Fruitfly in Three Asian Countries

Incidence and control, 1999-06-01

A survey of fruit fly in Vietnam, Thailand, and the Philippines was carried out in 1998. Fruitfly is economically the most important insect pest of fruit in Southeast Asia, and can cause losses as high as 90-100%.

Indirect Losses from Fruitfly

Fruitfly can also prevent the development of export markets. Countries which do not have fruitfly are anxious to remain free of the pest. They usually impose strong quarantine restrictions on fruit imported from countries where the pest is endemic, or ban imports altogether. A survey of Asian corn borer was carried out at the same time.

The survey had three objectives. The first was to evaluate the occurrence of fruitfly and corn borer, and the economic damage they cause. The second was to observe current control measures. The third objective was to discuss with specialists in Southeast Asian countries the possibility of cooperative projects to control these two pests, based on the use of natural enemies and attractants.

Incidence and Control of Fruitfly

Vietnam

Fruitfly in Vietnam is mainly in the south, in the fruit-growing areas of the Mekong Delta. Most of the fruit grown in Vietnam is for domestic use. Although fruitfly is causing serious damage to crops, it is not causing quarantine problems. The attractant methyl eugenol was used in the northern part of Vietnam, but failed to trap any fruitfly.

Methyl eugenol is widely used in fruitfly control programs in Thailand, for example in guava plantations. It is effective, but rather expensive for many growers. Many fruits grown in Thailand, including guava and lychee, have great economic value and are important exports. However, the quarantine restrictions imposed by the presence of fruitfly hinder the development of export markets.

Thailand

Thailand's Department of Agriculture has recently completed a survey of fruitfly species in Thailand, and is field testing integrated control based on the use of methyl eugenol. There is also a Sterile Insect Technique (SIT) project supported by the International Atomic Energy Committee. However, since there is no natural boundary around control areas, the success of SIT is seriously jeopardized by the re-invasion of fertile flies.

The major fruitfly species in Thailand are Bactrocera correcta and B. dorsalis. Both are strongly attracted to methyl eugenol.

Malaysia

Malaysia has also completed a thorough nation-wide survey of fruitfly. Control programs in this country are based on the use of methyl eugenol, insecticide sprays, poisoned protein hydrolysate bait, and the bagging of fruit.

Malaysia is a major production area for papaya and starfruit. The two most important fruitfly species which attack these crops, Bactrocera papayae and B. carambolae. Like those in Thailand, both are strongly attracted to methyl eugenol.

Philippines

Fruitfly are a major concern in the Philippines, particularly in mango production. The Philippines produces 26 thousand mt of mango every year, many of them for processing and export.

There are three major mango production areas, one of which, Guimaras Island, has good potential to become completely free of fruitfly. This would mean that the fruit produced on the island could be shipped to Japan or United States, adding to the value of the harvest.

Eradicating fruitfly from Guimaras Island will be done in two stages. At first, numbers will be reduced to a minimum by mass trapping, using methyl eugenol. Finally, the residual fruitflies will be eradicated using the SIT technique. The FFTC survey team estimated that the cost of such a control program would be only 2% of the value of mango production on the island, so it would be a worthwhile investment.

Variation in Fruitfly Populations

During the FFTC project , the team gathered samples of fruitfly from each survey area, using methyl eugenol bait. The specimens collected have been brought back for morphological study and classification. This may provide interesting information on regional distribution and intra-specific variation.

Index of Images

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  Figure 1 Wrapping Pears to Protect Them from Fruitfly

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  Figure 2 Guava Damaged by Fruitfly

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  Figure 3 Fruitfly Trap Using the Attractant Methyl Eugenol