Fruit flies (Diptera: Tephritidae) are among the most economically important pest species in the world, attacking a wide range of fruits and fleshy vegetables throughout tropical and sub-tropical areas. These species are such devastating crop pests that major control and eradication programs have been developed in various parts of the world to combat them. The array of control methods includes insecticide sprays to foliage and soil, bait-sprays, male annihilation techniques, releases of sterilized flies and parasitoids, and cultural controls. During the twenty first century there has been a trend to move away from control with organophosphate insecticides (e.g., malathion, diazinon, and naled) and towards reduced risk insecticide treatments. In this article we present an overview of 73 pest species in the genus Bactrocera, examine recent developments of reduced risk technologies for their control and explore Integrated Pest Management (IPM) Programs that integrate multiple components to manage these pests in tropical and sub-tropical areas.
Bactrocera fruit fly species are economically important throughout the Pacific. The USDA, ARS U.S. Pacific Basin Agricultural Research Center has been a world leader in promoting biological control of Bactrocera spp. that includes classical, augmentative, conservation and IPM approaches. In Hawaii, establishment of Bactroceracucurbitae (Coquillett) in 1895 resulted in the introduction of the most successful parasitoid, Psyttaliafletcheri (Silvestri); similarly, establishment of Bactroceradorsalis (Hendel) in 1945 resulted in the introduction of 32 natural enemies of which Fopiusarisanus (Sonan), Diachasmimorphalongicaudata (Ashmead) and Fopiusvandenboschi (Fullaway) were most successful. Hawaii has also been a source of parasitoids for fruit fly control throughout the Pacific region including Australia, Pacific Island Nations, Central and South America, not only for Bactrocera spp. but also for Ceratitis and Anastrepha spp. Most recently, in 2002, F.arisanus was introduced into French Polynesia where B.dorsalis had invaded in 1996. Establishment of D.longicaudata into the new world has been important to augmentative biological control releases against Anastrepha spp. With the rapid expansion of airline travel and global trade there has been an alarming spread of Bactrocera spp. into new areas of the world (i.e., South America and Africa). Results of studies in Hawaii and French Polynesia, support parasitoid introductions into South America and Africa, where B.carambolae and B.invadens, respectively, have become established. In addition, P.fletcheri is a candidate for biological control of B.cucurbitae in Africa. We review past and more recent successes against Bactrocera spp. and related tephritids, and outline simple rearing and release methods to facilitate this goal.
In a field study in Hawaii, color-marked protein-deprived and protein-fed female melon flies, Bactrocera cucurbitae Coquillett, were released within canopies of unsprayed sorghum plants (a nonhost of melon flies) outside of a border area of unsprayed or bait-sprayed sorghum plants or open space that surrounded cucumbers, a favored host of melon flies. Application of bait spray to sorghum or sugarcane surrounding host plants of melon flies is a common practice for melon fly control in Hawaii. GF-120 Fruit Fly Bait spray proved very effective in preventing protein-deprived females from alighting on cucumbers (23% of released females were observed dead on bait-sprayed sorghum; 0% were observed alive on cucumbers), but proved less effective in suppressing protein-fed females (14% of released females were observed dead on bait-sprayed sorghum; 11% were observed alive on cucumbers). No females were found dead on unsprayed sorghum. Compared with open space surrounding cucumbers, the presence of unsprayed sorghum as surrounding border area neither significantly enhanced nor significantly inhibited the ability of either type of female with respect to finding cucumbers. Greenhouse cage assays revealed that compared with droplets of water, droplets of GF-120 Fruit Fly Bait spray were highly attractive to protein-deprived females within 1 h of bait spray application to sorghum, but lost about half of their attractiveness within 5 h and all of it within 24 h under the dry greenhouse conditions used for maintaining baited-sprayed sorghum plants in these assays. Laboratory cup assays showed that bait spray droplets remained highly toxic to protein-deprived females 24 h after application, but lost nearly half of their toxicity within 4 d under laboratory exposure and nearly all of it after approximately 8 mm of rainfall. Combined findings suggest that application of GF-120 Fruit Fly Bait spray to nonhost plants for melon fly control either be made often enough to overcome loss of attractiveness of bait spray droplets to females or that bait spray be applied to nonhost plants that are themselves attractive to the females.