Trap capture of three economically important fruit fly species (Diptera: Tephritidae): evaluation of a solid formulation containing multiple male lures in a Hawaiian coffee field

Invasive fruit flies (Diptera: Tephritidae) pose a global threat to agriculture through direct damage to food crops and the accompanying trade restrictions that often result. Early detection is vital to controlling fruit flies, because it increases the probability of limiting the growth and spread of the invasive population and thus may greatly reduce the monetary costs required for eradication or suppression. Male-specific lures are an important component of fruit fly detection, and three such lures are used widely: trimedlure (TML), cue lure (CL), and methyl eugenol (ME), attractive to Mediterranean fruit fly, Ceratitis capitata (Wiedemann); melon fly, Bactrocera cucurbitae (Coquillett); and oriental fruit fly, Bactrocera dorsalis (Hendel), respectively. In California, Florida, and Texas, the two Bactrocera lures are applied to separate species-specific traps as liquids (with a small amount of the insecticide naled added), whereas TML is delivered as a solid plug in another set of traps. Thus, the detection protocol involves considerable handling time as well as potential contact with a pesticide. The purpose of this study was to compare trap capture between liquid male lures and "trilure" wafers that contain TML, ME, raspberry ketone (RK, the hydroxy equivalent of CL), and the toxicant DDVP embedded within a solid matrix. Field studies were conducted in a Hawaiian coffee (Coffea arabica L.) field where the three aforementioned species co-occur, showed that the wafer captured at least as many flies as the liquid baits for all three species. This same result was obtained in comparisons using both fresh and aged (6-wk) baits. Moreover, the wafers performed as well as the single-lure traps in an ancillary experiment in which TML plugs were substituted for liquid TML. Additional experiments demonstrated explicitly that the presence of ME and RK had no effect on captures of C. capitata males and similarly that the presence of TML had no effect on the capture of B. cucurbitae or B. dorsalis males.     

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.     

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.     

Capture of Bactrocera fruit flies (Diptera: Tephritidae) in traps baited with liquid versus solid formulations of male lures

Bactrocera dorsalis (Hendel) and B. cucurbitae (Coquillett) (Diptera: Tephritidae) are important agricultural pests of the Pacific region. Detection and control of these species rely largely on traps baited with male-specific attractants (parapheromones), namely methyl eugenol for B. dorsalis and cue lure for B. cucurbitae. Presently, these lures (plus naled, an insecticide) are applied in liquid form, although this procedure is time-consuming, and naled as well as methyl eugenol may pose human health risks. Recently, a solid formulation (termed a wafer) has been developed that contains both male lures (plus DDVP, an insecticide), and here we present data from field tests in California and Hawaii that compare the effectiveness of liquid versus solid formulations of the lures in capturing marked, released males of these two Bactrocera species. For both species and in both California and Hawaii, traps baited with the solid formulation of the male lure captured similar or significantly more released flies than the liquid formulation for both fresh and aged baits. Traps in Hawaii also captured wild (unmarked) males of both B. dorsalis and B. cucurbitae, and the results obtained for wild flies were similar to those recorded for released flies for both species. Collectively, the results presented suggest that the solid dispenser of the male lures constitutes a reliable substitute for the liquid formulation in detecting incipient Bactrocera outbreaks.     

Enhancement of attraction of alpha-ionol to male Bactrocera latifrons (Diptera: Tephritidae) by addition of a synergist, cade oil

Male lures are known for many tephritid fruit fly species and are often preferred over food bait based traps for detection trapping because of their high specificity and ability to attract flies over a wide area. Alpha-ionol has been identified as a male lure for the tephritid fruit fly Bactrocera latifrons (Hendel). The attraction of this compound to male B. latifrons individuals, however, is not as strong as is the attraction of other tephritid fruit fly species to their respective male lures. Cade oil, an essential oil produced by destructive distillation of juniper (Juniperus oxycedrus L.) twigs, synergizes the attraction of alpha-ionol to male B. latifrons. Catches of male B. latifrons at traps baited with a mixture of alpha-ionol and cade oil were more than three times greater than at traps baited with alpha-ionol alone. Substitution of alpha-ionol + cade oil for alpha-ionol alone in detection programs could considerably improve the chance of detecting invading or incipient populations of B. latifrons. However, detection programs should not rely solely on this lure but also make use of protein baited traps as well as fruit collections. Further work with fractions of cade oil may help to identify the active ingredient(s), which could help to further improve this male lure for B. latifrons.     

