Comparative field studies of various traps and attractants of the olive fruit fly,Bactrocera oleae

In the framework of an ongoing testing and refining process of a mass trapping method, using a combination of semiochemicals, for the control of the olive fruit fly,Bactrocera (Dacus) oleae, four trap designs, three trap colors, six different food attractants, and two pheromone formulations were compared under field conditions. No differences were observed between the trap designs and the food attractants tested. Trap color had a significant effect in preference tests only. Traps combining food attractants and pheromones attracted higher numbers of both male and female flies but the differences became statistically significant only in cases of low trap densities. Pheromones enclosed in cyclodextrenes were not as attractive as standard pheromone formulations. The findings of these tests allow a choice among trap types and semiochemicals for cost reduction and convenience, but not for enhancement of the efficacy of the method.     

Rapid cold hardening in the olive fruit fly Bactrocera oleae under laboratory and field conditions

A rapid cold hardening response was studied in females and males of the olive fruit fly Bactrocera (Dacus) oleae. When laboratory-reared females and males were transferred and maintained from the rearing temperature of 24 °C for 2 h to –6.5 °C approximately 5% survived. However, conditioning of both females and males for 2 h at various temperatures from 0 to 10 °C before their exposure for 2 h to –6.5 °C increased survival to 80 to 92%. A similar rapid cold hardening response in both females and males was also induced through gradual cooling of the flies at a rate of approximately 0.4 °C per min. The rapid increase in cold tolerance after prior conditioning of the flies to low temperatures, was rapidly lost when they returned to a higher temperature of 24 °C. In the field, in late February and early March, females and males were capable of a rapid cold hardening response. After exposure to the critical temperature they suffered a high mortality when tested in the afternoon and low mortality early in the morning on consecutive days, probably because of differences in the prevailing field temperatures a few hours before testing. This plasticity of cold tolerance gained through rapid cold hardening may allow the flies to survive during periods of the year with great fluctuation in circadian temperatures.     

Susceptibility of Hoplia philanthus (Coleoptera: Scarabaeidae) larvae and pupae to entomopathogenic nematodes (Rhabditida: Steinernematidae, Heterorhabditidae)

Biological control potential of nine entomopathogenic nematodes, Heterorhabditis bacteriophora CLO51 strain (HbCLO51), H. megidis VBM30 strain (HmVBM30), H. indica, Steinernema scarabaei, S. feltiae, S. arenarium, S. carpocapsae Belgian strain (ScBE), S. glaseri Belgian strain (SgBE) and S. glaseri NC strain (SgNC), was tested against second-, and third-instar larvae and pupae of Hoplia philanthus in laboratory and greenhouse experiments. The susceptibility of the developmental stages of H. philanthus differed greatly among tested nematode species/strains. In the laboratory experiments, SgBE, SgNC, HbCLO51 and HmVBM30 were highly virulent to third-instar larvae and pupae while SgBE was only virulent to second-instar larvae. Pupae were highly susceptible to HbCLO51, HmVBM30, SgBE and SgNC (57–100%) followed by H. indica and S. scarabaei (57–76%). In pot experiments, HbCLO51, SgBE and S. scarabaei were highly virulent to the third-instar larvae compared to the second-instar larvae. Our observations, combined with those of previous studies on other nematode and white grub species, show that nematode virulence against white grub developmental stages varies with white grub and nematode species.     

Oviposition response and development of the egg-pupal parasitoid Fopius arisanus on Bactrocera oleae, a tephritid fruit fly pest of olive in the Mediterranean basin

