Can natural enemies of current insect pests provide biotic resistance to future pests?

1. Economic pests jeopardize agricultural production worldwide. Classical biological control, comprising the import of exotic natural enemies to control target pest populations, has a successful history in many countries. However, little is known about how these natural enemies contribute to the suppression of pests that are yet to arrive. Biotic resistance theory, though, posits that communities resist species invasions as a result of natural enemies.
2. We assessed the potential of the resident exotic parasitoid wasp fauna in New Zealand (intentionally‐introduced biological control agents and unintentionally‐introduced species) to provide biotic resistance against possible future pests. A dataset was generated containing resident exotic parasitoid species (Ichneumonoidea: Braconidae; Ichneumonidae) in New Zealand, as well as their known global host ranges and the pest status of host species, to infer the potential for biotic resistance.
3. The known exotic ichneumonoid fauna in New Zealand comprises 65 species. These species associate with 107 host species in New Zealand, of which 54 species are pests. However, the current exotic species could potentially suppress 442 pest species not yet occurring in New Zealand.
4. This approach could be used to inform pest management programmes worldwide. Future research should consider how biotic resistance from the established parasitoid fauna can be used to inform specific decisions with respect to classical biological control.

     

Evaluating the link between predation and pest control services in the mite world

1. Pest regulation by natural enemies has a strong potential to reduce the use of synthetic pesticides in agroecosystems. However, the effective role of predation as an ecosystem service remains largely speculative, especially with minute organisms such as mites.
2. Predatory mites are natural enemies for ectoparasites in livestock farms. We tested for an ecosystem level control of the poultry pest Dermanyssus gallinae by other mites naturally present in manure in poultry farms and investigated differences among farming practices (conventional, free‐range, and organic).
3. We used a multiscale approach involving (a) in vitro behavioral predation experiments, (b) arthropod inventories in henhouses with airborne DNA, and (c) a statistical model of covariations in mite abundances comparing farming practices.
4. Behavioral experiments revealed that three mites are prone to feed on D. gallinae. Accordingly, we observed covariations between the pest and these three taxa only, in airborne DNA at the henhouse level, and in mites sampled from manure. In most situations, covariations in abundances were high in magnitude and their sign was positive.
5. Predation on a pest happens naturally in livestock farms due to predatory mites. However, the complex dynamics of mite trophic network prevents the emergence of a consistent assemblage‐level signal of predation. Based on these results, we suggest perspectives for mite‐based pest control and warn against any possible disruption of ignored services through the application of veterinary drugs or pesticides.

     

Modelling the effects of field spatial scale and natural enemy colonization behaviour on pest suppression in diversified agroecosystems

1. Diversifying agroecosystems by establishing or retaining natural vegetation in and around crop areas has long been recognized as a potentially effective means of bolstering pest control as a result of attracting more numerous and diverse natural enemies, although outcomes are inconsistent across species.
2. Little is known about the underlying mechanisms driving such differences in species responses, creating challenges for determining how best to manage landscapes for maximizing environmental services such as biological control.
3. The present study addresses gaps in our understanding of the link between noncrop vegetation in field margins and pest suppression by using a system of partial differential equations to model population‐level predator–prey interactions, as well as spatial processes, aiming to capture the dynamics of crop plants, herbivores and two generalist predators.
4. We focus on differences in how two predators (a carabid and a ladybird beetle) colonize crop fields where they forage for prey, examining differences in how they move into the fields from adjacent vegetation as a potential driver of differences in overall pest suppression.
5. The results obtained demonstrate that predator colonization behaviour and spatial scale are important factors with respect to determining the effectiveness of biological control.

     

Temporal variation of the effects of landscape composition on lacewings (Chrysopidae: Neuroptera) in vineyards

1. Increasing landscape heterogeneity, both in terms of composition and configuration, can promote natural enemies and biological control in agricultural landscapes. However, relatively poor information exists about the effects of landscape heterogeneity on lacewings, which are a major group of predators. Furthermore, temporal changes of landscape effects on natural enemy dynamics remain largely unexplored.
2. Here, we investigated how landscape composition and configuration affect lacewings and their biological control potential on leafhoppers. Lacewings and leafhoppers were sampled from April to July in 10 vineyards located in southwestern France. The vineyards were selected along a gradient of a proportion of semi‐natural habitats in the landscape.
3. The proportion of semi‐natural habitats positively affected the abundance of adults and eggs, as well as species richness, of lacewings, alone or in interaction with the sampling month. Landscape configuration was never found to enhance abundance or species richness of lacewings. Finally, the predator–prey ratio increased through time but did not respond to landscape composition or configuration.
4. Our study highlights that the proportion of semi‐natural habitats increases both abundance and diversity of lacewings in vineyard landscapes but that this effect varies over time. This result indicates the need to assess the variability of landscape effects over time to maximize biological pest control services in agricultural landscapes.

