Psyttalia ponerophaga (Hymenoptera: Braconidae) as a potential biological control agent of olive fruit fly Bactrocera oleae (Diptera: Tephritidae) in California

The olive fruit fly, Bactrocera oleae (Rossi), is a newly invasive, significant threat to California's olive industry. As part of a classical biological control programme, Psyttalia ponerophaga (Silvestri) was imported to California from Pakistan and evaluated in quarantine. Biological parameters that would improve rearing and field-release protocols and permit comparisons to other olive fruit fly biological control agents were measured. Potential barriers to the successful establishment of P. ponerophaga, including the geographic origins of parasitoid and pest populations and constraints imposed by fruit size, were also evaluated as part of this investigation. Under insectary conditions, all larval stages except neonates were acceptable hosts. Provided a choice of host ages, the parasitoids' host-searching and oviposition preferences were a positive function of host age, with most offspring reared from hosts attacked as third instars. Immature developmental time was a negative function of tested temperatures, ranging from 25.5 to 12.4 days at 22 and 30 degrees C, respectively. Evaluation of adult longevity, at constant temperatures ranging from 15 to 34 degrees C, showed that P. ponerophaga had a broad tolerance of temperature, living from 3 to 34 days at 34 and 15 degrees C, respectively. Lifetime fecundity was 18.7 +/- 2.8 adult offspring per female, with most eggs deposited within 12 days after adult eclosion. Olive size affected parasitoid performance, with lower parasitism levels on hosts feeding in larger olives. The implications of these findings are discussed with respect to field manipulation and selection of parasitoid species for olive fruit fly biological control in California and worldwide.     

Performance of Psyttalia humilis (Hymenoptera: Braconidae) reared from irradiated host on olive fruit fly (Diptera: Tephritidae) in California

The parasitoid Psyttalia humilis (Silvestri) was reared on Mediterranean fruit fly, Ceratitis capitata (Wiedemann), third instars irradiated at 0-70 Gy at the USDA, APHIS, PPQ, Moscamed biological control laboratory in San Miguel Petapa, Guatemala, and shipped to the USDA, ARS, Parlier, CA. Irradiation dose did not affect the parasitoid's offspring sex ratio (53-62% females), percentage of unemerged adults (12-34%), number of progeny produced per female (1.4-1.8), and parasitism (19-24%). Host irradiation dose had no significant effect on the forewing length of female P. humilis and its parasitism on olive fruit fly, Bactrocera oleae (Rossi) and offspring sex ratio, but dissection of 1-wk-old female parasitoids reared from hosts irradiated with 70 Gy had a significantly lower number of mature eggs than females from nonirradiated hosts. Longevity of P. humilis adults decreased with increased temperature from 15 to 35°C, regardless of food provisions, gender, and host irradiation dose. Females survived 37-49 d at 15°C with water and food, and only 1-2 d at 35°C without food, whereas males lived shorter than females at all temperatures and food combinations tested. Adult P. humilis reared from fertile C. capitata and aspirated for dispensing in cups lived significantly longer after shipment than those specimens chilled and dispensed by weight. At 21 and 32°C, 50% of parasitoids departed release cages after 180 and 30 min, respectively, but none departed at 12°C. Thirteen shipments of P. humilis (2,980-21,922 parasitoids per shipment) were received between September and December 2009, and seven shipments (7,502-22,560 parasitoids per shipment) were received between October and December 2010 from San Miguel Petapa, Guatemala. Daily number of olive fruit fly adult and percentage female trap captures ranged <1-19 and 8-58% in 2009, and <1-11 and 0-42% in 2010, respectively. The number of parasitoids released ranged 848-12,257 in 2009 and 3,675-11,154 in 2010. Percentage parasitism of olive fruit fly third instars at all locations ranged 0-9% in 2009 and 0-36% in 2010.     

