The soybean aphid, Aphis glycines Matsumura, is a recent invasive pest of soybean in North America. Currently, much research is focused on developing and characterizing soybean cultivars expressing host-plant resistance. During the initial phases of host-plant resistance screening, many of these studies use soybean aphid laboratory populations. Previous studies in other systems have documented substantial differences among laboratory and field populations. Whether or not this pattern exists in A. glycines is unknown, but it is extremely important when estimating the level of selection and virulence to host-plant resistant soybeans. In this study, we used seven microsatellite markers to estimate and compare genetic diversity and differentiation among five laboratory and 12 field populations. Our results indicate that soybean aphid laboratory populations are severely lacking in genotypic diversity and show extreme genetic differentiation among each other and to field populations. Continued use of laboratory populations for initial soybean aphid resistance screening could lead to erroneous estimations of the potential success for host-plant resistance.

The objective of this work was to study the effect of colony waste on the mortality of workers of Atta sexdens rubropilosa Forel colonies fed with different plant substrates. Eight nests were used; two colonies each were fed with Acalypha wilkesiana Müller.Arg, Ligustrum japonicum Thunb, Eucalyptus urophylla S.T. Blake or a mixture of the three substrates in equal proportions. Irrespective of diet, being kept with waste led to higher mortality. However, workers that were kept in contact with waste produced by colonies fed Acalypha had higher average survival rate and later death when compared with workers from the other treatments. Workers from the Eucalyptus-fed colonies had the lowest survival rate and 50% of them died within four days of exposure to Eucalyptus waste. Trichoderma viride Pers. ex Gray, a fungus garden antagonist, and the entomopathogen Aspergillus flavus Link. ex Gray were present in the colonies supplied with all plants. The largest fungus diversity was verified in the waste of colonies fed Acalypha and the mixture of Acalypha, Ligustrum and Eucalyptus. Therefore, antibiotic properties of Acalypha did not reduce contaminant diversity but apparently minimized effects of pathogenic microorganisms present in the waste such as Asp. flavus. This may explain the highest survival rate of workers in this treatment.

Field trials were conducted at four Canterbury, New Zealand locations in 2005–06 to determine if the synergistic effects of biological control by natural enemies and standard drenching techniques controlled lettuce aphid populations throughout the entire growing season. Chemical usage significantly lowered aphid densities in the outer, wrapper and heart leaves compared to control plants at most times. However, in mid-summer, natural enemies, such as the brown lacewing (Micromus tasmaniae), 11-spotted ladybird beetle (Coccinella undecimpunctata) and small hoverfly larvae (Melanostoma fasciatum), were more than sufficient to control lettuce aphids without the use of insecticides. Drenching, in addition to natural enemy attack, appears to be required in early spring and late summer to maintain very low levels of lettuce aphid. Given the potential for imidacloprid resistance to develop, it may be advisable to restrict drenches to these key periods in order to allow populations of natural enemies to maintain control of prey populations. We recommend industry support the validation of action thresholds across different regions within New Zealand and focus on the seasonal biology of predators to assist growers with the sustainable long-term control of lettuce aphids. The inclusion of additional data into an economic model to compare pest damage with predator loading would be useful for growers in managing aphid problems. These results will assist in the continued improvement and development of a sustainable IPM strategy for lettuce aphids in New Zealand and elsewhere.

The diel oviposition periodicity of two groups of Aedes aegypti females (Trinidad strain), (i) thoses allowed access to oviposition sites and (ii) females forced to retain-eggs for four days, were studied under laboratory conditions using one female per cage and monitoring by changing substrates every two hours. The individual females which were allowed access to oviposition sites showed peak oviposition between 16.00–18.00 h (50% of eggs), whereas individuals forced to retain eggs for four days showed a similar pattern but with a significantly (P<0.001) larger peak oviposition between 16.00–18.00 h (94% of eggs). However, females forced to retain eggs laid most or all of their eggs in one container (84%), while females given access to oviposition sites distributed their eggs among 2–4 containers. The results of this study are discussed in the context of the strength of the circadian rhythms, oviposition strategies and its impact on vector control activities.

