Evaluation of SPLAT with spinosad and methyl eugenol or cue-lure for "attract-and-kill" of oriental and melon fruit flies (Diptera: Tephritidae) in Hawaii

Specialized Pheromone and Lure Application Technology (SPLAT) methyl eugenol (ME) and cue-lure (C-L) "attract-and-kill" sprayable formulations containing spinosad were compared with other formulations under Hawaiian weather conditions against oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), respectively. Field tests were conducted with three different dispensers (Min-U-Gel, Acti-Gel, and SPLAT) and two different insecticides (naled and spinosad). SPLAT ME with spinosad was equal in performance to the standard Min-U-Gel ME with naled formulation up to 12 wk. SPLAT C-L with spinosad was equal in performance to the standard Min-U-Gel C-L with naled formulation during weeks 7 to12, but not during weeks 1-6. In subsequent comparative trials, SPLAT ME + spinosad compared favorably with the current standard of Min-U-Gel ME + naled for up to 6 wk, and it was superior from weeks 7 to 12 in two separate tests conducted in a papaya (Carica papaya L.) orchard and a guava (Psidium guajava L.) orchard, respectively. In outdoor paired weathering tests (fresh versus weathered), C-L dispensers (SPLAT + spinosad, SPLAT + naled, and Min-U-Gel + naled) were effective up to 70 d. Weathered ME dispensers with SPLAT + spinosad compared favorably with SPLAT + naled and Min-U-Gel + naled, and they were equal to fresh dispensers for 21-28 d, depending on location. Our current studies indicate that SPLAT ME and SPLAT C-L sprayable attract-and-kill dispensers containing spinosad are a promising substitute for current liquid organophosphate insecticide formulations used for areawide suppression of B. dorsalis and B. cucurbitae in Hawaii.     

Methyl eugenol and cue-lure traps for suppression of male oriental fruit flies and melon flies (Diptera: Tephritidae) in Hawaii: effects of lure mixtures and weathering

Methyl eugenol (4-allyl-1,2-dimethoxybenzene-carboxylate) and cue-lure [4-(p-acetoxyphenyl)-2-butanone] are highly attractive kairomone lures to oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, B. cucurbitae (Coquillett), respectively. Plastic bucket traps were evaluated as dispensers for methyl eugenol and cue-lure for suppression of the 2 fruit flies in Hawaii. Methyl eugenol and cue-lure mixtures were compared with pure methyl eugenol or cue-lure over 4 seasons. B. dorsalis captures differed significantly with treatment and season. B. dorsalis captures with 100% methyl-eugenol were significantly greater than all other treatments (25, 50, and 75%). B. cucurbitae captures also differed significantly with treatment but not with season. Captures with 100, 75, and 50% cue-lure were not significantly different. Bucket traps baited with cue-lure (+ malathion) and weathered under Hawaiian climatic conditions were attractive to B. cucurbitae up to 8 wk. Two methyl eugenol dispensers (canec disks and Min-U-Gel) were compared with bucket traps. Dispensers (methyl eugenol + malathion) were weathered for 2-16 wk under Hawaiian climatic conditions and bioassayed during summer and winter. Initially, captures of B. dorsalis were not significantly different for the 3 dispensers. Bucket traps and canec disks were most resistant to weather, remaining attractive to B. dorsalis flies up to 16 wk. Min-U-Gel was least resistant, losing attractiveness to B. dorsalis flies within 2 wk. On the basis of performance, bucket traps and canec disks were equally long-lived up to 14 wk; thereafter, bucket traps were slightly more attractive during winter. Canec disks were cheapest, but on the basis of possible environmental concerns, bucket traps may be the best all-around choice for areawide suppression of fruit flies.     