Prospects for improving biological control of olive fruit fly,Bactrocera oleae (Diptera: Tephritidae), with introduced parasitoids (Hymenoptera)

Olive fruit fly is a key pest of olive and consequently a serious threat to olive fruit and oil production throughout the Mediterranean region. With the establishment of Bactrocera oleae in California a decade ago, interest was renewed in classical (introduction) biological control of the pest. Here we discuss the prospects of identifying natural enemies of B. oleae in Africa and Asia that may help reduce B. oleae populations in California and elsewhere. Based on the current understanding of Bactrocera phylogenetics, early opinions that B. oleae originated in Africa or western Asia rather than the Mediterranean region or the Near East are taxonomically and ecologically supportable. Closely related to cultivated olive, the wild olive Olea europaea cuspidata is widely distributed in southern and eastern Africa, the Arabian Peninsula, and eastwards into Asia as far as southwestern China. Little is known regarding the biology and ecology of B. oleae in Africa and eastern Asia, especially in wild olives. While the diversity of parasitoids of B. oleae in the Mediterranean region is low and unspecialized, a diverse assemblage of parasitoids is known from B. oleae in Africa. Conversely, regions in Asia have remained largely unexplored for B. oleae and its natural enemies.     

Non-target host risk assessment of the idiobiont parasitoid Bracon celer (Hymenoptera: Braconidae) for biological control of olive fruit fly in California

Non-target risk posed by an African parasitoid, Bracon celer Szépligeti (Hymenoptera: Braconidae), was assessed for a classical biological control program against olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae: Dacinae), in California, USA. Behavioral and reproductive responses to non-target tephritid species were tested with beneficial (Chaetorellia succinea [Costa] and Parafreutreta regalis Munro) (Tephritidae: Tephritinae) and native (Rhagoletis fausta [Osten Sacken]) (Tephritidae: Trypetinae) fruit fly species in successive no-choice and choice experiments under close confinement in quarantine. Non-target host-plant substrates exposed to B. celer were yellow-starthistle flower heads containing C. succinea, Cape ivy stem galls containing P. regalis, and bitter-cherry fruit containing R. fausta. The parasitoid probed all three infested non-target plant substrates, but significantly less than olives infested with B. oleae. It produced offspring from P. regalis in Cape ivy stem galls, but appeared unable to penetrate yellow-starthistle flower heads with its ovipositor. Bracon celer killed some B. oleae and R. fausta larvae without parasitism. Reproduction on P. regalis indicates that B. celer has a broad physiological host range, which, combined with the parasitoid's acceptance of all three host-plant substrates, indicates a strong potential to negatively impact non-target species. Although physical and temporal barriers to host attack may reduce risk to most non-target tephritids by B. celer in California, the parasitoid should not be released due to its risk of harming the beneficial P. regalis. Release of P. regalis is still under consideration, however, and final risk assessment should depend on whether the fly proves useful for weed control.     

Releases of Psyttalia fletcheri (Hymenoptera: Braconidae) and sterile flies to suppress melon fly (Diptera: Tephritidae) in Hawaii

Ivy gourd, Coccinia grandis (L.) Voigt, patches throughout Kailua-Kona, Hawaii Island, HI, were identified as persistent sources of melon fly, Bactrocera cucurbitae (Coquillett). These patches had a low incidence of Psyttalia fletcheri (Silvestri), its major braconid parasitoid natural enemy in Hawaii, and were used to evaluate augmentative releases of P. fletcheri against melon fly. In field cage studies of releases, numbers of melon flies emerging from ivy gourd fruit placed inside treatment cages were reduced up to 21-fold, and numbers of parasitoids were increased 11-fold. In open field releases of P. fletcheri into ivy gourd patches, parasitization rates were increased 4.7 times in release plots compared with those in control plots. However, there was no significant reduction in emergence of melon flies from fruit. In subsequent cage tests with sterile melon flies and P. fletcheri, combinations of sterile flies and P. fletcheri produced the greatest reduction (9-fold) in melon fly emergence from zucchini, Cucurbita pepo L. Reductions obtained with sterile flies alone or in combination with parasitoids were significantly greater than those in the control, whereas those for parasitoids alone were not. Although these results suggest that the effects of sterile flies were greater than those for parasitoids, from a multitactic melon fly management strategy, sterile flies would complement the effects of P. fletcheri. Cost and sustainability of these nonchemical approaches will be examined further in an ongoing areawide pest management program for melon fly in Hawaii.     

