Significance of a new field oviposition record for Graphium eurypylus (L.) (Lepidoptera: Papilionidae) on Michelia champaca (Magnoliaceae)

Abstract  Phytochemical similarities among ancient Angiosperms presumably played a role in the ecological and evolutionary diversification of the swallowtail butterflies (Papilionidae). Host family feeding specialisation is typical of most Papilionidae species, but field records of oviposition are rare for most swallowtail butterflies. It is even more uncommon to witness oviposition and larval feeding on new host plant species, especially in plant families not previously reported for the butterfly species. Oviposition by a female on a new host, or even on a toxic plant, may represent ancestral behaviour (with a loss of larval acceptance, detoxification or processing abilities) or novel behaviour (providing genetic variation for a potential expansion of host range, or host shift). We document the oviposition, larval use and pupation of the Annonaceae specialised and geographically widespread Graphium eurypylus on a Magnoliaceae species, all under field conditions in Queensland, Australia. This is the first time such field observations of oviposition and larval feeding on Michelia champaca (Magnoliaceae) have been documented anywhere for this species.     

Dominating species of entomophilous ascomycetes anamorphs in West Siberia,Primorsky krai,and Kyrgyzstan

The paper studies mycobiota of the dead insects in West Siberia, Primorsky krai, and Kyrgyzstan. Ascomycetes anamorphs of 13 genera are revealed. In all regions Beauveria bassiana (Bals.-Criv.) Vuill. dominated comprising on average 68% of the total number of isolates. The fungus hosts list the insects of 7 orders and 32 families with Coleoptera, Lepidoptera, and Hemiptera dominating. The rarely found entomopathogens include Tolypocladium inflatum Gams (primarily on Lepidoptera), Metarhizium anisopliae (Metschn.) Sorokin (on Coleoptera). The mortality rate of the insects due to micromycetes is observed mainly on enzootic level. The study of the pathogenic properties of the dominating species (B. bassiana) show the absence of specificity of its environmental isolates for a number of representatives of Orthoptera, Lepidoptera, Coleoptera, and Diptera.     

Potential for biotic interference of a classical biological control agent of the soybean aphid

The degree to which resident biota can inhibit the ability of an introduced biological control agent to establish and be effective is termed biotic interference. Studying biotic interference prior to a release using the actual agent is logistically difficult, however, due to quarantine restrictions. An alternative solution is to study biotic interference against a surrogate species in the intended range of introduction, with the expectation that biotic interference against the actual agent will be similar. This study assessed how biotic interference, mostly by generalist predators, may affect establishment of classical biological control agents of the soybean aphid, Aphis glycines Matsumura, in North America. The parasitoid Aphidius colemani Viereck was used as a surrogate for Asian aphidiine braconids such as Binodoxys communis (Gahan). We conducted a factorial field experiment that measured the effect of releasing A. colemani and of excluding resident natural enemies using field cages on soybean aphid populations. We also conducted molecular gut-contents analyses on predators collected in release plots to determine which species fed upon A. colemani. Releasing A. colemani in open field plots increased soybean aphid control beyond that observed in open field plots alone, despite indications that intraguild predation of A. colemani occurred. Thus, biotic interference was not sufficient to eliminate the contribution of A. colemani on soybean aphid suppression during the course of our experiment. Molecular gut-contents analysis revealed that at least two predators, Harmonia axyridis (Pallas) and Chrysoperla carnea Stephens, engaged in intraguild predation against A. colemani. The prolonged effect of intraguild predation on parasitoid establishment remains to be determined.     

Induction of systemic acquired resistance in Zea mays also enhances the plant’s attractiveness to parasitoids