Dactylopius tomentosus is composed of biotypes adapted to different Cylindropuntia species. One biotype is an important biological control agent of C. imbricata in South Africa while another has the potential for the control of C. fulgida var. fulgida. These two weed species occur in sympatry in some areas of South Africa, so the introduction of the second biotype could result in hybridization, which, in turn, could impact on the biological control programs through altered host specificity and fitness of the hybrids. To anticipate what might happen, reciprocal crosses were made between the two biotypes, and the biological performance of the resultant hybrids was compared with that of each parental lineage on C. imbricata and C. f. var. fulgida. The biotypes interbred freely and reciprocally in the laboratory. Comparisons of crawler and adult female traits showed differences in performance that were dependent on the origin of the maternal and paternal genomes. However, when all traits were combined into a ‘fitness index’, both hybrids clearly outperformed the parental lineages. The increase in fitness shown by the hybrids over their maternal lineage was greater on the alternative host of the maternal parent than on the natural host of the maternal parent. Therefore, in areas where the two cacti occur in sympatry, hybridization between the biotypes is not expected to be detrimental to the biological control of either weed.

The biology of the immature stages and adult eclosion of Ufens principalis Owen, an important parasitoid of Homalodisca eggs in southern California, were studied. The duration of the egg, larval and pupal stages at 26.7°C were 0–1, 7 and 9 days, respectively. Sacciform larvae, which developed gregariously within host eggs, were motile until about five days of age, and then became sessile. Parasitized host eggs changed from whitish and soft when freshly-laid to yellow-orange and hard at five days and older. This change was accompanied by formation of septal walls separating the mature larvae and pupae. The rate of immature development had a strong positive linear relationship (R2=0.853, n=98) with temperatures in the range of 20.0–30.3°C. The theoretical minimum threshold for immature development was 13.5°C, and the required heat units were 241.0 degree-days. Adult eclosion from host eggs occurred mostly (85%) on the first two days of emergence. Although most females emerged during the morning hours (0600–1200 h), males tended to emerge earlier than females with equal emergence during the morning and late night hours (2400–0600 h). The rate of successful adult emergence was high (88%). The ratio of eclosed adults to the number of exit holes was 1.18, indicating that most adults tended to independently cut their exit holes. The number of exit holes had a strong negative relationship (R2=0.711, n=125) with exit hole size, suggesting that larger numbers of developing immatures per host egg result in an overall decrease in adult size.

The egg, larval, pupal and adult abundance of the clover root weevil Sitona lepidus Gyllenhal (Coleoptera: Curculionidae) was monitored at three sites for the first ten years following the discovery of this exotic pest in the Waikato region of New Zealand. The species went through an initial boom and bust cycle at two sites, with populations reaching up to 1800 larvae m−2. Thereafter, winter larval populations were relatively stable, ranging between 450–750 m−2. Unlike in the Northern Hemisphere, S. lepidus was found to have two generations a year in the Waikato region of New Zealand. Pasture white clover content at the time of peak adult numbers was positively related to the subsequent peak larval populations for each generation. The factors contributing to the emergence of S. lepidus as one of the most important pasture pests in New Zealand are discussed.

Aggregative responses are commonly observed in insects, including chrysomelids, affecting both individual and population growth rates. In two closely related chrysomelid beetles (Galerucella calmariensis and G. pusilla) feeding on purple loosestrife (Lythrum salicaria), recent studies suggest that male-produced pheromones may cause both inter- and intraspecific attraction. This paper further examines the causes and consequences of feeding aggregations in these species. Olfactometer studies confirm previous findings, showing cross-species attraction to damaged plants, but suggest that also damaged induced plant volatiles may be involved. In addition, the studies suggest that the cross-species attraction observed in previous studies have asymmetric effects on the two beetles. Galerucella pusilla was more attracted to damage by G. calmariensis than to damage by conspecifics. Laboratory and field data suggest that feeding aggregations in these species increase pupal mass, at least at low to intermediate larval densities. This positive feedback may have important consequences for the spatiotemporal dynamics and as a consequence on the role of the two chrysomelid beetles on biological control of purple loosestrife.

