Accidental and intentional global movement of species has increased the frequency of novel plant–insect interactions. In Patagonia, the European woodwasp, Sirex noctilio, has invaded commercial plantations of North American pines. We compared the patterns of resin defenses and S. noctilio-caused mortality at two mixed-species forests near San Carlos de Bariloche, Argentina. We observed lower levels of resin flow and higher levels of mortality in Pinus contorta compared with Pinus ponderosa. In general, S. noctilio attacked trees with lower resin compared with neighboring trees. Resin production in P. ponderosa was not related to growth rates, but for P. contorta, slower growing trees produced less resin than faster growing conspecifics. For all infested trees, attack density and number of drills (ovipositor probes) per attack did not vary with resin production. Most attacks resulted in one or two drills. Attack rates and drills/attack were basically uniform across the bole of the tree except for a decrease in both drills/attack and attack density in the upper portion of the crown, and an increase in the attack density for the bottom 10% of the tree. Planted pines in Patagonia grow faster than their counterparts in North America, and produce less resin, consistent with the growth-differentiation balance hypothesis. Limited resin defenses may help to explain the high susceptibility of P. contorta to woodwasps in Patagonia.

Creontiades dilutus (green mirid) and C. pacificus (brown mirid) are major hemipteran pests of transgenic (Bt) cotton in Australia. Current integrated pest management (IPM) guidelines for mirids in Australian cotton, based on economic thresholds and sampling recommendations, were developed and disseminated to industry at the start of the 2005–06 growing season and have remained largely unchanged since then. However, adoption of mirid IPM guidelines by industry has been highly variable and generally well below expectation. Annual surveys of crop protection practices across the Australian cotton industry, from 2010 to 2017, indicate that a third of all mirid sprays are applied below the recommended thresholds each year. More than half of all survey respondents in the 2017 survey indicated lack of confidence in the mirid thresholds due to highly variable and disproportionate damage, a phenomenon best described as the ‘mirid enigma’. A critical review of RD&E outputs since 1998 shows that potential contributors to the mirid enigma include but are not limited to biological, ecological and methodological factors. Mirid feeding damage is likely to vary with developmental stage, gender and reproductive status. Ecological factors including trophic effects and multiple host plant usage are potential modifiers of mirid feeding damage. Methodological and technological constraints and shortcomings are evident in the threshold research done to date. Inadequate commercial sampling that results in unreliable estimates of pest density in the crop is a major contributor to the mirid enigma. Failure to account for the complexity of factors that can influence the nature and severity of mirid damage to cotton often results in fruit loss due to non-mirid related factors being incorrectly attributed to mirids. An alternative approach to mirid management based on modelling the dynamics of net fruit load (production–loss) proposed over 15 years ago is discussed.

The use of Bt cotton varieties has greatly reduced the amount of conventional insecticides required to control lepidopteran pests, Helicoverpa armigera and Helicoverpa punctigera, in Australia, but the possibility that these moths might become resistant to Bt remains a threat. Consequently, a Resistance Management Plan, which includes the mandatory growing of refuge crops (pigeon pea and non-Bt cotton; both C3 plants), has been established for Bt cotton farmers. However, knowledge of the relative contributions made to overall moth populations from the many host origins (both C3 and C4 plants) available to these insects throughout cotton production regions remains limited, as do the scales of movement and spatial mixing of moths within and between these areas. This study used stable isotope signatures (in particular δ13C) to help identify where moths fed as larvae within separate cotton production regions which differed in their proportions of C3 and C4 host crops (e.g. cotton and sorghum, respectively). C3-derived moths predominated in the early season, but C4-derived moths increased in frequency later. The overall proportion of C4 moths was higher in H. armigera than in H. punctigera. Whilst the relative proportions of C3 and C4 moths differed between regions, no differences in such proportiorns were found at smaller spatial scales, nor were there significant correlations between crop composition and isotope signatures in moths. Overall, these results suggest that C4 host plants are likely to be very important in offsetting the development of Bt resistance in these insects and such influences may operate across multiple regions within a single growing season.

