Whitefly

CISR: Giant Whitefly

Anonymous — Mon, 20 Jan 2020 20:56:37 +0000

CISR: Giant Whitefly Anonymous (not verified) Mon, 01/20/2020 - 12:56 More Blog Posts CISR Team October 22, 2009

The Situation: The giant whitefly, a pest of over 50 common ornamental plants, was discovered in southern San Diego County in 1992. It continues to extend its range northward into California where it was found around San Luis Obispo on the central Coast by the late 1990’s, and by around 2005 this pest was established in northern California in the Bay Area and surrounds (e.g., San Jose). Giant whitefly poses a serious threat to the nursery and landscape industry. The giant whitefly is native to Mexico and probably moved into California through accidental introductions of infested plants.

Damage: The giant whitefly attacks and seriously damages many ornamental plants familiar in California home landscapes, including hibiscus, begonia, bird of paradise, lilies, and banana, and has recently been found on citrus. The potential host list is around 200 plants in at least 35 families. The giant whitefly can reproduce rapidly, and populations can become quite large, especially on red hibiscus. Young whitefly nymphs produce large amounts of wax, and the entire undersurface of leaves can become covered with a thick, white mat of wax. Whitefly adults and young feed on plant sap, extracting important nutrients that lead to defoliation, stunting and plant death. A sticky honeydew is also excreted by whiteflies while they feed, covering leaf surfaces and other nearby plants and leading to the growth of black sooty mold.

Economic Impact: California’s nursery industry represents a $2 billion enterprise while the landscape maintenance industry generates $5.4 billion annually. The wide host range of the giant whitefly, its ability to reproduce rapidly in the absence of natural enemies and its prolific feeding habits, make it the most serious pest of ornamental plants and home landscapes in California today.

Distribution: The giant whitefly is currently found from San Diego County to the Bay Area in northern California. Its populations are extraordinarily heavy in most affected areas. Some plants surveyed have been entirely covered with whiteflies. The distribution of the whitefly continues to expand northward. It is unknown at this time how far it will spread. The major impact of this whitefly will be felt in the nursery industry and California’s urban landscapes. This pest was detected in Texas in 1991; 1996 it was found in Florida and Louisiana, and in Hawaii in 2002.

Research: Researchers from UC Riverside and UC Cooperative Extension have mapped the distribution of the giant whitefly in California and have surveyed the impact of any native natural control. Exploration of Mexico, the whitefly’s presumed native home, resulted in the discovery of two parasitic wasps Idioporus affinis and Encarsiella noyesii, that attack the nymphs of giant whitefly. These natural enemies have been cleared through federal and state quarantine and are undergoing evaluation in California, where they have shown considerable impact in some areas. Other species of parasitic wasp parasitizing giant whitefly nymphs in California include Entedononecremnus krauteri and Encarsia hispida, but their overall impact appears to be limited.

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CISR: Silverleaf Whitefly

Anonymous — Mon, 20 Jan 2020 20:55:22 +0000

CISR: Silverleaf Whitefly Anonymous (not verified) Mon, 01/20/2020 - 12:55 More Blog Posts CISR Team October 22, 2009

The Situation: When the silverleaf whitefly (SLW) (also known as Bemisia tabaci strain B) struck southern California’s desert valleys in fall 1991, clouds of these tiny insects could be seen moving across the region, which produces 90 percent of the fall and winter vegetables grown in the U.S. Research conducted at the University of California and elsewhere has helped growers better manage SLW, but this pest can still cause crop losses each year in this important agricultural region. The exact geographic origin of SLW is unknown, but may be somewhere around India and was thought to have been accidentally introduced in the USA around 1986 and spread via the ornamental plant trade out of the southeast USA.

Damage: SLW has been reported on an estimated 500 plants worldwide. Favorite hosts include melons, broccoli, cabbage, cotton, squash and a number of ornamental (e.g., poinsettia) and native plant species. SLW damages crops in a variety of ways. Feeding whiteflies extract important plant nutrients, causing defoliation, stunting and poor yield. Sticky honeydew is excreted by whitefly nymphs and adults, promoting the growth of black sooty mold on leaves. The mold renders cotton difficult to process and requires washing of vegetables, thus increasing production costs. SLW also causes several plant physiological disorders, including tomato irregular ripening and squash silverleaf (hence the common name). SLW can vector several viral plant diseases.

Economic Impact: Since 1991, SLW has cost an estimated $500 million to California agriculture. This translates to roughly $774 million in private sector sales, 12, 540 jobs and $112.5 million in personal income. Nationally, SLW damage has been estimated to be in excess of $1 billion.