     

Risk posed by the invasive defoliator Uraba lugens to New Zealand native flora

• 1 The risk posed to New Zealand native flora by the recently‐established pest of Australian origin Uraba lugens Walker (Lepidoptera: Nolidae) (gum leaf skeletonizer) was assessed. Weed biological control host range testing methods were applied to identify those New Zealand plant species potentially at risk. Native plants tested were primarily in the Myrtaceae, the family that contains all the Australian hosts of U. lugens.
• 2 Experimental methods included no‐choice larval feeding assays and field cage and laboratory oviposition trials. Difficulty in ascertaining reliable oviposition preference data from cage oviposition trials limited the confidence with which the invader's field host range could be predicted.
• 3 Field surveys of plants attacked by U. lugens in the infested area supported the initial predictions but only some of the at‐risk native Myrtaceae were present in the area.
• 4 The risk to native New Zealand plants is presented in terms of two mechanisms: development of self‐sustaining populations and temporary spill‐over of solitary larvae. Development of self‐sustaining populations of the pest within native forests is deemed to be highly improbable.
• 5 Temporary spill‐over impacts are most likely in urban areas within mixed species plantings or boundaries between native/exotic forests and coinciding with the mobile larval life stages. Spill‐over impacts from U. lugens have only been recorded to date on Metrosideros excelsa.

     

Parasitoid associated with Liriomyza huidobrensis (Diptera: Agromyzidae) outbreaks in tomato fields in Brazil

1. The knowledge of natural factors that affect pest populations is essential in predicting the occurrence of pest outbreaks and in developing integrated pest management programmes. Natural enemies, climatic elements and host plants are among the most important factors affecting pest dynamics.
2. Tomato (Solanum lycopersicum) is the second most consumed vegetable worldwide. The pea leaf miner Liriomyza huidobrensis (Diptera: Agromyzidae) is a major pest to the tomato in Brazil.
3. This study aimed to determine the main natural factors that regulate L. huidobrensis populations in tomato fields in Brazil.
4. Liriomyza huidobrensis densities were evaluated by directly counting the number of active mines on the basal leaf of the middle section of the plant canopy, and predators and parasitoids were assessed using the leaf‐beating‐against‐a‐tray technique. Eight commercial tomato fields were assessed over two years. The phenological growth stages of the tomato plants (vegetative and reproductive) were noted during the assessments.
5. Liriomyza huidobrensis populations peaked between the middle and end of the planting season.
6. Opius sp. (Hymenoptera: Braconidae) was the main natural enemy of L. huidobrensis.
7. Our results suggest that phenological growth stage and Opius sp. are associated with population dynamics of L. huidobrensis in tomato fields.
8. Therefore, integrated pest management programmes should aim to preserve populations of the parasitoid Opius sp.

     

Roads and bats: a meta‐analysis and review of the evidence on vehicle collisions and barrier effects

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Aspidiotus rigidus Reyne (Hemiptera: Diaspididae): a devastating pest of coconut in the Philippines

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Life history and mortality factors of Agrilus mali Matsumura (Coleoptera: Buprestidae) in wild apples in Northwestern China

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The mating strategy and reproductive performance of Agriphila aeneociliella (Lepidoptera: Crambidae), a new insect pest of wheat in China