Olive fruit fly (Diptera: Tephritidae) ovipositional preference and larval performance in several commercially important olive varieties in California

The olive fruit fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae),is an invasive pest of olives (Olea spp.) in the United States. The objectives of this study were to determine whether B. oleae exhibits ovipositional preference under California field conditions similar to that demonstrated in European populations and whether the resulting larvae fare better in preferred varieties. Female B. oleae exhibited strong ovipositional preference for certain varieties of the domesticated olive, Olea europaea L, and the resulting larvae performed better by some measures in preferred varieties than in lesser preferred varieties. Ovipositional preference was observed in the field from 2003 to 2005, and laboratory assays were conducted to evaluate larval performance in 2005 and 2006. Among the olive varieties tested, Sevillano, Manzanillo, and Mission olives were the most heavily infested during three consecutive years. The larval performance measurements used were pupal yield, pupal weight, larval developmental time, and pupal emergence time. Ovipositional preference and pupal yield do not seem associated. There were significant differences in pupal emergence time, but these also measures did not reflect ovipositional preference. Two measures on performance did seem related to ovipositional preference; there were significant effects of variety on pupal weight and larval developmental time. Pupae developing in Manzanillo and Sevillano olives were heavier than those developing in less preferred varieties, and larval developmental time was significantly shorter in Sevillano olives relative to the other varieties. Oviposition preference and enhanced larval performance has implications for the pest status of this invasive insect in California.     

Lethal and sublethal toxicity of fipronil and imidacloprid on Psyttalia concolor (Hymenoptera: Braconidae)

Psyttalia concolor (Szèpligeti) (Hymenoptera: Braconidae) is a koinobiont endoparasitoid of several species of tephritid (Diptera) larvae, such as Bactrocera oleae (Gmelin) and Ceratitis capitata (Wiedemann). Here, we report on the effects of imidacloprid and fipronil on P. concolor females, when different routes of exposure were evaluated: residual contact (cover and bait sprays) and via treatment of host species. Moreover, the persistence of the bait formulated compound also was studied. For each experiment, lethal (mortality) and sublethal effects (parasitization rate or longevity) were studied. Fipronil produced 100% mortality irrespective of exposure route, and it was very persistent, because 34-d-old residues still produced this high mortality rate, being as toxic or even more toxic than the reference product dimethoate. Toxicity of imidacloprid depends on the mode of exposure, although always remained less toxic than dimethoate. Imidacloprid caused high mortality or sublethal effect to the progeny in cover sprays and when applied via treated host, being harmless in bait sprays application. In conclusion, our results suggest that fipronil should not be used in the field when the parasitoid is present. On the contrary, although imidacloprid is physiologically active against females of P. concolor, ecological selectivity may result through the use of bait treatment.     

Improvement of quality control methods for augmentative releases of the fruit fly parasitoids,Diachasmimorpha longicaudata and Psyttalia fletcheri (Hymenoptera: Braconidae)

Criteria were established to improve quality control methods for augmentative releases of the opiine parasitoids, Diachasmimorpha longicaudata (Ashmead) and Psyttalia fletcheri (Silvestri). These included correlating puparial weight with adult emergence and sex ratio at the Honolulu rearing facility, and determining the effect of air shipments and field releases on parasitoid emergence and subsequent mortality. There was a positive relationship between the weight of 7–10‐day‐old host puparia and percentage of emergence for both D. longicaudata and P. fletcheri. Standardization of shipping methods included placement of ice blocks in the top levels of the ice chests, prompt shipment and pick‐up of samples, and cooling of puparia before shipment to minimize metabolic heat generated in the samples, and to delay emergence of samples. Before standardization, emergence losses of up to 58% were observed for D. longicaudata and 18% for P. fletcheri. When shipping methods were standardized, emergence was no longer reduced. In addition, low emergence rates were associated with reduced flight propensity of D. longicaudata (R_s = ‐ 0.45 at Kilauea and ‐ 0.54 at Kealia). At the two release sites, 88–95% of adult D. longicaudata that did not escape the release containers were males.     