Field trials of spinosad as a replacement for naled, DDVP, and malathion in methyl eugenol and cue-lure bucket traps to attract and kill male oriental fruit flies and melon flies (Diptera: Tephritidae) in Hawaii

Spinosad was evaluated in Hawaii as a replacement for organophosphate insecticides (naled, dichlorvos [DDVP], and malathion) in methyl eugenol and cue-lure bucket traps to attract and kill oriental fruit fly, Bactrocera dorsalis Hendel, and melon fly, B. cucurbitae Coquillett, respectively. In the first and second methyl eugenol trials with B. dorsalis, naled was in the highest rated group for all evaluation periods (at 5, 10, 15, and 20 wk). Spinosad was equal to naled at 5 and 10 wk during both trials 1 and 2, and compared favorably with malathion during trial 2. During the first cue-lure trial with B. cucurbitae, naled and malathion were in the top rated group at 5, 10, 15, and 20 wk. Spinosad was equal to naled at 5 wk. During the second cue-lure trial, spinosad and naled were both in the top rated group at 10, 15, and 20 wk. Use of male lure traps with methyl eugenol or cue-lure had no effect on attraction of females into test areas. Our results suggest that spinosad, although not as persistent as naled or malathion, is safer to handle and a more environmentally friendly substitute for organophosphate insecticides in methyl eugenol and cue-lure traps for use in B. dorsalis and B. cucurbitae areawide integrated pest management programs in Hawaii.     

Effectiveness of attract-and-kill systems using methyl eugenol incorporated with neonicotinoid insecticides against the oriental fruit fly (Diptera: Tephritidae)

Laboratory bioassays and field trials were conducted to evaluate an "attract-and-kill" system using methyl eugenol (ME) with neonicotinoid insecticides against male oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). In laboratory bioassays, mortality of male flies resulting from the conventional toxicant, naled was 98.3-100% at 24 through 72 h after treatment, whereas the neonicotinoid insecticides imidacloprid and acetamiprid caused only approximately 60-80% at 24 through 72 h after treatment. In the assays of residual effect, naled was persistent up to 96 wk, whereas imidacloprid or acetamiprid was persistent up to 150 wk, resulting in 38.9 or 61.2% male mortality, respectively. Imidacloprid, in particular, caused a delayed lethal effect on flies. In another experiment, male mortality within 28 wk from clothianidin, another neonicotinoid insecticide, was approximately 80% after exposure for 24 h, suggesting a delayed lethal effect similar to those treated with imidacloprid, and mortality was up to 91.8%, if observed, 72 h after treatment. In field trials, attractiveness was similar between ME alone and ME incorporated with naled or neonicotinoids, indicating that addition of these insecticides to ME in traps is not repellent to B. dorsalis males. Using an improved wick-typed trap with longer attractiveness for simulating field application, addition of imidacloprid or acetamiprid maintained 40.1 or 64.3% male mortality, respectively, when assayed once every 2 wk from traps placed in orchards for 42 wk without changing the poison, whereas incorporation with naled resulted in as high as 98.1% after 34 wk and approximately 80% at 42 wk, indicating that persistence is increased compared with sugarcane fiberboard blocks for carrying poison attractants. This study also suggests that neonicotinoid insecticides could be used as an alternative for broad-spectrum insecticides as toxicants in fly traps.     

Efficacy of wax matrix bait stations for Mediterranean fruit flies (Diptera: Tephritidae)

Tests were conducted that evaluated efficacy of wax matrix bait stations for Ceratitis capitata (Wiedemann) adults in Guatemala. Bait stations were exposed to outdoor conditions to determine effect of weathering on longevity as indicated by bait station age. Results of laboratory tests found that bait stations with spinosad and ammonium acetate remained effective for at least 31 d compared with pesticide-free controls, although there was some loss of efficacy over time. Percentage mortality for bait station strips with 2% spinosad and 1% ammonium acetate decreased from 100 +/- 0.0% on day 0 to 70 +/- 7.1% after 31 d. Ammonia concentration had little effect on percentage mortality although there was some indication that ammonia concentration affected number of flies observed on the bait stations. Bait station strips (one per cage) were more effective than controls for 6-8 wk when tests were conducted in field cages (3 m diameter x 2 m), but only 2-3 wk when tests were conducted in large (2.5 m high and 6.0 m wide and 7.5 m long) field cages. Longevity was restored when multiple bait stations (3, 6, or 12) were deployed per cage. Bait stations containing methomyl were used for field tests of efficacy for wild flies. Dipped lure bait stations, which were made by coating two edges of commercial ammonium acetate and trimethylamine lures, killed six times more flies than corn cob bait stations dipped into a Nulure/malathion solution. They also killed more flies than pesticide-free controls for 8 wk.     