1. The Eastern Grass‐veneer Agriphila aeneociliella (Eversmann) (Lepidoptera: Crambidae) is a serious stem‐feeding pest of wheat crops that has become established in China in recent years. A better understanding of the mating strategy and reproductive performance of A. aeneociliella could improve integrated pest management programmes against this newly established species by disturbing its behaviour and reducing its reproduction potential. Based on ethological and reproductive biological approaches, the mating and reproductive performances of A. aeneociliella were investigated.
2. Unlike the common nocturnal lepidopterans, the mating rhythm of A. aeneociliella moths showed a marked diurnal pattern. The female courtship rhythm and the mating rhythm reached peaks within the first 2 h after the onset of photocycle.
3. The mating success rate of monogamous pairs was 55.6%, whereas the male‐biased sex ratio (2♂:1♀) increased the mating rate (72.2%) and the female‐biased ratio (1♂:3♀) led to the lowest mating rate (27.8%).
4. Both females and males were able to mate twice. The duration of copulation decreased substantially with male mating frequency, whereas, when a previously mated female was paired with a virgin male, fecundity significantly increased. Monogamous couples who mated only once in their lives have the highest hatchability (97.13 ± 0.49%).

     

Rating the rat: global patterns and research priorities in impacts and management of rodent pests

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Risk assessment of Hass avocado and Mexican Lauraceae for attack by redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae)

1. The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), vectors the mycopathogen that causes laurel wilt, a lethal vascular disease of trees in the Lauraceae. Since being detected in Georgia, USA in 2002, this invasive pest has become established in 11 additional states.
2. With continued spread, X. glabratus will likely enter Mexico. In advance of this event, this study was initiated to assess the risk posed to eight native laurels and Hass avocados, the predominant cultivar grown in Mexico.
3. Wood bolts from each species were used in (a) field tests to determine the relative attraction of female X. glabratus, (b) laboratory bioassays to evaluate boring preferences, and (c) GC–MS analyses to identify host kairomones. For comparison, tests included control bolt treatments consisting of silkbay (an attractive U.S. laurel) and Simmonds avocado (a Florida cultivar susceptible to laurel wilt).
4. Hass avocado and two native laurels (Persea schiedeana and Ocotea heribertoi vel aff.) were highly attractive to females and elicited strong boring responses. These species were high in sesquiterpene hydrocarbons, including α-copaene and α-cubebene.
5. Results of this study suggest that X. glabratus could become a serious agricultural and forest pest upon incursion into Mexico, with severe economic and ecological impacts.

     

The mango seed weevil Sternochetus mangiferae (Fabricius) (Coleoptera: Curculionidae) is characterized by low genetic diversity and lack of genetic structure

1. The mango seed weevil Sternochetus mangiferae (Fabricius) is distributed across the major mango-producing areas of the world and causes significant economic losses of mango fruit. Despite its importance as a crop pest, we have only limited information on the population genetics of the mango seed weevil.
2. Here, we examined the genetic diversity of this important pest using specimens intercepted by Beijing Customs District P. R. in China from 41 countries and regions. We used segments of the mitochondrial gene cytochrome c oxidase subunit I and the nuclear gene elongation factor 1-alpha to examine population genetic structure in this species.
3. Our results showed that genetic diversity is low in S. mangiferae, with a mean genetic distance of 0.095–0.14%. Other population genetic parameters also indicated a low level of genetic diversity among samples from a large geographic range. Analysis of molecular variance revealed little population genetic structure, and mismatch distribution analyses provided evidence of a population expansion, although other demographic metrics of population expansion were nonsignificant.
4. We suggest that the observed low level of genetic diversity and population genetic structure in S. mangiferae supports the hypothesis that the population genetics of this species has been impacted by anthropogenic transportation of mangoes and weevils.

     

Tree species identity and forest composition affect the number of oak processionary moth captured in pheromone traps and the intensity of larval defoliation

1. Pure forests are often seen as being more prone to damage by specialist pest insects than mixed forests, and particularly mixed forests associating host and nonhost species. We addressed the effect of tree diversity on oak colonization and defoliation by a major specialist pest, the oak processionary moth (OPM)
2. We quantified the number of male OPM moths captured and larval defoliation in pure stands of two oak host species (Quercus robur and Quercus petraea) and in mixed stands associating the two oak species or each oak species with another nonhost broadleaved species. We conducted two complementary studies to test the effect of host species and stand composition: (i) we used pheromone trapping to compare the number of males OPM captured throughout the distribution of oak hosts in France and (ii) we noted the presence of OPM nests and estimated defoliation in mature forests of north‐eastern France.
3. Oak species and stand composition significantly influenced the number of male OPM captured and defoliation by OPM larvae. Quercus petraea was consistently more attractive to and more defoliated by OPM than Q. robur. Both oak trees were attacked more in pure stands than in mixed stands, in particular mixed stands associating oaks with another (nonhost) broadleaved species.
4. The results of the present study support the view that mixed forests are more resistant to specialist pest insects than pure stands, and also indicate that this trend depends on forest composition. Our study provides new insights into OPM ecology and has potential implications for forest management, including the management of urban forests where OPM causes serious human health issues.