Genetic and cytogenetic analysis of the olive fruit fly Bactrocera oleae (Diptera: Tephritidae)

The genetic and cytogenetic characteristics of one of the major agricultural pests, the olive fruit fly Bactrocera oleae, are presented here. The mitotic metaphase complement of this insect consists of six pairs of chromosomes including one pair of heteromorphic sex chromosomes, with the male being the heterogametic sex. The analysis of the polytene complements of three larval tissues, the fat body, the salivary glands and the Malpighian tubules of this pest has shown (a) a total number of five long chromosomes (10 polytene arms) that correspond to the five autosomes of the mitotic nuclei and a heterochromatic mass corresponding to the sex chromosomes, (b) the constancy of the banding pattern of the three somatic tissues, (c) the absence of a typical chromocenter as an accumulation of heterochromatin, (d) the existence of reverse tandem duplications, and (e) the presence of toroid tips of the chromosome arms. The in situhybridization of genes or DNA sequences to the salivary gland polytene chromosomes of B. oleaeprovided molecular markers for all five autosomes and permitted the establishment of chromosomal homologies among B. olea, B. tryoniand Ceratitis capitata. The heat shock response of B. oleae, as revealed by heat-inducible puffing and protein pattern, shows a higher thermotolerance than Drosophila melanogaster.     

Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species (Diptera: Tephritidae) and their parasitoids (Hymenoptera: Braconidae)

The feeding toxicity of the natural insecticide spinosad in Provesta protein bait was evaluated for three economically important fruit fly species, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the melon fly, Bactrocera cucurbitae Coquillett; and the oriental fruit fly, Bactrocera dorsalis Hendel. Both females and males were evaluated. Spinosad was remarkably similar in toxicity to all three fruit fly species. Male C. capitata (24 h LC50 values and 95% fiducial limits = 2.8 [2.60-3.0] mg/liter spinosad) were significantly, although only slightly more susceptible to spinosadthan females (4.2 [3.8-4.6] mg/liter). Male (5.5 [4.7-6.6] mg/liter) andfemale (4.3 [3.7-4.9] mg/liter) B. cucurbitae were equally susceptible to spinosad. Female (3.3 [3.1-3.6] mg/liter) and male (3.1 [2.9-3.3] mg/liter) B. dorsalis also were equally susceptible to spinosad. Provesta bait containing spinosad also was evaluated against two parasitoids of tephritid fruit flies, Fopius arisanus (Sonan) and Pysttalia fletcheri (Silvestri). These parasitoids did not feed on the bait, so a contact toxicity test was conducted. Significant amounts of mortality were found only after exposure of parasitoids to spinosad-coated glass vials with concentrations > or =500 mg/liter spinosad. Parasitoids were less susceptible than fruit flies to such a degree that use of spinosad in bait spray should be compatible with these parasitoid species. Because the fruit flies tested in this study were so susceptible to spinosad, this product seems to be promising as a bait spray additive and a replacement for malathion for control of these species.     

Suppression of melon fly (Diptera: Tephritidae) populations with releases of Fopius arisanus and Psyttalia fletcheri (Hymenoptera: Braconidae) in North Shore Oahu, HI, USA

Field experiments and surveys were conducted to evaluate the efficacy of releasing Fopius arisanus (Sonan) and Psyttalia fletcheri (Silvestri) parasitoids for suppression of Bactrocera cucurbitae (Coquillett) infesting wild Coccinia grandis L. In 2003 and 2004, P. fletcheri releases combined with natural emergence from wild fly populations resulted in better fly suppression, compared to the control site. While P. fletcheri developed freely on melon fly, F. arisanus was less successful at producing its own progeny, yet causing mortality and a twofold decrease in pupae recovered from ivy gourds. Concurrent releases of both parasitoids exerted a compounded suppressive effect on the melon fly population 2–3 times higher than during the pre-release phase. A similar, less obvious, pattern occurred in 2004, due to reduction of the ivy gourd fruit canopy. In 2005, only P. fletcheri was released, with greatly reduced impact, due to ivy gourd destruction and by growers leaving crop culls in fields, producing large numbers of melon flies unaffected by parasitoid releases.     