The genus Rhagoletis (Diptera: Tephritidae) comprises more than 65 species distributed throughout Europe, Asia and America, including many species of high economic importance. Currently, there are three Rhagoletis species that infest fruits and nuts in Europe. The European cherry fruit fly, Rhagoletis cerasi (may have invaded Europe a long time ago from the Caucasian area of West Asia), and two invasive species (recently introduced from North America): the eastern American cherry fruit fly, R. cingulata, and the walnut husk fly, R. completa. The presence of different Rhagoletis species may enhance population dynamics and establish an unpredictable economic risk for several fruit and nut crops in Europe. Despite their excessive economic importance, little is known on population dynamics, genetics and symbiotic associations for making sound pest control decisions in terms of species-specific, environmental friendly pest control methods. To this end, the current paper (a) summarizes recently accumulated genetic and population data for the European Rhagoletis species and their association with the endosymbiont Wolbachia pipientis, and (b) explores the possibility of using the current knowledge for implementing the innovative biological control methods of sterile insect technique and incompatible insect technique.

The sterile insect technique (SIT) is a key element for the integrated management of pest populations of the Mexican fruit fly, Anastrepha ludens, in Mexico. Its success depends on the survival of mass-reared sterile males and their ability to mate with wild females. However, colonization and mass-rearing conditions can adversely affect their ability to avoid predators. To test if colony management strategies could contribute to improve field survival abilities of mass-reared flies, we compared the survival of males exposed to the orb-weaver spider Argiope argentata. Males compared originated from three strains with different colonization strategies: (a) a colony started from field-collected wild flies (replacement), (b) a colony started by hybridizing wild males with mass-reared adapted females (hybrid) and (c) a colony started with mass-reared males selected on the basis of their survival ability and mating competitiveness in field cages (selected). Mass-reared males and wild males were used as controls. Males were exposed to spiders under laboratory cage conditions. Overall, wild males showed better survival ability than mass-reared males. Regarding the colonization approach, wild males survived better than a hybrid, replaced and selected males. We conclude that mass-rearing conditions have a strong negative effect on the ability of males to escape spiders. The colonization systems evaluated did not counter this effect. The lower survival of males from the selected colony suggests that the selection over one generation did not contribute to improve males’ predator avoidance and escape abilities and probably needs to be modified. Possible explanations for this and implications on colonization and colony management for SIT purpose are discussed.

Strawberry is affected by several pests and diseases. Neopamera bilobata is an emerging pest that has been reported by several strawberry growers, usually associated with catfacing symptoms in fruits. We evaluated intercropping garlic or Chinese chives on N. bilobata populations on strawberry crops grown in high tunnels in two experiments. In the first experiment, we evaluated N. bilobata populations on strawberry intercropping with garlic plants (three densities: 8, 16, 24 GP – garlic plant per plot) on the bags by taking 12 samples from December 2015 to April 2017. N. bilobata populations on strawberry were also assessed when Chinese chives were grown under the suspended wooden structures in which strawberry plants are grown (‘undercropping’) (14 samples), in two high tunnels, from November 2016 to March 2017. The number of nymphs and adults on 14 randomly selected fruits per plot were assessed. During the garlic intercropping experiment, the treatments of three densities of garlic reduced N. bilobata populations; however, the 24 GP treatment caused a greater reduction than the 8 GP treatment. Garlic densities reduced N. bilobata populations by 35, 50, and 64% for the 8, 16, and 24 GP treatments, respectively. Chinese chives cultivated under the structures reduced N. bilobata populations by 47%. The results suggest that intercropping garlic or undercropping Chinese chives are suitable tools to be tested in integrated pest management in strawberry crops.