To date, information is wanting with regard to the use of new exotic parasitoids against olive fruit fly, Bactrocera (=Dacus) oleae (Gmelin) (Diptera: Tephritidae), a serious pest of olives Olea europaea L., in the Mediterranean basin. We investigated the oviposition response and developmental biology on B. oleae of Fopius (=Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae), an egg-pupal parasitoid of tephritid fruit flies, never tested before as a potential parasitoid of this host. Our results showed that olive fruits infested with B. oleae eggs exerted a relevant attraction to gravid F. arisanus and represented a stimulus for oviposition. Nevertheless they were not as attractive to female parasitoids as the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), eggs infested papaya fruits (Carica papaya L.). In our experimental conditions, F. arisanus completed development in B. oleae within 33 ± 1.7 days (males) and 35 ± 1.6 (females). Increases in host egg to female parasitoid ratios of 1:1, 5:1, 10:1 and 20:1 corresponded with decreases in the percentage of B. oleae parasitisation and host killing but corresponded also with increases in absolute parasitisation. Our findings are discussed in light of possibilities of utilising F. arisanus for biological control of olive fruit fly.     

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.     

橘小实蝇与番石榴实蝇卵及蛹的种间竞争

【背景】实蝇的竞争可能发生在生活史的各个阶段,但未见卵和蛹的种间竞争的相关报道。【方法】将橘小实蝇与番石榴实蝇的卵及蛹按照相应的比例或龄期分别进行混合培养,分析2种实蝇的卵或蛹混合后的发育历期和存活率是否受到彼此影响。【结果】橘小实蝇与番石榴实蝇的卵同龄等量混合,对彼此卵的历期和孵化率无影响。当橘小实蝇和番石榴实蝇的蛹为新鲜蛹时,分别与比它们蛹龄大1 d的对方蛹混合,蛹的羽化率分别为(87.67±3.61)%和(84.33±2.56)%,显著小于对照,说明在此混合蛹处理中,后化蛹者的发育可能受到先化蛹者的抑制。【结论与意义】总体上,在卵和蛹期,橘小实蝇与番石榴实蝇未产生竞争作用;但不排除蛹期竞争的可能性,这种竞争可能存在于特定的蛹期。     

温度对蝇蛹俑小蜂寄生瓜实蝇蛹功能反应的影响

【目的】蝇蛹俑小蜂是很多双翅目害虫的蛹寄生蜂。了解温度对寄生蜂寄生效能的影响是利用寄生蜂控制害虫的重要前提。【方法】实验室条件下设置温度为21、24、27、30、33℃,测定温度对蝇蛹俑小蜂雌蜂寄生瓜实蝇蛹功能反应的影响。蝇蛹俑小蜂对瓜实蝇蛹的功能反应用Michaelis-Menten-Ⅱ型功能反应模型N_a=AN/(F+N)进行拟合。【结果】不同温度下蝇蛹俑小蜂的寄生潜能(A)和寄主半饱和密度(F)不同。当温度在27℃时,其寄生潜能最大;而寄主半饱和密度随着温度升高而降低。【结论】瓜实蝇在瓜地盛发期的栖境温度适宜蝇蛹俑小蜂的寄生。     

Natural establishment of a parasitoid complex on Bactrocera latifrons (Diptera: Tephritidae) in Hawaii

Bactrocera latifrons (Hendel) (Diptera: Tephritidae) is the most recent of four tephritid fruit fly species accidentally introduced into Hawaii. Although parasitoids have been released against other tephritid fruit fly species and have shown partial success in Hawaii, no parasitoids were released until 2004 to suppress populations of B. latifrons. The present study was conducted to document the parasitoid complex that has naturally established against B. latifrons in Hawaii and to assess whether there is a need for improving the biological control of this species. Based on ripe turkeyberry (Solanum torvum Sw) fruit collections over three consecutive years B. latifrons was the dominant tephritid fruit fly infestating turkeyberry at all four sites surveyed, across three major islands in Hawaii. The overall percentage parasitism of B. latifrons ranged from a low of 0.8% (Hana, Maui) to a high of 8.8% (Kahaluu, Oahu). Five primary parasitoid species were recovered from individually held B. latifrons puparia: Fopius arisanus (Sonan), Psyttalia incisi (Silvestri), Diachasmimorpha longicaudata (Ashmead), D. tryoni (Cameron), and Tetrastichus giffardianus Silvestri. F. arisanus was the predominant parasitoid at three of the four sites. Low levels of parasitism suggest that there is a need to improve biological control of B. latifrons, to minimize chances of this species causing economic impacts on crop production in Hawaii. We discuss the possibility of improving biological control of B. latifrons through augmentative releases of F. arisanus or introduction and release of specific and efficient new parasitoid species.     

