common name: oriental fruit fly
scientific name: Bactrocera (= Dacus) dorsalis (Hendel) (Insecta: Diptera: Tephritidae)

Introduction - Distribution - Identification - Life History - Hosts - Damage, Quarantine and Management - - Selected References

Introduction

The true fruit flies (family Tephritidae), comprising over 4,000 species distributed over most of this planet, include several of the greatest potential threats to Florida agriculture. The New World genus Anastrepha, the primarily African genus Ceratitis, and the genus Bactrocera contain most of the world's most serious fruit fly pests. The genus Bactrocera, with 350 to 375 species, is indigenous to Africa, the Mediterranean Region, the Near and Far East, Australia, and the Pacific. One of these species, the oriental fruit fly, Bactrocera dorsalis (Hendel), is a very destructive pest of fruit in areas where it occurs.

adult female laying eggs

Distribution

The oriental fruit fly is widespread throughout much of Pakistan, India, Sri Lanka, Sikkim, Myanmar, Indonesia (Celebes, Borneo, Sumatra, Java), Malaya, Thailand, Cambodia, Laos, Vietnam, southern China, Taiwan, Philippine Islands, Micronesia, and Mariana Islands (Guam, Rota, Saipan, Tinian).

In the U.S. it is currently present on all major Hawaiian islands after being accidentally introduced into Hawaii in 1944 or 1945 (Mau 2007).

Four major oriental fruit fly infestations in California were eradicated between 1960 and 1997. A new infestation of this pest was detected in San Bernardino County, California, in August 2002. In 2004, the USDA quarantined a portion of San Bernardino and Orange counties in California. Regulatory activities in those counties ceased in December 2006 and July 2007 respectively. Several other counties in central and southern California also reported finds during 2007 (CDFA 2008).

While not established in Florida, oriental fruit flies are occasionally trapped in this state. During 1999, 17 adults were trapped in central Florida, but by September the infestation was declared eradicated. A single male oriental fruit fly was detected in Bradenton during June 2000. Several more were trapped in Florida during 2001: one in Osceola County during June, and two in Sarasota County during July. Additional single fly finds were made in Broward County in 2002 and Hillsborough County in 2007 (Steck 2007). In June 2008, two flies were found in Orange County, in the Winter Park area of Orlando.

Identification

Egg: The white, elongate and elliptical egg measures about 1.17 x 0.21 mm and has a chorion without sculpturing.

eggs in fruit

Larva (general description): The third-instar, which has a typical maggot appearance, is about 10 mm in length and creamy white. The only band of spinules encircling the body is found on the first segment. The external part of the anterior respiratory organs, the spiracles, located one on each side of the pointed or head end of the larva, has an exaggerated and deflexed lobe at each side and bears many small tubercles. The caudal segment is very smooth. The posterior spiracles are located in the dorsal third of the segment as viewed from the rear of the larva. The mature larva emerges from the fruit, drops to the ground, and forms a tan to dark brown puparium about 4.9 mm in length.

larvae in fruit

Larva (scientific description): The larva of the oriental fruit fly is quite similar to that of the Mediterranean fruit fly (medfly) (Berg 1979, Hardy and Adachi 1956, Pruitt 1953). The following characters in particular distinguish larvae of the oriental fruit fly from the medfly (Heppner 1985): the anterior spiracles are aligned with a straighter distal margin than in the medfly and the tubules (9-11) are noticeably bulbous; the cephalo-pharyngeal skeleton has a distinct sclerotized area between the post-hypostomial plates and the dorsal bridge; the caudal end has papillules I1-2 as distinct points, widely separated, on a raised margin, and D1-2 are less approximate; and the posterior spiracles are not as elongated (only about 3X width compared to 4-5X width in the medfly).

Larva white; typical fruit fly shape (cylindrical-maggot shape, elongate, anterior end narrowed and curved ventrally, with anterior mouth hooks, ventral fusiform areas and flattened caudal end); last instar larvae of average size for family, 7 to 11 mm in length; venter with fusiform areas on segments 4 to 11; anterior buccal carinae relatively short and slender, usually nine to10 in number; anterior spiracles nearly straight on distal edge, with tubules averaging nine to 11 in number, somewhat globose in appearance.

buccal carinae

anterior spiracle

Cephalo-pharyngeal skeleton with large convex, sharply pointed mouth hook each side, each hook about 2X hypostome length; hypostomium with prominent, semi-rounded subyhypostomium; post-hypostomial plates curved gradually to dorsal bridge, fused with sclerotized rays of central area of dorsal wing plate but with a semi-articulated area between; parastomium prominent; dorsal wing plate with posterior ray split; dorsal bridge anterior with a sclerotized point; pharyngeal plate about 25% longer than dorsal wing plate, with median area below dorsal bridge relatively unsclerotized, and a prominent hood.