The use of multiple species in biological control programmes is controversial when interactions among them are not fully understood. We determined the response of the pupal parasitoid Coptera haywardi (Oglobin) to different availability of Anastrepha ludens (Loew) pupae previously parasitized or not by larval–pupal Diachasmimorpha longicaudata (Ashmead). The two types of pupae were exposed at different ages and proportions to different numbers of C. haywardi females for 48 h. The performance of C. haywardi adults emerging from parasitized and unparasitized pupae was measured. Coptera haywardi prefers to attack unparasitized A. ludens pupae rather than pupae parasitized by D. longicaudata. However, when the availability of unparasitized pupae was low or the number of foraging females was high, C. haywardi competed against early immature stages of the D. longicaudata, or hyperparasitized, feeding directly on the advanced-immature developmental stages of the early acting species. Adults of C. haywardi emerging as hyperparasitoids were no different in size, fecundity and longevity from those emerging as primary parasitoids. Our data suggest that simultaneous use of these species in augmentative biological control projects may be feasible but should be carefully planned in order to avoid any detrimental effect of its interaction.

Hypotheses about the worldwide colonization routes of the melon fly, Zeugodacus cucurbitae (Diptera: Tephritidae), are mainly based on sparse historical records. Here we aim at reconstructing the colonization history of the African continent based on an improved description of the population structure of Z. cucurbitae and approximate Bayesian analyses. Individuals of Z. cucurbitae were sampled in 17 localities from East, West and Central Africa and genotyped at 19 microsatellite markers. Bayesian analyses showed intracontinental population structuring with populations from Uganda diverging from those of Tanzania and populations from Burundi and Kenya showing traces of admixture with West African samples. Approximate Bayesian Computation provided support to the hypothesis of a single introduction Z. cucurbitae into East Africa and subsequent expansion to West Africa, each colonization event was followed by a bottleneck that promoted population divergence within Africa. Parameter estimates suggested that these events are roughly compatible with the historical records of Z. cucurbitae presence in sub-Saharan Africa (viz. 1936 in East Africa and 1999 in West Africa) and allow excluding alternative hypotheses on older or multiple introductions of Z. cucurbitae.

The Enemy Release Hypothesis (ERH) predicts that introduced plant species can escape herbivory and therefore have a competitive advantage over native plants, which are exposed to both generalist and specialist natural enemies. In this study, the ERH was explored using the invasive alien species, Arundo donax and two native tall-statured grasses, the cosmopolitan Phragmites australis and African endemic Phragmites mauritianus in South Africa. It was predicted that A. donax would have reduced species richness of herbivores compared with the native Phragmites spp., that it would be devoid of specialist herbivores and would thus be experiencing enemy escape in the adventive range. The herbivore assemblages were determined from both field surveys and a literature review. The assumptions of the ERH were for the most part not met; 13 herbivores were found on A. donax compared with 17 on P. australis and 20 on P. mauritianus. Arundo donax had two specialist herbivores from its native range, and shared native herbivores with Phragmites spp. Although A. donax had reduced species richness and diversity compared with that found in the native distribution, it has partially re-acquired a herbivore assemblage which is similar to that found on analogous native species. This suggests that enemy release may not fully explain the invasive success of A. donax in South Africa.

Heat shock proteins (HSPs) participate in diverse physiological processes in insects, and HSP70 is one of the most highly conserved proteins in the HSP family. In this study, full-length cDNAs of three HSP70 genes (Lthsc70, Lthsp701, and Lthsp702) were cloned and characterized from Liriomyza trifolii, an important invasive pest of vegetable crops and horticultural crops worldwide. These three HSP70s exhibited signature sequences and motifs that are typical of the HSP70 family. The expression patterns of the three Lthsp70s during temperature stress and in different insect development stages were studied by real-time quantitative PCR. Lthsp701 was strongly induced by high- and low-temperature stress, but Lthsc70 and Lthsp702 were not very sensitive to temperature changes. All three Lthsp70s were expressed during insect development stages, but the expression patterns were quite different. The expression of Lthsc70 and Lthsp702 showed significant differences in expression during leafminer development; Lthsc70 was most highly expressed in female adults, whereas Lthsp702 was abundantly expressed in larvae and prepupae. Lthsp701 expression was not significantly different among leafminer stages. These results suggest that functional differentiation within the LtHSP70 subfamily has occurred in response to thermal stress and insect development.

