Weevil Pest Research Articles

Biological Control Success of a Pasture Pest: Has Its Parasitoid Lost Its Functional Mojo?

Sustainable and integrated pest management often involves insect parasitoids. However, the effectiveness of parasitoids biocontrol has often failed, frequently for obscure reasons. A parasitoid’s success is partly due to its behavioral response to pest density, i.e. its consumer functional response. For many years in New Zealand, a braconid parasitoid, Microctonus hyperodae successfully suppressed a severe ryegrass weevil pest, Listronotus bonariensis. However, there is now evidence that this has severely declined, but that the extent of decline can depend on the pasture species. Here, we tested whether the current functional responses of M. hyperodae to L. bonarensis in two of the most common New Zealand pasture grasses (Lolium multiflorum and L. perenne) reflect observed differences in field parasitism and whether this functional response has changed over time. Our analysis involved data both from 1993 and 2018. We found a type I functional response in L. multiflorum in both years, but the slope of the relationship declined over time. There was no evidence for any type of functional response in L. perenne. This lack of response in the L. perenne coincided with consistently found lower parasitism rates on this host plant than in L. multiflorum; both in the field and laboratory. Here, we found that apparently declining searching efficiency was correlated with the decline in parasitism. This observation supports the hypothesis that parasitism decline could be the result of evolution of resistance based on enhanced evasive behaviour by L. bonariensis.

Pest categorisation of Sternochetusmangiferae.

The European Commission requested EFSA to conduct a pest categorisation of Sternochetus mangiferae (Coleoptera: Curculionidae), a monophagous pest weevil whose larvae exclusively feed on mango seeds, whereas adults feed on mango foliage. S. mangiferae is a species with reliable methods available for identification. It is regulated in the EU by Council Directive 2000/29/EC where it is listed in Annex IIB as a harmful organism whose introduction into EU Protected Zones (PZ) (Alentejo, Algarve and Madeira in Portugal, and Granada and Malaga in Spain) is banned. S. mangiferae is native to South East Asia and has spread to other mango‐growing areas in Africa, South America and Oceania, causing significant damage. Larvae of S. mangiferae have been detected several times in mango fruit imported into the EU. In 2013, an outbreak was declared in one PZ in Spain. Official measures taken achieved eradication, which was officially declared in January 2018. The EFSA Plant Health Panel concludes that S. mangiferae could establish again and spread in the mango‐growing areas of southern EU. Considering the criteria within the remit of EFSA to assess the status as a potential Union quarantine pest (QP), as a potential protected zone quarantine pest (PZQP) or as a potential regulated non‐quarantine pest (RNQP), S. mangiferae meets with no uncertainties the criteria for consideration as a potential Union QP, as it is absent from the EU, potential pathways for entry exist, and its establishment would cause an economic impact. The criterion of the pest being present in the EU, which is a prerequisite for RNQP and PZ QP, is not met.

Screening for resistance against major lepidopteran and stem weevil pests of amaranth in Tanzania

Insect pests pose major challenges to optimum productivity of amaranth in Africa and Asia. The use of insecticides is the main control strategy, but is expensive and may pose health and environmental concerns, especially if proper care is not taken. Host plant resistance offers a cheap and sustainable pest management alternative. Open field experiments were conducted during two cropping seasons in 2016 and 2017 to screen 35 amaranth accessions and lines for resistance to leaf-webbers and stem weevils. The diversity (H) of lepidopteran defoliators and their parasitoids on each accession ranged from 0.00 to 1.57 and 0.00 to 1.65, respectively during the long rainy season and from 0.00 to 1.58 and 0.00 to 1.01 in the short rainy season. Accessions VI036227, RVI00027, VI054569, VI033487, VI044432, VI048076, VI049639, VI049530 and VI049698 had high levels of pest resistance with significantly lower infestations (≤ 11.11 ± 2.14%) and damage (≤ 68.06 ± 3.90%) by leaf-webbers and leaf-worms. Stem weevil infestations ranged from 68.70 ± 2.0% to 90.42 ± 1.0% during the long and short rainy seasons, respectively. Accessions VI047517-B, VI036227 and VI056563 had the least stem weevil infestations (< 62.5%) but differences among accessions for damage incidences were non-significant. Parasitism was observed in all the accessions except seven of them. Amaranth accessions exhibiting pest resistance or at least non-preference traits are important for success of breeding programs. The importance of deploying such accessions to breed for improvement of susceptible lines (by introgression) or their release to farmers, if they have desirable horticultural traits that are required by vegetable producers and consumers, for effective management of amaranth pests is also discussed.

