Melon fly

Melon fly
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Section: Schizophora
Family: Tephritidae
Genus: Bactrocera
Species: B. cucurbitae
Binomial name
Bactrocera cucurbitae
(Coquillett, 1849)
Synonyms

Chaetodacus cucurbitae
Dacus cucurbitae
Strumeta cucurbitae
Zeugodacus cucurbitae

The melon fly (Bactrocera cucurbitae) is a fruit fly of the family Tephritidae. It is a serious agricultural pest, particularly in Hawaii.

Identification

Adult fly

The adult melon fly is 6 to 8 mm in length. Distinctive characteristics include its wing pattern, its long third antennal segment, the reddish yellow dorsum of the thorax with light yellow markings, and the yellowish head with black spots.

Egg

The egg is elliptical, about 2 mm long, and pure white. It is almost flat on the ventral surface, and more convex on the dorsal. Eggs are often somewhat longitudinally curved.

Larva

The larva is a cylindrical-maggot shape, elongated, with the anterior end narrowed a somewhat curved ventrally. It has anterior mouth hooks, ventral fusiform areas and a flattened caudal end. Last instar larvae range from 7.5 to 11.8 mm in length. The venter has fusiform areas on segments 2 through 11. The anterior buccal carinae are usually 18 to 20 in number. The anterior spiracles are slightly convex in lateral view, with relatively small tubules averaging 18 to 20 in number.

Pupa

The puparium ranges in color from dull red or brownish yellow to dull white, and is about 5 to 6 mm in length.

Life history

Development period from egg to adult ranges from 12 to 28 days. The female may lay as many as 1,000 eggs. Eggs are generally laid in young fruit, but are also laid in the succulent stems of host plants. The eggs are deposited in cavities created by the female using its sharp ovipositor.

Pupation usually occurs in the soil. There may be as many as 8 to 10 generations a year.

Behaviour

Melon flies are most often found on low, leafy, succulent vegetation near cultivated areas. In hot weather they rest on the undersides of leaves and in shady areas. They are strong fliers and usually fly in the mornings and afternoons. They feed on the juices of decaying fruit, nectar, bird feces, and plant sap.[1]

Mature melon fly males are attracted to several attractants e.g. anisyl acetone, cue-lure, raspberry ketone and zingerone. They are pollinators/visitors of some orchids, especially Bulbophyllum (Orchidaceae) species, that release floral fragrance containing either raspberry ketone or zingerone as floral attractant and reward (< Nishida,R., O. Iwahashi, K.H. Tan (1993) Accumulation of Dendrobium superbum (Orchidaceae) fragrance in the rectal glands by males of the melon fly, Dacus cucurbitae. Journal of chemical ecology 19 (4), 713-722.>, < Tan,K.H. and R. Nishida (2000) Mutual reproductive benefits between a wild orchid, Bulbophyllum patens, and Bactrocera fruit flies via a floral synomone. Journal of Chemical Ecology 26 (2), 533-546.>, <Tan,K.H. and R. Nishida (2005) Synomone or kairomone? – Bulbophyllum apertum flower releases raspberry ketone to attract Bactrocera fruit flies. Journal of chemical ecology 31 (3), 497-507.> <Tan,K.H.and R. Nishida (2007) Zingerone in the floral synomone of Bulbophyllum baileyi (Orchidaceae) attracts Bactrocera fruit flies during pollination.Biochemical systematics and ecology 35 (6), 334-341.>

Distribution

Distribution

The melon fly is native to India, and is distributed throughout most parts of the country. It can be found throughout most of southern Asia, several countries in Africa, some island groups in the Pacific.[1]

In the United States, it was the first tephritid fruit fly species established in Hawaii. It was introduced there from Japan around 1895, and by 1897, when it was first observed, it had already become a serious pest.[2]

Not yet established in the continental United States, it is often intercepted at ports. Occasionally, an infestation is established, but is then eradicated. The latest such incident was several flies discovered in August 2010, in Kern County, California. The area is now under quarantine and an eradication program is underway.[1]

Host plants

Adult melon fly on a leaf

Melon flies use at least 125 host plants. They are major pests of beans, bittermelon, winter melon, cucumbers, eggplant, green beans, hyotan, luffa, melons, peppers, pumpkins, squashes, togan, tomatoes, watermelon, and zucchini.[3][4]

Damage

In the Indomalaya ecozone region, the melon fly is considered the most destructive pest of melons and other related crops. In Hawaii, it has caused serious damaged to melon, cucumber and tomato crops.

The melon fly can attack flowers, stem, root tissue, and fruit.

Management

Non-chemical control

Mechanical

The two most common mechanical methods of control are wrapping developing fruit with a protective covering and the use of baited traps.

Cultural

The most effective cultural management technique is the destruction of all infested and unmarketable fruit, and the disposal of crop residues immediately after harvest.

Biological control

A technician prepares to irradiate male melon fly pupae to sterilize them

Between 1947 and 1952, thirty-two species and varieties of natural enemies to fruit flies were introduced in Hawaii. These parasites lay their eggs in the eggs or maggots and emerge in the pupal stage.

When the braconid parasitoids Fopius arisanus or Pysttalia fletcheri were used, and attacked both melon fly eggs and larvae at the same time, suppression of development was as much as 56%.[5]

Irradiation

Sterilization of male melon flies through irradiation has proven effective in significantly reducing the number of eggs hatching.[6]

Chemical control

Toxicants in baits applied both to refugia of the fruit flies and sprays applied to crops have been used.

Proteinaceous liquid attractants in insecticide sprays is an effective method of controlling melon fly populations. This bait insecticide is sprayed on broad leaf plants that serve as refugia for melon flies. These baits encourage the adults to feed on the spray residue.

References

Further reading

External links

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