consulted for positive identification of adults and larvae due to their similarity to other closely related species.

The Problem: By 2005, about three years after the redbay ambrosia beetle was first found on the East coast of the USA, it was found to be associated with redbay (Persea borbonia) and sassafras (Sassafras albidum) mortality in coastal areas of Georgia, South Carolina, and Florida. Potential host plants in the Eastern USA will likely include all members of the Lauraceae family such as Asian spicebush (Lindera latifolia), yellow litsea (Litsea elongate), and the threatened and endangered native(…)

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.  In 2008, it was found in the same county attacking coast live oak, Quercus agrifolia, canyon live oak, Q. chrysolepis, and California black oak, Q. kelloggii, on the Cleveland National Forest.  GSOB is playing a major role in on-going oak mortality on federal, state, private, and Native American lands in southern California.  GSOB larvae feed under the bark primarily at the interface of the sapwood and phloem on the main stem and larger branches.  Larvae kill patches and strips of phloem and cambium, resulting in limb and branch die back and, eventually, tree death.  Because of host distribution, GSOB has the potential to spread further north in California and cause similar tree mortality.  Since very little published information is available on this insect, additional research is needed to determine the life cycle, behavior, and management strategies.

Identification
Adults are about 10 mm long and 2 mm wide.  They are bullet-shaped and can be identified by the six golden-yellow spots on the dark green forewings.  Mature larvae are about 18 mm long and 3(…)

The Situation: Originating in Asia, the citrus leafminer (CLM) was first discovered in Florida in 1993.  These small moths 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 Texas, Central America, western Mexico (Colima), and several Caribbean islands.  In 2000, it arrived in southern California via Mexico and is now expanding its range northward.

Damage: Larvae of the citrus leafminer form serpentine mines in the tender new flush leaves of all varieties of citrus.  The mining causes the new flush to twist and curl and prevents it from expanding fully.  The citrus leafminer has a short developmental time (2-3 weeks), and as many as 7-8 generations occur in California.  In Florida, where bacterial canker is present, leaf mining activity creates opportunities for canker to enter, increasing the incidence of this disease.  Canker is not present in California.  In California, thus far, the damage has been primarily to nursery trees and new plantings because the larvae must have young citrus foliage to mine and feed on.  The pattern of CLM infestation of mature citrus has been predominantly in the(…)

The Situation: In southern California, the native western flower thrips (WFT) Frankliniella occidentalis is the most common vector responsible for transmission of an exotic plant virus, Tomato Spotted Wilt Virus (TSWV). The pathogen was discovered on tomatoes in 1915 in Australia, and has been spreading around the world ever since. TSWV is a tospovirus (Bunyaviridae) of which there are at least 12 known plant pathogenic species that are spread by around 10 species of thrips. TSWV became problematic in California when a new highly pathogenic isolate established. This virus has become a major problem for pepper and tomato growers from Orange County to the Mexican border in San Diego County.

Damage: Once the plant is infected it can not be cured and different symptoms may be expressed depending on the strain of the virus. Typical symptoms include stunting, distortion, mottling, general necrosis, and ring spots. Virulent forms of the virus can kill plants resulting in major economic losses. When feeding thrips larvae acquire TSWV they are permanently infected (the virus replicates in the thrips and stays with them as they mature.) An infected adult that lands on a susceptible plant and starts feeding can transmit the pathogen in as little as(…)

The Situation: The Sting nematode is an important pathogen 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. In 1992, UC Riverside nematologists discovered that several golf courses in the Coachella Valley were heavily infested with sting nematodes. The warm climate, irrigated sandy soils of California inland deserts and the ability of the nematode to feed on a very wide range of hosts offer ideal conditions for rapid multiplication and spread of the invasive pathogen.

Damage: Like all plant parasitic nematodes, B. longicaudatus feeds by puncturing plant cells with a mouth stylet and withdrawing cell contents. It does not enter the roots but attacks from the outside, mainly near the root tip. Its long mouth stylet can damage the meristematic cells leading to stunting of the roots. Feeding wounds are often points of entry for disease-causing microorganisms which otherwise would not be able to enter healthy plant tissues. These secondary infections increase the stress on the plants and can accelerate cell and root death. Above-ground disease symptoms are non-specific. They typically resemble symptoms associated with plant drought stress and nutritional deficit such as

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The Situation: Africanized honey bees (AHB) are a hybrid between European and African bee subspecies which were inadvertently released in Brazil in the 1950s. They have spread to the south as far as northern Argentina and to the north into the United States, as well as throughout much of South and Central America. They entered Texas in 1990, Arizona and New Mexico in 1993, and California in 1994. European bees have long been established in much of the United States, including California. Following colonization, unmanaged bee populations are replaced or mixed with AHB.

Damage: Immigration of AHB results in a greater density of highly defensive bee colonies. AHB respond to activity near their colonies with increased numbers of stinging bees over much greater distances. This can make them life-threatening, especially to people allergic to stings or with limited capacity to escape (the young, old and handicapped), and to confined livestock or pets. In each country into which they have migrated, they have killed humans and animals. Beekeeping is also disrupted by AHB, which are more difficult to manage and transport. Maintaining colonies of European bees in areas with AHB is the best defense, but to do so beekeepers face greater expense,(…)

The Situation: Ash whitefly represents an outstanding 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 such as ash, pear and pomegranate. In the absence of natural enemies, ash whitefly populations exploded out of control. The pest originated and occurs widely in the Middle East and Mediterranean and was accidentally introduced into California via infested plant material. The University of California, Riverside’s Department of Entomology has provided aid in controlling this pest in areas in which ash whitefly has subsequently invaded.

Damage: Ash whitefly infests 40 species of plants in California. Left unchecked, its numbers rise to substantial levels within a wide variety of host plants. Feeding by adult and young whiteflies extracts plant nutrients, resulting in defoliation of trees, loss of fruit and, in severe cases, death of the host tree. Severe impact on outdoor activities in urban areas was caused by the enormous numbers of flying whitefly adults. Honeydew build-up on exposed surfaces also resulted in ruined paint on cars parked beneath shade trees along city streets.

Economic Impact: The economic impact of the ash whitefly has been estimated in the millions of(…)