Detection of live larvae in cocoons of Bathyplectes curculionis (Hymenoptera: Ichneumonidae) using visible/near-infrared multispectral imaging.

The multispectral (MS) imaging system is a non-destructive method with potential to reduce the labour and time required for quality control in the production of beneficial arthropods such as the parasitoid Bathyplectes curculionis. In Denmark, a project is being undertaken that focuses on the possible use of B. curculionis in augmentative control of Hypera weevil pests in white clover seed production where cocoons of the parasitoid remain as a by-product of seed processing. Only a fraction of the by-product contains live parasitoid larvae and an effective method is required detect live cocoons for later augmentative control of the pest. Therefore, this study aims to identify live larval cocoons of B. curculionis using the MS imaging system. Live and dead cocoons were identified using the canonical discriminant analysis (CDA) model with an accuracy of 91% and 80% (error rate 14%) in the training set, and a predicted accuracy of 89% and 81% (error rate 15%) in the test set. Reflectance from the near-infrared region was valuable in identifying live cocoons compared with that from the visible region. The MS imaging system is a rapid method for the separation of live and dead cocoons of B. curculionis. This study shows the potential of developing an MS imaging system to facilitate sorting of live and dead cocoons and optimize augmentative control of Hypera weevil pests. © 2018 Society of Chemical Industry.

Fungi Associated with Disease and Weevil Damage ofAmaranthus cruentusin South Africa

Agronomic trials were conducted in central SouthAfrica to establish Amaranthus cruentus as a commercial grain crop. Knowledge of potential pest- and pathogen-related problems that might arise during cultivation is essential for future industry development. Previous studies linked fungi belonging to the genera Fusarium and Alternaria with weevil damage of leafy amaranth (A. hybridus). The aim of the present study was to conduct a disease survey to identify possible fungal association with weevils (Coleoptera: Curculionidae) and weevil damage in A. cruentus fields at Potchefstroom and Taung in the North-West Province, South Africa. Isolations were made from lesion margins, larval galleries of the weevil Hypolixus haerens, and stem lesions associated with the weevils Athesapeuta dodonis and Baris amaranthi. Weevil larvae associated with lesions as well as adults collected from plants in amaranth plots were euthanased and plated out onto fungal growth media. Fungi arising from the weevils were purified and identified to genus level based on morphology. Alternaria was predominantly isolated from leaf spots in contrast to Fusarium species that were isolated from root rot, cankered roots and stems. Fusarium species were by a considerable margin the dominant group associated with weevil damage and stem lesions, as well as larval tunnels, larval bodies and free living adults. Species of Cladosporium and Alternaria were also isolated from adult weevils with significant consistency. Other less dominant fungi isolated from adult weevils and larval tunnels included species of Aspergillus, Epicoccum, Humicola, Mucor, Penicillium, Rhizopus and Trichoderma. It is evident that Fusarium and Alternaria are the genera that host the most important and potentially dominant fungal pathogen taxa linked with grain amaranth disease symptoms and associated weevil pests. As such they will have to be investigated further in future.

Pest categorisation of Anthonomus grandis.

The European Commission requested EFSA to conduct a pest categorisation of Anthonomus grandis (Coleoptera: Curculionidae), an oligophagous pest weevil feeding on Malvaceae, including Gossypium spp., Hampea spp., Cienfuegosia spp. and Hibiscus pernambucensis. Marginal reproduction has also been observed on the ornamental Hibiscus syriacus. A. grandis is a taxonomic entity with reliable methods available for identification. It is regulated in the EU by Council Directive 2000/29/EC where it is listed in Annex IIB as a harmful organism whose introduction into EU Protected Zones (PZ) (Greece and the Spanish Communities of Andalusia, Catalonia, Extremadura, Murcia and Valencia) is regulated. A. grandis is native to tropical regions of Mesoamerica and has spread to other cotton‐growing areas in the Americas, from the USA to Argentina, causing significant damage to this crop. An eradication programme is in progress in the USA and has been successful in 16 previously infested states. In the EU, phytosanitary measures are in place in order to limit entry via traded commodities. Cotton seeds and fruit, as well as unginned cotton are currently regulated for the PZ but remain a potential pathway. Furthermore, ornamental Malvaceae (e.g. Hibiscus spp.) originating in infested areas may provide additional pathways. The EFSA Plant Health Panel concludes that A. grandis could establish and spread in the cotton‐growing areas of southern EU. Considering the criteria within the remit of EFSA to assess the status as a potential Union quarantine pest (QP), as a potential protected zone quarantine pest (PZQP), or as a potential regulated non‐quarantine pest (RNQP), A. grandis satisfies with no uncertainties the criteria to be regarded as a Union QP. However, it does not meet the criterion of occurrence in the EU territory (for PZQP) plus that of plants for planting being the principal means of spread (for RNQP).