Stress-induced septicemia as an impediment to laboratory rearing of the fruit fly parasitoid Biosteres (opius) longicaudatus (Hymenoptera: Braconidae) and the Caribbean fruit fly Anastrepha suspensa (Diptera: Tephritidae)

High pupal mortality experienced during laboratory rearing of Biosteres longicaudatus, a parasitoid of the Caribbean fruit fly Anastrepha suspensa was attributed primarily to the action of two species of opportunistic pathogens, Serratia marcescens and Pseudomonas aeruginosa. These bacteria were best able to overwhelm both parasitized and nonparasitized fly larvae and pupae when they were subjected to thermal stress (rearing temperatures >30°C). Methenamine mandelate chemotherapy had no prophylactic effect, but potentially deleterious side effects (aberrant fly premating sounds) were caused by incorporation of this antibiotic in the A. suspensa larval rearing medium. Control was effected by optimizing the cultural conditions rather than by the use of antibiotics.     

Olfactory response of three parasitoid species (Hymenoptera: Braconidae) to volatiles of guavas infested or not with fruit fly larvae (Diptera: Tephritidae)

The olfactory responses of the native parasitoids Doryctobracon areolatus (Szépligeti) and Asobara anastrephae (Muesebeck) and of the exotic parasitoid Diachasmimorpha longicaudata (Ashmead) to guava (Psidium guajava L.) infested or not with fruit fly larvae were evaluated. D. areolatus and D. longicaudata females responded to the odors of uninfested rotting guavas, although D. areolatus was also attracted to fruits at the initial maturation (turning) stage. The females of these species recognized the volatiles of guavas containing Ceratitis capitata (Wied.) larvae. However, in bioassays involving fruits with larvae of different instars, D. longicaudata females were not able to separate between fruits containing C. capitata larvae at the initial instars and larvae at the third instar. In the evaluations of volatiles released by guavas containing C. capitata and Anastrepha fraterculus (Wied.) larvae, the D. longicaudata females were oriented toward the volatiles of fruits containing both host species, but differed significantly from volatiles of guavas containing C. capitata larvae. The D. areolatus females also showed responses to both species, although with a preference for volatiles of fruits containing A. fraterculus larvae. The A. anastrephae females were oriented toward the odors of fruits infested with both fruit fly species. In the shade house, D. longicaudata females were oriented to volatiles of rotting fruits containing larvae or not, but could not significantly differentiate between hosts. D. areolatus females were not attracted toward fruits on the ground in the shade house, regardless of host, suggesting that this parasitoid does not forage on fallen fruits.     

Diachasmimorpha longicaudata and D. kraussii (Hymenoptera: Braconidae), potential parasitoids of the olive fruit fly

The olive fruit fly, Bactrocera oleae (Tephritidae), is a significant threat to California's olive industry. As part of a classical biological control program started in 2002, the parasitoids Diachasmimorpha kraussii and D. longicaudata (Hymenoptera: Braconidae) were imported to California from laboratory colonies in Hawaii. Studies on their biology and behavior as parasitoids of the olive fruit fly were conducted in quarantine. Both species tend to oviposit into 2nd and young 3rd instars, with the offspring completing development in the flies’ puparia. Most eggs are deposited in the first two weeks of adult life. Observed lifetime fecundity was low, possibly as a consequence of the relatively poor quality of the harvested olives used as a host substrate. Both pre-imaginal development and adult longevity were limited at constant temperatures above 30°C, which may indicate that these species will have difficulty establishing in the warmest regions of California.     