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.     

福州实蝇监测初报

自2005年5月29日至2006年5月28日在福州金山福建农林大学校园内进行了实蝇监测。采用甲基丁香酚(M e)、诱蝇酮(Cue)和地中海实蝇诱芯(T),诱集到橘小实蝇[Bactrocera(Bactrocera)dorsalis]、瓜实蝇[B.(Zeugodacus)cucurbi-tae]、南瓜实蝇[B.(Zeugodacus)tau]和具条实蝇(B.scutellata)4种实蝇,但未诱到地中海实蝇(Ceratitis capitata)。其中,橘小实蝇诱集量最大,8月中下旬达到高峰。本研究为掌握福州地区实蝇发生动态提供了基础资料。     

基于性信息诱捕监测广东桔小实蝇和瓜实蝇发生动态及其对2种常用农药的抗药性评价

利用性信息素诱捕的方法对广东省茂名、佛山、梅州和韶关的桔小实蝇Bactrocera dorsalis (Hendel)和瓜实蝇Bactrocera cucurbitae (Coquillett)种群动态进行监测;并用药膜法测定了两种实蝇不同地理种群成虫对阿维菌素和甲维盐的抗药性情况。结果表明,桔小实蝇和瓜实蝇在所监测的4个地市全年均有发生,桔小实蝇和瓜实蝇种群数量发生高峰期集中在5月中旬至8月中旬,从4月中旬开始田间种群数量开始增加,10月中旬以后种群数量急剧下降,高峰期与果实成熟期基本吻合。抗药性监测结果表明,桔小实蝇和瓜实蝇对阿维菌素和甲维盐的抗药性有逐年上升趋势,广东4个地市桔小实蝇和瓜实蝇已对阿维菌素产生中等抗性水平;2019年11月监测梅州地区桔小实蝇种群和韶关瓜实蝇种群对甲维盐抗性倍数分别为4.32和3.42倍,仍处于敏感水平,其余地区种群对甲维盐均达到了低水平或中等水平抗性。     

Capture of Bactrocera fruit flies in traps baited with liquid versus solid formulations of male lures in Malaysia

Approximately 70 species of Bactrocera fruit flies (Diptera: Tephritidae) are polyphagous economic pests that attack many important agricultural crops. Several of these Bactrocera species are also highly invasive, and many countries operate continuous, large-scale trapping programs to detect incipient infestations. Detection programs rely heavily on traps baited with male lures, with males of some species responding to raspberry ketone (RK; or its synthetic analogue cue-lure [CL]) and males of other species responding to methyl eugenol (ME). These lures (plus naled, an insecticide) are currently applied as liquids, although this procedure is time-consuming and may expose workers to health risks. Recent field tests, conducted largely in Hawaii, have shown that traps baited with a solid formulation (termed a wafer) that contains both RK and ME (plus dichlorvos, an insecticide) capture as many or more B. dorsalis (Hendel) and B. cucurbitae (Coquillett) males as traps baited with the standard liquid lures. While these results are promising, a more complete evaluation of the solid formulation requires testing in a region with a diverse assemblage of Bactrocera species, since interspecific variation in male response to lures has been reported. The objective of the present investigation was to assess the relative effectiveness of liquid versus solid formulations of male lures in Malaysia, a country known to harbor a large assemblage of Bactrocera species. Based on a 12-week sampling period, we found that, contrary to the Hawaiian results, traps baited with the wafer captured significantly fewer males than traps baited with liquid lures for all five ME-responding taxa analyzed and for one of the three RK/CL-responding species analyzed. Possible explanations for the discrepancy between these and earlier findings are offered.     