Possible New Species of Araecerus (Coleoptera: Anthribidae) associated with Mastixiodendronpachyclados (Rubiaceae) of Papua New Guinea

Araecerus is genus of beetles of the Anthribidae family which are important economic pests of various crops including coffee (Rubiaceae), with A.fasciculatus (Degeer) being the common pest (weevil) of coffee beans. This paper presents a study in which five undescribed species of genus Araecerus were reared predominantly from the seeds of M.pachyclados (Rubiceae), a native tree of Papua New Guinea (PNG). Fruits of M. pachyclados were regularly sampled and insects attacking them were reared, preserved and identified. Fruits were hand collected, photographed, weighed and reared. Insects emerging from the fruits were captured and preserved in 99% ethanol. All the specimens were identified into morphospecies at the laboratory. The five new species discovered were designated as A. sp.1, A. sp.2, A. sp.3, A. sp.4 and A.sp.5. This was accorded based on differences in body length; scutellum color, size, hair-scales and visibility; length of first and second segments of fore tarsus; apical and subapical teeth-size (mandible and maxillary palpi); declivity of dorsal abdomen; basal-anterior eye markings; lateral eye markings; absence of eye markings; and shape of pygidium. We discovered A. sp.1 has yellowish gold marking inside the base of the eye, A. sp.2 with pygidium almost vertically-flat at abdominal apex, A. sp.3 has eyes without yellowish gold marking and generally dark in color, A. sp.4 with distinct yellowish gold interior-lateral marking in its eye, and A. sp.5 with pygidium pointed at abdominal apex.

Antennal transcriptome and expression analyses of olfactory genes in the sweetpotato weevil Cylas formicarius

The sweetpotato weevil, Cylas formicarius (Fabricius), is a serious pest of sweetpotato. Olfaction-based approaches, such as use of synthetic sex pheromones to monitor populations and the bait-and-kill method to eliminate males, have been applied successfully for population management of C. formicarius. However, the molecular basis of olfaction in C. formicarius remains unknown. In this study, we produced antennal transcriptomes from males and females of C. formicarius using high-throughput sequencing to identify gene families associated with odorant detection. A total of 54 odorant receptors (ORs), 11 gustatory receptors (GRs), 15 ionotropic receptors (IRs), 3 sensory neuron membrane proteins (SNMPs), 33 odorant binding proteins (OBPs), and 12 chemosensory proteins (CSPs) were identified. Tissue-specific expression patterns revealed that all 54 ORs and 11 antennal IRs, one SNMP, and three OBPs were primarily expressed in antennae, suggesting their putative roles in olfaction. Sex-specific expression patterns of these antenna-predominant genes suggest that they have potential functions in sexual behaviors. This study provides a framework for understanding olfaction in coleopterans as well as future strategies for controlling the sweetpotato weevil pest.

Potential non-target effects of Sclerodermus harmandi (Hymenoptera:Bethylidae) on Triaspis sp. (Hymenoptera:Braconidae)