In theory, inferior apparent competitors sharing a natural enemy with superior apparent competitors should be excluded in the absence of stabilising factors. Nevertheless, plentiful examples of coexisting apparent competitors exist. In this paper, we show that parasitoid resource competition within hosts affects both parasitoid sex ratio and female body size, with implication for population growth and apparent competition between the two closely related hosts experiencing a strong asymmetry in their interaction. While the superior competitor delivers parasitoids with higher fitness to the shared parasitoid pool, the inferior competitor delivers a higher proportion of female parasitoids. Hence, the inferior host experience an inflow of fit parasitoids from the superior competitor, which should increase the risk of exclusion, but also an outflow of parasitoid females, which should reduce the risk of exclusion and increase stability. We conclude that differential outcomes of parasitoid resource competition in different host species may have profound effects on shared parasitoid populations and should be included in future studies of apparent competition between hosts.

Ruminant dung is a highly ephemeral, patchily distributed resource, which is used by a diverse community of invertebrate species. In such environments, high levels of insect aggregation may be important in facilitating stability and coexistence across patchily distributed populations. The aim of the present work was to quantify the aggregation of the insects colonising cow-dung in cattle pasture in southwest England and to test the hypothesis that the dung-pat community assemblage observed was the result of stochastic colonization. This was examined using batches of ten standardised, 1.5 kg, artificial cow pats placed out in cattle pastures in each of 24 weeks between May and October in 2001. Pats were left exposed in the field for seven days before being brought back to the laboratory, where any insect colonizers were collected and identified. Individual pats contained, on average, only half the number of insect taxa present in an entire batch put out at any one time. All larval coleopteran taxa, 20 of the 22 adult coleopteran taxa and 22 of the 23 dipteran taxa, showed significant aggregation, with the abundance of most taxa within pats approximating a negative binomial distribution. A simulation analysis was used to show that the observed relative frequency of taxa within pats did not differ from that expected by chance if colonisation is a random binomial event in which each species colonises a pat independently of all other species. Aggregated populations, of even highly abundant insects, may be more susceptible to the deleterious effects of insecticidal contaminants in dung than if they were evenly distributed, if by chance they colonize a pat containing insecticidal residues from a recently treated animal.

Discrimination of conspecific and heterospecific signals is a key element in the evolution of specific mate recognition systems. Lepidopteran pheromone signals are typically composed of several compounds that synergize attraction of conspecific and inhibit attraction of heterospecific males. Blends convey specificity, but not their single components, that are typically shared by several species. Many sex pheromones are blends of geometric or positional isomers of straight-chain acetates, while species-specific blends of analogous alcohols have not been described. We have, therefore, studied the attraction of tortricid moths to the geometric isomers (E,E)-, (E,Z)-, (Z,E)- and (Z,Z)-8,10-dodecadien-1-ol. Only one species responding to these alcohols seemed to be attracted to a blend of two isomers, while most species are attracted to only one alcohol isomer. Lack of a pronounced synergist or antagonist effect of the other geometric isomers explains the lack of specific attraction to isomer blends and reduces accordingly the number of specific communication signals composed of these alcohols. In comparison, many more species respond to the analogous (E,E)-, (E,Z)-, (Z,E)- and (Z,Z)-8,10-dodecadienyl acetates and their binary blends. The acetate isomers all play a behavioural role, either as attractants, attraction synergists or antagonists, and thus promote specific communication with acetate blends. Male moths seem to discriminate the acetate isomers with greater precision than the analogous alcohols. It is proposed that discrimination is facilitated by steric differences between the four acetate isomers, as compared to the more uniform steric properties of the alcohols.

Nesidiocoris tenuis (Reuter) (Hem. Miridae) is a native zoophytophagous predator of the Mediterranean region, and its populations colonize tomato crops when they are not heavily treated with insecticides. This generalist predator has a high capacity for controlling insect pests, and it is currently commercially produced and released in some areas to control Bemisia tabaci (Gennadius) (Hem. Aleyrodidae). However, its status as a pest and/or as beneficial is controversial. Therefore, the aim of this study was to evaluate the risk of damage to tomatoes in extreme conditions of prey scarcity, as well as high predator populations. Three predator densities were tested in a greenhouse cage experiment during a summer tomato crop. The crop did not display any negative effect caused by the predators during the first six weeks of interaction, independently of the density released. However, subsequently, the effect was dramatic, both on the vegetative growth of the plant and on the production of fruits. The reduction in vegetative growth was located at truss eight and it was expressed mainly by a lower number of leaves and a shorter length of the shoot above the truss. There was a significant reduction of yield with a lower number of fruits collected and a smaller mean weight, although this was not observable until truss seven. It seems that feeding on the plant by this mirid bug competed with the vegetative growth and fruiting processes of the plant in the extreme conditions of prey shortage maintained in our experiment.