Susceptibility of the Mediterranean fruit fly (Ceratitis capitata) and the Natal fruit fly (Ceratitis rosa) to entomopathogenic nematodes

The potential of entomopathogenic nematodes, Heterorhabditis bacteriophora, Heterorhabditis zealandica and Steinernema khoisanae, to infect pupariating larvae, pupae and adults of Ceratitis capitata and Ceratitis rosa was investigated in laboratory bioassays. Pupariating larvae and adult flies were susceptible to nematode infection, with no infection recorded for the pupae. Pupariating larvae of C. capitata were generally more susceptible to infection than those of C. rosa. Significantly more larvae of C. capitata were infected by H. bacteriophora. For C. rosa, highest infectivity of larvae was obtained with H. zealandica. In contrast, adults of both species were highly infected by S. khoisanae.     

Evaluation of Beauveria bassiana and B. brongniartii strains and four wild-type fungal species against adults of Bactrocera oleae and Ceratitis capitata

The virulence of two isolates of the hyphomycete fungi, Beauveria bassianaand B. brongniartii, and additional fungal species isolated from diseased Bactrocera oleae pupae and Sesamia nonagrioideslarvae were assessed against adults of the olive fruit fly B. oleae and the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae). Contact and oral bioassays revealed that moderate to high mortality rates for the olive fruit fly occurred when the adults were exposed to conidia of Mucor hiemalis, Penicillium aurantiogriseum, P. chrysogenum and B. bassianaisolates. A strain of M. hiemalis isolated from S. nonagrioides larvae was the most toxic resulting in 85.2% mortality to the olive fruit fly adults. B. brongniartiiand B. bassiana were the most pathogenic to the C. capitataadults causing 97.4 and 85.6% mortality. Metabolites collected from the M. hiemalis and P. chrysogenum isolates were toxic to adults of both species.     

Susceptibility of Queensland fruit fly,Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), to entomopathogenic nematodes

Queensland fruit fly, Bactrocera tryoni (Froggatt), is the economically most significant Australian tephritid pest species with a large invasion potential, yet relatively little work on its biological control has been undertaken. Entomopathogenic nematodes (EPNs) are of potential interest for control of this fruit fly species as it pupates in the soil. Specifically, the pre-pupal stage of B. tryoni may present a unique window for EPN application, as fully developed larvae drop from infested fruit to the soil for pupation. For the first time, we tested the capacity of three EPN species with different foraging strategies, Steinernema feltiae, Steinernema carpocapsae and Heterorhabditis bacteriophora, to cause larval and pupal mortality in B. tryoni across a range of EPN concentrations (50, 100, 200, 500 and 1000 infective juveniles IJs cm^-2), substrate moisture (10, 15, 20 and 25% w/v) and temperatures (15, 20, 25 and 30 °C). We found that all EPN species tested caused environment and density dependent mortality in the third larval instar while pupae were not affected. Steinernema feltiae caused high mortality across different IJ concentrations and over a wider moisture and temperature range than the other two EPN species. High mortality caused by S. carpocapsae and H. bacteriophora was more limited to high IJ concentrations and a narrower moisture and temperature range. Our findings highlight the potential of EPNs for the control of B. tryoni and warrant further laboratory and field experiments to evaluate their efficacy under the wide environmental conditions that B. tryoni can occur in.     