ABSTRACTSclerodermus harmandi (Buysson) (Hymenoptera: Bethylidae) is a generalist parasitoid that has been mass-produced and released for biological control of many agricultural and forest pests in China. However, few studies have examined the potential non-target risks of this parasitoid in targeted agriculture or forest ecosystems. In this study, we demonstrate that S. harmandi successfully attacks Triaspis sp. (Hymenoptera: Braconidae), an important native natural enemy of the pine weevil pest Pissodes punctatus Langor et Zhang in Yunnan Province of China. When exposed to older larvae of Triaspis sp. at three different parasitoid-to-host group sizes (1:1, 2:2 and 3:3) with a constant 1:1 parasitoid-to-host ratio, S. harmandi successfully attacked 100%, 75% and 83.3% of the test larvae, respectively. All life stages (egg, larva, pupa and adult) of S. harmandi were observed on Triaspis sp. larvae, indicating that Triaspis sp. are suitable for the completion of S. harmandi development. There were no significant differences in the number of S. harmandi progeny produced among the different parasitoid-to-host exposure treatments. Immature stages of S. harmandi on parasitized Triaspis sp. took 25.4 days to complete their development (the egg stage: 3.6 days, the larval stage: 5.0 days, the pupal stage: 16.5 days). Together, results from our study indicate that mass-releases of S. harmandi for biological control of forest pests in Yunnan Province may adversely affect some valuable non-target insects such as Triaspis sp. We suggest that the potential non-target risk of S. harmandi be considered in future augmentative release biological control programmes against forest pests.

Reassessment of Resistance to Sunflower Stem Weevil, Cylindrocopturus adspersus LeConte (Coleoptera: Curculionidae), in Cultivated Sunflower Germplasm

Sunflower stem weevil, Cylindrocopturus adspersus LeConte (Coleoptera: Curculionidae), larval feeding on pith and vascular tissues can weaken stalks of cultivated sunflower, leading to breakage and loss of harvestable yield. Previous research has suggested host plant resistance (HPR) to this pest is possible, but results have been difficult to interpret because of limited comparisons to cultivated inbreds and hybrids, along with possible confounding effects of stem diameter. Trials in Kansas (2012) and Nebraska (2015) were used to help reassess the value of germplasm with putative resistance to sunflower stem weevil. Field tests in 2012 included 28 inbreds and hybrids and three entries previously identified as resistant. Though a putative resistance source, PI 386230, was infested with fewer weevil larvae per stem than several hybrids, differences primarily appeared to be due to stem diameter, which is strongly correlated with the number of weevil larvae per stem. A follow-up trial in 2015 suggested differences in larval infestation were not attributable to other qualities in groups of germplasm that differ in stem diameter (i.e., males, females or hybrids), but that changes in plant density predictably alter both stem diameter and numbers of stem weevil larvae. Though resistance to sunflower stem weevil and other stem-feeding pests may be possible, the cost and difficulty of developing HPR, declining severity of the pest, and availability of other simple management options are significant disincentives to additional research.

Intensified agriculture favors evolved resistance to biological control.

Increased regulation of chemical pesticides and rapid evolution of pesticide resistance have increased calls for sustainable pest management. Biological control offers sustainable pest suppression, partly because evolution of resistance to predators and parasitoids is prevented by several factors (e.g., spatial or temporal refuges from attacks, reciprocal evolution by control agents, and contrasting selection pressures from other enemy species). However, evolution of resistance may become more probable as agricultural intensification reduces the availability of refuges and diversity of enemy species, or if control agents have genetic barriers to evolution. Here we use 21 y of field data from 196 sites across New Zealand to show that parasitism of a key pasture pest (Listronotus bonariensis; Argentine stem weevil) by an introduced parasitoid (Microctonus hyperodae) was initially nationally successful but then declined by 44% (leading to pasture damage of c. 160 million New Zealand dollars per annum). This decline was not attributable to parasitoid numbers released, elevation, or local climatic variables at sample locations. Rather, in all locations the decline began 7 y (14 host generations) following parasitoid introduction, despite releases being staggered across locations in different years. Finally, we demonstrate experimentally that declining parasitism rates occurred in ryegrass Lolium perenne, which is grown nationwide in high-intensity was significantly less than in adjacent plots of a less-common pasture grass (Lolium multiflorum), indicating that resistance to parasitism is host plant-dependent. We conclude that low plant and enemy biodiversity in intensive large-scale agriculture may facilitate the evolution of host resistance by pests and threaten the long-term viability of biological control.