Revised irradiation doses to control melon fly, Mediterranean fruit fly, and oriental fruit fly (Diptera: Tephritidae) and a generic dose for tephritid fruit flies

Currently approved irradiation quarantine treatment doses for Bactrocera cucurbitae (Coquillet), melon fly; Ceratitis capitata (Wiedemann), Mediterranean fruit fly; and Bactrocera dorsalis (Hendel), oriental fruit fly, infesting fruits and vegetables for export from Hawaii to the continental United States are 210, 225, and 250 Gy, respectively. Irradiation studies were initiated to determine whether these doses could be reduced to lower treatment costs, minimize any adverse effects on quality, and support a proposed generic irradiation dose of 150 Gy for fruit flies. Dose-response tests were conducted with late third instars of wild and laboratory strains of the three fruit fly species, both in diet and in fruit. After x-ray irradiation treatment, data were taken on adult emergence, and adult female fecundity and fertility. Melon fly was the most tolerant of the three species to irradiation, and oriental fruit fly was more tolerant than Mediterranean fruit fly. Laboratory and wild strains of each species were equally tolerant of irradiation, and larvae were more tolerant when irradiated in fruit compared with artificial diet. An irradiation dose of 150 Gy applied to 93,666 melon fly late third instars in papayas resulted in no survival to the adult stage, indicating that this dose is sufficient to provide quarantine security. Irradiation doses of 100 and 125 Gy applied to 31,920 Mediterranean fruit fly and 55,743 oriental fruit fly late third instars, respectively, also resulted in no survival to the adult stage. Results support a proposed generic irradiation quarantine treatment dose of 150 Gy for all tephritid fruit flies.     

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.     

Effectiveness of protein baits on melon fly and oriental fruit fly (Diptera: Tephritidae): attraction and feeding

Attraction and feeding responses of oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, Bactrocera cucurbitae (Coquillett), were determined for different protein baits. In separate choice attraction assays for each species, significantly more flies arrived at stations with bait than water, but no differences existed among baits of GF-120 Fruit Fly Bait, GF-120 NF Naturalyte Fruit Fly Bait, Provesta 621 autolyzed yeast extract, and Mazoferm E802. In comparison with B. dorsalis, B. cucurbitae had 2.8 times more responders and a 4.8 times better discrimination between baits and water. In a second attraction assay with only B. dorsalis, volume of bait was negatively correlated to numbers of flies alighting on the bait. Feeding assays for both species demonstrated that time spent feeding and duration on a leaf were both significantly affected by bait type. B. dorsalis fed the longest on Provesta 621, with significantly less feeding on the other baits, and with all baits resulting in more feeding than water. The longest feeding times for B. cucurbitae resulted with Mazoferm E802 and Provesta 621, and all baits except GF-120 NF resulted in eliciting a significantly longer feeding duration than water. In separate toxicology assays for each species, significantly higher mortality resulted from bait formulations containing spinosad compared with blank baits, but no differences existed between GF-120 and GF-120 NF formulations. The differences are discussed between the two Bactrocera species primarily in regard to bait preference, extent of response, and previous work on laboratory flies.     

Susceptibility of low-chill blueberry cultivars to Mediterranean fruit fly, oriental fruit fly, and melon fly (Diptera: Tephritidae)