A molecular tool, focused on the mitochondrial Control Region (CR), was developed to discriminate the two hawthorn-feeding psyllid species, Cacopsylla melanoneura (Förster) and C. affinis (Löw), and to estimate their frequencies in mixed populations. The test was carried out in paired and single-tube amplifications and validated analysing 52 male specimens previously determined by morphological analysis. The frequencies of the two species in mixed populations in the Aosta Valley (northwestern Italy) were analysed. The presence and type of 16SrX-group phytoplasmas was detected by nested PCR and RFLP tests in both species. C. melanoneura was the predominant species (86.5%; 80.4–91.2 CI); of these, 0.9% of the samples were positive for ‘Ca. Phytoplasma mali’ and 1.8% for ‘Ca. Phytoplasma pyri’. One of 21 specimens of C. affinis was positive for ‘Ca. Phytoplasma pyri’. The test also allowed us to identify two genetic variants of C. melanoneura, depending on the presence or absence of a 56 bp indel; these were named WI (with indel) and WOI (without indel), respectively. Further analyses were carried out on C. melanoneura specimens collected in apple orchards at six different locations in northern Italy where different levels of transmission efficiency have been described. Our preliminary observations suggest that some differences might exist between the two genetic variants in their ability to transmit phytoplasmas and to colonise different host plants.

Wolbachia bacteria are among the most common endosymbionts in insects. In Wolbachia research, the Wolbachia surface protein (wsp) gene has been used as a phylogenetic tool, but relationships inferred by single-locus analysis can be unreliable because of the extensive genome recombination among Wolbachia strains. Therefore, a multilocus sequence typing (MLST) method for Wolbachia, which relies upon a set of five conserved genes, is recommended. In this study, we examined whether the alnus ambrosia beetle, Xylosandrus germanus (Blandford), is infected with Wolbachia using wsp and MLST genes. Wolbachia was detected from all tested specimens of X. germanus (n=120) by wsp amplification. Five distinct sequences (i.e. five alleles) for wsp were found, and labeled as wXge1–5. MLST analysis and molecular phylogeny of concatenated sequences of MLST genes identified wXge3 and wXge5 as closely-related strains. The detection rate of wXge4 and wXge1 was 100% and 63.3%, respectively; wXge2, wXge3 and wXge5 were detected from less than 15% of specimens. We performed mitochondrial haplotype analyses that identified three genetic types of X. germanus, i.e. Clades A, B and C. Wsp alleles wXge1, wXge2 and wXge4 were detected in all clade A beetles; wXge2 allele was absent from Clades B and C. We concluded that (i) five wsp alleles were found from X. germanus, (ii) use of MLST genes, rather than the wsp gene, are more suited to construct Wolbachia phylogenies and (iii) wsp alleles wXge2 and wXge3/wXge5 would infect clade A and clade B/C of X. germanus, respectively.

Massive mosquito nuisance problems, caused by the flood-water mosquito Aedes sticticus, occur after floods in the flood plains of the River Dalälven, central Sweden. Since 2002, the biological mosquito larvicide Bacillus thuringiensis var. israelensis (Bti) has been used to control these mosquitoes. Here, we report results from the first six years of monitoring Chironomidae, the most susceptible non-target organisms, in three wetlands with Bti-treatment against mosquitoes and in three wetlands without treatment. Emergence traps were used for continuous insect sampling from May to September each year, 2002–2007, and were emptied once a week. A total of 21,394 chironomids of 135 species were collected, and the subfamily Orthocladiinae dominated the fauna followed by Chironominae and Tanypodinae. The annual chironomid production in the wetlands was low, with an average of 1917 individuals per m2, and 42 g ash-free dry weight per m2. We found no reduced production of chironomids at neither family, nor subfamily level, in Bti-treated as compared to untreated wetlands. This is the first long-term follow-up study of the possible effects of Bti-based mosquito larval control on chironomid species production. In the short-term view, one species had higher production in treated areas. In the long-term view, four species had higher and one species had lower production in treated areas. We conclude that the Bti-based control of flood-water mosquitoes does not cause any major direct negative effects on chironomid production, and therefore does not seem to induce any risk for indirect negative effects on birds, bats or any other predators feeding on chironomids.