EVALUATION OF NATURAL ENEMIES IN CONTROLLING OF THE BANANA WEEVIL BORER Cosmopolites sordidus Germar IN WEST SUMATRA

&lt;br /&gt;The banana weevil, Cosmopolites sordidus Germar, is an important pest of highland banana and plantain in Africa, but it exists in low densities in presumed area of origin in Southeast Asia such as in Indonesia. This suggests a possible existence of effective co-evolved natural enemies in the origin area of Indonesia, especially West Sumatra. The objectives of this study were: (1) to evaluate banana weevil pest status at selected sites in West Sumatra, (2) to survey parasitoids and predators, and (3) to determine the control potential of the most important natural enemies. Surveys were undertaken in March 2002-August 2003 in five locations in West Sumatra, i.e., Bukittinggi, Sitiung, Pariaman, Pasaman, and Batusangkar. Five farms per site were selected randomly among all farms that contained banana stands of &amp;gt; 0.5 ha. Sampling for banana weevil adults and damage, and for predators was done throughout small banana stands and within a 20 m x 40 m (0.08 ha) subplot on larger farms. Field-collected larvae were taken to the laboratory and reared on corm pieces (3 cm x 3 cm x 3 cm) until pupation. Larvae were collected from pseudostem as well as corm residues. To estimate the abundance of non-social predators, i.e., those other than ants, 10 residues each on each farm were examined from plants that had been harvested 1-4 weeks, 5-8 weeks or 9 or more weeks before our visit to the site. Samples of the different morphospecies were saved in alcohol for later identification. The result showed that the banana weevil incidence was found to be low, 0.6-1.7 adults per trap. Plant damage indices were below 2.2%. We collected and reared 24,360 eggs and 3118 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid beetles, &lt;em&gt;Plaesius javanus &lt;/em&gt;Erichson. In laboratory tests, adults and larvae of P. &lt;em&gt;javanus&lt;/em&gt; attacked 75-88% and 38-53% of banana weevil larvae and pupae, respectively. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found to be associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The adult banana weevil mortalities caused by the entomopathogen fungi of Beauveria bassiana from Baso, Sungaitarab, Sei Sariek, and Sikabau at highest density (3.2 x 108 spores ml-1) after two weeks were 96.67%, 90.00%, 60.00% and 83.33%, respectively. The high diversity of habitat conditions in which crop-pest-natural enemies systems exist, support the idea that banana weevil population and damage intensity in the study area is low due to active role of natural enemies.

EVALUATION OF NATURAL ENEMIES IN CONTROLLING OF THE BANANA WEEVIL BORER Cosmopolites sordidus Germar IN WEST SUMATRA

&lt;br /&gt;The banana weevil, Cosmopolites sordidus Germar, is an important pest of highland banana and plantain in Africa, but it exists in low densities in presumed area of origin in Southeast Asia such as in Indonesia. This suggests a possible existence of effective co-evolved natural enemies in the origin area of Indonesia, especially West Sumatra. The objectives of this study were: (1) to evaluate banana weevil pest status at selected sites in West Sumatra, (2) to survey parasitoids and predators, and (3) to determine the control potential of the most important natural enemies. Surveys were undertaken in March 2002-August 2003 in five locations in West Sumatra, i.e., Bukittinggi, Sitiung, Pariaman, Pasaman, and Batusangkar. Five farms per site were selected randomly among all farms that contained banana stands of &amp;gt; 0.5 ha. Sampling for banana weevil adults and damage, and for predators was done throughout small banana stands and within a 20 m x 40 m (0.08 ha) subplot on larger farms. Field-collected larvae were taken to the laboratory and reared on corm pieces (3 cm x 3 cm x 3 cm) until pupation. Larvae were collected from pseudostem as well as corm residues. To estimate the abundance of non-social predators, i.e., those other than ants, 10 residues each on each farm were examined from plants that had been harvested 1-4 weeks, 5-8 weeks or 9 or more weeks before our visit to the site. Samples of the different morphospecies were saved in alcohol for later identification. The result showed that the banana weevil incidence was found to be low, 0.6-1.7 adults per trap. Plant damage indices were below 2.2%. We collected and reared 24,360 eggs and 3118 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid beetles, &lt;em&gt;Plaesius javanus &lt;/em&gt;Erichson. In laboratory tests, adults and larvae of P. &lt;em&gt;javanus&lt;/em&gt; attacked 75-88% and 38-53% of banana weevil larvae and pupae, respectively. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found to be associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The adult banana weevil mortalities caused by the entomopathogen fungi of Beauveria bassiana from Baso, Sungaitarab, Sei Sariek, and Sikabau at highest density (3.2 x 108 spores ml-1) after two weeks were 96.67%, 90.00%, 60.00% and 83.33%, respectively. The high diversity of habitat conditions in which crop-pest-natural enemies systems exist, support the idea that banana weevil population and damage intensity in the study area is low due to active role of natural enemies.

