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Mediterranean Fruit Fly

On Sept. 16, 2004, five adult Mediterranean fruit flies, Ceratitis capitata (Weidemann), commonly called Medflies, were detected in a residential neighborhood within the southern limits of the city of Tijuana, Mexico, by program personnel with the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service during routine servicing of pest detection traps. Identification of the pest was confirmed by the California Department of Food and Agriculture (CDFA) in cooperation with USDA. In response to the detection, the Mexican Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food and USDA have implemented a program to eradicate the potentially devastating pest. Employees of CDFA and the San Diego County Agriculture Commissioner's Office are assisting in eradication efforts.

What are the "basics"?

The Mediterranean fruit fly (Ceratitis capitata), commonly called Medfly, or Moscamed in Spanish, is one of the world's most destructive agricultural pests.

The female Medfly attacks ripening fruit, piercing the soft skin and laying eggs in the puncture. The eggs hatch into larvae (maggots), which feed inside the fruit pulp.

What do they look like and how long do they live?

The adult Medfly is slightly smaller than a common housefly and is very colorful. It has dark blue eyes, a shiny, black thorax (back), and a yellowish abdomen with silvery cross bands. Its wings, normally drooping, display a blotchy pattern with yellow, brown, and black spots and bands.

The life cycle of the Medfly has five phases:

(1) the adult female deposits eggs under the skin of fruit, (2) the eggs hatch and produce maggots or wormlike larvae, (3) the larvae feed on the pulp of fresh fruits and vegetables before dropping to the ground, (4) the larvae transform into pupae in the soil, and (5) the pupae mature into adults and emerge from the soil. Under tropical summer weather conditions, the Medfly completes its life cycle in 21 to 30 days.

What is the history of this pest?

The Medfly originated in Africa. It has since spread throughout the Mediterranean region, southern Europe, the Middle East, western Australia, South and Central America, and Hawaii. In general, it is found in most tropical and subtropical areas of the world.

The Medfly became established in Hawaii in 1910. Hawaii remains infested with this pest, and no eradication program is currently under way. The first U.S. mainland infestation occurred in Florida in 1929. Several infestations have occurred on the mainland since then. However, State and Federal eradication programs in California, Florida, and Texas have prevented it from becoming established.

How do we get rid of it?

The eradication of the Medfly is accomplished by action in three areas: survey, regulation, and control.

Survey-The U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS), along with State departments of agriculture, maintains trapping programs in high-risk areas of States susceptible to Medfly establishment. When one or more Medflies is collected in an area, APHIS and State officials immediately implement a delimiting survey. Using the detection site as the focal point, field crews position additional traps to determine if an infestation exists and to locate and define the limits of the infested area.

Regulation-If an infestation exists, Federal and State quarantine regulations are imposed to help prevent artificial spread of the pest. Federal quarantine laws regulate the interstate movement of any article that may harbor the fly. State regulations control the movement of these articles going to uninfested areas of the same State. Articles regulated by State and Federal authorities include all Medfly-host fruits and vegetables present in the area. Open-air fruit and vegetable stands must provide protective covers for the produce to prevent infestation, and commercial and home-grown produce may not be moved without special inspection and treatment.

Control-Three kinds of treatment are used alone or in combination to eradicate the Medfly.

Aerial and Ground Bait Spray Application

This spray is approved for use by the Environmental Protection Agency. The spray contains minimal amounts of an insecticide and a protein/sugar bait that attracts the flies.

Sterile Insect Technique (SIT)

In the SIT, Medflies are reared in large quantities, sterilized with a small amount of irradiation, and released into areas where they mate with wild Medflies. Such matings do not produce offspring. Eventually the wild population is eliminated through attrition.

SIT is most effective against low-level Medfly populations where a high proportion of sterile to wild flies can be achieved to ensure success. Initial applications of insecticide bait spray are sometimes necessary to bring local populations down to low densities.

Insecticide Application to Soil Under Host Trees

These products will kill some larvae as they enter the soil to pupate and most of the adults as they later emerge.

Currently, application of insecticide to the soil is used only when larvae are detected. The preferred and most popular eradication strategy is an integrated approach combining all three treatments, with emphasis on the use of SIT.

What damage can these pests cause?

In the United States, the Medfly could attack peaches, pears, plums, apples, apricots, avocados, citrus, cherries, figs, grapes, guavas, kumquats, loquats, nectarines, peppers, persimmons, tomatoes, and several nuts.

If the Medfly were to become established, consumer prices would go up and produce would become less available. In addition, backyard gardens, as well as commercial production areas, would require increased use of pesticides on a routine basis.

In 1993, APHIS estimated that annual losses attributable to the Medfly in the continental United States would be about $1.5 billion annually if this exotic pest were to become established. These losses would come in the form of export sanctions, lost markets, treatment costs, reduced crop yields, deformities, and premature fruit drop.

How do we prevent them?

Many of the insects, weeds, and plant diseases that attack U.S. crops are foreign invaders. APHIS administers agricultural quarantine laws to help keep foreign plant pests and diseases out and to control domestic pests and diseases of limited distribution.

Travelers returning to the continental United States from Hawaii or a foreign country are prohibited from bringing into the country fresh fruits, meats, plants, birds, and plant and animal products that may harbor pests or diseases.

In fiscal year 1998, agricultural officers cleared for entry more than 400,000 aircraft that brought travelers and cargo to the United States. In the same year, officers intercepted more than 1.8 million illegal plants, animals, or plant and animal byproducts. More than 52,000 plant pests and diseases identified as dangerous to the U.S. agricultural industry were also intercepted.

What are you doing in Arizona regarding Medfly?

On September 16, 2004, Mediterranean fruit fly (Medfly) was discovered in the municipality of Tijuana, Mexico. The medfly is one of the world’s most devastating agricultural pests attacking over 250 hosts. On September 23, 2004, Governor Napolitano declared a state of emergency in the counties of Yuma, La Paz, Pima and Santa Cruz releasing $200,000 to support the department’s Plant Services Division's efforts to exclude and detect any incursions of this devastating pest. Eradication is not expected to be achieved until summer 2005 according to current models. Detection trapping is expected to continue in Yuma County at current levels (high-risk trapping protocol), and will be increased further beginning in spring 2005 in La Paz, Pima and Santa Cruz until eradication is declared in the Tijuana, MX municipality and validated by USDA.

In addition, laboratory scientists provide training to field personnel, provide official identification services to PSD regulatory officials (including confirmation of sterile release Medflies), and confirm QC samples for PSD.

What are you doing in Arizona regarding Medfly? 

On September 16, 2004, Mediterranean fruit fly (Medfly) was discovered in the municipality of Tijuana, Mexico. The medfly is one of the world’s most devastating agricultural pests attacking over 250 hosts. On September 23, 2004, Governor Napolitano declared a state of emergency in the counties of Yuma, La Paz, Pima and Santa Cruz releasing $200,000 to support the department’s Plant Services Division's efforts to exclude and detect any incursions of this devastating pest. Eradication is not expected to be achieved until summer 2005 according to current models. Detection trapping is expected to continue in Yuma County at current levels (high-risk trapping protocol), and will be increased further beginning in spring 2005 in La Paz, Pima and Santa Cruz until eradication is declared in the Tijuana, MX municipality and validated by USDA.

In addition, laboratory scientists provide training to field personnel, provide official identification services to PSD regulatory officials (including confirmation of sterile release Medflies), and confirm QC samples for PSD.

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