In Europe, aphids contribute significantly to the so-called ‘aerial plankton’ during the spring to autumn months (growing season), although individual flight behaviour has been found, especially from molecular ecological studies, to be species-specific in terms of migratory range (ambit). Many of these species individuals may be assumed to be clonal in origin, that is, derived from a single asexual foundress. We are presently studying two specialist aphid species on Tansy, Tanacetum vulgare L. from samples collected in Jena, Germany – Macrosiphoniella tanacetaria (Kaltenbach) and Metopeurum fuscoviride Stroyan, using microsatellite markers. On plotting the number of sets of different multilocus genotypes or MLGs (i.e. multiple clonal repeats: 1, 2, 3 copies, etc.), against the frequency of their occurrence, a negative exponential relationship was found, with populations of both species consisting mostly of single (i.e. unique) or low number repeats rather than larger multiple copy (clonal) MLG repeats. To test this further, microsatellite data collected from a previous study on M. tanacetaria in Jena in the year 2000 and on samples of the Grain aphid, Sitobion avenae (F.), collected in the UK in 1997/8, the latter both in the field and from 12.2 m high suction traps, were examined in the same way. Again, similar relations were found, with most MLGs occurring as unique or low copy number repeats. The data are briefly discussed in the light of our evidence, as well as that of other similar studies on other aphid species, relating aphid molecular genetic data to aphid life cycle, behaviour and ecology.

The effect of ground cover upon the communities of beneficial arthropods established in the canopy of lemon trees was investigated, by comparing three ground-cover management treatments applied: RV, resident vegetation; S, sowed selected species; and BS, bare soil by controlling weeds with herbicide. Over two consecutive years, arthropod communities in the tree canopy were sampled periodically by beating and suction techniques. Significantly higher numbers of beneficial arthropods were found in the RV and S treatments in comparison with bare soil. Spiders and parasitoid wasps were the two most common groups, representing, respectively, 70% and 19% of all catches in beating samples and 33% and 53% in suction samples. For the RV and S treatments, significant seasonal deviations from the bare soil treatment were observed using principal response curves. Similar seasonal patterns were observed over the two years. The RV and S treatments showed significant positive deviations from the BS treatment in late spring and summer, accounted for the higher numbers of parasitoid wasps, coccinelids and lacewings present. By contrast, the seasonal deviations observed for the spider community differed from those of the remaining arthropods. During late winter and early spring, the RV and S treatments presented a higher abundance of spiders in the tree canopy, in comparison with bare soil, whereas in the summer significantly more spiders were found in the bare soil treatment. Spider movements between tree canopy and ground vegetation layers may justify this result.

Host specialization to form biotypes is common among phytophagous insects, and it has been hypothesised that biotypes of Dactylopius tomentosus L. (Hemiptera: Dactylopiidae) occur. D. tomentosus is an important biological control agent for Cylindropuntia cacti when they occur as weeds. Additionally, there is uncertainty surrounding the taxonomic status of some species of Cylindropuntia. This study aimed to confirm the existence of D. tomentosus biotypes and to assess whether host specialization can help to resolve this systematic uncertainty. For this study, the host specificity and performance of ten provenances of D. tomentosus collected from C. cholla, C. fulgida var. fulgida, C. imbricata, C. f. var. mamillata, C. rosea and C. tunicata and reared on C. cholla, C. fulgida var. fulgida, C. imbricata and C. rosea were investigated. Five life-history parameters were measured including: crawler development time and survival, female development time, and the weight and number of eggs produced by females. Results revealed significant variation in host specificity with provenances either thriving, surviving or dying on the different hosts, thus demonstrating the existence of biotypes. Also, host specificity was related to host species and not to the geographic locality from which either the host or provenance was sourced. These findings suggest that the characteristics of Cylindropuntia species may differ sufficiently, there by presenting different selection pressures that induce and sustain distinct biotypes of D. tomentosus. The observed host use patterns of the biotypes separated the plant species into two groups that accorded with known phylogenetic relationships among Cylindropuntia species, suggesting that biotypes can be used to elucidate their taxonomic relatedness. Besides advancing our knowledge of the ecology and evolution of D. tomentosus, these novel findings have important implications for the biological control of Cylindropuntia species.