Out of the forest: past and present range expansion of a parthenogenetic weevil pest, or how to colonize the world successfully.

Previous research revealed complex diversification patterns in the parthenogenetic weevil Naupactus cervinus. To understand the origin of clonal diversity and successful spreading of this weevil, we investigated its geographic origin and possible dispersal routes and whether parthenogens can persist in habitats under unsuitable environmental conditions. This study is based on samples taken throughout a broad area of the species’ range. We used both mitochondrial and nuclear markers and applied phylogenetic and network analyses to infer possible relationships between haplotypes. Bayesian phylogeographic analyses and ecological niche modeling were used to investigate the processes that shaped genetic diversity and enabled the colonization of new geographic areas. Southeastern Brazil emerges as the original distribution area of N. cervinus. We detected two range expansions, one along natural corridors during the Pleistocene and the other in countries outside South America during recent times. Isolation due to climate shifts during the early Pleistocene led to diversification in two divergent clades, which probably survived in different refugia of the Paranaense Forest and the Paraná River delta. The origin of the clonal diversity was probably a complex process including mutational diversification, hybridization, and secondary colonization. The establishment of N. cervinus in areas outside its native range may indicate adaptation to drier and cooler conditions. Parthenogenesis would be advantageous for the colonization of new environments by preventing the breakup of successful gene combinations. As in other insect pests, the present distribution of N. cervinus results from both its evolutionary history and its recent history related to human activities.

Biology and Management of Billbugs (Coleoptera: Curculionidae) in Turfgrass.

Billbugs (Coleoptera: Curculionidae: Sphenophorus spp.) are a complex of weevil pests affecting turfgrass throughout the United States. Billbug larvae cause damage by feeding in stems, on roots, and on the crowns of turf, causing severe discoloration and eventual plant death. Monitoring efforts have focused on nondestructive pitfall sampling of ground-active billbug adults and on destructive sampling using soil cores for larval stages in the soil. Given the cryptic nature of the susceptible larval stages, billbugs are typically managed by preventive applications of long-residual, systemic insecticides, including neonicotinoids and anthranilic diamides. Despite knowledge of effective management practices including pest-resistant turf varieties, irrigation management, and microbial controls that contribute to an IPM approach, billbug management continues to rely heavily on prophylactic synthetic insecticides. This review will summarize the identification and biology of billbugs and strategies for their management.

Survival Analysis and Actuarial Parameters of Sternechus subsignatus (Coleoptera: Curculionidae) Adults.

The soybean stalk weevil, Sternechus subsignatus Boheman 1836 (Coleoptera: Curculionidae), is a very serious soybean pest in the Neotropical region. Both adults and larvae feed on soybean, causing significant yield losses. Adult survival was evaluated during three soybean growing seasons under controlled environmental conditions. A survival analysis was performed using a parametric survival fit approach in order to generate survival curves and obtain information that could help optimize integrated management strategies for this weevil pest. Sex of the weevils, crop season, fortnight in which weevils emerged, and their interaction were studied regarding their effect on adult survival. The results showed that females lived longer than males, but both genders were actually long-lived, reaching 224 and 176 d, respectively. Mean lifetime (l50) was 121.88±4.56 d for females and 89.58±2.72 d for males. Although variations were observed in adult longevities among emergence fortnights and soybean seasons, only in December and January fortnights of the 2007–2008 season and December fortnights of 2009–2010 did the statistically longest and shortest longevities occur, respectively. Survivorship data (lx) of adult females and males were fitted to the Weibull frequency distribution model. The survival curve was type I for both sexes, which indicated that mortality corresponded mostly to old individuals.