Heat-shock proteins 90 (hsp90s) are a class of molecules able to stabilize a network of ‘client’ proteins that are involved in several processes. Furthermore, recent studies indicated that mutations in the hsp90-encoding gene induce a wide range of phenotypic abnormalities, which have been interpreted as an increased sensitivity of different developmental pathways to hidden/cryptic mutations. In order to verify the role of hsp90 in aphids, we amplified and sequenced the hsp90 gene in 17 lineages of the peach potato aphid Myzus persicae (Sulzer, 1776) looking for the presence of mutations. In particular, we compared lineages with different reproductive modes (obligate vs. cyclical parthenogenesis), propensity to develop winged females and karyotype stability. Differently from the cyclical parthenogenetic lineages that possessed functional hsp90 genes, the seven analysed asexual lineages showed severe mutations (including frameshift and non-sense mutations). In vivo functional assays with the hsp90-inhibitor geldanamycin showed that some lineages with cyclical parthenogenesis may lose their ability to induce sexuales in the absence of active hsp90 revealing the presence of cryptic mutations in their genomes. As a whole, our data suggest that hsp90 could play in aphids a role in buffering hidden/cryptic mutations that disrupt cyclical parthenogenesis.

Knowledge on the reproductive biology of target insect pest is essential for the effective implementation of pheromone-based pest management tactics. In mealybugs, the second largest family of scale insects, the existence of female multiple mating was recently suggested. In this study, we aimed at testing how general is this behavior in mealybugs, by investigating polygyny and polyandry in two cosmopolitan pest mealybugs, Planococcus citri and Pseudococcus calceolariae. Males of these species were able to mate an average of 11.9 and 13.3 females, respectively, during their lifespan. The number of fertilized females per male decreased with male age/mating history for both mealybugs. We found no differences in female fecundity and fertility, when fertilized by males with different mating history. When we used male age as a proxy of mating history, we observed a significant negative effect on female fecundity. The females of both species remained receptive after first copula and eventually mated multiple times. The percentage of remated females of P. citri decreased linearly with time since first copula, with some maintaining receptivity up to 24 h. Males showed no preference between virgin and mated females, in static-air olfactometer tests. We found no benefit of female multiple mating in relation to fecundity. In biparental mealybugs, the mating system of males is possibly scramble competition polygyny; and that of females is possibly polyandry, with female receptivity restricted to a relatively short period. We discuss the practical implications of the results for pest management.

The eastern larch beetle (Dendroctonus simplex Le Conte) is recognized as a serious destructive forest pest in the upper part of North America. Under epidemic conditions, this beetle can attack healthy trees, causing severe damages to larch stands. Dendroctonus species are considered as holobionts, as they engage in multipartite interactions with microorganisms, such as bacteria, filamentous fungi, and yeasts, which are implicated in physiological processes of the insect, such as nutrition. They also play a key role in the beetle's attack, as they are responsible for the detoxification of the subcortical environment and weaken the tree's defense mechanisms. The eastern larch beetle is associated with bacteria and fungi, but their implication in the success of the beetle remains unknown. Here, we investigated the bacterial and fungal microbiota of this beetle pest throughout its ontogeny (pioneer adults, larvae and pupae) by high-throughput sequencing. A successional microbial assemblage was identified throughout the beetle developmental stages, reflecting the beetle's requirements. These results indicate that a symbiotic association between the eastern larch beetle and some of these microorganisms takes place and that this D. simplex symbiotic complex is helping the insect to colonize its host tree and survive the conditions encountered.

The development of the Mediterranean flour moth, Ephestia kuehniella (Zeller), was evaluated at 10, 15, 17.5, 20, 22.5, 25, 27.5, 30 and 32.5°C with no lighting. None successfully completed development at 10 and 32.5°C. The total development time from egg to adult emergence was 164, 140, 98, 76, 61, 62 and 50 days, respectively, at the remaining temperatures. The developmental rate of E. kuehniella was described by the common linear model and six non-linear models. The lower temperature threshold for the immature stages and the thermal constant for E. kuehniella were 9°C and 1111 degree-days (DD) to complete development from egg to newly emerged adult. Non-linear models estimated the lower and upper thermal thresholds (Tmin and Tmax) and optimal temperature (Topt). The values of Tmax calculated by three nonlinear models ranged from 34°C to 46°C; Topt for each stage of development varied from 24 and 31°C, consistent with the temperature (30°C) at which the most rapid development occurred. Information on the threshold temperatures for development and thermal requirements can be utilized to predict E. kuehniella population dynamics and phenology and to evaluate optimal temperature conditions for mass rearing in stored products.