A novel approach to biological control with entomopathogenic nematodes: Prophylactic control of the peachtree borer, Synanthedon exitiosa

Generally, microbial control agents such as entomopathogenic nematodes are applied in a curative manner for achieving pest suppression; prophylactic applications are rare. In this study, we determined the ability of two Steinernema carpocapsae strains (All and Hybrid) to prophylactically protect peach trees from damage caused by the peachtree borer, Synanthedon exitiosa, which is a major pest of stone fruit trees in North America. In prior studies, the entomopathogenic nematodes S. carpocapsae and Heterorhabditis bacteriophora caused field suppression when applied in a curative manner to established S. exitiosa populations. In our current study, nematodes were applied three times (at 150,000–300,000 infective juveniles/tree) during September and October of 2005, 2006, and 2007. A control (water only) and a single application of chlorpyrifos (at the labeled rate) were also made each year. The presence of S. exitiosa damage was assessed each year in the spring following the treatment applications. Following applications in 2006, we did not detect any differences among treatments or the control (possibly due to a low and variable S. exitiosa infestation of that orchard). Following applications in 2005 and 2007, however, the nematode and chemical treatments caused significant damage suppression. The percentage of trees with S. exitiosa damage in treated plots ranged from 0% damage in 2005 to 16% in plots treated with S. carpocapsae (Hybrid) in 2007. In control plots damage ranged from 25% (2005) to 41% (2007). Our results indicate that nematodes applied in a preventative manner during S. exitios’s oviposition period can reduce insect damage to levels similar to what is achieved with recommended chemical insecticide treatments.     

Stage-specific mortality of Rhagoletis indifferens (Diptera: Tephritidae) exposed to three species of Steinernema nematodes

Mortality of larval, pupal, and adult western cherry fruit fly, Rhagoletis indifferens (Tephritidae) exposed to the steinernematid nematodes Steinernema carpocapsae, Steinernema feltiae, and Steinernema intermedium, was determined in the laboratory and field. Larvae were the most susceptible stage, with mortality in the three nematode treatments ranging from 62 to 100%. S. carpocapsae and S. feltiae were equally effective against larvae at both 50 and 100 infective juveniles (IJs)/cm². S. intermedium was slightly less effective against larvae than the other two species. Mortalities of R. indifferens larvae at 0, 2, 4, and 6 days following their introduction into soil previously treated with S. carpocapsae and S. feltiae at 50 IJs/cm² were 78.6, 92.5, 95.0, and 77.5% and 87.5, 52.5, 92.5, and 70.0%, respectively, and at 100 IJs/cm² were 90.0, 92.0, 100.0, and 84.0% and 90.0, 50.0, 42.0, and 40.0%, respectively. There was no decline in mortality caused by S. carpocapsae as time progressed, whereas there was in one test with S. feltiae. Larval mortalities caused by the two species were the same in a 1:1:1 vermiculite:peat moss:sand soil mix and a more compact silt loam soil. In the field, S. carpocapsae and S. feltiae were equally effective against larvae. Pupae were not infected, but adult flies were infected by all three nematode species in the laboratory. S. carpocapsae was the most effective species at a concentration of 100 IJs/cm² and infected 11–53% of adults that emerged. The high pathogenicity of S. carpocapsae and S. feltiae against R. indifferens larvae and their persistence in soil as well as efficacy in different soil types indicate both nematodes hold promise as effective biological control agents of flies in isolated and abandoned lots or in yards of homeowners.     

Steinernema scarabaei, an entomopathogenic nematode for control of the European chafer

