Dacus cucurbitae (Diptera: Tephritidae)

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Dec 9, 1988 - by trapping males at 100 sites throughout the island of Rota, Commonwealth of the Northern. Mariana Islands. Melon flies were most numerous ...
Seasonal Distribution and Abundance of Dacus cucurbitae (Diptera: Tephritidae) in Rota, Commonwealth of the Northern Mariana Islands TIM T. Y. WONG, ROY T. CUNNINGHAM, DONALD O. McINNIS, ANDJ. E. GILMORE Tropical Fruit and Vegetable Research Laboratory, USDA-ARS, Honolulu, Hawaii 96804

Environ.Entomol.18(6):1079-1082(1989) ABSTRACT Distribution of the melon fly, Dacus cucurbitae Coquillett, was determined by trapping males at 100 sites throughout the island of Rota, Commonwealth of the Northern Mariana Islands. Melon flies were most numerous along the south coastal trap sites. Flies caught in traps were significantly correlated to pupal yield from samples of infested fruits of Momordica charantia L. for two of three years. Rainfall was significantly correlated with trap catches for the two low rainfall years of 1984 and 1987,but not for the two high rainfall years of 1985 and 1986. The highest trap catch of 5.8 fliesper trap per day in 1986 was 100 times less than the number of flies caught in an earlier study in 1961 when the peak was 614 flies per trap per day and precipitated eradication efforts in 1963. KEY WORDS Insecta, melon £lies,Dacus cucurbitae, trap catches

THE MELONFLY, Dacus cucurbitae Coquillett, is a serious pest of more than 80 species of fruits and vegetables, especially cucurbits and tomatoes (Christenson & Foote 1960). The fly is distributed throughout India, which is considered its native origin. It has spread across southeast Asia and to several islands in the Pacific, including Hawaii (Back & Pemberton 1917). The melon fly attacks the fruits, the young seedlings, the flowers, the roots, and the stems (Back & Pemberton 1917). During the warmest seasons in Hawaii (average 26.5°C), the egg, larval, and pupal stages may be completed in as few as 12 or as many as 28.5 d, according to individual host conditions. However, at lower temperatures (1l-16.5°C), the immature stages may be lengthened to 4 mo (Back & Pemberton 1917). The melon fly was eradicated from the Commonwealth of the Northern Mariana Islands (GN.M.I.) by the sterile insect release technique in 1963 (Steiner et a!. 1965, Mitchell 1980), but it was reintroduced in 1981 onto the island of Rota, GN.M.I., presumably from the island of Guam. This paper reports on detailed trapping of the melon fly on Rota from 1984 through 1987. Materials and Methods Rota is the southernmost island of the GN.M.I., and is situated about 59.5 km north of Guam and Table 1. Melon fly infestation in collections of M. Year 1985 1986 1987

Fruits collected 7,034 5,171 3,649

Fruits infested

%

17.2 45.0 39.0

80.5 km southwest of Tinian, GN.M.1. It is volcanic in origin, 20 km long, 6 km wide, and covers an area of 85 km2• An uplifted mesa, 490 m in elevation and 2 by 4 km in size, dominates the topography of the southwestern half of the island. At the top of this mesa, the soil is rich in organic material and is moist throughout the year. Most of the island's vegetables are grown on this mesa. More than half of Rota's coastline is steep and rocky, though coral sand beaches are found on the western side of Songsong Village and extend along most of the northern coast. The climate of this tropical island is warm and humid, with little seasonal or daily variation in temperature. Temperatures at sea level range from 22 to 34°C annually. Monthly rainfall ranges from 2.5 to 33.0 cm from January through June, and from 20.3 to 73.7 cm in July through December. Total annual rainfall is about 200 to 250 cm. Northeast trade winds (5 to 15 km/h) blow much of the year. Plastic traps (Steiner 1957) were used to catch D. cucurbitae adult males. Each trap was baited with about 10 ml of a mixture of 98% cue-lure and 2% naled by volume (Keiser et a!. 1973) in a cotton wick (5 cm long by 2 cm diameter). The wick was retreated at 8-wk intervals. The 100 baited traps were placed on plants 2 to 2.5 m aboveground near roadsides and trails. The distance between traps in

charantia

fruit on Rota, 1985-1987 Melonfliesemerged

Totalpupae Pupae/fruit dd

2,735 4,338 3,531

0.39 0.84 0.97

1,277 1,972 1,531

99

1,357 2,235 1,840

Total

Parasitoids emerged

2,634 4,207 3,371

50 9 20

1080 Table

ENVIRONMENTAL

2.