No-choice tests were conducted to determine whether fruit of southern highbush blueberry, Vaccinium corymbosum L., hybrids are hosts for three invasive tephritid fruit flies in Hawaii. Fruit of various blueberry cultivars was exposed to gravid female flies of Bactrocera dorsalis Hendel (oriental fruit fly), Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), or Bactrocera cucurbitae Coquillet (melon fly) in screen cages outdoors for 6 h and then held on sand in the laboratory for 2 wk for pupal development and adult emergence. Each of the 15 blueberry cultivars tested were infested by oriental fruit fly and Mediterranean fruit fly, confirming that these fruit flies will oviposit on blueberry fruit and that blueberry is a suitable host for fly development. However, there was significant cultivar variation in susceptibility to fruit fly infestation. For oriental fruit fly, 'Sapphire' fruit produced an average of 1.42 puparia per g, twice as high as that of the next most susceptible cultivar 'Emerald' (0.70 puparia per g). 'Legacy', 'Biloxi', and 'Spring High' were least susceptible to infestation, producing only 0.20-0.25 oriental fruit fly puparia per g of fruit. For Mediterranean fruit fly, 'Blue Crisp' produced 0.50 puparia per g of fruit, whereas 'Sharpblue' produced only 0.03 puparia per g of fruit. Blueberry was a marginal host for melon fly. This information will aid in development of pest management recommendations for blueberry cultivars as planting of low-chill cultivars expands to areas with subtropical and tropical fruit flies. Planting of fruit fly resistant cultivars may result in lower infestation levels and less crop loss.     

Quarantine security of bananas at harvest maturity against Mediterranean and Oriental fruit flies (Diptera: Tephritidae) in Hawaii

Culled bananas (dwarf 'Brazilian', 'Grand Nain', 'Valery', and 'Williams') sampled from packing houses on the islands of Hawaii, Kauai, Maui, Molokai, and Oahu identified specific "faults" that were at risk from oriental fruit fly, Bactrocera dorsalis (Hendel), infestation. Faults at risk included bunches with precociously ripened bananas, or bananas with tip rot, fused fingers, or damage that compromised skin integrity to permit fruit fly oviposition into fruit flesh. No Mediterranean fruit fly, Ceratitis capitata (Wiedemann), or melon fly, B. cucurbitae (Coquillett), infestations were found in culled banana samples. Field infestation tests indicated that mature green bananas were not susceptible to fruit fly infestation for up to 1 wk past the scheduled harvest date when attached to the plant or within 24 h after harvest. Recommendations for exporting mature green bananas from Hawaii without risk of fruit fly infestation are provided. The research reported herein resulted in a USDA-APHIS protocol for exporting mature green bananas from Hawaii.     

Odorant receptor co-receptor Orco is upregulated by methyl eugenol in male Bactrocera dorsalis (Diptera: Tephritidae)

Bactrocera dorsalis is a destructive fruit-eating pest that causes severe economic damage to the fruit and vegetable industry. Methyl eugenol (ME) has been widely used as an effective sexual attractant for male fruit flies through olfactory perception. However, the molecular mechanism underlying the olfactory perception of ME remains unknown. Here, we report the characterization and functional analysis of a newly discovered cDNA that encodes a Drosophila melanogaster odorant receptor co-receptor Orco ortholog in B. dorsalis. qRT-PCR analysis revealed that it was abundantly expressed in the antenna of adult B. dorsalis. Notably, Orco was upregulated by ME in the antenna of male flies. Mature males of B. dorsalis showed significant taxis toward ME within 0.5h, and Orco was significantly upregulated in the attracted adults within the same period. Silencing Orco through the ingestion of dsRNA reduced the attractive effects of ME. These data suggest that Orco may play an essential role in ME attraction in the olfactory signal transduction pathway.     

Captures of pest fruit flies (Diptera: Tephritidae) and nontarget insects in BioLure and torula yeast traps in Hawaii

MultiLure traps were deployed in a Hawaiian orchard to compare the attraction of economically important fruit flies and nontarget insects to the three-component BioLure and torula yeast food lures. Either water or a 20% propylene glycol solution was used to dissolve the torula yeast or as capture fluid in BioLure traps. Torula yeast in water was more attractive than BioLure for male and female Bactrocera cucurbitae (Coquillett) and Bactrocera dorsalis (Hendel) and as attractive for Ceratitis capitata (Wiedemann), and the addition of propylene glycol significantly inhibited the attractiveness of torula yeast. The known synergistic effect of propylene glycol with BioLure, resulting in increased captures of Anastrepha flies, was not observed with Bactrocera. Nontarget Drosophilidae, Neriidae, Phoridae, Calliphoridae, Sarcophagidae, and Muscidae were more strongly attracted to BioLure, and both lures collected Chloropidae equally. As with fruit flies, propylene glycol in torula yeast significantly decreased nontarget captures. The results therefore suggest that torula yeast in water is a more effective attractant than BioLure for pest Bactrocera while minimizing nontarget captures.     