A new entomopathogenic nematode species, Steinernema scarabaei, was evaluated for efficacy against two white grub species, the European chafer, Rhizotrogus majalis, and the Japanese beetle, Popillia japonica, in laboratory, greenhouse, and field trials. In laboratory assays, S. scarabaei caused greater mortality than Heterorhabditis bacteriophora. S. scarabaei was highly virulent with an LC₅₀ of 5.5–6.0 and 5.7 infective juveniles (IJs) per third-instar larva in R. majalis and P. japonica, respectively. In a greenhouse trial, S. scarabaei provided greater mortality of R. majalis at all application rates (0.156–1.25 × 10⁹ IJs/ha) than Steinernema glaseri and H. bacteriophora (both at 1.25 × 10⁹ IJs/ha). Combination of imidacloprid and S. scarabaei resulted in an antagonistic interaction. In a fall field trial, S. scarabaei provided 88 and 75% control of R. majalis at 2.5 × 10⁹ and 10⁹ IJs/ha, respectively, and 54% control of P. japonica at 10⁹ IJs/ha; H. bacteriophora had no effect on mortality of either white grub species. In a spring field trial, unusually cool temperatures impeded nematode activity. Against R. majalis, S. scarabaei provided moderate control (56–59%), whereas Heterorhabditis marelatus provided no control. Mortality of P. japonica was moderate (49–66%) in both S. scarabaei and H. marelatus treatments. Overwinter persistence of S. scarabaei activity was demonstrated in a spring assay of soil from fall treated plots in which nematode infection was absent from control plots and present in treated plots.     

Virulence of the entomopathogenic nematodes Heterorhabditis bacteriophora, Heterorhabditis zealandica, and Steinernema scarabaei against five white grub species (Coleoptera: Scarabaeidae) of economic importance in turfgrass in North America

We compared the virulence of the entomopathogenic nematodes Steinernema scarabaei, Heterorhabditis zealandica, and Heterorhabditis bacteriophora (GPS11 and TF strains) against third instars of the Japanese beetle, Popillia japonica, the oriental beetle, Anomala (=Exomala) orientalis, the northern masked chafer, Cyclocephala borealis, the European chafer, Rhizotrogus majalis, and the Asiatic garden beetle, Maladera castanea, in laboratory and greenhouse experiments. The virulence of the nematode species relative to each other differed greatly among white grub species. H. bacteriophora and H. zealandica had similar modest virulence to P. japonica, A. orientalis, C. borealis, and M. castanea. But against R. majalis, H. zealandica showed low virulence with a clear concentration response whereas H. bacteriophora caused only erratic and very low mortality. In contrast, S. scarabaei had modest virulence against C. borealis, but was highly virulent against R. majalis, P. japonica, A. orientalis, and M. castanea with R. majalis being the most susceptible and M. castanea the least susceptible.     

Virulence of entomopathogenic nematodes to larvae of the guava weevil, Conotrachelus psidii (Coleoptera: Curculionidae), in laboratory and greenhouse experiments

The guava weevil, Conotrachelus psidii, is a major pest of guava in Brazil and causes severe reduction in fruit quality. This weevil is difficult to control with insecticides because adults emerge over a long period, and larvae develop to the fourth-instar inside the fruit and move to the soil for pupation. We assessed the virulence of entomopathogenic nematodes to fourth-instar larvae in soil by comparing their susceptibility to nine species or strains: Heterorhabditis bacteriophora HP88, H. baujardi LPP7, and LPP1, H. indica Hom1, Steinernema carpocapsae All and Mexican, S. feltiae SN, S. glaseri NC, and S. riobrave 355. In petri dish assays with sterile sand at a concentration of 100 infective juveniles (IJs) of a given nematode species/strain, larval mortality ranged from 33.5 to 84.5%, with the heterorhabditids being the most virulent. In sand column assays with H. baujardi LPP7, H. indica Hom1, or S. riobrave 355 at concentrations of 100, 200, and 500 IJs, mortality was greater than the control only for H. baujardi (62.7%) and H. indica (68.3%) at the highest concentration. For H. baujardi LPP7 in a petri dish assay, the time required to kill 50 and 90% of the larvae (LT₅₀ and LT₉₀) for 100 IJs was 6.3 and 9.9 days, whereas the lethal concentration required to kill 50 and 90% of the larvae (LC₅₀ and LC₉₀) over 7 days was 52 and 122.2 IJs. In a greenhouse study with guava trees in 20-L pots, 10 weevil larvae per pot, and concentrations of 500, 1000 or 2000 IJs, H. baujardi LPP7 caused 30 and 58% mortality at the two highest concentrations. These results show that H. baujardi is virulent to fourth-instar larvae and has potential as a biological control agent in IPM programs.     

