|Crop Knowledge Master|
Ronald F.L. Mau, Extension Entomologist
Jayma L. Matin Kessing, EducationalSpecialist
Department of Entomology
Updated by: J.M. Diez April 2007
Melon flies have more than 80 hosts. They are major pests of beans, bittermelon, Chinese wax gourd, cucumbers, edible gourds, eggplant, green beans, hyotan, luffa, melons, peppers, pumpkins, squashes, togan, tomatoes, watermelon, and zucchini.
Originally from the Indo-Malayan region, the fly was introduced into Hawaii from Japan in 1895. This pest is found in Burma, Ceylon, Formosa, Guam, Hawaii, India, Japan, Java, Kenya, Malaya, Mauritius Island, Philippines, Singapore, Southern China and Timor Island. It is the first tephritid fruit fly species established in Hawaii.
The damage to crops caused by melon flies result from 1) oviposition in fruit and soft tissues of vegetative parts of hosts 2) feeding by the larvae, and 3) decomposition of plant tissue by invading secondary microorganisms.
Larval feeding damage in fruits is the most damaging. Mature attacked fruits develop a water soaked appearance. Young fruits become distorted and usually drop. The larval tunnels provide entry points for bacteria and fungi that cause the fruit to rot. These maggots also attack young seedlings, succulent tap roots of watermelon, and stems and buds of host plants such as cucumber, squash and others.
Melon flies are considered occasional pests on papaya. In comparison, oriental fruit flies are considered as primary pests and Mediterranean fruit flies are rare pests in typical situations. Although the actual injury on papaya by fruit flies is relatively low, these flies are considered a major pest of papaya in terms of exporting from Hawaii to the US Mainland and Japan. It is therefore necessary to treat the papaya fruits with post-harvest quarantine treatments.
The economic importance of the melon fly cannot be evaluated entirely from the standpoint of the direct damage to the various crops affected. Quarantine laws aimed at preventing the entry and establishment of melon flies in areas where it does not occur often reduces the export potential of locally grown crops.
The life cycle from egg to adult requires 14-27 days.
The eggs of the melon fly are slender, white and measure 1/12 inch in length. Eggs are inserted into fruit in bunches of 1 to 37. They hatch in 2 to 4 days.
There are 3 larval stages for this insect. The larvae, or maggots, are typical fruit fly shape: cylindrical-maggot, elongate, narrowed and somewhat curved downward at the end and mouth hooks at the head. These maggots reach approximately 1/2 inch in length upon maturity. Refer to Heppner (1989) for a detailed description of larvae. The larval period lasts from 6 to 11 days, with each stage lasting 2 or more days. Duration of larval development is strongly affected by host..
Pupae occur in the soil beneath the host plant. They are 1/5 to 1/4 inch long, elliptical and dull white to yellowish brown in color. They are distinctly ringed by narrow yellow bands around each segment. During warm weather the pupal stage lasts 9 to 11 days.
Adult melon flies are slightly larger than houseflies. They measure 1/3 to 1/2 inch long with a wingspan of 1/2 to 3/5 inch. The head and eyes are dark brown. Their bodies are yellowish brown with a yellow spot above the base of the first pair of legs. A yellow stripe, with curved lines on either side, is present down the center of the back. The tip of the body furthermost from the head is yellow. Wings are patterned with a thick brown band extending along the leading edge, ending in a larger brown spot at the tip. Another thin band extends from the wing base just inside the trailing edge of each wing. A brown spot occurs near the wing margin. Abdomens are reddish yellow with darker bands on the second and third abdominal segments. Legs are yellowish. They have a similar appearance to the oriental fruit fly except for the patterned wing.
Oviposition occurs about 10 days after emergence and continues at intervals. One female may deposit up to 1,000 eggs, although 300 eggs total are estimated in natural conditions. Females prefer to oviposit in new plant growth such as young seedlings, growing tips, and developing ovaries of all cucurbits except young cucumbers. Ripe fruits are preferred; green fruits are sometimes used. Because of their high egg laying capacity and mobility, each female is capable of destroying large numbers of fruit in her lifespan.
Adults generally live for 10 months to a year.
Melon flies are strong fliers. Adults spend considerable time on low, succulent, leafy vegetation surrounding cultivated areas. They may be found among the foliage on any dense plant, bush or tree, sometimes a considerable distance from host plants. During hot days they rest on the underside of leaves or in shaded areas. Flight is most common in the morning and late afternoon. Adults feed on juices from decaying or damaged fruit, nectars, plant sap and bird feces.
The utilization of pre-harvest management practices is important to reduce direct losses and to increase efficacy of post-harvest quarantine treatments. Since the discovery of the melon fly in Hawaii a number of methods have been employed in attempts to reduce or prevent damage by this pest. They include: 1) mechanical control, 2) cultural control, 3) biological control and 4) chemical control.