Quarantine strategies for olive fruit fly (Diptera: Tephritidae): low-temperature storage, brine, and host relations

A dose-response relationship was not observed in olive fruit fly, Bactrocera oleae (Gmelin), larvae exposed to acetic acid concentrations (0-2.5%) used in commercial brine solutions to cure olives. Immersion in a 1% acetic acid brine solution impeded emergence of the immature stages. A 1-wk exposure of olives infested with olive fruit fly larvae to low-temperature storage as a postharvest treatment at 0-1 degree C resulted in 8% survival of the population, and exposures of 2 through 5 wk further reduced pupal and adult emergence to <1.0%. One- to 2-wk exposures at 2-3 degrees C resulted in a significant decrease in survival from 20 to 3%, respectively, and longer durations of 3-5 wk reduced survival to <1.0%. Mean daily fruit pulp temperatures in olives in the top, middle, and bottom of plastic bins stored at 2-3 degrees C decreased by 5-8 degrees C from the first to the second day. Lowest temperatures were observed in the top, and highest temperatures were observed in the middle layer of fruit, which attained a mean temperature of 3.8 degrees C on day 5. Laboratory choice tests showed that olive fruit fly oviposited at a higher rate in late season Mission olives that were green than in fruit that were in the red blush maturity stage in tests with 1- and 3-4-d exposure periods, and an increase in duration of exposure was related to an increase in the total number of ovipositional sites. Higher percentages of olive fruit fly third instars, pupae, and adults were reared from green fruit than from fruit in the red blush stage after a 1-d exposure to oviposition. Manzanillo olives were more attractive for oviposition by olive fruit fly than Mission olives, and significantly more third instars, pupae, and adults developed in Manzanillo fruit than in Mission fruit in the red blush stage. These differences were related to the better quality and higher flesh content of the Manzanillo versus Mission olives used in the tests.     

Opiine parasitoids (Hymenoptera: Braconidae) of tropical fruit flies (Diptera: Tephritidae) of the Australian and South Pacific region

Opiine wasps are parasitoids of dacine fruit flies, the primary horticultural pests of Australia and the South Pacific. A taxonomic synopsis and distribution and host records (44% of which are new) for each of the 15 species of dacine-parasitizing opiine braconids found in the South Pacific is presented. Species dealt with are Diachasmimorpha hageni (Fullaway), D. kraussii (Fullaway), D. longicaudata (Ashmead), D. tryoni (Cameron), Fopius arisanus (Sonan), F. deeralensis (Fullaway), F. ferrari Carmichael & Wharton sp. n., F. illusorius (Fischer) comb. n., F. schlingeri Wharton, Opius froggatti Fullaway, Psyttalia fijiensis (Fullaway), P. muesebecki (Fischer), P. novaguineensis (Szépligeti) and Utetes perkinsi (Fullaway). A potentially undescribed species, which may be a colour morph of F. vandenboschi (Fullaway), is diagnosed but not formally described. Fopius vandenboschi sensu stricto, Diachasmimorpha fullawayi Silvestri, Psyttalia concolor Szépligeti and P. incisi Silvestri have been liberated into the region but are not considered to have established: a brief diagnosis of each is included. Biosteres illusorius Fischer is formally transferred to the genus Fopius. A single opiine specimen reared from a species of Bactrocera (Bulladacus) appears to be Utetes albimanus (Szépligeti), but damage to this specimen and to the holotype (the only previously known specimen) means that this species remains unconfirmed as a fruit fly parasite: a diagnosis of U. cf. albimanus is provided. Psyttalia novaguineensis could not be adequately separated from P. fijiensis using previously published characterizations and further work to resolve this complex is recommended. A key is provided to all taxa.     

Volatile host fruit odors as attractants for the oriental fruit fly (Diptera: Tephritidae)

We examined the responses of oriental fruit flies, Bactrocera dorsalis Hendel, to the odors of different stages and types of fruit presented on potted trees in a field cage. Females were most attracted to odors of soft, ripe fruit. Odors of common guava were more attractive to females than papaya and starfruit, and equally as attractive as strawberry guava, orange, and mango. In field tests, McPhail traps baited with mango, common guava, and orange captured equal numbers of females. Traps baited with mango were compared with 2 commercially available fruit fly traps. McPhail traps baited with mango captured more females than visual fruit-mimicking sticky traps (Ladd traps) and equal numbers of females as McPhail traps baited with protein odors. Results from this study indicate that host fruit volatiles could be used as lures for capturing oriental fruit flies in orchards.     