Prerelease exposure to methyl eugenol increases the mating competitiveness of sterile males of the oriental fruit fly (Diptera: Tephritidae) in a Hawaiian orchard

Males of the oriental fruit fly, Bactrocera dorsalis (Hendel), are strongly attracted to methyl eugenol (ME), and recent work demonstrated that ingestion of this chemical enhances male mating success, apparently owing its role as a precursor in the synthesis of the male sex pheromone. The current study expanded upon earlier laboratory and field-cage experiments by assessing whether prerelease exposure to ME increased the mating competitiveness of mass-reared, sterile males in Hawaiian orchards. Releases of sterile males from a pupal color-based sexing strain were made weekly in two fruit orchards over 8 mo, with the sterile males at one site given ME for 24 h before release (treated) and the sterile males at the other site given no ME before release (control). Fruits were collected periodically during the study period, and eggs were dissected and incubated to score hatch rate. At both sites, releases of sterile males increased the proportion of unhatched eggs well above prerelease levels, but the incidence of egg sterility was consistently, and statistically, greater in the orchard receiving ME-exposed males. Computed over the entire release period, the average value of Fried's competitive index (that characterizes the mating success of sterile males relative to their wild counterparts) for ME-treated males was 3.5 times greater than that for control males, although this difference was not statistically significant. However, when computed over the period during which egg sterility values were elevated and stable, presumably when females inseminated before the releases were rare or absent, the competitive indices were significantly higher for ME-treated sterile males. The implications of these results for implementing the Sterile Insect Technique against this species are discussed.     

桔小实蝇雄成虫联系性嗅觉学习

【目的】为了探究桔小实蝇 Bactrocera dorsalis (Hendel)雄成虫的嗅觉学习能力。【方法】本研究采用经典性嗅觉条件反射训练法（classical olfactory conditioning）在室内对固定的羽化后14-17日龄的桔小实蝇雄成虫进行气味与食物的联合学习训练, 即薄荷精油和10%蔗糖溶液联合的奖赏性训练（appetitive conditioning）以及甲基丁香酚(methyl eugenol, ME)和饱和盐溶液联合的惩罚性训练（aversive conditioning）,并以伸喙反射行为（proboscis extension reflex, PER）作为学习与否的判定标准。【结果】经过奖赏性训练后,桔小实蝇雄成虫对薄荷精油的伸喙反射率可从0%增加至68%;而经过惩罚性训练后,桔小实蝇对甲基丁香酚的伸喙反射率可从100%降低至36.54%,且这种伸喙反射率的变化是通过气味条件刺激（conditioned stimulus）和食物非条件刺激（unconditioned stimulus）的对称性联合而产生的。【结论】结果表明,桔小实蝇雄性成虫具有较强的联系性嗅觉学习能力,并且两种刺激的联合是形成学习记忆的必要条件。     

Wheat germ oil and its effects on a liquid larval rearing diet for oriental fruit flies (Diptera: Tephritidae)

Wheat germ oil was added to a larval liquid diet for rearing Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) to optimize fruit fly quality. Effects of various concentrations of wheat germ oil at 0.04, 0.07, 0.15, 0.30, and 0.66% and their possible mode of action were evaluated. Results suggest that addition of wheat germ oil does not affect pupal weight, larval developmental period, adult emergence, mating ability, or peak time for egg production. But there was a significant increase in pupal recovery, percentage of adult fliers, egg production, or egg hatch for larvae fed the diet with wheat germ oil compared with those reared on the liquid diet without wheat germ oil. The increase in egg hatch and fliers was dose dependent. Therefore, addition of wheat germ oil to fruit fly rearing diet is a novel way to improve fruit fly quality, especially in egg hatch, fliers, egg production, and pupal recovery.