Capture of melon flies, Zeugodacus cucurbitae (Diptera: Tephritidae), in a food-baited Multilure trap: Influence of distance,diet, and sex

Many countries operate trapping programs to detect invasions of pestiferous fruit fly species (Diptera: Tephritidae). Surveillance relies heavily on traps baited with male lures, which, while highly attractive, have limited effectiveness, because (i) they are sex-specific and (ii) males of some species do not respond to the lures currently in use. For these reasons, detection programs also include food-baited traps that are neither sex- nor species-specific. Compared to male lure-baited traps, however, few studies have measured the attractiveness of food-based traps. The present study describes a mark-release-recapture study conducted in a fruit orchard in Hawaii that measured the attractiveness of a liquid protein hydrolysate-based (torula yeast/borax slurry) trap to adults of the melon fly Zeugodacus cucurbitae (Coquillett). Multiple release points were used at varying distances from a single, central trap to generate estimates of distance-dependent capture probabilities. The potential influences of sex and pre-release diet on capture probability were also examined. Flies were released at 14 d of age and were maintained on one of four dietary regimes that offered a protein hydrolysate-rich diet for varying intervals (i.e., 0, 3, 7, or 14?d, respectively). Recapture rates were similar between the sexes and over both sexes and all diets averaged 3.6%, 3.2%, and 0.6% for release distances of 10, 25, and 50?m, respectively. Pre-release diet had a significant effect on recapture probability for releases at 10 and 25?m: flies fed sugar only or protein hydrolysate-rich diet for only 3?d were captured more frequently than flies that had longer access to yeast extract prior to release.     

Additional measurements of distance-dependent capture probabilities for released males of Bactrocera cucurbitae and B. dorsalis (Diptera: Tephritidae) in Honolulu

This paper describes a mark-release-recapture study involving males of two economically important fruit flies (Diptera: Tephritidae), Bactrocera cucurbitae (Coquillett) and B. dorsalis (Hendel), conducted in Honolulu, Hawaii. In each of three residential neighborhoods in Honolulu, we placed two traps, one baited with cue lure and the other with methyl eugenol (male attractants for B. cucurbitae and B. dorsalis, respectively), in a single tree. For both species, dyed, mature males from recently established laboratory colonies were released 25, 50, 100, and 200 m from the traps along the four compass directions, and for B. dorsalis releases were also made 300 m from the traps. For both B. cucurbitae and B. dorsalis, the proportion of males captured varied significantly among study areas and among release distances. Averaged over the 3 sites, the percentage of released males captured varied from 14% for releases at 25 m to 0.5% for releases at 200 m for B. cucurbitae and from 21% for releases at 25 m to 3% for releases at 300 m for B. dorsalis. In general, the capture rates of B. cucurbitae males were similar between California and Hawaii, whereas the captures rates of B. dorsalis males were significantly higher in California than Hawaii for all releases distances tested. Distance-dependent capture rates were used to estimate detection sensitivities for the two species under a trapping regime utilizing 5 cue lure- and 5 methyl eugenol-baited traps per 2.59 km² (as currently employed in California) and then compare these sensitivities between California and Hawaii.     

Weathering trials of Amulet cue-lure and Amulet methyl eugenol "attract-and-kill" stations with male melon flies and oriental fruit flies (Diptera: Tephritidae) in Hawaii

Amulet C-L (cue-lure) and Amulet ME (methyl eugenol) molded paper fiber "attract-and-kill" dispensers containing fipronil were tested under Hawaiian weather conditions against Bactrocera cucurbitae (Coquillett) (melon fly) and Bactrocera dorsalis (Hendel) (oriental fruit fly), respectively. In paired tests (fresh versus weathered), C-L dispensers were effective for at least 77 d, whereas ME dispensers were effective for at least 21 d. Thus, C-L dispensers exceeded, whereas ME dispensers did not meet the label interval replacement recommendation of 60 d. Addition of 4 ml of ME to 56-d-old ME dispensers restored attraction and kill for an additional 21 d. This result suggested the fipronil added at manufacture was still effective. By enclosing and weathering ME dispensers inside small plastic bucket traps, longevity of ME dispensers was extended up to 56 d. Fipronil ME and C-L dispensers also were compared, inside bucket traps, to other toxicants: spinosad, naled, DDVP, malathion, and permethrin. Against B. dorsalis, fipronil ME dispensers compared favorably only up to 3 wk. Against B. cucurbitae, fipronil C-L dispensers compared favorably for at least 15 wk. Our results suggest that fipronil C-L dispensers can potentially be used in Hawaii; however, fipronil ME dispensers need to be modified or protected from the effects of weathering to extend longevity and meet label specifications. Nonetheless, Amulet C-L and ME dispensers are novel prepackaged formulations containing C-L or ME and fipronil that are more convenient and safer to handle than current liquid insecticide formulations used for areawide suppression of B. dorsalis and B. cucurbitae in Hawaii.     