Two common mechanical methods of control are wrapping developing fruit with a protective covering and the use of baited traps. The use of protective coverings is more effective and costly than the use of traps. In spite of its cost, protective coverings are still used to a certain extent largely by home gardeners. Baited traps are used to destroy adults. Shrubs within 100 yards of larval hosts may be used advantageously in placing traps.
There are two principal cultural methods that can be used for controlling this pest. These methods are: 1) field sanitation, and 2) use of trap crops.
Of utmost importance and effectiveness is field sanitation. It is concerned primarily with the destruction of all unmarketable and infested fruits and the disposal of crop residues immediately after harvest. Infested fruit should be buried 3 feet under soil surface. Addition of lime is helpful to kill emerging larvae.
Thirty-two species and varieties of natural enemies to fruit flies were introduced to Hawaii between 1947 and 1952 to control the fruit flies. These parasites lay their eggs in the eggs or maggots and emerge in the pupal stage. Only three, Opius longicaudatus var. malaiaensis (Fullaway), O. vandenboschi (Fullaway), and O. oophilus (Fullaway), have become abundantly established. These parasites are primarily effective on the oriental and Mediterranean fruit flies in cultivated crops.
The most efficacious parasite of the melon fly is O. fletcheri (Silvestri). It was introduced in 1916 from India. This parasite attacks the melon fly during the larval stage. Bess, et. al. (1961) reported that this parasite killed 20 - 40 percent of fruit fly larvae. It is more effective in reducing populations in wild areas than in cultivated crops.
The chemicals used for melon fly control have been used as 1) toxicants in baits applied to refugia of the fruit flies and 2) sprays applied to the crop.
Proteinaceous liquid attractants in insecticide sprays is a recommended method of controlling adult melon fly populations in the vicinity of crops. The bait insecticide sprays are applied to broad leaf plants that serve as refugia for melon fly adults. Baits serve to encourage the adults (especially females) to feed on the spray residue and can provide good rates of kill. To be effective, bait-insecticide sprays must be used in combination with good sanitation practices. These practices include destruction of unmarketable fruit on every harvest date, and destruction of crop residues immediately after economic harvest has been completed.
Nu-Lure is a commercial liquid bait that is available for use against fruit flies.
There is no listing for Nu-Lure as of April 2007..
Agarwal, M. L., D. D. Sharma and O. Rahman. 1987. Melon Fruit-Fly and Its Control. Indian Horticulture. 32(3): 10-11.
Bess, H. A., R. van den Bosch and F. H. Haramoto. 1961. Fruit Fly Parasites and Their Activities in Hawaii. Proc. Hawaiian Entomol. Soc. 27(3): 367-378.
Heppner, J. B. 1989. Larvae of Fruit Flies. V. Dacus cucurbitae (Melon Fly) (Diptera: Tephritidae). Fla. Dept. Agric. & Consumer Services, Division of Plant Industry. Entomology Circular No. 315. 2 pages.
Hill, D. S. 1983. Dacus cucurbitae Coq. pp. 391. In Agricultural Insect Pests of the Tropics and Their Control, 2nd Edition. Cambridge University Press. 746 pages.
Lall, B. S. 1975. Studies on the Biology and Control of Fruit Fly, Dacus cucurbitae COQ. Pesticides. 9(10): 31-36.
Liquido, N. J., R. T. Cunningham, and H. M. Couey. 1989. Infestation Rate of Papaya by Fruit Flies (Diptera: Tephritidae) in Relation to the Degree of Fruit Ripeness. J. Econ. Ent. 82(10): 213-219.
Lockwood, S. 1957. Melon Fly, Dacus cucurbitae. Loose-Leaf Manual of Insect Control. California Department of Agriculture.
Marsden, D. A. 1979. Insect Pest Series, No. 9. Melon Fly, Oriental Fruit Fly, Mediterranean Fruit Fly. University of Hawaii, Cooperative Extension Service, College of Tropical Agriculture & Human Resources.
Nishida, T and H. A. Bess. 1957. Studies on the Ecology and Control of the Melon Fly Dacus (Strumeta) cucurbitae Coquillett (Diptera: Tephritidae). Hawaii Agric. Exp. Station Tech. Bull. No. 34. pages 2-44.
Nishida, T. and F. Haramoto. 1953. Immunity of Dacus cucurbitae to Attack by Certain Parasites of Dacus dorsalis. J. Econ. Ent. 46(1): 61-64.
Vargas, R. I. and J. R. Carey. 1990. Comparative Survival and Demographic Statistics for Wild Oriental fruit Fly, Mediterranean Fruit Fly, and Melon Fly (Diptera: Tephritidae) on Papaya. J. Econ. Ent. 83(4): 1344-1349.