     

Prey‐specific foraging tactics in a web‐building spider

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Biology of the Eucalyptus leaf beetle Paropsisterna selmani (Chrysomelidae: Paropsini): a new pest of Eucalyptus species (Myrtaceae) in Ireland

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The infestation and habitat of the ambrosia beetle Euwallacea interjectus (Coleoptera: Curculionidae: Scolytinae) in the riparian zone of Shanghai,China

1. Extensive boring damage into trunks of living poplar trees in the urban forest of Shanghai, eastern China, was investigated in 2017.
2. In order to determine the taxonomic identity of the pest, we used morphological identification and sequenced mitochondrial COI gene. Based on both morphology and molecular data, it was concluded that the pest boring into the poplars was the ambrosia beetle Euwallacea interjectus (Blandford).
3. Its occurrence and damage on poplar across Shanghai were also investigated. In the Pudong District, a total of 104.52 ha of urban forest were investigated thoroughly, and 16.22% of surveyed forests were found to be infested. This insect species is an important native pest capable of causing damage across the Shanghai area.
4. Observations in the field suggested that the damage may be related to distance to water sources. Our statistical analysis confirmed this hypothesis, as the close distance to water bodies correlated with higher levels of damage. We conclude that E. interjectus prefers host trees stressed by an occasional excessive abundance of water, and acts as a parasite on living trees without killing them.

     

Responses of native egg parasitoids to the invasive seed bug Leptoglossus occidentalis

1. The Western conifer seed bug Leptoglossus occidentalis, a native insect of North America, was accidentally introduced in Europe in the late 1990s. Since then, it has spread rapidly. Biological control could provide an efficient management option but natural enemies of the pest have been poorly examined in Europe.
2. In this study, we exposed sentinel egg masses and collected naturally laid egg masses in southern France in 2016 and 2017, to identify the egg parasitoids of L. occidentalis and investigate their potentials.
3. Three egg parasitoids were detected: Anastatus bifasciatus, Ooencyrtus pityocampae and Ooencyrtus telenomicida. The overall parasitism was low compared to that observed in the native range with 6.4% of all eggs being parasitized, while 17.1% of egg masses carried at least one parasitized egg. The total number of parasitized egg masses was similar between parasitoid species, but the mean number of parasitized eggs per egg mass was highest for A. bifasciatus (5.57 vs. 1.25 for Ooencyrtus spp.).
4. Sentinel egg masses underestimated the parasitism compared to natural egg masses (respectively, 1.42% and 7.71%).
5. Our results suggested that the three generalist parasitoids detected can respond in a Leptoglossus egg density-dependent manner, but this requires further investigations.

     

Climate-based ensemble modelling to evaluate the global distribution of Anoplophora glabripennis (Motschulsky)

1. Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) is a forest pest that damages a wide range of trees in areas where it has recently been introduced, demanding a proactive evaluation of its possible future distribution.
2. This study aimed to project the potential distribution of A. glabripennis using species distribution modelling and constructed an ensemble map for evaluating global risk areas.
3. We used CLIMEX and MaxEnt to evaluate the potential distribution of A. glabripennis as a function of current and future climates.
4. The results showed that the models predicted a high probability of A. glabripennis distribution where this species is currently found, and the suitable climate was shifted northward due to climate change.
5. The projected area differed between the models because of different modelling algorithm and climate change scenario; thus, an ensemble map projecting the consensus areas from two models was constructed to identify the risk areas that corresponded to the eastern United States, Europe, and native countries, Korea and China, and nearby Japan.
6. From the perspective of ensemble modelling for evaluating species distributions with reduced uncertainties, this study will enhance the model reliability for defining areas at risk of A. glabripennis occurrence.

     

Migration and dispersal patterns of bats and their influence on genetic structure

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