Plants under attack by caterpillars emit volatile compounds that attract the herbivore’s natural enemies. In maize, the caterpillar-induced production of volatiles involves the phytohormone jasmonic acid (JA). In contrast, pathogen attack usually up-regulates the salicylic acid (SA)-pathway and results in systemic acquired resistance (SAR) against plant diseases. Activation of the SA-pathway has often been found to repress JA-dependent direct defenses, but little is known about the effects of SAR induction on indirect defenses such as volatile emission and parasitoid attraction. We examined if induction of SAR in maize, by chemical elicitation with the SA-mimic benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), attenuates the emission of volatiles induced by Spodoptera littoralis or exogenously applied JA. In addition, we determined how these treatments affected the attractiveness of the plants to the parasitoid Microplitis rufiventris in a six-arm-olfactometer. BTH treatment alone resulted in significant systemic resistance of maize seedlings against the pathogen Setosphaeria turcica, but had no detectable effect on volatile emissions. Induction of SAR significantly reduced the emission rates of two compounds (indole and (E)-β-caryophyllene) in JA-treated plants, whereas no such negative cross-talk was found in caterpillar-damaged plants. Surprisingly, however, BTH treatment prior to caterpillar-feeding made the plants far more attractive to the parasitoid than plants that were only damaged by the herbivore. Control experiments showed that this response was due to plant-mediated effects rather than attractiveness of BTH itself. We conclude that in the studied system, plant protection by SAR activation is compatible with and can even enhance indirect defense against herbivores.     

Experimental evaluation of the impacts of two ant species on banana weevil in Uganda

The banana weevil, Cosmopolites sordidus (Germar), is an important pest of bananas. Predatory ants are increasingly being viewed as possible biological control agents of this pest because they are capable of entering banana plants and soil in search of prey. We studied ant predation on banana weevil in Uganda in crop residues and live plants in both laboratory and field experiments. Field studies with live plants used chemical ant exclusion in some plots and ant enhancement via colony transfer in others to measure effects of Pheidole sp. 2 and Odontomachus troglodytes Santschi on plant damage and densities of immature banana weevils.In crop residues, an important pest breeding site, twice as many larvae were removed from ant-enhanced plots as in control plots. In young (2 month) potted suckers held in shade houses, ant ability to reduce densities of banana weevil life stages varied with the weevil inoculation rate. At the lowest density (2 female weevils per pot), densities of eggs, larvae, and pupae were reduced by ants. At higher rates there was no effect. In older suckers (5–11 months) grown in larger containers, banana weevil densities were not affected by ants, but damage levels were reduced. In a field trial lasting a full crop cycle (30 months), we found that the ants tested reduced the density of banana weevil eggs in suckers during the crop, but did not affect larval densities in the sampled suckers. However, most larvae occur in the main banana plants, rather than associated suckers. Nevertheless, levels of damage in mature plants at harvest did not differ between Amdro-treated and ant-enhanced plots, suggesting the ant species studied were not able to provide economic control of banana weevil under our test conditions.     

Intrinsic inter-specific competition in a guild of tephritid fruit fly parasitoids: Effect of co-evolutionary history on competitive superiority

Tephritid fruit fly parasitoid guilds are dominated by solitary koinobiont species that attack different host stages, but most emerge as adults from host puparia. Previous studies suggest intrinsic competitive superiority by the egg-attacking parasitoid Fopius arisanus (Sonan) against all larval-attacking parasitoids in Hawaii. In this study, we tested the early-acting competitive superiority prediction in relation to the co-evolutionary history of competition between an egg–larval parasitoid (Fopius ceratitivorus Wharton), and each of three larval parasitoids [Psyttalia concolor (Szépligeti), Diachasmimorpha kraussii (Fullaway), and Diachasmimorpha longicaudata (Ashmead)]. F. ceratitivorus and P. concolor share a common origin (eastern Africa), while D. kraussii is an Australian species, and D. longicaudata is from Southeast Asia. The outcomes of intrinsic competition between the egg-attacking parasitoid and each of the three larval-attacking parasitoids within their common host, the Mediterranean fruit fly Ceratitis capitata (Wiedemann) were compared. F. ceratitivorus invariably eliminated the co-evolved P. concolor through physiological suppression of the later-attacking parasitoid’s egg development, providing evidence that supports the early-acting-superiority hypothesis. However, F. ceratitivorus was unable to suppress development of the two non co-evolved larval parasitoids. Instead, the larvae of both later-acting parasitoid species physically killed F. ceratitivorus larvae inside the host. The results suggest that co-evolutionary history influences competitive superiority. The evolution of inter-specific competition and its implications for biological control are discussed.     