Distance-dependent capture probability of male Mediterranean fruit flies in trimedlure-baited traps in Hawaii

Many countries operate regional trapping programs for the detection of exotic tephritid fruit flies, which because of their polyphagous habits pose a serious threat to fruit and vegetable crops. Detection of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), relies primarily on trimedlure (TML), a synthetic male-specific lure, yet few studies have measured the relationship between distance from TML-baited traps and the probability of male capture, and consequently the detection sensitivity of medfly trapping programs is largely unknown. The present study measured distance-dependent capture probabilities for male C. capitata in TML-baited traps using mark–release–recapture procedures. Releases were performed at distances of 25, 50, 100, and 200 m at 4 sites in Hawaii, and the resulting capture rates were used to estimate the minimum detectable population size (detection probability > 99.9%) for a trapping density of 5 TML traps per 2.59 km² (= 1 mi², the density used in California, USA). Capture rates were similar for 3 of the sites (6.5%, 3.8%, 1.1%, and 0.1% for the 4 distances, respectively) and yielded an estimated minimum detectable population of ≈ 2300 males, a value similar to that obtained in a comparable study conducted in California. For unknown reasons, capture rates were significantly lower at the remaining site (1.8%, 0.6%, 0.1%, 0.04%) and the estimated minimum detectable population was correspondingly much larger (≈ 10,000 males). Implications of these results for medfly detection programs are discussed.     

三种常见实蝇的形态学、生物学和生态学比较

对瓜实蝇Bactrocera (Tetradacus) minax (Enderlein)、桔小实蝇Bactrocera (Bactrocera) dorsalis (Hendel)和桔大实蝇Bactrocera (Zeugodacus) cucurbitae (Coquillett)的形态学、生物学、生态学等方面进行了比较和分析,包括三种实蝇在国内外的分布情况,对寄主选择的差异,各种虫态的形态特征,发育历期和生活史,并对它们的危害状况和防治方法分别作了介绍,可为3种实蝇的鉴定和防治提供参考.     

A comparative assessment of the response of three fruit fly species (Diptera: Tephritidae) to a spinosad-based bait: effect of ammonium acetate, female age, and protein hunger

Ammonia-releasing substances are known to play an important role in fruit fly (Diptera: Tephritidae) attraction to food sources, and this information has been exploited for the development of effective synthetic food-based lures and insecticidal baits. In field studies conducted in Hawaii, we examined the behavioural response of wild female oriental fruit fly (Bactrocera dorsalis (Hendel)), melon fly (B. cucurbitae (Coquillett)), and Mediterranean fruit fly (Ceratitis capitata (Wiedemann)) to spinosad-based GF-120 NF Naturalyte Fruit Fly Bait(?) formulated to contain either 0, 1 or 2% ammonium acetate. Use of visually-attractive yellow bait stations for bait application in the field allowed for proper comparisons among bait formulations. Field cage tests were also conducted to investigate, using a comparative behavioural approach, the effects of female age and protein starvation on the subsequent response of F1 generation B. cucurbitae and B. dorsalis to the same three bait formulations that were evaluated in the field. Our field results indicate a significant positive effect of the presence, regardless of amount, of AA in GF-120 for B. dorsalis and B. cucurbitae. For C. capitata, there was a significant positive linear relationship between the relative amounts of AA in bait and female response. GF-120 with no AA was significantly more attractive to female C. capitata, but not to female B. dorsalis or B. cucurbitae, than the control treatment. Our field cage results indicate that the effects of varying amounts of AA present in GF-120 can be modulated by the physiological stage of the female flies and that the response of female B. cucurbitae to GF-120 was consistently greater than that of B. dorsalis over the various ages and levels of protein starvation regimes evaluated. Results are discussed in light of their applications for effective fruit fly suppression.     