The Asian chestnut gall wasp, Dryocosmus kuriphilus, is an invasive pest causing significant damage to chestnut trees (Castanea spp., Fagaceae). Originating from China, it has recently invaded a wide range of regions in Europe and North America. Understanding the population genetic structure of important invasive pests is very useful for improving the knowledge concerning routes of expansion and colonizing capacity. Despite its economic importance, limited attention has been given to D. kuriphilus origin and spread, or to its genetic structure. In this study, D. kuriphilus populations sampled in eight European countries were screened using both mitochondrial (cytochrome c oxidase subunit 1; COI) and nuclear (internal transcribed spacer 2; ITS2) sequences, and Amplified Fragment Length Polymorphism (AFLP) markers. The molecular markers COI and ITS2 highlighted the presence of a single haplotype in all the studied populations. The recorded mitochondrial haplotype was identical to one of the most widespread haplotypes occurring in the native area (China). AFLP results indicated that D. kuriphilus individuals belong to two genetically distinct clusters without any further geographic clustering. These results suggest that D. kuriphilus populations in Europe could be the result of a single introduction of a Chinese founder population characterized by two genetically distinct lineages that subsequently spread rapidly across Europe. However, the possibility that populations originated from multiple introductions of the same Chinese mitochondrial haplotype cannot be excluded. The reported results provide useful information concerning this invasive species, potentially facilitating integrated pest management.

An artificial diet formulated for continuous rearing of the predator Arma chinensis was inferior to natural prey when evaluated using life history parameters. A transcriptome analysis identified differentially expressed genes in diet-fed and prey-fed A. chinensis that were suggestive of molecular mechanisms underlying the nutritive impact of the artificial diet. Changes in the diet formulation were made based on the transcriptome analysis and tested using life history parameters. The quantity of pig liver, chicken egg, tuna fish, biotin, nicotinamide, vitamin B6, thiamine, riboflavin, vitamin C, L-glutamine, and sucrose was reduced, and wheat germ oil, calcium pantothenate and folic acid were increased. Ecuadorian shrimp was added as a partial substitute for tuna fish. Several parameters improved over six generations, including increased egg viability, and decreased egg and adult cannibalism. Additionally, several parameters declined, including longer developmental times for 2nd–5th instars, and decreased nymphal weights. The improvements in life history parameters support the use of transcriptome analyses to help direct formulation improvements. However, the decline in some parameters suggests that additional information, e.g., proteomic data, may be useful as well to maximize diet formulations.

Three large saproxylic cerambycids with different pest/legal status co-occur in the Iberian oak woodlands, Cerambyx welensii (Cw), Cerambyx cerdo (Cc) and Prinobius myardi (Pm): Cw is an emerging pest, Cc is a protected but sometimes harmful species and Pm is a secondary/minor pest. A precise taxonomic diagnosis is necessary for research, management or protection purposes, but may be problematic mainly because Cw and Cc larvae are morphologically indistinguishable. To resolve this constraint, we genotyped adults, larvae and eggs collected over a wide geographical range using the mitochondrial barcoding of the cytochrome c oxidase subunit I (COI). A Neighbour-Joining tree phylogram revealed three distinct clusters corresponding to Cw, Cc and Pm. We further first sequenced for Cw and Cc two mitochondrial (12S rRNA and 16S rRNA) and one nuclear (28S rRNA) gene fragments. For the first two genes, interspecific divergence was lower than in COI, and for the 28S (lower mutation rate), the two species shared identical haplotypes. Two approaches for species delimitation (General Mixed Yule Coalescent (GMYC), Barcode Index Number (BIN)) confirmed the species distinctiveness of Cc and Cw. The Bayesian COI gene tree showed a remarkable genetic divergence between Cc populations from Iberia and the rest of Europe. Such divergence has relevant taxonomic connotations and stresses the importance of a wide geographical scale sampling for accurate DNA barcoding species identification. Incongruities between morphology/lineage and COI barcodes in some individuals revealed natural hybridization between Cw and Cc. Natural hybridization is important from a phylogenetic/evolutionary perspective in these cerambycids, but the prevalence of (and the behavioural/ecological factors involved in) interspecific cross-breeding remain to be investigated.