Selecting non-target species for arthropod biological control agent host range testing: Evaluation of a novel method

Regulators often require risk assessment to ascertain biosafety of biocontrol agents before approval for release. Selecting the most informative non-target species for host range testing can be challenging. Here we compare traditional test list selection with a more objective method that selects species from a dataset of invertebrates from the receiving environment. A model, PRONTI (priority ranking of non-target invertebrates) ranks species using five criteria: hazard, exposure, potential ecological impacts from exposure, anthropocentric value and testability. For a case study, we used the braconid parasitoid Microctonus aethiopoides Loan released in New Zealand in 1982 for biocontrol of the pest weevil Sitona discoideus Gyllenhal. We compared species prioritised by PRONTI as worthy of testing with those selected prior to release. Several species which have been attacked in the field by M. aethiopoides since its release ranked highly suggesting that if PRONTI had been available pre-release, better predictions of non-target attack might have been made. The investment in time needed to adopt PRONTI needs to be balanced against its objectivity when comparing it with current conventional methods.

Transgenic cry1C⁎ gene rough rice line T1C-19 does not change the host preferences of the non-target stored product pest, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae), and its parasitoid wasp, Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae)

Rough rice grains are often stored for extended periods before they are used or consumed. However, during storage, the rough rice is vulnerable to insect infestation, resulting in significant economic loss. Previous studies have shown that volatiles cues, physical characteristics, and taste chemicals on the grains could be the important key behavior factors for storage insect pests to locate the hosts and select oviposition sites. It is also well known that the transgenic Bt rough rice line T1C-19, which expresses a cry1C⁎ gene has a high resistance to Lepidoptera pests. However, there were no evidences to show the consequences of host preference for non-target insect pests after growing Bt transgenic rice. In this study, the potential key factors of Bt rough rice were investigated for their impacts on the behaviors of non-target pest lesser grain borer Rhyzopertha dominica, the main weevil pest of grain and its parasitic wasps Anisopteromalus calandrae, the natural enemy of the beetle. Both electronic nose and electronic tongue analyses showed that the parameters of Bt rough rice were analogous to those of the non-Bt rough rice. The volatile profiles of Bt and non-Bt rough rice examined by gas chromatographic mass spectrometry (GC–MS) were similar. For most volatile compounds, there were no significantly quantitative differences in compound quantities between Bt and non-Bt rough rice. The densities of sclereids and trichomes on the rough rice husk surface were statistically equal in Bt and non-Bt rough rice. The non-target pest, R. dominica, and its parasitoid wasp, A. calandrae, were attracted to both rough rice and could not distinguish the transgenic T1C-19 from the isogenic rough rice. These results demonstrated that Bt rough rice has no negative impacts on the host preference behaviors of non-target stored product pest R. dominica and its parasitoid A. calandrae.

Distribution of weevils (Coleoptera: Curculionidae) in alfalfa fields of Iran’s northern provinces with a new record for the country

Alfalfa is an economic crop with a great number of natural or invasive pest species mainly from the Curculionoidea superfamily. The weevil fauna of some parts of Iran has been recently studied, but the knowledge of weevil pests in alfalfa fields is still incomplete. We carried out surveys of 11 localities in five northern provinces of Iran (Razavi Khorasan, Mazandaran, Semnan, Alborz and Hamedan) for two years for species of Curculionidae. A total of 1019 specimens were collected, and 19 species from six subfamilies, seven tribes and 10 genera were identified. The percentage abundance and frequency of each species showed that Hypera postica, Sitona cylindricollis, S. humeralis and S. longulus were important pests in most of the alfalfa fields in Iran’s northern provinces. Moreover, Sitona demoflysi is a new record for Iran.

Oviposition preference and offspring performance of Mechoris ursulus (Coleoptera: Attelabidae) in Cyclobalanopsis glaucoides (Fagales: Fagaceae) and Quercus franchetii (Fagales: Fagaceae) in Central Yunnan, China.

Mechoris ursulus (Roelofs) (Coleoptera: Attelabidae) is a pest weevil of Fagaceae oak trees in eastern Asia. The female has a distinct branch-cutting behavior in conjunction with oviposition in the acorns of its host plant. This study analyzed the factors influencing oviposition preference by carrying out continuous field surveys over the course of 2009–2010 and through laboratory rearing. The field survey showed that for both of the hosts, Cyclobalanopsis glaucoides Schottky (Fagales: Fagaceae) and Quercus franchetii Skan, M. ursulus preferred branches with fewer acorns and larger acorns on the same branch for oviposition. Laboratory rearing experiments showed offspring performance (i.e., survival rate and fresh weight of larvae) was significantly and positively correlated with acorn size. Preference for larger acorns could maximize the fitness of offspring by providing sufficient food source and space.