Nontarget insects captured in fruit fly (Diptera: Tephritidae) surveillance traps

Traps baited with synthetic lures (ammonium acetate and putrescine) captured as many Mexican fruit flies as the traditional torula yeast/borax slurry, but with far fewer (ratio 5:1) nontarget insects. Ninety percent of the nontarget insects were dipterans. Consequently, neither trap is efficacious against other citrus pests, which are mainly Hemiptera or Lepidoptera. Although the nontarget catch is sometimes referred to as "trash," many nontarget insects are beneficials, including predators and parasites (especially tachinids). The traps with synthetic lures killed fewer of these beneficials by a ratio of 4:1 compared with the yeast-baited traps. Certain taxa, notably the chrysopids and halictid bees, exhibited a somewhat greater preference (10 and 50%, respectively) for the synthetic lures. Overall, with regard to the deployment of the newer baits, the threat to predators, parasites, and pollinators was found to be negligible, and certainly much less than that posed by the traditional traps.     

Impact of introduction of Bactrocera dorsalis (Diptera: Tephritidae) and classical biological control releases of Fopius arisanus (Hymenoptera: Braconidae) on economically important fruit flies in French Polynesia

Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), was discovered on Tahiti Island in July 1996. Eradication programs were conducted from 1997 to 2001, but failed. From 1998 to 2006, B. dorsalis was recovered from 29 different host fruit from the five Society Islands: Tahiti, Moorea, Raiatea, Tahaa, and Huahine. Analysis of coinfestation patterns by B. dorsalis, Bactrocera tryoni (Froggatt), and Bactrocera kirki (Froggatt) suggested B. dorsalis had displaced these two species and become the most abundant fruit fly in coastal areas. To suppress B. dorsalis populations, a classical biological control program was initiated to introduce the natural enemy Fopius arisanus (Sonan) (Hymenoptera: Braconidae) into French Polynesia from Hawaii. Wasps were released and established on Tahiti, Moorea, Raiatea, Tahaa, and Huahine Islands. In guava, Psidium guajava L., collections for Tahiti, F. arisanus parasitism of fruit flies was 2.1, 31.8, 37.5, and 51.9% for fruit collected for 2003, 2004, 2005 and 2006, respectively. Based on guava collections in 2002 (before releases) and 2006 (after releases), there was a subsequent decrease in numbers of B. dorsalis, B. tryoni, and B. kirki fruit flies emerging (per kilogram of fruit) by 75.6, 79.3, and 97.9%, respectively. These increases in F. arisanus parasitism and decreases in infestation were similar for other host fruit. Establishment of F. arisanus is the most successful example of classical biological control of fruit flies in the Pacific area outside of Hawaii and serves as a model for introduction into South America, Africa, and China where species of the B. dorsalis complex are established.     

Evaluation of entomopathogenic nematodes against the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae)

Infectivity of six entomopathogenic nematode (EPNs) species against Bactrocera oleae was compared. Similar infection levels were observed when third-instar larvae were exposed to infective juveniles (IJs) on a sand-potting soil substrate. When IJs were sprayed over naturally infested fallen olives, many larvae died within treated olives as well as in the soil; Steinernema feltiae caused the highest overall mortality of 67.9%. In addition, three laboratory experiments were conducted to optimize a time period for S. feltiae field application. (1) Abundance of fly larvae inside fallen olives was estimated over the 2006–2007 season with the highest number of susceptible larvae (3 mm and larger) per 100 olives being observed during December, 2006. (2) S. feltiae efficacy against fly larvae dropped to the soil post-IJ-application was determined. B. oleae added to the substrate before and after nematode application were infected at similar levels. (3) Effect of three temperature regimes (min–max: 10–27, 6–18, and 3–12 °C) corresponding to October through December in Davis, California on S. feltiae survival and infectivity was determined. After 8 weeks, the IJs at the 3–12 °C treatment showed the highest survival rate. However, the cold temperature significantly limited S. feltiae infectivity. Our results demonstrate that B. oleae mature larvae are susceptible to EPN infection both in the soil and within infested olives. Being the most effective species, S. feltiae may have the potential to suppress overwintering populations of B. oleae. We suggest that November is the optimal time for S. feltiae field application in Northern California.