The importance of the right food source for the survival and reproduction of certain insect species is well documented. In the case of biocontrol agents, this is even more important in order to reach a high predation or parasitation performance. The egg parasitoid Telenomus laeviceps (Förster, 1861) (Hymenoptera: Scelionidae) is a promising candidate for mass release as a biological control agent of the cabbage moth Mamestra brassicae (Linnaeus, 1758) (Lepidoptera: Noctuidae). However, adult T. laeviceps need a sugar-rich food source to increase their parasitation performance and produce a good amount of female offspring. Released biocontrol agents were shown to benefit from conservation biocontrol, which includes the provision of selected flowers as nectar resources for beneficial insects. In Switzerland, Centaurea cyanus L. (Asteraceae), Fagopyrum esculentum Moench (Polygonaceae) and Vicia sativa L. (Fabaceae) are successfully implemented in the field to attract and promote natural enemies of different cabbage pests. In this study, we investigated the potential of these selected flowers to attract and promote T. laeviceps under laboratory conditions. In Y-tube olfactometer experiments, we first tested whether the three nectar providing plant species are attractive to T. laeviceps. Furthermore, we assessed their effects on survival and parasitation performance of adult T. laeviceps. We found that flowers of F. esculentum and C. cyanus were attractive in contrast to V. sativa. Also fecundity and the number of female offspring produced were higher for females kept on F. esculentum and C. cyanus than on V. sativa. In contrast, survival was similar on all treatments. Our findings present a further key step towards the implementation of T. laeviceps as a biocontrol agent.

The mirid bug Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae) is a major pest on cotton, fruit trees and other crops in China. A. lucorum adults often switch host plants in the agro-ecosystem, and such host-plant switching may promote more rapid population growth of A. lucorum. Here, we examined the population fitness of A. lucorum on different combinations of two plant foods [fresh maize kernels (Zea mays) and green bean pods (Phaseolus vulgaris)] in the laboratory when reared either individually or in groups. Our results suggested that, compared with A. lucorum nymphs reared on green bean alone, the survival rate, developmental rate, and adult weight significantly increased when they were fed fresh maize kernels for both rearing methods. Both two-plant combinations of foods (i.e., maize as nymphal food then green bean as adult food, and green bean as nymphal food then maize as adult food) generally prolonged adult longevity, improved female fecundity, and higher egg hatching rate compared with maize or green bean as food for both nymphs and adults. The combination of nymphs with maize and adults with green bean showed the highest population growth rate for both individual and group rearing of mirid bugs. Host food switching greatly promoted the population growth of A. lucorum, and suggests a new diet for laboratory rearing of A. lucorum.

Phenotypic plasticity is thought to evolve in response to environmental unpredictability and can shield genotypes from selection. However, selection can also act on plastic traits. Egg-laying behaviour, including clutch size regulation, is a plastic behavioural trait among tephritid fruit flies. We compared plasticity in clutch size regulation among females of Anastrepha ludens populations stemming from environments that differed in the degree of predictability in egg-laying opportunities. Clutch size regulation in response to hosts of different sizes was compared among flies from (a) a wild, highly isolated population, (b) a wild population that switches seasonally from a small wild host fruit that varies greatly in abundance to an abundant large-sized commercial host, and (c) a laboratory population. Flies from all three populations adjusted clutch number and size according to host size. However, flies from the heterogeneous wild environment were more plastic in adjusting clutch size than flies from agricultural settings that also laid fewer eggs; yet both populations were more plastic in adjusting clutch size in line with host size when compared with laboratory females. When wild and orchard females encountered the largest host, clutch size was extremely variable and egg regulation did not follow the same trend. Heterogeneity in host availability in space and time appears to be as important as seasonal variation in host size in maintaining plastic clutch size regulation behaviour. In stable environments, there was a clear reduction in the plasticity of these traits.