Attraction of Bactrocera dorsalis (Diptera: Tephritidae) and nontarget insects to methyl eugenol bucket traps with different preservative fluids on Oahu Island, Hawaiian Islands

Attraction of oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), and nontarget insects to preservative fluids ethylene glycol antifreeze, propylene glycol antifreeze, or mineral oil in bucket traps that contained captured decaying male oriental fruit flies, a male lure (methyl eugenol), and a toxicant (DDVP vapor insecticidal strip) were compared with dry control traps. Significantly (P < 0.05) greater numbers of B. dorsalis were captured in propylene glycol antifreeze traps than in other attractant trap types. Among attractant trap types with lowest negative impacts on nontarget insects, control traps captured significantly lower numbers of three species and one morphospecies of scavenger flies, one species of plant-feeding fly, and one species each of sweet-and lipid-feeding ants. Mineral oil traps captured significantly lower numbers of two species of scavengers flies and one morphospecies of plant-feeding fly, and one species of sweet-feeding ant. Because of the fragile nature of endemic Hawaiian insect fauna, the propylene glycol antifreeze bucket trap is best suited for use in environments (e.g., non-native habitats) where endemic species are known to be absent and mineral oil traps are more suited for minimizing insect captures in environmentally sensitive habitats.     

Jackson trap efficiency capturing Bactrocera dorsalis and Zeugodacus cucurbitae with male lures with and without insecticides

Jackson traps baited with male lures with or without insecticides are essential components of surveillance and monitoring programmes against pest tephritid fruit flies. The ability of a trap to capture a fly that enters, sometimes termed ‘trap efficiency’, is dependent on many factors including the trap/lure/toxicant combination. We tested the effects of three important components of Jackson traps on efficiency of capture of two important fruit fly species, using the ‘standard’ (i.e. as they are used in the state-wide surveillance programme in California) and alternative setups: Insecticide (Naled, DDVP or None), type of adhesive on the sticky panel (Seabright Laboratories Stickem Special Regular or Stickem Special HiTack) and use of a single or combination male lure (Methyl eugenol and/or cuelure). Experiments were conducted in large outdoor carousel olfactometers with known numbers of Bactrocera dorsalis and Zeugodacus cucurbitae and by trapping wild populations of the same two species. Lures were aged out to eight weeks to develop a comprehensive dataset on trap efficiency of the various combinations. Results indicate that the current liquid lure/naled combinations on cotton wicks used in California for surveillance of these flies can be effectively replaced by plastic polymer plugs for the lure and pre-packaged DDVP strips with no loss of trap efficiency for eight weeks of use or longer. The ‘high tack’ adhesive showed no advantage over the current standard against these flies, and both have low efficiency when used without an insecticide in the trap. Combination lure + DDVP varied when compared to the current standard liquid lure + naled: Olfactometer assays showed similar efficiency between them for B. dorsalis, but higher efficiency for the wafer against Z. cucurbitae. Field result showed similar or slightly higher performance of the wafer compared with the standard for B. dorsalis, but a much lower catch of Z. cucurbitae.     

Comparative evaluation of spinosad and phloxine B as toxicants in protein baits for suppression of three fruit fly (Diptera: Tephritidae) species

Spinosad and phloxine B are two more environmentally friendly alternative toxicants to malathion for use in bait sprays for tephritid fruit fly suppression or eradication programs. Laboratory tests were conducted to assess the relative toxicity of these two toxicants for melon fly, Bactrocera cucurbitae Coquillett; oriental fruit fly, Bactrocera dorsalis Hendel; and Mediterranean fruit fly, Ceratitis capitata (Wiedemann) females. Field tests also were conducted with all three species to compare these toxicants outdoors under higher light and temperature conditions. In laboratory tests, spinosad was effective at much lower concentrations with LC50 values at 5 h of 9.16, 9.03, and 4.30 compared with 250.0, 562.1, and 658.9 for phloxine B (27, 62, and 153 times higher) for these three species, respectively. At 16 ppm spinosad, LT50 values were lower for all three species (significantly lower for C. capitata and B. dorsalis) than 630 ppm phloxine B LT50 values. At 6.3 ppm spinosad, the LT50 value for C. capitata (3.94) was still significantly less than the 630 ppm phloxine B LT50 value (6.33). For all species, the 100 ppm spinosad concentrations gave LT50 values of < 2 h. In comparison among species, C. capitata was significantly more sensitive to spinosad than were B. cucurbitae or B. dorsalis, whereas B. cucurbitae was significantly more sensitive to phloxine B than were C. capitata or B. dorsalis. LC50 values were reduced for both toxicants in outdoor tests, with greater reductions for phloxine B than for spinosad for B. dorsalis and B. cucurbitae. Fly behavior, though, is likely to keep flies from being exposed to maximum possible outdoor light intensities. Comparable levels of population suppression for any of the three species tested here will require a much higher concentration of phloxine B than spinosad in the bait.     

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.     

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.