Melon fly infestation

in collections

of culti~ated

fruits on Rota,

Cantaloupe Cucumber Cultivated bittermelon Okra Pumpkin Squash Tomato Watermelon Others (bell pepper, eggplant, mango, papaya)

Pupae/kg

No. collections

No. fruits

37 137

38.8 28.6

22 34

1 0 4 8 20 17

6 0 6 38 157 38

0 0 0 0.6 0.2 16.9

55

386

0

No. collections

No. fruits

5 19

1985-1987

1986

1985 Fruits

Vol. 18, no. 6

ENTOMOLOGY

a trap line ranged from 0.32 to 1.6 km with most about 0.60 km apart (Fig. 1). Trapped flies were collected weekly and counted. The potential hosts of D. cucurbitae on Rota are cultivated vegetables and wild bittermelons, Momordica charantia L. Patches of M. charantia are found scattered throughout the southern and southeastern ends of the island, with vines growing in exposed areas along roadsides and edges of woods (but not in the interior of woodlots), on recently disturbed soil, and on the sides of steep cliffs away from sea sprays. From 1985 to 1987, 30 fruit-collecting sites, each about 20 by 20 m, were selected

1987 Pupae/kg

No. collections

No. fruits

79 411

37.8 50.6

16 22

73 243

66.6 93.0

3 5 0 2 15 30

10 12 0 2 68 110

16.9 31.0 0 0 0 35.6

0 1 1 8 12 23

0 8 4 42 71 143

0 0 2.2 227.1 0 62.7

10

209

0

34

232

0

Pupae/kg

from wild bittermelon patches. The total number of mature orange or yellow fruits in each sampling site was counted, and 10% of the fruits were randomly collected at weekly intervals. These fruit samples were brought back to the laboratory in Songsong Village and held over moist sand in plastic containers with screen lids for pupation of larvae and emergence of adults. These containers were examined daily and the sand was replaced when putrified fruits produced excessive liquid material. We used these fruit collection data to provide irtformation about the relationships between fruit infestation and pupal yield to trap catches. Corre-

1

NORTH

ROTA, CNMI Fig. 1. Locations of 100 plastic traps baited with cue-lure to catch D. cucurbitae adult males. Twenty trap sites with high catches for 1 to 4 yr in Rota, 1984-1987, are indicated at each location.

December 1989

WONG

ET AL.:

D. cucurbitae

DISTRIBUTION

1081

ON ROTA

60

E

~

40

....I ....I

~ z

80% (Willard 1920), 44% (Newell et al. 1952) and 37% (Nishida 1955). The parasitism in the land of this parasitoid, Northern India, did not exceed 3% (Nishida 1963). Acknowledgment We thank Nicklaus Leon Guerrero and Joaquin Tenorio, of Saipan, C.N.M.I., and Manases Atalig, Vincent Manglona, Frank Barcinas and Joe Ayuyu of Rota for their assistance in the field.

References

Cited

Back, E. A. & C. E. Pemberton. 1917. The melon fly in Hawaii. USDA Bulletin 491. Christenson, L. D. & R. H. Foote. 1960. Biology of fruit flies. Annu. Rev. Entomol. 5: 171-192. Keiser, I., S. Nakagawa, R. M. Kobayashi, D. L. Cbambers, T. Urago & R. E. Doolittle. 1973. Attractiveness of cue-lure and the degradation product 4-(p-hydroxyphenol)-2-butanone to male melon flies in the field in Hawaii. J. Econ. Entomol. 66: 112114. Mitchell, W. C. 1980. Verification of the absence of oriental fruit and melon fruit fly following an eradication program in the Mariana Islands.Proc. Hawaii. Entomol. Soc. 23; 239-243. Newell, I. M., W. C. Mitchell & F. L. Rathburn. 1952. Infestation norms for Dacus cucurbitae in Momordica balsamina, and seasonal differences in activity of the parasite, Opius fietcheri. Proc. Hawaii. Entomol. Soc. 14; 497-508. Nishida, T. 1955. Natural enemies of the melon fly, Dacus cucurbitae Coq. in Hawaii. J. Econ. Entomol. 48; 171-178. 1963. Zoogeographical and ecological studies of Dacus cucurbitae (Diptera- Tephritidae) in India. Hawaiian Agricultural Experiment Station, University of Hawaii, Hawaii. Technical Bulletin 54. Steiner, L. F. 1957. Low-cost plastic fruit fly trap. J. Econ. Entomol. 50: 508-509. Steiner, L. F., E. J. Harris, W. C. Mitehell, M. S. Fujimoto & L. D. Christenson. 1965. Melon flyeradication by overflooding with sterile flies. J. Econ. Entomol. 58; 519-522. Willard, H. F. 1920. Opius fietcheri as a parasite of the melon fly in Hawaii. J. Agric. Res. 6; 423-438. Received for publication 31 March 1989.

9 December 1988; accepted