Standardization of a colorimetric method to quantify growth and metabolic activity of Wolbachia-infected mosquito cells

The Aedes albopictus Aa23 cell line, which is persistently infected with Wolbachia pipientis strain wAlbB, tends to grow as aggregated clusters of cells that are difficult to disperse for conventional quantification based on cell number. We used A. albopictus C7-10 cells to validate conversion of methylthiazole tetrazolium (MTT) to a colored formazan product with respect to incubation time, cell number over a 40-fold range, and metabolic activity as cells enter stationary phase. Using this assay, we showed that the doubling time of Aa23 cells increases from about 45 h early after plating to more than 70 h as the cells reach stationary levels. Growth of Aa23 cells proceeds at similar rates in the presence or absence of tetracycline concentrations that decrease the abundance of Wolbachia. Insofar as the MTT assay reflects mitochondrial function, our results indicate that, in Aa23 cells, abundance of intracellular Wolbachia has no measurable effect on mitochondrial activity in the presence of tetracycline.     

Molecular and Biochemical Characterization of an Endochitinase (ChiA-HD73) from Bacillus thuringiensis subsp. kurstaki HD-73

An endochitinase gene (chiA-HD73) from the insecticidal bacterium Bacillus thuringiensis subsp. kurstaki HD-73 was cloned, sequenced, and expressed in Escherichia coli DH5αF′. The chitinase activity of the encoded protein was studied in assays with different fluorogenic substrates. The chiA-HD73 gene contained an open-reading frame that encoded an endochitinase with a deduced molecular weight and an isoelectric point of, respectively, 74.5 kDa and 5.75. A putative signal peptide with cleavage sites for both Gram-positive and Gram-negative bacteria was identified. Comparison of ChiA-HD73 with other chitinases revealed a modular structure composed of a catalytic domain and a putative chitin-binding domain. ChiA-HD73 hydrolyzed both tetrameric and trimeric fluorogenic substrates, but not a chitobiose analog substrate, suggesting that the activity of ChiA-HD73 is mainly endochitinolytic. In addition, ChiA-HD73 showed high enzymatic activity within a broad pH range (pH 4–10), with a peak activity at pH 6.5. The optimal temperature for enzymatic activity was observed at 55°C. Its activity in a broad range of temperatures and pH suggests ChiA-HD73 could have biotechnological applications in insect control, particularly in synergizing the insecticidal crystal protein toxins of B. thuringiensis.     

Harmonia axyridis in Europe: spread and distribution of a non-native coccinellid

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is considered an invasive alien ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. In Europe, H. axyridis was sold by various biological control companies from 1995 in France, Belgium and the Netherlands, and was also intentionally released in at least nine other countries. It has spread very rapidly, particularly since 2002, and is now regarded as established in thirteen European countries. The established range extends from Denmark in the north to southern France in the south, and from Czech Republic in the east to Great Britain in the west. In this paper we map the spread and distribution of H. axyridis in Europe, and examine the situation on a country-by-country basis. We report first records of the species in five countries; Spain, Sweden, Denmark, Czech Republic and Italy; and first evidence of H. axyridis establishment in the latter three countries. Despite releases of H. axyridis in Portugal, Spain and Greece, there is little evidence of establishment in southern Europe. It is predicted that the spread and increase within Europe will continue and that H. axyridis will become one of the most widely distributed coccinellids in the continent.     

Thermal requirements of Fidiobia dominica (Hymenoptera: Platygastridae) and Haeckeliania sperata (Hymenoptera: Trichogrammatidae), two exotic egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Diaprepes abbreviatus is an exotic root weevil occurring in southern US. It is a highly polyphagous species which can complete its entire life cycle on citrus and several woody ornamental plants. The lack of native egg parasitoids for this weevil in citrus orchards has triggered efforts to evaluate candidate egg parasitoids from the Caribbean Region into Florida. The egg parasitoids Fidiobia dominica and Haeckeliania sperata are two exotic natural enemies of D. abbreviatus recently introduced in the US in a classical biological control program. The thermal requirements of both parasitoids were studied in the laboratory. The upper development threshold (UDT) of F. dominica was 30.0°C, its maximal development rate (MDR) occurred at 27.6°C, its lower development threshold (LDT) was 9.6°C and its thermal constant (K) for development from egg to adult was 293.1 DD. For H. sperata, UDT was 35.0°C, MDR occurred at 31.0°C, LDT was around 15°C and K was 188.1 DD. Based on these results, both species would be able to complete 17 to 18 generations annually in southern Florida. However, host availability during critical periods could severely impair the ability of these egg parasitoids to establish and successfully control D. abbreviatus in areas where winter temperatures fluctuate around 12°C, the LDT for this pest.