cephalo-pharyngeal skeleton

Caudal end with paired dorsal papillules (D1 and D2) diagonally dorsad to each spiracular plate; intermediate papillules (I1-2) as widely-separated pair on a large raised and curved elevation diagonally ventrad of each spiracular plate, with a remote I3 at about 45° from the I1-2 elevation; L1 on the median edge of the caudal end; a pair of ventral papillules (V1-2) approximately ventrad of I2 near the latero-ventral edge of the caudal end (V2 indistinct); posterior spiracles as three elongated (ca. 3X width) oval openings on each kidney-shaped spiracular plate, with dorsal and ventral spiracles angled to the caudal end center, and the median spiracle relatively straight; interspiracular processes (hairs) numerous, at four sites on each plate, latero-distal to spiracles, and the tips usually bifurcate; anal lobes entire and prominent.

caudal end of larva

posterior spiracles and anal lobes

The above from larvae examined in verified samples from Hawaii (in immatures collection of the Florida State Collection of Arthropods).

Adult: The adult, which is noticeably larger than a house fly, has a body length of about 8.0 mm; the wing is about 7.3 mm in length and is mostly hyaline. The color of the fly is very variable, but there are prominant yellow and dark brown to black markings on the thorax. Generally, the abdomen has two horizontal black stripes and a longitudinal median stripe extending from the base of the third segment to the apex of the abdomen. These markings may form a T-shaped pattern, but the pattern varies considerably. The ovipositor is very slender and sharply pointed.


Adult female (center) and anterior spiracle of third instar larva (lower left).

adult male and female

lateral view of female

SEM of ovipositor

Life History

Development from egg to adult under summer conditions requires about 16 days. The mature larva emerges from the fruit, drops to the ground, and forms a tan to dark brown puparium. Pupation occurs in the soil. About nine days are required for attainment of sexual maturity after the adult fly emerges. The developmental periods may be extended considerably by cool weather. Under optimum conditions, a female can lay more than 3,000 eggs during her lifetime, but under field conditions from 1,200 to 1,500 eggs per female is considered to be the usual production. Apparently, ripe fruit are preferred for oviposition, but immature ones may be attacked also.

Hosts

The oriental fruit fly has been recorded from more than 150 kinds of fruit and vegetables, including citrus, guava, mango, papaya, avocado, banana, loquat, tomato, surinam cherry, rose-apple, passion fruit, persimmon, pineapple, peach, pear, apricot, fig, and coffee. Avocado, mango, and papaya are the most commonly attacked.

Damage, Quarantine and Management

Injury to fruit, as with other members of this genus of fruit flies, occurs through oviposition punctures and subsequent larval development. It was introduced into the Hawaiian Islands about 1945, apparently by U.S. military troops returning to the islands. Once there, the oriental fruit fly soon became a more injurious species than the Mediterranean fruit fly or the melon fly before it was partially brought under control by introduced parasitoids.

parasitoids

In Hawaii, larvae have been found in more than 125 kinds of hosts. Infestations of 50 to 80% have been recorded in pear, peach, apricot, fig, and other fruits in West Pakistan. It is the principal pest of mangoes in the Philippines. It was a serious pest of citrus and other subtropical fruits in Japan, Okinawa, and the Japanese islands of Amami, Miyako, and Bonin before it was eradicated. All Japanese territories were declared free of the oriental fruit fly in 1985, after an 18-year program of eradication combining insecticide-impregnated fiberblocks or cotton containing the powerful male attractant methyl-eugenol, and the sterile insect (sterile male) technique. Steiner traps baited with a lure and toxicant are also used to monitor the presence and control of the flies.

fly ovipositing on fruit

Steiner trap

This pest has been intercepted on many occasions at ports of entry on the U.S. mainland. The extensive damage caused by the oriental fruit fly in areas similar to Florida indicates that this species could rapidly become a very serious pest of citrus and other fruit and vegetables if it became established in Florida.

USDA-APHIS, in cooperation with threatened states, has established action plans that go into effect when fruit flies are trapped and reported (USDA 2008).

In Florida, the FDACS-Division of Plant Industry will cooperate with USDA-APHIS in regulating the actions of both commercial entities and homeowners.

Selected References

Authors: H.V. Weems, and J.B. Heppner, Florida Department of Agriculture and Consumer Services, Division of Plant Industry; James L. Nation and Thomas R. Fasulo, University of Florida.
Originally published as DPI Entomology Circulars 21 and 303. Updated for this publication.
Photographs: Okinawa Prefectural Fruit Fly Eradication Project Office; Scott Bauer, USDA
Illustrations: Division of Plant Industry
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-83
Publication Date: May 1999. Latest revision: June 2008.
Copyright 1999-2008 University of Florida

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