Distribution: Silverleaf whitefly populations persist in California’s southern deserts, primarily the Imperial, Palo Verde and Coachella valleys. They also are found in the southern San Joaquin Valley, where the impact is heaviest on cotton. Other US states affected by SLW are Arizona, Texas and Florida.

Research: The University of California developed a four-pronged approach to combat SLW: (1) Whitefly Biology – Taxonomic and life history studies of the insect enabled researchers to identify and develop control strategies to exploit perceived weaknesses. (2) Cultural Control – The use of host-plant relationships in order to recommend cultural practices which may negatively impact the whitefly’s development without having to depend on insecticides. (3) Biological Control – The use of parasites, predators and pathogens for the suppression of pest populations. (4) Chemical Control – The use of agrichemicals, including naturally derived plant extracts that have strong efficacy against the pest, and little negative impact on beneficial organisms and the environment.

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CISR: Ash Whitefly

Anonymous — Mon, 20 Jan 2020 20:41:56 +0000

CISR: Ash Whitefly Anonymous (not verified) Mon, 01/20/2020 - 12:41 More Blog Posts CISR Team October 22, 2009

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 dollars, most severely impacting the shade and fruit tree nursery industry and commercial pomegranate orchards. Since the biological control program of the ash whitefly established widespread control with the use of a small parasitic wasp, Encarsia inaron(Hymenoptera: Aphelinidae), there have been no reports of economic damage and this pest no longer poses an economic threat to California. One year after E. inaron releases began in 1992, parasitism of ash whitefly nymphs averaged between 63 and 97%. Based on the economic value of preserving healthy ornamental/evergreen pear and ash trees, the ash whitefly biocontrol effort provided $219,822,823 and $298,803,970 in esthetic benefits to California in wholesale and retail replacement values, respectively. For every dollar spent by the State Biological Control Program and the University of California, approximately $181 in wholesale and $245 in retail esthetic value for the primary hosts of the ash whitefly were preserved.

Distribution: The ash whitefly occurs in low densities throughout California except in mountainous areas where temperatures are too low for its survival. The range of this pest has extended into other states in the U.S. and around the world (e.g., New Zealand, Mexico, and Argentina) and complete biological control has been achieved in these invaded areas.

Research: The University of California, Riverside’s Department of Entomology and the California Department of Food & Agriculture developed a biological control program which involved scientists exploring for natural enemies in the pest’s area of origin in the Middle East and Mediterranean. Several candidate species were shipped where they were tested for efficacy against the ash whitefly. One candidate, Encarsia inaron, shipped to the University of California, Riverside’s federal quarantine facility was cleared for release in areas of ash whitefly infestation in California and was soon responsible for the dramatic crash of local ash whitefly populations. This tiny parasite is still keeping the ash whitefly under strict control in all areas of California.

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CISR: Citrus Leafminer

Anonymous — Mon, 20 Jan 2020 20:27:08 +0000

CISR: Citrus Leafminer Anonymous (not verified) Mon, 01/20/2020 - 12:27 More Blog Posts CISR Team October 22, 2009

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 fall months. Mature citrus trees, except for coastal lemons, can tolerate heavy fall flush damage with little impact to fruit production. Coastal lemons have continuous flushing of leaves and produce multiple crops of fruit. The continuous flushing allows prolonged infestations of CLM that reduce vigor of trees and fruit production.

Economic Impact: Economic losses due to the citrus leafminer include: 1) increased costs for producing nursery trees due to pesticide treatments, 2) reduced sales to home gardeners, and 3) increased orchard production costs in new plantings and coastal lemons, either directly, through the use of pesticides (largely ineffective), or indirectly, through the disruption of biological control and integrated pest management programs. Chemical control methods against the citrus leafminer are estimated to cost between $25 per acre in nurseries and $50 per acre in new plantings and lemon orchards for each treatment.

Distribution: CLM is native to Asia and can be found throughout Asia, Australia, South Africa, parts of West and East Africa, the Mediterranean area, Saudi Arabia to India, the Caribbean Islands, Central America, Mexico and South America. CLM arrived in Florida in 1993 and spread into Louisiana and Texas. In 2000, CLM became established in southern California, and has since spread northward into all major citrus growing regions on the state.

Research: Enhancement of biological control using parasitic wasps that attack CLM larvae or pupae is considered the most effective means of managing infestations of the citrus leafminer. In Florida, at least nine species of parasitoids have moved naturally onto this introduced pest. Research in California is focused on the identification and distribution of native and exotic natural enemies of CLM larvae, economic studies of the impact of CLM on lemon production, and the utilization of pheromone confusion and pesticides to control CLM in nurseries.

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