桔小实蝇线粒体基因组全序列及其分析

桔小实蝇Bactrocera dorsalis线粒体基因组全序列对研究实蝇分子系统进化具有重要意义。本研究通过DNA测序和克隆技术,对桔小实蝇mtDNA全序列进行了测定和分析。结果表明：桔小实蝇线粒体基因组全长15 915 bp（GenBank序列号: DQ845759）。基因组碱基组成为39.3%A,16.2%C,10.2%G,34.3%T,由13个蛋白编码基因、22个tRNA基因、2个rRNA基因以及一个非编码的控制区域（A+T-rich区）组成。7个蛋白编码基因和13个tRNA基因从J链编码,其余6个蛋白编码基因和9个tRNA基因从N链编码。位于J链上的蛋白编码基因具有近似的A、T含量,而位于N链上的蛋白编码基因的A的含量明显高于T的含量。以mtDNA COⅠ基因为例,比较了桔小实蝇与其他14种实蝇的亲缘关系,结果显示其与同亚属（果实蝇亚属Bactrocera）内的其他近缘种相互间的同源性很高。     

Soil properties affect the availability, movement, and virulence of entomopathogenic fungi conidia against puparia of Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), is the major tephritid pest in the Mediterranean region. This insect may overwinter as pupae inside fruits or in soil. Therefore, infection with entomopathogenic fungi is a potentially useful control technique during the insect’s soil-dwelling stage. Entomopathogenic fungi have an important role in Integrated Pest Management programs as an alternative to conventional chemical control, but they have been usually selected on the basis of laboratory results with little regard to fungal ecology. In this work, we designed several experiments to study the availability and movement of the EF Beauveria bassiana (Balsamo) Vuill. and Metarhizium anisopliae (Metsch.) conidia in 16 soils differing widely in pH, texture, organic matter, and carbonate contents. Experiments of adsorption and drag of conidia by soil particles suspended in CaCl₂ solutions of different ionic strength showed B. bassiana conidia to be retained by clay particles, and this effect disappeared with increasing ionic strength. The availability of M. anisopliae conidia in the suspension tended to be lower for sandy than for clayey soils and was not influenced by ionic strength. Regardless of soil properties, over 90% of the added fungal propagules were recovered from the surface layer of columns of packed soils representing model combinations of texture (sandy or clayey) and pH values (acid or alkaline). However, retention of B. bassiana conidia in the surface layer was higher in clayey than in sandy soils, and the retention of M. anisopliae conidia in the surface layer was higher in sandy than in clayey soils. Finally, neither soil texture nor ionic strength affected the infectivity of conidia of both fungal strains to C. capitata puparia.     

Antagonism between entomopathogenic fungi and bacterial symbionts of entomopathogenic nematodes

Mutual effects between the symbiotic bacteria of entomopathogenic nematodes, Photorhabdus luminescens and Xenorhabdus poinarii, and entomopathogenic fungi were investigated in vitro. A dual culture assay on nutrient agar supplemented with bromothymol blue and triphenyltetrazolium chloride (NBTA) medium revealed that P. luminescens is antagonistic to Metarhizium anisopliae, Beauveria bassiana, B. brongniartii and Paecilomyces fumosoroseus by inhibiting their growth and conidial production; the fungal growth was not inhibited by X. poinarii. In a second laboratory experiment, crude extract produced by M. anisopliae was tested for its activity against P. luminescens and X. poinarii. Crude extract from M. anisopliae was antibacterial to P. luminescens and X. poinarii at 1000 g/ml and inhibited their growth on NBTA, but had no effect at 100 or 10 g/ml. The influence of the crude extract of M. anisopliae on the dispersal of infective juveniles (IJs) of Heterorhabditis megidis and Steinernema glaseri was assayed on Sabouraud Dextrose Agar (SDA) plates. Results showed that the crude extract of M. anisopliae had no toxic effects even at highest concentration (1000 g/ml).